Patent Publication Number: US-2005128951-A1

Title: Apparatus and methods for dynamic bandwidth allocation

Description:
RELATED APPLICATIONS  
      This application is a continuation of U.S. application Ser. No. 09/317,381, filed May 24, 1999, issued as U.S. Pat. No. ______, the entire teachings of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      A typical data communications network includes many hosts interconnected by various data communication devices. The data communication devices can be routers, bridges, switches, access servers, gateways, hubs, concentrators, proxy servers, repeaters and so forth which exchange data over an interconnection of data links. The data links may be physical connections or may be provided using wireless communication mechanisms. The network allows data to propagate between various applications that execute on the hosts. The hosts are often general purpose computer systems such as personal computers, workstations, minicomputers, mainframes and the like, or the hosts may be dedicated devices such as web-site kiosks, facsimile servers, video servers, audio servers, and so forth. Each host couples to one or more of the data communications devices that form the network.  
      Various physical or hardware data communications connection mechanisms allow the hosts to interconnect with the network. Physical data communications connection mechanisms can include modems, transceivers, network interface cards, fiber optic cards, ports and other hardware devices which allow data to be transferred at various data transfer rates (i.e., bandwidths) to and from the hosts and between data communications devices. For example, certain hosts may have high-speed network interfaces which provide connections to the network at high data rates such as fractional-T1, T1, E1 or higher, while other hosts may use an inexpensive modem that provides a maximum data transfer rate of 56.6 kilobits per second (Kbps) to and from the network.  
      Depending upon a specific use of the host which often depends on an application running on a host, data traveling across the network that is associated with those applications may require different levels of data service (i.e., data transfer rates or network bandwidth). For example, a distributed applications protocol such as the Multicasting Protocol can be used to serve streams of data from one or more source hosts to one or more destination hosts which subscribe to the stream (called joining a multicast group). A multicasting video server coupled to the network may require a minimum amount of network bandwidth to be supplied from itself to all other hosts that require access to the streams of transmitted multicasted video. Another host may be supplying multicasted audio streams to remote destination hosts throughout the network. Though streaming audio data typically requires less network bandwidth than streaming video data (which usually contains encoded audio data as well as video images), both data types require a certain guaranteed minimum quality of service or QoS since each of these data types requires real-time transmission. The real-time bandwidth requirements of video or audio data contrast sharply with best-effort only bandwidth requirements associated with non-urgent data such as E-mail communications which can be delayed in the network for prolonged periods without affecting the intended purpose or performance of the E-mail application.  
      As another example of the need for varying bandwidth requirements, hosts that connect or subscribe to networks using high speed connection mechanisms such T1 interface cards generally expect to be provided with, and often pay a premium for the ability to send and receive data across the network at T1 data rates. Other hosts may not require such high data transfer rates and therefore only subscribe to the network and pay for the capability to transfer data at lower data transfer rates. In either case, the data communications devices in the network must be able to distinguish and handle the flows of data from hosts having differing levels or qualities of service.  
      Since many connections, sessions or data traffic flows (i.e., data associated with an end-to-end application or stream) from multiple hosts with potentially different data rates are frequently switched, routed or transferred through the same data communication devices in a network such as the Internet, the data communications devices must provide a way to establish, allocate or reserve the bandwidth requirements for the various flows, sessions, or connections. Once the bandwidth is allocated, the devices must distinguish the different data flows or connections requiring the different levels of service (i.e., different data rates or bandwidth requirements). Once distinguished, the data communications devices must be able to service each connection or flow at its prescribed level of service. For example, if T1 service is required, the data communications devices must identify and transport data on T1 or higher speed links through the network at T1 speeds, while data from slower links should at least be transferred through the network at a minimum subscription rate of those links. Management of the various data transmission and propagation requirements associated with data having differing levels of service is a well known problem associated with data communications devices in modem networks.  
      Various bandwidth allocation or reservation protocols have been developed for use in modern networks to provide guaranteed QoS or controlled end-to-end delays for transmitted data. These protocols allow applications that exchange data between sending and receiving hosts to establish reservations of bandwidth over the network for the various services required by the applications. One such protocol is called RSVP, which stands for the ReSerVation Protocol.  
      As its name implies, hosts use RSVP to request a specific QoS from the network on behalf of an application data stream. RSVP carries the request through the network, visiting each data communications device or node that the network will use to carry the stream. At each node, RSVP attempts to make a resource (i.e. bandwidth) reservation for the stream. Once bandwidth is reserved in each node on the network path from sender to receiver, the sender can commence transmission of the stream using the reserved network bandwidth. The QoS for that stream is generally guaranteed since the bandwidth is reserved for use by that particular stream (e.g., Multicast group) and no other.  
       FIG. 1  illustrates a typical architecture and data flow of a prior art data communications device  100  configured to use RSVP. Traditionally, to make a resource reservation in the data communications device  100  (e.g. a router), an RSVP daemon  101  executing on the device  100  communicates with two local decision modules, admission control  102  and policy control  103 . Admission control  102  determines whether the device  100  has sufficient available resources (e.g., buffer capacity, processor and I/O bandwidth) to supply the requested QoS. Policy control  103  determines whether a user, host or application (typically on another device or host) requesting the bandwidth reservation has administrative permission (i.e. access control) to make the reservation. If either check fails, the RSVP daemon  101  returns an error notification to the application process that originated the request. If both the admission and policy control checks succeed, the RSVP daemon  101  defines a set of filterspec parameters provided to a packet classifier  104  and a set of flowspec parameters provided to the packet scheduler  106  to configure and obtain the desired QoS in the device  100  for that stream.  
      The packet classifier  104  uses the filterspec parameters to filter each packet (data in) that arrives at the device to determine the route and queue for the packet within the data queuing mechanism  105 . For example, there may be many prioritized queues, each providing a specific level of service or QoS. The packet scheduler  106  uses the flowspec parameters to properly service the queues in the data queuing mechanism  105  to achieve the promised QoS for each stream. Typically, the packet scheduler  106  employs a weighted fair queuing algorithm to dequeue the data from the various queues in the data queuing mechanism  105  according to the bandwidth allocation requirements or QoS defined in the flowspec parameters.  
       FIG. 2  illustrates a prior art packet data structure  510  used to transport data in a data stream for which RSVP has reserved bandwidth in data communications device  110 . The data packet  510  includes an RSVP header field  180  followed by UDP and IP headers  181 ,  182  and the data  183 . The RSVP header  180  typically includes various fields  184  through  191 . Of particular interest is the Tspec field  191  which provides a description or identification of the traffic flow, session, or data stream to which this data packet  510  is associated. The packet classifier  104  and the packet scheduler  106  can use the Tspec field  191  to identify different flows of data and enforce the bandwidth allocations or QoS for each identified flow.  
     SUMMARY OF THE INVENTION  
      The RSVP protocol does not define how a device (e.g.  100  in  FIG. 1 ) is to implement the actual bandwidth reservations allocated to a session or flow of data communication between hosts. Rather, RSVP simply provides a mechanism to exchange bandwidth reservation and path messages along the path of data communication between sending and receiving hosts. The reservation messages simply identify a session or stream of data communication and indicate a requested level of service for that stream of data. The path messages indicate where the data is to come from and also indicate where to transmit the data. The mechanisms to set aside or reserve the bandwidth resources in the device are implementation dependant.  
      Accordingly, RSVP only provides a framework for hosts to notify and request reservations of bandwidth in all data communications devices that are on paths between sending and receiving hosts. Once the data communications devices have agreed to reserve the requested bandwidth (i.e., admission and policy control), the implementation of how that bandwidth is actually reserved or set aside within each device is left up to the device and is not part of the RSVP protocol. The previously described prior art implementations of device bandwidth reservation mechanisms using customized packet classifiers and packet schedulers which operate in conjunction with the RSVP protocol have become quite popular.  
      However, one problem that stems from these prior art implementations is that they do not allow adjustments to be made to the amount of bandwidth reserved to a session of data communication without requiring the session to be interrupted. That is, once the prior art implementations of bandwidth reservation techniques (i.e. modified classifiers and schedulers) reserve a set amount of bandwidth between two or more hosts, the prior art implementations cannot adjust the amount of reserved bandwidth without clearing the session from end-to-end of all data in the path(s) between sending and receiving hosts. This essentially requires the sender(s) to stop sending session data to provide time for all session data in the network to clear and reach the intended receiver(s). In other words, if the bandwidth or QoS requirements of a session need to change (e.g., the receiver needs more bandwidth to properly receive the stream), the RSVP negotiation that must take place requires that the sending host halt data transmission for a period of time, while the sending and receiving hosts, and all data communication devices in between, clear themselves of the session data. Then, the sender and receiver must use another set of RSVP reservation and path messages to adjust (i.e., increase or decrease) the amount of bandwidth allocated between the sender and receiver hosts to meet the new requirements.  
      One reason that current implementations of RSVP do not allow bandwidth adjustments once a communication session is in progress is not due to limitations of the RSVP protocol. Rather, the design of prior art data communications devices that support RSVP, such as show in  FIG. 1 , impose the limitations. A customized data classifier  104  and scheduler  106  support RSVP bandwidth reservation requests and enforce the bandwidth allocation requirements in prior art data communications devices that support RSVP. The RSVP daemon  101  periodically updates the customized classifier  104  with filterspec information which allows the classifier  104  to properly examine and classify packets of data with the flow identification associated with the packets. If a packet is associated with a flow of data for which bandwidth has been allocated via RSVP, the customized classifier  104 , for example, directs this packet to a queue reserved for this flow. Once queued, the customized scheduler  106  typically uses a weighted fair queuing algorithm to dequeue the data from the various queues according to the bandwidth allocation requirements associated with the various flows of data in relation to each queue as defined by flowspec requirements.  
