Abstract:
The invention relates to a method for routing Internet traffic. The method generally includes the steps of receiving a packet from multimedia network, allocating a message block header for the packet, wherein the header is used to hold behavior aggregate values for internal router mapping, and queuing and routing the packet to a differentiated services network domain in a manner that ensures a specific QoS.

Description:
FIELD OF THE INVENTION 
   The present invention is an improvement to conventional Internet Engineering Task Force (IETF) quality of service (QoS) protocol specification. 
   BACKGROUND OF THE INVENTION 
   In today&#39;s complex Internet environment, traffic flow data packets (packets) are processed through routing systems (routers) without regard to the type of data they represent. This approach is referred to as “Best Effort” service. However, with the advent of digitized multimedia content, including voice and other signal types, there is a growing need to process packets according to specific routing requirements associated with each data packet. 
   Quality of service (QoS) is the forwarding priority processing of signal types through a routing system. The aim of QoS is to provide multiple distinct classes of service where each service class matches network performance requirements of the packet. For example, voice calls require a particular QoS service class that guarantees low latency, the time required to locate the first bit or character in a storage location. Low latency ensures that packets received by a router are forwarded within a certain minimum set of time requirements. For example, if a router receives a non-voice packet and a voice packet at roughly the same time, the voice packet should be given higher priority and forwarded through the router as quickly as possible to ensure timely end-to-end delivery. There are other types of multimedia signals that are not delay sensitive, but may be bandwidth sensitive. These signal types require bandwidth guarantees throughout the network to accommodate a particular traffic type. 
   Certain types of traffic do not require low latency guarantees, but do require an increased amount of bandwidth to route larger amounts of signal data. Particular bandwidth guarantees must exist throughout the network to accommodate certain types of traffic, e.g., bulk data traffic. Conventional network topologies process data signals indiscriminately. That is, voice signal packets are processed with the same forwarding priority as data signal packets. This technique does not effectively evaluate and identify signals based on customer service level agreements (SLAs). The concept of Differentiated Services (DiffServ) was developed by the Internet engineering community to formalize an architecture for providing guaranteed service to aggregate service classes. Nevertheless there remains a need in the art for a way to provide hardware to efficiently implement Differentiated Services in a multimedia network routing system. 
   U.S. Pat. No. 6,091,709, “Quality of Service Management for Packet Switched Networks,” assigned to International Business Machines Corporation (Armonk, N.Y.), describes a packet router for a data packet transmission network, the router is described as offering priority services of the type required for isochronous handling of data representing real-time voice, and includes a Quality of Service (QoS) management system for ensuring that guarantees associated with such priority service can be met with a high degree of certainty. This management system is stated to provide prioritized queues, including a highest priority queue supporting reservations for the priority service suited to isochronous handling. The highest priority queue and other queues are closely monitored by a QoS manager element for states of near congestion and critical congestion. When neither state exists, filler packet flows are promoted from lower priority queues to the highest priority queue in order to keep the latter queue optimally utilized. If all lower priority queues are empty at such times, dummy packets are inserted as filler flows. Dummy packets have a form causing routers and other stations receiving them to immediately discard them. The volume of dummy traffic allowed for each queue of the system is a predetermined fraction of the queue&#39;s estimated peak traffic load, and that volume is displaceable to allow forwarding of additional traffic through the queue when conditions require it. When a state of near congestion exists, the QoS manager demotes filler flow units from the highest priority queues to lower priority queues, in order to lessen the potential forwarding delays presented to real traffic occupying the highest priority queue. When a state of critical congestion exists in the highest priority queue, admission of new incoming traffic flows to that queue is suspended and forwarding of filler flows from that queue out to the network is also suspended. 
   U.S. Pat. No. 6,075,791, “System for Guaranteeing Data Transfer Rates and Delays in Packet Networks,” assigned to Lucent Technologies Inc. (Murray Hill, N.J.), describes a system which services a plurality of queues associated with respective data connections. The system is described as guaranteeing data transfer rates and data transfer delays to the data connections. This is achieved by associating each connection having at least one data packet waiting in its associated queue (such a connection called a backlogged connection) with a timestamp generated as a function of system parameters including (a) the number of queues that are backlogged, (b) the data transfer rate guaranteed to each connection, (c) the sum of data transfer rates guaranteed to all backlogged connections, (d) the previous timestamp of the connection, and (e) the weighted sum of the timestamps of all backlogged connections, each timestamp weighted by the data transfer rate guaranteed to the corresponding connection. The backlogged connection associated with the timestamp having the smallest value among all of the backlogged connections is then identified and a data packet is transmitted from the queue corresponding to that connection. A new timestamp is then generated for that connection if it is still backlogged. Once the transmission of the data packet is completed, the foregoing determination of the connection with the minimum timestamp is then repeated to identify the next queue to be serviced. 