      By way of example, if the classifier  104  identifies data associated with a session having a high bandwidth reservation, the classifier  104  may queue the data in a high bandwidth queue. The scheduler  106  may service the high bandwidth queue more frequently that other queues which may have lower bandwidth allocations or reservations which are serviced less frequently. Since the classifier, the scheduler, and sometimes the queuing structure are all involved in prior art device specific implementations of bandwidth reservation using RSVP, data associated with a specific session may exist in any one of these components in the device at any point in time. Hence, if the RSVP daemon  101  were to attempt to change the allocation of reserved bandwidth during an active session of data communication, the scheduler  106  might need to reconfigure queuing structures and the classifier  104  might need to be made aware of the new bandwidth allocation scheme for that session. If data communications devices using prior art implementations of RSVP attempted to dynamically reconfigure bandwidths allocated to sessions of data communication during transport of those sessions, significant delays and/or lost data would result for flows using the data communications device.  
      To avoid such losses or delays of data, prior art implementations of RSVP require that the sending host halt the transmission of data and that all data be flushed through the network to the receiver. Once the prior art devices clear the network of any data associated with a specific session of data communication, the prior art devices use another sequence of RSVP messages to adjust bandwidth and establish a new session. Once the prior art devices have established a new bandwidth allocation, a new session of data communication must be reinitiated.  
      The present invention avoids the prior art situation of requiring a break in a data communication session in order to re-allocate or adjust bandwidth reserved for a session. The present invention provides a device implementation that can accept bandwidth allocation changes and can dynamically adjust bandwidth during an active session of data communication using a protocol such as RSVP without requiring a pause or break in the transmission of data along the entire path from sender(s) to receiver(s). This can be accomplished since the present invention manages resources, and is not focused on managing time.  
      More specifically, the present invention provides a data communications device capable of dynamically adjusting reserved bandwidth while maintaining a session of data communication. The device includes an input for receiving data including bandwidth reservation requests and a data storage mechanism including data storage locations. Also included is a bandwidth reservation processor coupled to the input port which accepts a first bandwidth reservation request indicating a first amount of bandwidth to reserve for the session of data communication in the data communications device. The bandwidth reservation processor then establishes a first bandwidth reservation associated with a session of data communication in the data storage locations. A data scheduler is included and is coupled to the input port and coupled to the data storage mechanism. The data scheduler receives data associated with the session of data communication and deposits the data associated with the session of data communication into the data storage locations associated with the first bandwidth reservation. Using such a mechanism, data transport is separated from bandwidth reservation and allocation. The bandwidth reservation may enforce reservations for high priority traffic, for example.  
      In another embodiment which allows dynamic adjustments to the bandwidth reservation already in effect, the bandwidth reservation processor receives bandwidth allocation adjustment information from the input port during the session of data communication and dynamically adjusts the first bandwidth reservation in the data storage locations to produce a second bandwidth reservation for the session of data communication in accordance with the bandwidth allocation adjustment information. This apparatus performs this operation while the data scheduler continually receives and deposits data associated with the session of data communication into the data storage locations associated with the session of data communication. In other words, the session of data communication continues during the bandwidth adjustment processing.  
      In a more detailed embodiment, the bandwidth reservation processor includes a bandwidth request handler coupled to the input port to receive bandwidth reservation requests. Also provided is a bandwidth labeler coupled to the bandwidth request handler and coupled to the data storage locations. The bandwidth labeler receives bandwidth allocation information indicated in the first bandwidth reservation request and labels, with an identity of the session of data communication, a first available percentage of the data storage locations used to store data transported through the data communications device thus establishing the first bandwidth reservation.  
      Another embodiment is provided in which the bandwidth reservation processor further includes a resource allocation table accessible by the bandwidth labeler and a resource allocation calculator coupled to access the resource allocation table independently of the bandwidth labeler. The resource allocation calculator receives the bandwidth allocation information indicated in the first bandwidth reservation request and calculates and stores in the resource allocation table a first percentage of total device bandwidth to allocate to the session of data communication based upon the first bandwidth reservation request. Using these mechanisms, the bandwidth reservation processor can continually allow for bandwidth adjustments over time without disturbing the session of data communication for which the bandwidth reservation exist.  
      Another embodiment of the invention provides a system for reserving bandwidth in a data communications device. The system includes a bandwidth request handler that accepts a first bandwidth reservation request indicating a first amount of bandwidth to reserve for a session of data communication in the data communications device. Also included is a bandwidth labeler coupled to the bandwidth request handler. The bandwidth labeler labels, with an identity of the session of data communication, a percentage of available data storage locations used to store data transported through the data communications device to establish a first bandwidth reservation. The percentage of storage locations labeled is based upon the first amount of bandwidth requested as indicated in the first bandwidth reservation request. Preferably, the data storage locations for a path or session of data communication are in the form of a single rotating queue structure.  
      Similar to this embodiment, another embodiment is a data communications device that includes a bandwidth reservation processor that processes requests to reserve bandwidth for a session of data communications and labels a percentage of available data storage locations in the data communications device with a session identifier. A data transporter in this embodiment concurrently processes and transports data through a data communications device using the available data storage locations to store data as it is processed. The data transporter deposits only data having a corresponding identifier equivalent to the session identifier of the storage locations into the data storage locations labeled with the session identifier. In this manner, only labeled storage location are use for session data and comprise the reserved bandwidth.  
      The aforementioned apparatus embodiments perform processing that is unique to this invention as well. The processing steps also are embodiments of the invention and are summarized below.  
      Specifically, one processing or method embodiment provides a method for separately handling bandwidth reservation processing in a data communications device from data transport processing. The method includes the steps of processing requests to reserve bandwidth for a session of data communications and labeling a percentage of available data storage locations in the data communications device with a session identifier. Also, the method includes the step of concurrently processing and transporting data through a data communications device using the available data storage locations to store the data as it is processed, and depositing only data having a corresponding identifier equivalent to the session identifier of the storage locations into the data storage locations labeled with the session identifier. Using such a method, the device can reserve bandwidth while concurrently processing session data in the device.  
      In another method of the invention, the step of processing requests, processes requests to change an amount of reserved bandwidth associated with the session of data communication.  
      In yet another method embodiment, a method of storing bandwidth reservation information is provide and includes the steps of accepting a bandwidth reservation request indicating an amount of bandwidth to reserve for a session of data communication. Then, the step of calculating a percentage of total device bandwidth to allocate to the session of data communication based upon the bandwidth reservation request is performed. This is then followed by the step of storing the percentage in a resource allocation table which is independently accessible by a flow labeler.  
      Another embodiment of the invention provides a method for dynamically adjusting reserved bandwidth in a data communications device while transporting a session of data communication within the device. This method embodiment includes the steps of establishing a first bandwidth reservation associated with a session of data communication in the data communications device. This may be done, for example, by accepting a first bandwidth reservation request indicating a first amount of bandwidth to reserve for the session of data communication in the data communications device and by labeling, with an identity of the session of data communication, a first percentage of available data storage locations used to store data transported through the data communications device thus establishing the first bandwidth reservation. The first percentage of storage locations labeled is generally based upon the first amount of bandwidth requested as indicated in the first bandwidth reservation request.  
      Preferably, after the step of accepting a first bandwidth reservation request, the step of establishing a first bandwidth reservation further includes the step of calculating and storing a first percentage of total device bandwidth to allocate to the session of data communication based upon the first bandwidth reservation request. The first percentage of data storage locations labeled in the step of labeling is based upon the calculated first percentage of total device bandwidth to allocate to the session of data communication. Also, the step of calculating and storing preferably stores the calculated first percentage in a resource allocation table which is independently accessible by the step of labeling and the step of dynamically adjusting, so as to allow the step of dynamically adjusting to alter the calculated percentage in the resource allocation table without disrupting the step of labeling, thus allowing the bandwidth reservation in the device to be adjusted without effecting operation of a step of transporting (summarized below). Accordingly, data storage locations are labeled in accordance with the bandwidth requests and the labeling of the locations inherently reserves the bandwidth for sessions associated with the label.  
      As noted above, the embodiment also includes the step of transporting, through the data communication device, data associated with the session of data communication utilizing data storage locations associated with the first bandwidth reservation. The step of transporting can deposit the data associated with the session of data communication into data storage locations having an identification associated with the session of data communication and does so independently of how the identification associated with the session of data communication is created. Preferably, this step of transporting deposits the data associated with the session of data communication only into those data storage locations having an identification associated with the session of data communication. In other words, storage locations are labeled with an identity of a session of data communication for which bandwidth is reserved and during data transport, data associated with that session of data communication is placed into the labeled storage locations corresponding to the session. Preferably, other data not associated with the session of communication does not use the labeled locations, since they are reserved for the session data only. In this manner, the number of labeled locations selected from a total set of available location, such as labeling selected data storage locations in a single large rotating queue, are reserved for the session data.  
      The embodiment also includes the step of receiving bandwidth allocation adjustment information during the session of data communication. Preferably, this is done via a resource allocation protocol such as RSVP. That is, the data communications device uses an RSVP protocol to determine an amount of bandwidth to reserve.  
      Furthermore, the embodiment includes the step of dynamically adjusting the first bandwidth reservation to produce a second bandwidth reservation for the session of data communication in accordance with the bandwidth allocation adjustment information while continually maintaining the session of data communication.  
      In another embodiment based on the former embodiment, the step of dynamically adjusting the first bandwidth reservation to produce a second bandwidth reservation includes the steps of accepting a second bandwidth reservation request indicating a second amount of bandwidth to reserve for the session of data communication, and labeling, with an identity of the session of data communication, a second percentage of available data storage locations used to store data transported through the data communications device thus establishing the second bandwidth reservation. The second percentage of storage locations labeled is based upon the second amount of bandwidth requested as indicated in the second bandwidth reservation request, and the second percentage of storage locations labeled is different than the first percentage of storage locations labeled. This allows bandwidth to be adjusted by altering the labeled percentages for storage locations (e.g. in the single rotating queuing structure) associated with (i.e., labeled to receive) various sessions of data communication.  
      In another embodiment, after the step of dynamically adjusting the first bandwidth reservation to produce a second bandwidth reservation completed, the method further includes the step of calculating and storing a second percentage of total device bandwidth to allocate to the session of data communication based upon the second bandwidth reservation request. The second percentage of data storage locations labeled in the step of labeling is based upon the calculated second percentage of total device bandwidth to allocate to the session of data communication. The second percentage replaces the first percentage calculated previously.  
      Preferably, the step of calculating and storing stores the calculated second percentage in a resource allocation table as a replacement for the calculated first percentage. The step of calculating can include the steps of obtaining a current measurement of data communications device data storage locations available for data storage and a current bandwidth utilization rate and then computing an amount of bandwidth to reserve for the session of data communication based on the current bandwidth utilization rate and on the current measurement of data communication device data storage locations available for data storage.  
      The resource allocation table is independently accessible by the step of labeling and the step of dynamically adjusting, so as to allow the step of dynamically adjusting to alter the calculated first percentage in the resource allocation table without disrupting the step of labeling, thus allowing the first bandwidth reservation in the device to be adjusted without effecting operation of the step of transporting. The resource allocation table may be a database, table, linked list, object, or other data structure or storage mechanism used to store resource allocation data as described herein.  
      In another embodiment, the step of dynamically adjusting the first bandwidth reservation to produce a second bandwidth reservation includes the steps of accepting a bandwidth reservation request indicating a specific amount of bandwidth to reserve for the session of data communication. Next, a step of calculating and storing a percentage of total device bandwidth to allocate to the session of data communication based upon the bandwidth reservation request is performed, followed by a step of labeling, with an identity of the session of data communication, a percentage of available data communication device data storage locations used to store data transported through the data communications device. In this embodiment, the labeled percentage is based upon the calculated percentage of total device bandwidth to allocate to the session of data communication. Thus, the data storage locations are labeled according to reserved bandwidth requirements.  
      Other apparatus embodiments include computer program product(s) having a computer-readable medium including computer program logic encoded thereon for allocating bandwidth in a data communications device. The computer program logic, when executed on one or more processing units with the data communications device, cause the processing unit(s) to perform any and all of the aforementioned methods steps. That is, since certain embodiments of the invention can be implemented in software, the computer program embodiments cover a disk or other computer readable medium encoded with instructions to execute the invention as a software program. The disks or other mediums themselves containing the code are actual embodiments of this invention.  
      The resource allocation information for bandwidth reservations is preferably stored in the resource allocation table. In one embodiment, a computer readable medium is provided that is encoded with a data structure. The data structure stores bandwidth allocation information. The bandwidth allocation information includes an identity of at least one session of data communication and a number representing a percentage of data storage locations to associate with the identity of the at least one session of data communication. The number representing the percentage of data storage locations to associate with the identity of the session of data communication is preferably a number indicating a number of labels to apply to data storage locations so as to reserve the data storage locations for the data associated with the at least one session of data communication. This data structure embodiment can be used to maintain bandwidth reservation information within a data communications device and can be dynamically changed to re-apportion bandwidth resources while the device concurrently and separately maintains the sessions of data communication. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.  
       FIG. 1  illustrates a typical prior art implementation of the RSVP protocol used to reserve bandwidth within a data communications device.  
       FIG. 2  illustrates the structure of a prior art packet used to transfer data according to the RSVP protocol.  
       FIG. 3  illustrates a data communications networking environment using data communications devices configured to reserve bandwidth according to the invention.  
       FIG. 4  illustrates an internal architecture and data flow diagram of a data communications device configured according to one embodiment of the invention.  
       FIG. 5  illustrates a more detailed architecture and data flow diagram for a data communications device configured according to the invention.  
       FIG. 6A  illustrates a resource allocation table created illustrating example data flow resource allocations according to an embodiment of the invention.  
       FIG. 6B  illustrates a detailed view of a queue entry labeling arrangement according to one embodiment of the invention.  
       FIG. 7  illustrates bandwidth policy and admission control processing steps performed by a bandwidth reservation processor configured according to one embodiment of the invention.  
       FIG. 8A  illustrates resource allocation calculation processing steps performed according to one embodiment of the invention.  
       FIG. 8B  illustrates queue entry label processing steps performed by a bandwidth labeler configured according to one embodiment of the invention.  
       FIG. 9A  illustrates how data storage locations can be labeled according to percentages of flow bandwidth per flow according to one embodiment of the invention.  
       FIG. 9B  illustrates how data storage locations can be labeled according to another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      An brief overview of the invention will assist in understanding the discussion of detailed embodiments. Generally, the system of the invention allows a data communications device to dynamically reserve bandwidth and adjust bandwidth reservations for sessions of data communication without session disruption. The device can perform reservation and adjustment operations independently of sessions of data communication that are in progress (i.e. actively being transmitted) in the device and that may be using any currently reserved bandwidth resources. However, as the bandwidth is adjusted, the session(s) for which bandwidth adjustment is made are transported according to the new bandwidth reservation. That is, adjustments in reserved bandwidth for a session of data communication can be made without concerning or bothering the continual process of transporting data for that session, but the session data itself will be transported using the new bandwidth reservation as it is put in place, whether the new reservation is an increase or decrease in available bandwidth.  
      By having the device separate the operation of bandwidth allocation and adjustment from the continual operation of transporting data through the device, the device can perform bandwidth reservations and adjustments without disturbing the flow or sessions of data communication. The system can accept requests to allocate or reserve bandwidth in a data communications device using bandwidth reservation protocols such as RSVP. The reservation requests create sender state data that can be used to compute resource allocation data. The device uses the resource allocation data to associate labels with data storage locations in a data storage mechanism according to the required bandwidth reservations. A data scheduling apparatus, which is ignorant of particular sessions having specific amounts of reserved bandwidth, examines data and deposits data into data storage locations having an associated label corresponding to a session identification specified in the data, if any. This way, the device only places session data into the labeled storage locations reserved for that session data. If the data contains an unknown session identification (or none at all), the data scheduler deposits data into a data storage location that is unlabeled or that has an unreserved label. Thus the percentage of data storage locations labeled in a device for a session determines bandwidth reserved for the session. The data storage labeling scheme of the invention operates separately from the data scheduling, enqueuing and data dequeuing mechanisms to allow data sessions to continue without interruption during bandwidth adjustments.  
       FIG. 3  illustrates an example of a communications network  200  configured according to the invention. The network  200  includes data links  202  which interconnect data communications devices  201 -A through  201 -E, network policy server  150 , and hosts  210  (including hosts  210 -A 1 ,  210 -A 2  and  210 -A 3 ). The data links  202  allow communications to take place between the various components shown in the figure and can be any type of communication medium including physical network cables, wires, fiber optic links, any type of wireless transmission links or another communications medium. Though the network  200  is illustrated as a relatively small network for ease of description of the invention, the invention is applicable to networks of all sizes, including interconnected local area networks (LANs), wide area networks (WANs), intranets, extranets, and conglomerations of many networks, such as the Internet, for example.  
      As illustrated, the hosts  210  are general purpose computer systems such as personal computers, mini-computers, mainframes or the like that exchange data, as will be explained, over the network  200 . It is to be understood, however, that the hosts  210  may be many different types of computing or data exchanging devices such as file servers, web-site servers, network-telephony devices, audio or video servers, and so forth and that the invention is not limited to application only in a computer network or only for data exchange between devices of a specific type.  
      The data communication devices  201  provide the processing resources (routing and switching algorithms, queues, buffers, switching fabrics, data busses, backplanes, input and output ports, and so forth) to propagate data through the network  200  between the hosts  210 . The data communication devices  201  may be any type of data processing device that can transfer, switch, route or otherwise direct or propagate data in a network. Possible examples of data communications devices  201  are network access servers, routers, switches, hubs, bridges, gateways, proxy servers, firewalls, modem banks, concentrators, repeaters, and similar data transfer devices, or any combination thereof. Preferred embodiments of invention are implemented within the data communications devices  201  and allow each device  201  to dynamically reserve bandwidth to one or more sessions of data communication between hosts  210  and allow the amount of bandwidth that is reserved by or to those sessions to be changed without disrupting the sessions that are using the reserved bandwidth or that require a change in the amount of reserved bandwidth in each data communications device  201 .  
       FIG. 3  is suitable for illustrating some example operations of embodiments of the invention which are helpful in understanding more detailed embodiments presented later. In  FIG. 3 , suppose, for example, that host  210 -A 1  is a video server that serves a stream of video packets  203  (the “A” video stream) across the communications network  200  to recipient hosts  210 -A 2  and  210 -A 3  using a multicasting protocol. Furthermore, assume that in order for a receiving host  210 -A 2 ,  210 -A 3  to properly receive the “A” video stream  203  with adequate quality, the hosts  210 -A 2 ,  210 -A 3  require an end-to-end network bandwidth of 100 Kilobits per second (Kbps). That is, each data communications device  201 -B through  201 -E that transports the stream of “A” video packets  203  between sending host  210 -A 1  and recipient hosts  210 -A 2  and  210 -A 3  must supply a minimum data transfer rate (i.e., bandwidth) of 100 Kbps for the “A” video stream  203 .  