   U.S. Pat. No. 5,946,311, “Method for Allowing More Efficient Communication in an Environment Wherein Multiple Protocols are Utilized,” assigned to International Business Machines Corporation (Armonk, N.Y.), describes a method and system that allow one or more network protocol emulators, composed of one or more network protocol emulation controllers and one or more network protocol emulation entities, which are overlaid onto the one or more base networks utilizing different communications protocols for the purpose of allowing said one or more networks to be accessed and utilized as if the one or more networks were utilizing protocols emulated by the one or more network protocol emulators. The method and system are described as using the following steps: (1) Apprising the one or more network protocol emulation controllers of network capability information inherent within protocols utilized by the one or more networks onto which the one or more network protocol emulation controllers are overlaid; (2) directing that the one or more network emulation controllers utilize the one or more network capability information of which they have been apprised to define communication capabilities for certain network protocol emulation entities within the control of the one or more network protocol emulation controllers; and (3) directing either the one or more network protocol emulation controllers or the one or more certain network protocol emulation entities within the control of the network protocol emulation controllers to utilize such defined communications capabilities to ensure that the network protocol emulation entities do not request a communications link to one or more other network protocol emulation entities that substantially exceeds the defined communication capabilities of the one or more other network protocol emulation entities. 
   SUMMARY OF THE INVENTION 
   The invention relates to a method for routing Internet traffic. The method generally includes the step of receiving a packet from multimedia network. Additionally, the method includes the step of allocating a message block header for the packet, wherein the message block header is used to hold behavior aggregate values for internal router mapping. The method further includes the step of queuing and routing the packet to a differentiated services network domain in a manner that ensures specific QoS. In one embodiment, the block header contains a default QoS 3-tuple value that reflects best effort per hop behavior treatment. Furthermore, each behavior aggregate may be a collection of packets that are treated with the same QoS. Furthermore, the QoS 3-tuple represents a QoS behavior aggregate that is based on the DifServ codepoint value of the incoming packet. 
   In another embodiment, the queuing step of the method for routing Internet traffic is accomplished using a queuing manager software module configured with queuing precedents. Additionally, the queuing step uses a primary set of queues corresponding to the supported behavior aggregates. Furthermore, the queuing step uses two or more prioritized egress queues. Furthermore, the egress queues include a high priority egress queue, a medium priority egress queue, and a low priority egress queue. 
   In another embodiment, the method for routing Internet traffic compares the DifServ codepoint field in the packet header to the DifServ codepoint to a per hop behavior table and placing a corresponding QoS 3-tuple value in the message block header message block header by the message block header marker. Furthermore, the method for routing Internet traffic further comprises presenting packets to a queuing manager from a meter or directly from a classifier, and the packets carry in the message block header information that identifies the primary queue (and indirectly the secondary queue) to which it belongs, drop precedence, and a conversation identifier. Furthermore, the queuing manager identifies the primary class queue to which the packet belongs and if the token bucket meter associated with that queue has available tokens, the packet is passed straight through to the secondary queue. If the primary queue is empty, the method comprises the step of checking to see if the secondary queue can accommodate the packet, and if the egress queue can accommodate the packet, the packet is passed through to the secondary queue, thereby permitting AF and BE traffic to consume up to full link bandwidth. 
   In another embodiment, the method for routing Internet traffic further comprises token bucket metering assured forwarding queues to a minimum configured rate, but allows the queues to consume unused bandwidth up to full line rate. Additionally, the method permits best effort traffic to be assigned no minimum guaranteed bandwidth but permits the traffic to contend for unused bandwidth. Furthermore, the method further assigns the QoS 3-tuple based on traffic profile using fields contained in the data packet header information. The fields contained in the data packet header information comprise a DiffServ codepoint field. If the QoS 3-tuple is different than the default message block header value, the method further comprises overwriting the default message block header with the new QoS 3-tuple based on configurable rules. 
   In another embodiment, as space in the egress device driver transmit ring becomes available, the method for routing Internet traffic comprises transferring packets to the egress driver based on priority queuing precedents. Additionally, the method involves the egress driver striping the message block header field from the IP packet. Moreover, the IP packet retains egress DiffServ codepoint. Furthermore, the DiffServ codepoint is optionally modified through the routing process. 
   The invention can also be expressed as relating to a differentiated services edge router. The differentiated services edge router is configured to receive a packet from multimedia network. Additionally, the router is configured to allocate a message block header for the packet, wherein the message block header is used to hold behavior aggregate values for internal router mapping. Furthermore, the router queues and routes the packet to a differentiated services network domain in a manner that ensures specific QoS. 
   In one embodiment, the differentiated services edge router comprises an ingress driver coupleable to a multimedia network and configured to allocate a message block header for an incoming packet that contains default QoS 3-tuple values which reflect best effort per hop behavior treatment. Additionally, the differentiated services edge router can be configured to employ a message block header to hold Behavior Aggregate values for internal router mapping. Moreover, the differentiated services edge router can be configured to treat network traffic having a common behavior aggregate in a manner that ensures that individual packets of such traffic receive the same QoS. Furthermore, the differentiated services edge router may include a classifier configured with a DifServ codepoint to per hop behavior table. 