      Due to the critical or real-time nature of data in the “A” video stream  203 , the sending and receiving hosts  210 -A 1 ,  210 -A 2  and  210 -A 3 , in conjunction with the data communications devices  201 -B,  201 -C  201 -D and  201 -E use a bandwidth reservation protocol such as RSVP to establish and reserve a 100 Kbps channel for the “A” video stream  203  through the network  200 . Specifically, using RSVP, each data communications device  201 -B,  201 -C  201 -D and  201 -E receives RSVP path and bandwidth reservation request messages (not specifically shown in this figure) which specify, among other things, an identity of a specific session of data communication (the “A” video stream  203  in this example), an amount of bandwidth to reserve for the session of data communication (100 Kbps in this example), and the path for which the requested bandwidth is to be reserved for the specified data stream (i.e.,  203 ) within each particular device  201 -B through  201 -E. In an alternative embodiment, the network policy server  150  supplies the requests to each device  201  (in the form of commands) which tell the devices  201  how much bandwidth to reserve for flows, streams, or sessions of data communication in the network  200 .  
      According to the invention, each data communication device  201  contains a bandwidth reservation processor  500  (abbreviated B.R.P. in  FIG. 4 ) and a data transporter  300  (abbreviated D.T. in  FIG. 4 ). In the illustrated example, only device  201 -B is illustrated with the bandwidth reservation processor  500  and the data transporter  300 , though it is assumed for this example that all devices  201  are configured in a similar manner. All of the processing associated with the reservation and allocation of bandwidth is performed by the bandwidth reservation processor  500  in a device  201 , while all of the processing associated with the transport of data (e.g., stream  203 ) through a device  201  is handled separately and concurrently by the data transporter  300 . Using this configuration, a data communications device  201  can configure, control and adjust (if needed) bandwidth reservation requirements for streams of data (e.g., alter the 100 Kbps channel for the “A” video data stream  203 ) independently of transferring the actual data (e.g., the “A” data stream packets) through the device  201 .  
      Continuing with the example, the bandwidth reservation processor  500  in each device  201 -B through  201 -E receives the RSVP path and bandwidth reservation request messages. If the bandwidth reservation processor  500  determines that a requesting application or host (e.g., receiving hosts  210 -A 2  or  210 -A 3 ) has permission or privileges to reserve the requested bandwidth (e.g., RSVP policy control) and also determines that the requested resource (e.g., the 100 Kbps bandwidth) is available in the device  201 , the bandwidth reservation processor  500  in each data communications device  201 -B through  201 -E grants the request and establishes the 100 Kbps bandwidth reservation for the “A” data stream  203  along the path from sending host  210 -A 1  to receiving hosts  210 -A 2  and  210 -A 3 . Once the bandwidth reservation is established, each data communications device  201 -B through  201 -E transports data (i.e., packets) associated with the session of data communication (i.e. the “A” video data stream  203 ) using the reserved 100 Kbps resources (data storage locations in this invention, as will be explained).  
      Extending the example, assume that each recipient host  210 -A 2  and  210 -A 3  receives the “A” data stream  203  at the reserved rate of 100 Kbps. That is, the bandwidth reservation processor  500  configures each data communications device  201 -B through  201 -E with a bandwidth reservation of 100 Kbps of its total bandwidth (i.e., its total data transfer capacity or throughput for the path specified for, or required by, the data stream) for the “A” video stream packets  203  which are continuously delivered to the recipient hosts  210 -A 2  and  210 -A 3  in real-time across network  200 . If a video client application (not shown) executing on recipient host  210 -A 3  senses that more network bandwidth is required (such as 120 Kbps) to effectively receive the “A” video data stream  203 , the host  210 -A 3  can use RSVP to make a bandwidth reservation request (not shown) containing bandwidth allocation adjustment information to each network device  201 -E,  201 -D,  201 -C and  201 -B. The bandwidth allocation adjustment information in the bandwidth reservation request specifies a request for 120 Kbps of bandwidth to be reserved for the “A” video data stream  203 .  
      Using the invention, the bandwidth reservation processor  500  in each device  201 -E through  201 -B along the path of the “A” data stream  203  receives the RSVP bandwidth allocation adjustment information. Assuming bandwidth resources (i.e., an extra 20 Kbps) are available to meet the needs of the additional request (e.g. RSVP admission control), and that permission is granted for the requesting host (e.g.,  210 -A 3 ) or client application to increase bandwidth to the requested level, the bandwidth reservation processor  500  in each device  201 -E through  201 -B dynamically adjusts the original bandwidth reservation of 100 Kbps to produce a new bandwidth reservation of 120 Kbps for the “A” video data stream  203  while continually maintaining (i.e., transporting) the “A” video data stream  203 . Essentially, the invention&#39;s implementation of the separation of bandwidth reservation, adjustment and control from the transportation of data through a data communications device, as configured according to the invention allows a session of data communication to be uninterrupted during adjustments to bandwidth for that session.  
       FIG. 4  illustrates a more detailed architecture of a data communications device  201  configured according to one embodiment of the invention which provides the processing capabilities explained above. In this embodiment, the data communications device  201  contains the data transporter  300  including a data scheduler  320  and a data storage mechanism  340 , and the bandwidth reservation processor  500  including a bandwidth request handler  520  and a bandwidth labeler  550 . At least one input port  505  is provided in the data communications device  201  which is illustrated as receiving application or session data (e.g., the “A” video data stream packets  203  in  FIG. 1 ) and RSVP reservation requests and path messages  511 , shown as an “R” packet. An output port  506  is also provided which transmits data onto the network  200 . Only one input and output port  505 ,  506  are illustrated for ease of description of the invention. It is to be understood that many ports serving as both input and output ports may exist in a preferred embodiment of the data communications device  201 .  
      The network policy server  150  is also shown in this embodiment to illustrate that the bandwidth reservation processor  500  can receive commands  530  to govern bandwidth allocation operations (as explained herein), instead of using bandwidth reservation requests  511  from individual hosts  201 . This alternative arrangement may be beneficial when each data communications device  201  network-wide is to have a permanent amount of dedicated reserved bandwidth for use by a special purpose application or network wide (e.g. multicast) session of data communication, for example.  
      According to the general operation of the data communications device  201 , initial bandwidth reservation for a particular session of data communication is generally performed before data communication for the session actually begins. The invention however is equally applicable to situations where a session of data communication is already established (i.e., data transport is underway across the network) but there is no particular amount of bandwidth pre-allocated for that session in the data communications devices  201  which are transporting the data. That is, the invention can be used to establish a bandwidth reservation concurrently with an active session of data communication that is already being transported through a network without having to disrupt or interrupt the session in any way. In a similar manner, as explained in the above example, the invention can also be used to adjust or modify a bandwidth reservation already assigned to a data communication session that is underway and that is currently being transported through a network.  
      To reserve bandwidth for a session(s) of data communication in any of these situations, the data communications device  201  receives bandwidth reservation requests and path messages  511  which are directed to the bandwidth request handler  520 . The bandwidth request handler  520  is a process that executes on the data communications device  201  and is responsible for accepting or denying the bandwidth reservation requests  511 . If accepted, the bandwidth request handler  520  provides one or more data structures called sender state data  504  ( FIG. 5 ) to the bandwidth labeler  550 . Sender state data  504  specifies source and destination points for a particular session or sessions of data communication that exist (or that will exist) (i.e., the “A” video stream data  203  in  FIG. 3 ), a path (i.e., input port to output port) for the session or sessions of data communication, and an amount of bandwidth (e.g., 100 Kbps) required to be reserved for the session or sessions over the specified path.  
      The path in the sender state data  504 , in this example embodiment, indicates a route through which the session data travels (DATA IN, DATA and DATA OUT in  FIG. 4 ) within the data communication device  201  from an input port  505  at which the session data is received, through the data transporter  300  (to be explained shortly), to an output port  506  which transmits the session data towards its destination. In this example embodiment, assuming a session of data communication enters and exits only through a single pair of input and output ports  505 ,  506  in the data communications device  201 , the slowest port of a single input/output port pair  505 ,  506  limits the amount of bandwidth available. By way of example, assuming the input and output ports  505 ,  506  are configured the same (i.e., have the same maximum bandwidths), if the ports  505 ,  506  each support a connection data rate of 400 Kbps, then the bandwidth reservation processor  500  can reserve a maximum of 400 Kbps for a session of data communication on these ports. In the example provided above with respect to the initial bandwidth reservation provided for the “A” video data stream  203  in  FIG. 1 , the bandwidth request handler  520  produces sender state data  504  that specifies that a session of “A” video data requires 100 Kbps of bandwidth between input port  505  and output port  506 .  
      Once the bandwidth labeler  550  obtains the sender state data  504 , the bandwidth labeler  550  accesses  512  the data storage mechanism  340  to establish the requested bandwidth reservation as specified in the sender state data  504 . The bandwidth labeler  550 , as its name implies, operates (as will be explained in more detail) to label a certain percentage of data storage locations (not shown in this figure) maintained within the data storage mechanism  340  with the identity (i.e., a label) of the session of data communication for which bandwidth is to be reserved as specified in the sender state data  504 . Using the aforementioned example, the bandwidth labeler  550  labels a certain percentage of data storage locations used to transfer data between input port  505  and output port  506  in the data storage mechanism  340  with a label corresponding to the “A” video data stream  203 . The percentage of storage locations labeled is based upon the amount of bandwidth requested (100 Kbps) as indicated in the bandwidth reservation request, which is also provided in the sender state data  504 .  
      In this manner, bandwidth reservation is accomplished via use of the bandwidth reservation processor  500  which accesses the data storage mechanism  340  to label certain data storage locations with a labels corresponding to the sessions of data communication requiring reserved bandwidth.  
      During a session of data communication, the input port  505  receives packets of application data  203  (which in this invention generally refers to data transferred in a session of data communication) directs them to the data scheduler  320 . The data scheduler  320  schedules or deposits the data packets  203  into data storage locations (not specifically shown) within the data storage mechanism  340  which have corresponding labels provided by the bandwidth labeler  550 . The data storage mechanism  340  then operates to transport the application data packets  203  back onto the network  200  from an appropriate output port  506 , in order to send the application data  203  further towards its eventual destination (e.g., one of receiving hosts  210 -A 2 ,  210 -A 3  in  FIG. 1  in this example).  
      It is important to understand that the data scheduler  320  does not need to be made aware or provided with an indication of each different session (active or not) of data communication (i.e., “A” data stream  203 ) for which bandwidth is reserved in the data communications device  201  configured according to this embodiment of the invention. Rather, the data scheduler  320  only needs to look at each data packet  203  to determine if the packet is associated with any session of data communication and if so, the data scheduler  320  deposits the packet into a data storage location in the data storage mechanism  340  that has a corresponding label equivalent to the label for the session contained in the packet header  180  (e.g., in the Tspec field  191  in  FIG. 2 ). One or more fields  184  through  191  in packet header  180 , as explained with respect to  FIG. 3 , are preferably used to determine if a particular packet  203  is associated with any session(s) of data communication or not. In other embodiments, non-header fields such as data field  183  ( FIG. 2 ) may be used to determine if the packet  510  ( FIG. 2 ) (or cell, frame, etc.) is associated with a session of data communication corresponding to a labeled storage location.  
      In this manner, the bandwidth reservation processor  500  reserves bandwidth in a data communications device  201  without requiring the data scheduler  320  to be notified each time bandwidth is allocated for a session of data communication. This aspect of the invention also allows the bandwidth reservation processor  500  to adjust bandwidth for a session of data communication without requiring any runtime changes or notifications to be made, or provided, to the data scheduler  320 . That is, the data scheduler  320  can remain ignorant of how many sessions of data communication are currently active and/or have bandwidth reserved in the data communications device  201 . Instead, the data scheduler  320  can focus on repetitively depositing packets into data storage locations having labels that match an RSVP packet header  180 , if any. If no RSVP packet header  180  or other session identifier information exists for a packet, then the data scheduler  320  deposits that packet into any data storage location that is not presently labeled.  
       FIG. 5  illustrates a more detailed embodiment of a data communications device  201  configured according to the invention. In the example illustrated in  FIG. 5 , there are four active flows of data  203 ,  204 ,  205  and  206  that are transported through the data communications device  201 . Each flow is pictured at various positions of transit within the device  201  as one or more small circular packets which are labeled with a letter “A”, “B”, “C” or “U” to indicate the flow to which that packet belongs. The flows “A”  203 , “B”  204  and “C”  205  represent sessions of data communication for which bandwidth is reserved in the data communications device  201 . The flow “U”  206 , in which the “U” stands for unreserved, represents all other application data that is transported through the device  201  for which there is no specific amount of bandwidth reserved. Since there is no specific bandwidth reservation established for the “U” data flow  206 , the device  102  services the “U” flow  206  in a best-effort manner using any remaining unreserved device bandwidth (e.g., using any unlabeled or unreserved data storage locations, such as location  556  in  FIG. 5 ).  
      In this embodiment, the data storage mechanism  340  ( FIG. 4 ) is represented as a single circular rotating queue structure  340 - 1  that includes a number of queue entries  345 . In this particular example, there are twelve available queue entries  345  arranged in the circular formation as shown in  FIG. 5 . Each queue entry  345  is capable of storing one packet of data (i.e., one packet of a flow  203 ,  204 ,  205  or a packet of unreserved data  206 ) while the packet awaits transmission from a port (e.g. output port  506 ) in the device  201 . In this illustration, the conveyor belt-like queue structure  340 - 1  rotates in a clockwise direction. The data scheduler  320  deposits data packets (e.g., packets from flows  203  through  206 ) into the various queue entries  345 , as indicated by the arrows  535 , as will be explained in more detail shortly. Note that in this example, the data scheduler  320  can deposit data packets  203 - 206  into more than one queue entry  345  at one time as they arrive at the data scheduler  320 . This is indicated by arrows  535  that point to more than one queue entry  345 . As a packet  203  through  206  waits in the queue  340 - 1 , a dequeuing mechanism  350  services the queue  340 - 1  at periodic intervals and the queue  340  rotates clockwise as the dequeuing mechanism  500  services each entry  345  (rotation indicated by the circular arrows at each end of the queue  340 - 1 ) so that queue  340 - 1  shifts the packets from left to right and closer to a dequeuing mechanism  350  on the right end of the queue  340 - 1 .  
      The dequeuing mechanism  350  removes the data packets  203  through  206  from the queue  340 - 1  as they appear at the right-most end and transfers the data packets from the device  201  via output port(s)  506  onto the network  200 . The speed at which the dequeuing mechanism  350  dequeues packets, the rotation of the queue  340 - 1 , and the number of queue entries  345  that make up the queue  340 - 1  generally determine the overall bandwidth that can be provided to transport data to the output port  506 . It is assumed in this example that the input and output ports  505 ,  506  can handle data faster that the data transporter  300  and that, for purposes of this explanation, the data scheduler  320  can examine the packet headers (e.g., RSVP header  180 ) to determine where to direct a packet (e.g.,  203  through  206 ) at a rate that is greater than the overall maximum bandwidth for a port or session of data communication. Thus the data scheduler  320  does not act as a bottleneck in the device  201 .  
      Of particular importance to the invention is the manner in which the data scheduler  320  deposits data packets  203  through  206  into the queue  340 - 1  within the data storage mechanism  340 . Since the invention in this embodiment eliminates the need for the data scheduler  320  to be made aware of what particular data flows or sessions of data communication (e.g.,  203  through  205 ) have associated reserved bandwidth at any point in time, the data scheduler  320  simply examines information in each packet  203  through  206  that arrives at the input port  505  and deposits that packet into a queue entry  345  that contains a label, such as label  555  “C”, that matches the information examined in the packet (i.e.,  203  through  206 ).  
      The information examined in each packet  203  through  206  is preferably packet or RSVP header information contained in one or more of header fields  180 ,  181  and  182 , as illustrated in  FIG. 2 . As indicated above in the discussion of  FIG. 4 , the bandwidth labeler  550  labels (during the independent operation of the bandwidth reservation processor  500 ) certain queue entries  345  (i.e., data storage locations) based upon the sender state data  504 . This labeling process will be discussed in more detail shortly. In any event, as packets  203  through  206  arrive from the input port  505 , the data scheduler  320  determines if each packet  203  through  206  has an associated identification of one or more sessions of data communication (that may or may not have reserved bandwidth, which is unimportant as far as the data scheduler  320  is concerned), as specifically indicated, for example, by the Tspec field  191  in each packet  510  ( FIG. 2 ). Based on the value in the Tspec field  191 , the data scheduler  320  deposits the packets  203  through  205  ( 206  not having a Tspec field since packet  206  is not associated with a particular flow or session of data communication having reserved bandwidth) into queue entries  345  that have identification labels (e.g.,  555 ) corresponding to the identification (Tspec field  191 ) of the session of data communication for those packets  203  through  205 .  
      In other words, the data scheduler  320  is coupled to the input port  505  to receive data packet  203  through  206  associated with one or more sessions of data communication (e.g., “A”  203 , “B”  204 , etc.) and deposits the data packets  203  through  205  associated with that session(s) into data storage locations (queue entries  345  in this embodiment) associated with the bandwidth reservation for each session. The data scheduler  320  deposits “U” Packets  206  that are not associated with a particular session of data communication into queue entries  345  that have either no label (i.e., do not contain a label  555  for a reserved bandwidth session) or a label indicating that the entry  345  is unreserved, as illustrated by the example queue entry label “U”  556 .  
      In this manner, the data transporter  300  including the data scheduler  320  and the data queuing mechanism  340  operate independently of the bandwidth reservation processor  500  to continually maintain and transport one or more sessions of data communication along with data (e.g.,  206 ) not specifically associated with reserved bandwidth reserved in the device  201 . The operations of the data scheduler  320  and data storage mechanism  340  (e.g. queue  340 - 1 ) can be performed irrespective of the current bandwidth reservations (i.e., number of labeled queue entries  345 ) that may exist or that may change for session(s) of data communication (e.g. streams “A”  203 , “B”  204 , “C”  205 ).  
      The bandwidth reservation processor  500  including the bandwidth request handler  520  and the bandwidth labeler  550  operates asynchronously with the data transporter  300  mechanisms (e.g.,  320 ,  340 ) and is responsible for labeling the queue entries  345  in the queue  340 - 1 . Using the data storage location labeling techniques explained herein, bandwidth reservations are established and maintained for each session of data communication  203  through  205 . The techniques also allow for data  206  which is not specifically associated with reserved bandwidth sessions to be transported as well.  
      More specifically, with respect to the example embodiment in  FIG. 5 , the bandwidth request handler  520  receives bandwidth reservation requests and path messages  511  (e.g., from hosts  210  on network  200  in  FIG. 3 ). The reservation request and path messages  511 , as previously explained, are used to request bandwidth reservations in the device  201  for one or more flows or sessions of data communication, such as  203  through  205  in this example. In this embodiment, the bandwidth request handler  520  includes a bandwidth daemon  501  which preferably is an RSVP protocol daemon process (e.g., RSVPD) that executes on a processor (not specifically shown) within the device  201 . The bandwidth daemon  501  receives the bandwidth request and path messages  511  and consults the admission control module  502  and the policy control module  503  to determine, respectively, bandwidth resource availability and access control permission with respect to a requesting host  205  or application. Once access is granted and the bandwidth resources are determined to be available, the bandwidth daemon  501  creates the sender state data  504 .  
      In this example embodiment, sender state data  504  includes, for each session of data communication for which bandwidth resources are requested (e.g., each session listed in the sender state data, such as streams  203  through  205 ), an identity of the session of data communication, an amount of bandwidth associated with the session of data communication, and the path (e.g., input/output port pair) through the device  201  that the session of data communication is to traverse using the reserved bandwidth resources. More specifically, Table 1 below illustrates an example of the sender state data  504  created by the bandwidth daemon  501 , including some example requested bandwidth rates to be reserved for the sessions or flows “A”  203 , “B”  204  and “C”  205  in  FIG. 5 .  
               TABLE 1                          Example of Sender State Data 504                             REQUESTED           SESSION   RESERVED   SESSION PATH       IDENTIFICATION   BANDWIDTH    (PORT-TO-PORT)               “A”   100 Kbps   Input Port 505-Output Port 506       “B”    64 Kbps   Input Port 505-Output Port 506       “C”   132 Kbps   Input Port 505-Output Port 506                  
 
      As shown in Table 1, the request  511  ( FIG. 5 ) for the “A” session  203  (i.e., hosts sending and receiving this stream or flow of data) indicates that 100 Kbps of bandwidth is to be reserved, while the “B” session  204  has requested 64 Kbps of bandwidth, and the “C” session  205  has requested 132 Kbps. In this example, each of these flows or sessions of data communication “A”  202 , “B”  204  and “C”  205  are traveling on the same path through the device  201  configured with the sender state data  504  in Table 1. In other words, in the example embodiment shown in  FIG. 5 , an assumption is made that queue  340 - 1  services a single path within the data communications device  201 . For example, queue  340 - 1  may be associated with the output port  506 . Assuming there are many output ports in the device  201 , each output port (e.g.  506 ) in this embodiment thus has its own associated queue structure similar to  340 - 1  provided in order to buffer or store data packets (e.g., packets  203  through  206 ) that are to be transported from that output port onto the network  200 .  
      To assist in the explanation of the operation of this example embodiment, it is also assumed that the maximum total bandwidth for the output port  506  is 400 Kbps. Thus when the data scheduler  320 , queue  340 - 1  and dequeuing mechanism  350  all operate at peak capacity, a maximum bandwidth or throughput of 400 Kbps is available from the output port  506 .  
      To configure bandwidth reservations for each flow or session of data communication (e.g., “A”, “B”, “C”) defined in the sender state data  504 , the bandwidth labeler  550  in this embodiment includes a resource allocation calculator  552 , a resource allocation table  553 , and a label calculator  554 .  
      The resource allocation calculator  552  creates labeling information that is maintained in the resource allocation table  553  based on the sender state data  504 . To do so, in this embodiment, the resource allocation calculator  552  obtains as input  560  the size and speed of rotation of the data storage mechanism  340  (e.g. queue  340 - 1 ). Essentially, the resource allocation calculator  553  calculates and stores a percentage of total bandwidth (for the path to the output port  506  in this example) to allocate or reserve for each session of data communication based on the sender state data  504  as defined by the received bandwidth reservation requests  511 .  
       FIG. 6A  illustrates an example of the contents of the resource allocation table  553 . In Column  1  “FLOW ID”, the resource allocation table  553  provides an identification of each flow or session of data communication (e.g., “A”, “B”, “C”), and includes an entry marked “U” representing resource allocation data for all data (e.g. packets  206 ) not specifically associated with any session or reserved bandwidth. Column  2  “PERCENT UTILIZATION” indicates a percent utilization of total bandwidth for the queue  340 - 1  to which this resource allocation table  553  is associated. Column  3  “ENTRY COUNT OF TOTAL QUEUE SIZE” indicates the number of queue entries  345  that should be labeled in the queue  340 - 1  for each particular flow (i.e., row) represented in the resource allocation table  553 .  
      As noted above, the resource allocation calculator  552  obtains as input the queue size and speed data  560  from the data storage mechanism  340 . Using this information in conjunction with the sender state data  504 , the resource allocation calculator  552  computes PERCENT UTILIZATION and ENTRY COUNT OF TOTAL QUEUE SIZE values for each flow or session of data communication (e.g., “A”  203 , “B”  204 , “C”  205 ) in the sender state data  504 .  
      The resource allocation calculator  552  computes PERCENT UTILIZATION by converting the requested bandwidth to be reserved for each data flow or session to a percentage of total bandwidth for the queue  340 - 1 . In this embodiment, the queue size/speed data  560  determines total bandwidth for the path. In this example, the queue  340 - 1  has a queue size equal to twelve queue entries  345 . Each entry  345  can store one packet (e.g., one packet  203  through  206 ). A packet size in this embodiment is assumed to constant at 1000 bits. The queue speed in this example is assumed to be 33⅓ rotations per second. Based on these values, the total bandwidth for this queuing structure  340 - 1  can be computed as follows: 
 
QUEUE_BANDWIDTH=TOTAL_NUMBER_OF_ENTRIES*ENTRY_SIZE*ROTATIONS_PER_SECOND. 
 
      Or for this particular embodiment, overall total queue bandwidth equals: 
 
400  Kbps =(12 Queue entries)*(1000 bit entry size)*(33⅓ Rotations per second). 
 
      Once the total queue bandwidth is calculated, PERCENT UTILIZATION may be calculated as follows: 
 
PERCENT UTILIZATION=REQUESTED_BANDWIDTH_PER_FLOW/QUEUE_BANDWIDTH. 
 
      In the example embodiment, since the overall queue bandwidth is 400 Kbps using the requested reserved bandwidth values from Table 1 (sender state data  504 ), the PERCENT UTILIZATION for each FLOW ID for flows “A”, “B” and “C” ( 203  through  205 ) is computed as follows:  
                                                      FLOW ID A   .25 = 100 Kbps/400 Kbps           FLOW ID B   .16 = 64 Kbps/400 Kbps           FLOW ID C   .33 = 132 Kbps/400 Kbps           Total Reserved:   .74 * 100 = 74 Percent.                      
 
      Any remaining bandwidth, expressed as a percentage (i.e., 100 percent−Total Reserved percentage), is allocated to all unreserved data packets  206  (e.g. all data with FLOW ID=“U”). In this example, data associated with FLOW ID “U” gets 26 percent of the total bandwidth, since that is the remaining amount of bandwidth not reserved to the sessions of data communication  203  through  205 .  
      The resource allocation calculator  552  computes ENTRY COUNT OF TOTAL QUEUE SIZE (Column  3 ) values in the resource allocation table  553  based on the percent utilization of each FLOW ID in proportion to the number of total queue entries  345  in the queue  340 - 1 . The final result may be rounded or the allocation can be adjusted over each rotation of the data storage mechanism  340 - 1  so the average transmission rate converges to the correct percentage. Specifically, in this example embodiment: 
 
ENTRY COUNT OF TOTAL QUEUE SIZE=PERCENT UTILIZATION*TOTAL_NUMBER_OF_ENTRIES. 
 
      In the example embodiment, since there are twelve queue entries  345  in the queue  340 - 1 , the ENTRY COUNT OF TOTAL QUEUE SIZE values are computed as follows:  
                                                      FLOW ID A    3 = .25 * 12           FLOW ID B    2 = .16 * 12           FLOW ID C    4 = .33 * 12           FLOW ID U    3 = .25 * 12           TOTAL LABELED   12                      
 
      Once the resource allocation calculator  552  computes the data in the resource allocation table  553 , the label calculator  554  can use the resource allocation table  553  to properly produce labels (e.g.,  555 ) for the queue entries  345  in the queue  340 - 1 . As indicated in  FIG. 5 , the label calculator  554  accesses the resource allocation table  553  to determine how many entries  345  are to be labeled with each particular session identification label or FLOW ID which identifies the session ( FIG. 6A ). As indicated in the example resource allocation table  553  in  FIG. 6A , the label calculator  552  labels three queue entries  345  with “A”, two queue entries  345  with “B”, four queue entries  345  with “C”, and three queue entries  345  with “U”, for a total of twelve labeled queue entries that make up the total queue  340 - 1 .  
       FIG. 6B  illustrates in more detail an example structure of the queue entries  345  that make up the queue  340 - 1 . Each entry  345 - 1 ,  345 - 2  and  345 - 3  is essentially a data storage location  346 - 1 ,  346 - 2 ,  346 - 3  that includes an associated label portion  555 - 1 ,  555 - 2  and  555 - 3 , respectively. The data scheduler  321  deposits the data (i.e. packets  310 ) into the data storage location portion  346  of the entry  345  in this figure. As indicated in this sample segment of the queue  340 , the data storage location  346 - 1  for queue entry  345 - 1  currently stores an A-PACKET  310 - 1  that is associated with the “A” session of data communication  203  ( FIG. 5 ), while the data storage location  346 - 2  for queue entry  345 - 2  stores a B-PACKET  310 - 2  that is associated with the “B” session of data communication  204  ( FIG. 5 ), and the data storage location  346 - 3  for queue entry  345 - 3  stores a C PACKET  310 - 3  that is associated with the “C” session of data communication  205 . These packets  310 - 1 ,  310 - 2  and  310 - 3  are stored in these respective locations  346 - 1 ,  346 - 2  and  346 - 3  because the labels for these locations  555 - 1 ,  555 - 2  and  555 - 3  created by the label calculator  554  in the bandwidth labeler  550  match the session or flow identification information contained in the header  180  of each packet  310 - 1 ,  310 - 2  and  310 - 3 . That is, the data scheduler  320  places the A-packet  310 - 1  into the location  346 - 1  because the label  555 - 1  indicates that the location  346 - 1  is reserved for “A” data  203 .  
      Accordingly, by labeling the data storage locations  345  that form the queue  340 - 1  with the appropriate labels  555  for each flow identification (FLOW ID, Column  1 ) specified in the resource allocation table  553 , the bandwidth labeler  550  can constantly maintain the appropriate amount of reserved bandwidth for each session of data communication  203 ,  204 ,  205 . The data scheduler  320  uses the entries  345  that are either unlabeled by the bandwidth labeler  550  or that are labeled with a “U” (signifying unreserved or unlabeled), as indicated by label  556  in  FIG. 5 , to deposit any data (e.g. data packets  206 ) that does not contain a flow or session identification.  
      In this embodiment, the bandwidth labeler  550  can continuously monitor the sender state data  504  for changes in bandwidth requests (i.e., bandwidth reservations or changes that have been granted by the bandwidth daemon  501 ) for any session of data communication (e.g.  203 ,  204 ,  205 ). Once a change is detected in the sender state data  504 , the resource allocation calculator  552  recalculates the values in the resource allocation table  553 . The label calculator  554  detects this change and then correspondingly alters the labeling of the queue entries  345  to effectuate the requested bandwidth change.  
      In this manner, the system of the invention allows bandwidth to be dynamically adjusted without affecting the data scheduler  320 . That is, since the bandwidth reservation processor  500  adjusts a proportionate number of labels  555 ,  556 , etc. for sessions of data communication within the queue entries  345 , the maximum allowable bandwidth for the sessions (e.g.  203 ,  204  or  205  in this example) is inherently governed, since the data scheduler  320  can only place as many packets of session data (i.e.  310 ) into labeled queue entries  345  as there are matching labels  555  associated with the entries  345 .  
      By isolating the operation of the data scheduler  320  from the bandwidth reservation processor  500  as shown in the previous embodiments, it has been illustrated how bandwidth may be reserved and adjusted dynamically at any time before, during, or after one or more sessions of data communication (e.g.  203  through  205 ) are in operation. Once the data scheduler  320  queues a data packet  310  for a session of data communication in the queue  340 - 1 , the data  310  remains in the data storage location  346  until it is dequeued by dequeuing mechanism  350 . The label calculator  554  in this embodiment only labels  555  or changes labels of queue entries  345  that do not already contain data  310 . In this manner, the data scheduler  320  and queue  340 - 1  operate in continuously the same manner. This allows any session data in the “pipeline” comprising the input port  505 , data scheduler  320 , queue  340 - 1 , dequeuing mechanism  350 , and output port  506  to remain undisturbed during a change in bandwidth.  
      Recall that prior art implementations of bandwidth reservation require a session of data communication to be broken or halted for a period of time while classification, scheduling, queuing, and dequeuing mechanism are all reconfigured to handle the new bandwidth requirements. Once reconfigured, the session can then be reinstated. The system of the invention avoids much of this effort and allows the session to be continually transmitted before, during and after bandwidth allocations or adjustments. The adjustments take effect dynamically as the new label configurations for the data storage locations  345  in queue  340 - 1  are used. Thus the bandwidth labeler  550  can dynamically re-label queue entries  345  and the new labels are used by the data scheduler  320  to deposit session data.  
      An example highlights the particular importance of this aspect of the invention. Suppose that the device  201  is currently transporting the “B” session  204  of data communication at a maximum bandwidth of 64 Kbps, as illustrated in  FIG. 5  and in the resource allocation table in  553  in  FIG. 6A . Next assume that the “B” stream  204  requires more bandwidth. The new bandwidth required might be, for example, 100 Kbps. This may be sensed by one of the receiving hosts  205 -A 2 ,  205 -A 3  ( FIG. 3 ), for example, that determines that the current allocation of 64 Kbps is insufficient and that an additional 36 Kbps would correct the situation. Using RSVP or another bandwidth reservation protocol, the bandwidth request handler  520  receives the request for additional bandwidth  511  (either a request for an additional 36 Kbps, or a request for a change from 64 Kbps to 100 Kbps, or a new reservation request for 100 Kbps for the “B” stream).  
      Assuming the bandwidth daemon  501  grants the request  511 , the sender state data  504  for the SESSION IDENTIFICATION “B” indicates a REQUESTED RESERVED BANDWDITH value of 100 Kbps. The resource allocation calculator  552  detects the change in the sender state data  504  and updates the resource allocation table  553  as explained above so that FLOW ID “B,” (which was set at 16 percent with 2 queue entries labeled with “B”), now contains a PERCENT UTILIZATION value of 0.25 (or 25 percent of the total 400 Kbps bandwidth for this path) and an ENTRY COUNT OF TOTAL QUEUE SIZE value of 3. When the resource allocation table  553  is updated in this manner, the label calculator  554  detects the change and begins to re-label the queue entries  345  according to the new information in the resource allocation table  553 . Once the label calculator  554  re-labels all entries  345  in the queue  340 - 1 , three entries  345  are labeled with a “B” instead of two as in the previous configuration. Note that the label calculator  554  preferably operates to re-label queue entries  345  just after the dequeuing mechanism  350  removes the data ( 310  in  FIG. 6B ) from each entry  345 . The “X” in the data storage location  346  in  FIG. 5  indicates that the queue entry  346  is now void of any data packet  310  and can be re-labeled if required.  
      Alternative embodiments of the invention provide that the label calculator  554  always operates to continuously label entries  345  according to the resource allocation table  553 . In this manner, if the number of labels required for all sessions having reserved data exceeds the total number of queue entries  345  in the overall queue  340 - 1 , each entry  345  is provided with a different label upon being emptied by the dequeuing mechanism  350 . In other words, if the rotation speed  560  of a short queue  340 - 1  (i.e. a queue  340 - 1  having so few entries  345  that all entries  345  combined cannot hold the total amount of reserved bandwidth) is fast enough, the label calculator  554  can simply provide labels for every entry  345  after that entry passes the dequeuing mechanism  350 . In this manner, a short queue changes its labeling configuration with each rotation, and the label calculator controls the bandwidth allocation for each session via the labels for the entries  345 .  
      All data packets (e.g., packets for sessions  203  through  205  and unreserved data packets  206 ) that currently exist in the queue  340 - 1  during the labeling process remain queued and eventually propagate their way to the dequeuing mechanism  350 . Preferably, relabeling takes place as soon as each entry  345  in the queue  340 - 1  is emptied or dequeued of its data packet  310  by the dequeuing mechanism  350 . As the relabeled queue entries  345  make their way clockwise around to the data scheduler  320  to obtain more data packets  310 , the new labeling configuration (i.e., the queue  340 - 1  now containing three “B” labeled entries  345 ) will dictate what data can be placed into which entries  345 . In this manner, the bandwidth can be changed for the session of data communication  204  without disrupting the transport of data for the session.  
       FIG. 7  illustrates the processing steps performed by the bandwidth request handler  520  configured according to this invention. In step  600 , the bandwidth allocation request  511  is obtained from the network  200 . In step  601 , the bandwidth daemon  501  determines the requested resource availability via admission control. If the requested resource is not available, the bandwidth daemon  501  processing denies the request and returns to step  600 . If the bandwidth daemon  501  in step  601  does not deny the request, the bandwidth daemon  501  in step  602  authenticates access to the requested resource via policy control. If in step  602  the bandwidth daemon  501  determines that the access should not be granted to the requested resource, the bandwidth daemon  501  denies the request and processing returns to step  600 . If steps  601  and  602  pass, step  602  directs processing depending upon the type of request ( 511 ) received. If the request  511  is a new request to reserve bandwidth for a session that does not yet have bandwidth reserved, the processing proceeds to step  603  and the bandwidth daemon  501  produces the new sender state data  504  for a session identification associated with the newly requested resource. If however step  602  determines that the request  511  is requesting alteration of a resource already reserved to a particular session or sessions of data communication, then processing follows as explained in step  604 .  
      In step  604 , the bandwidth daemon  501  updates the sender state data  504  that already exists for the requested resource, without disturbing any session or sessions of data communication that may be using that resource (i.e., without notifying the data scheduler  320 ). In step  605 , the bandwidth daemon  501  makes the sender state data  504  available to the bandwidth labeler  550  so that the bandwidth labeler  550  can label (e.g.,  555 ) the data storage locations (e.g., entries  345 ) accordingly in the data storage mechanism  340 , which is preferably the rotating queue structure  340 - 1  discussed above. By making the sender state data  504  available to the bandwidth labeler  550 , the bandwidth request handler  520  can focus its operation primarily on bandwidth request processing and does not need to make the sender state data  504  available to other components of the system, such as the data scheduler  320  or the dequeuing mechanism  350 .  
       FIG. 8A  shows the general processing steps performed by the resource allocation calculator  552  in the bandwidth labeler  550  according to one embodiment of the invention. In step  700 , the resource allocation calculator  552  queries the sender state database  504 . Alternatively, step  700  may be performed by having any changes in the sender state data  504  be signaled (i.e., via step  605  in  FIG. 7 ) to the resource allocation calculator  552 . In step  701 , current statistics of the data storage mechanism  340  such as queue size (e.g., total number of entries  345 ) and speed (e.g., how many entries are dequeued over a period of time, rotation, etc.) are queried to determine the overall current bandwidth characteristics for the requested path. Step  702  then calculates and/or updates the resource allocation table  553  values (Columns  1 ,  2  or  3 ) with the current session attributes, as explained above. In this manner, the processing of  FIG. 8A  converts the sender state data  504  into meaningful data usable by the label calculator  554  to label ( 555  in  FIG. 6B ) the data storage location  346  (i.e., queue entries  345 ) in the data storage mechanism  340  (e.g., queue  340 - 1 ).  
       FIG. 8B  shows the general processing steps associated with the label calculator  554 . In step  750 , the label calculator  554  queries the resource allocation table  553  for flow label identification (i.e., Columns  1  and  3 ). This step could be triggered by a change in the resource allocation table  553 , or may be performed periodically or continuously. Step  751  then determines queue entry  345  label allocations.  
      In one embodiment, step  751  consults the entry label counts for each session of data communication as indicated in Column  3  of the resource allocation table  553 . Step  752  then labels  555  the entries  345  according to the entry label calculations. The labeling of queue entries  345  may proceed serially by labeling entries  345  with all of the “A” labels (e.g., 3 “A” labels  555 ), and then when there are no more “A” labels remaining, labeling entries  345  with “B” labels ( 2  in the example) until none remain, and so forth. With respect to the example resource allocation table  553  in  FIG. 6A , the twelve labeled entries in the example queue  340 - 1  in  FIG. 5  would have a labeling order as follows: 
          “A” “A” “A”“B” “B” “C” “C” “C” “C” “U” “U” “U”       

      However, as will be explained next with respect to  FIGS. 9A and 9B , the label calculator  554  may label the entries  345  in the queue  340  in step  752  in a variety of other patterns so as to evenly distribute labeled entries  345  for each session or FLOW ID, depending upon the selected embodiment.  
       FIG. 9A  illustrates an example of a labeling pattern. In  FIG. 9A , the bandwidth labeler  550  sequentially “uses up” the labels for each session having a reserved resource in a serial manner, and when none are left, moves on to the next set of labels. As indicated in the figure, which corresponds to the bandwidth reservations established in the resource allocation table  553  in  FIG. 6A , the “A” session of data communication  203  has twenty-five percent of the bandwidth reserved via “A” labels in the queue entries  345 . Thus the data scheduler  320  in  FIG. 5  is able to queue “A” data packets  203  into one quarter of the entire queue space on each rotation. The “C” data stream has thirty-three percent of the queue reserved, and the “B” stream has sixteen percent reserved. This leaves a remaining twenty-five percent of the queue entries  345  labeled with “U”, or not labeled at all. The “U” labeled entries  345  are used for all data  206  that does not belong to a session having a bandwidth reservation in this device  201 .  
      It may be apparent to those skilled in the art that a situation might arise where the data scheduler  320  detects an RSVP header that indicates a session identification (i.e., a labeled packet) for which there are currently no corresponding labeled queue entries  345 . The invention addresses this situation in a number of ways. First, the data scheduler  320  can simply buffer the data until an entry  345  having a corresponding label  555  appears. After a certain time period, which preferably corresponds to a certain number of rotations of the queue  340 , if no labeled entry  345  appears (to the data scheduler  320 ) that matches the packet data (with a session identification) that is buffered with the unknown session identification, the data scheduler  320  can either discard the unknown session data or can simply deposit the data into one of the data storage locations that is indicated as being unreserved (i.e. labeled “U”). The later mechanism (queuing into an unreserved entry  345 ) is preferred over the packet discard mechanism, since data will not be lost and will not require re-transmission from the sender if the unknown data stream has such error detection/correction capabilities enabled.  
      In this manner, if session data is transported to a device  201  which is unaware of the existence of the session, the invention still allows the data to be transported as if it were unlabeled data not associated with any particular session. In prior art systems in which a classifier and scheduler are made aware of all active sessions, the unknown session data might confuse the classifier and/or scheduler and may require either, at a minimum, to pause operation to consult with the RSVP daemon (e.g.,  101  in  FIG. 1 ) to determine how to handle the unknown session data. The invention avoids such cumbersome approaches and keeps the data transport mechanism separated from the bandwidth allocation and administration aspects of the device  201 .  
       FIG. 9B  illustrates another labeling pattern which can be used by the label calculator  554  to label queue entries  345  with session labels. The approach taught in  FIG. 9B  is cycling label approach. In this approach, the label calculator  554  repetitively cycles through each FLOW ID in the resource allocation table  553  and labels one queue entry  345  for each session or flow id per cycle. During the repetitive cycling, the label calculator  554  decrements the number of labels remaining for each FLOW ID. When a FLOW ID has no labels remaining (i.e., its ENTRY COUNT OF TOTAL QUEUE SIZE value is zero), no more labels are created for that session or flow identification. In this manner, a more balanced approach is provided for the queue entry labeling process of the invention, since each flow is provided with a labeled entry  345  that is separated from another similarly labeled entry  345  by other entries labeled for other flows that still have more bandwidth to be reserved (i.e., more entries that are to be labeled). As illustrated in  FIG. 9B , from left to right, the labels on queue entries  345  appear in this example as follows: 
          “A” “B” “C” “U” “A” “B” “C” “U” “A” “C” “U” “C”       
      In total, there are three “A” entries, two “B” entries, four “C” entries, and three “U” entries, and that the entries are somewhat staggered from each other. The sequence A-B-C-U begins at the left and repeats itself twice, after which there are no more “B” labels to be produced, and so the remaining “A” and “U” labels are produced. In this manner, the bandwidth labeler  550  presents a more even distribution of labeled (i.e., reserved) bandwidth entries  345  so that the data scheduler  320  does not have to wait for significant periods of time while buffering data and awaiting for an entry with the correct label to appear.  
      In yet another embodiment of the bandwidth labeler  550  and the label calculator  554 , the label calculator  554  only labels the queue entries  345  each time the resource allocation table  553  changes. As such, the labels (e.g.  555  in  FIGS. 5 and 6 B) remain allocated or associated with each entry  345  as the entry  345  continually circulates around and around the queue  340 . In this manner, the bandwidth reservations for each session are static until they need to be changed. That is, the only time the queue entries  345  are relabeled is if a change is detected to the bandwidth reservations as communicated by the change in data values in the resource allocation table  553 . This embodiment conserves processing resources used by the bandwidth labeler  550 , which can enter an idle state until the sender state data  504  changes. The change causes the resource allocation calculator  552  to “wake up” and update the resource allocation table  553 , which in turn causes the label calculator  554  to re-label entries  345  as required.  
      It is to be understood by those skilled in the art that the labeling patterns in  FIGS. 9A and 9B  are illustrative as examples only, and are not limiting of the present invention. Rather, other fair, weighted, or even distribution schemes known to those skilled can be used to label the sequence of queue entries  345  so as to best distribute the reserved bandwidth for each session of data communication across the entire queue  340 - 1 . For example, in an alternative embodiment, each queue entry  345  may be larger than the size of a single packet. In such cases, an entry  345  may hold many packets, cells, frames, or other unit of data from the session of data communication. In another alternative embodiment, each entry may have more than one label. That is, is two or more sessions of data communication are somehow related, or have equivalent bandwidth reservations (e.g., same percentage for both sessions), the bandwidth reservation processor might label a single entry with more than one session identification. In this manner, the data scheduler  320  can deposit any one or a number of different packets into the multi-labeled entry  345 .  
      It is also to be understood that the invention is not limited to applications providing bandwidth reservation and allocation using the RSVP protocol. Rather, the invention is intended to operate in conjunction with other bandwidth reservation, allocation, or adjustment protocols that currently exist or that may be developed in the future. For example, future versions of RSVP may provide specific message formats to enable bandwidth adjustments. The invention provides implementations of data communications devices as explained herein that can take advantage of such messages to dynamically adjust bandwidth as required for sessions of data communication.  
      For more details on the operation of bandwidth reservation protocols such as RSVP and its derivatives, the reader is directed to Request For Comments 2205 and 1633 and RSVP93 (RFC-2205, RFC-1633, RSVP93), published by the Network Working Group of the Internet Engineering Task Force (IEFT), and available on the Internet at ftp://ftp.isi.edu/in-notes/rfc2205.txt, each of which protocol references is hereby incorporated by reference in their entirety.  
      The invention applies to all types of data transmitted to or from any type of device through any type of network and/or network communications medium. While the illustrated examples discuss packet data which is primarily applicable to Transmission Control Protocol/Internet Protocol (TCP/IP) networks such as the Internet, the invention is equally applicable to networks that use such units of data as tokens, cells, frames, blocks, and so forth. Other network architectures such as Asynchronous Transfer Mode (ATM) networks can use the concepts of the invention as well to reserve bandwidth for cell transfer. Also, networking architectures such as packet-wireless, Fiber Distributed Data Interface (FDDI), Systems Network Architecture (SNA), Digital Subscriber Link (DSL), Advanced Peer-to-Peer Networking (APPN) and others may benefit from use of the invention.  
      Another alternative scenario that could illustrate the features of the invention would be to have several networked computers each running different types of applications having different data communications requirements. The data produced from each application may need to be transferred between the computers at different reserved rates. The invention could be used to provide this capability. It is also understood that a data communications device  201  configured according to the invention may have one or more data schedulers  320  and one or more data queues  340 . An arrangement such as a single data scheduler per input port that can deposit data into many different queues  340 - 1 ,  340 - 2 , etc., where there is one queue  340  per output port is contemplated as a device configured according to the invention. Other arrangements are possible as well which are contemplated by the invention. Such alternative arrangements and alternative designs of data communications devices can apply the concepts of the invention as disclosed herein to provide dynamic bandwidth reallocation without interrupting streams of data, since the operation of the bandwidth allocation mechanisms are generally separated from the data transport mechanisms, as explained herein.  
      While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.