   In another embodiment, the differentiated services edge router comprises a queuing manager software module configured with queuing precedents. Furthermore, the queuing manager identifies the primary class queue to which the packet belongs. Additionally, the differentiated services edge router comprises a primary set of queues corresponding to the supported behavior aggregates. Additionally, the differentiated services edge router is comprised of three prioritized egress queues. Moreover, if the token bucket (TB) meter associated with the primary class queue to which the packet belongs has available tokens, the packet is passed straight through to the secondary queue. 
   In another embodiment, the differentiated services edge router is comprised of assured forwarding queues token bucket metered to a minimum configured rate, but allowed to consume unused bandwidth up to full line rate. Furthermore, the differentiated services edge router may be configured so that best effort traffic ends up with no minimum guaranteed bandwidth, but the best effort traffic is permitted to contend for unused bandwidth. Additionally, the classifier includes a configurable database that assigns the QoS 3-tuple based on the traffic profile using fields contained in the data packet header information, including the DiffServ codepoint field. Furthermore, if the QoS 3-tuple is different than the default message block header value, the classifier may overwrite the default message block header with the new QoS 3-tuple based on configurable rules. 
   In yet another embodiment, the differentiated services edge router may be configured with a primary queue that, when empty, results in the queuing manager checking to see if the secondary queue can accommodate the packet. Furthermore, if the secondary queue can accommodate the packet, the packet is passed through to the secondary queue, thereby allowing AF and BE traffic to consume up to full link bandwidth. Additionally, the egress driver can be configured to strip the message block header field from the IP packet and so that the IP packet retains egress DiffServ codepoint. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a block diagram of a differentiated service network. 
       FIG. 2  shows a detailed block diagram of a differentiated services edge router. 
       FIG. 3  shows a block diagram of a classifier internal configuration. 
       FIG. 4  shows a block diagram of the meter internal configuration 
       FIG. 5  shows a block diagram of a differentiated queuing block. 
       FIG. 6  shows IP packet flow in a differentiated services edge router. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The invention is a system for and method of using differentiated queuing in an edge routing system to improve IETF-specified quality of service (QoS). The invention provides rate guarantees, latency guarantees and provides bandwidth sharing amongst certain classes of traffic. 
     FIG. 1  shows a block diagram of a differentiated services network  100  and includes a Differentiated Services edge router  110 , router ingress  115 , router egress  125 , the Differentiated Services (DiffServ) domain  105 , a Differentiated Services network region containing DiffServ Core Routers  130 . Multimedia network  120  is a non Differentiated Services multimedia network and is shown for system clarity. 
   Differentiated Services (DiffServ or DS) is a network topology that provides the ability to offer different kinds of network quality-of-service (QoS) to different customers and their traffic streams. The premise of DiffServ networks is that routers within the core of the network (DiffServ core routers  130 ) handle packets in different packet streams by forwarding them using different per-hop-behaviors (PHBs). By treating traffic flows in aggregate, DiffServ can implement Quality of Service guarantees without the need for per-flow signaling and state maintenance in each traversed node (other than the maintenance of the DSCP field in the IP header). 
   DiffServ domain  105  is a logical Internet region administered by a common authority. Service level agreements (SLAs) are identified by DiffServ domain  105  through contractual agreement between the DiffServ domain  105  administrative authority and the customer. Currently, the global Internet consists of hundreds of DS domains  105  administrated by different authorities. DiffServ domain  105  per hop behaviors honor the signal profile values established throughout the Internet. The currently defined standard PHB groups are Expedited Forwarding (EF), Assured Forwarding (AF), and Best Effort Forwarding (BE). Expedited Forwarding guarantees forwarding of all packets conforming to configured rate with lowest possible delay and jitter. Non-conforming packets are dropped. Assured Forwarding guarantees a minimum configured forwarding rate. Packets exceeding the configured rate may be forwarded if there are available resources (possibly with a higher drop precedence), or may be dropped. Best Effort Forwarding indicates that a packet will be forwarded if there are available resources, otherwise it may be dropped. The PHB to be applied is indicated by a DiffServ codepoint (DSCP) in the IP header of each incoming packet. At the ingress of the DiffServ network, the differentiated services edge router  110  is responsible for routing the data streams from a non-DiffServ network into the DiffServ network based on the value of the DSCP, aggregate behavior classes, and bandwidth availability. The routing process includes classification, metering, marking, dropping, and queuing. 
   Typically, egress bandwidth is divided up to provide rate guarantees according to code point valued signals. For example, if the code point field value is equivalent to expedited forwarding, then the signal is guaranteed to have 10% of the available bandwidth, while a code point field value of mapping to assured forwarding is guaranteed 60% of the available bandwidth. In this way, the differentiated services edge router  110  provides availability guarantees for packets marked in a specific way. Egress bandwidth (e.g., 10 Mbps for standard Ethernet) is configured to provide bandwidth reservation for particular traffic flows. Data packets are marked with particular code point forwarding behavior and behavior aggregate codes. Egress bandwidth is divided up to provide specific signal classes with greater bandwidth. 
     FIG. 2  shows a detailed block diagram of differentiated services edge router  110  and includes an ingress driver  210 , a classifier  220 , a meter  230 , a differentiated queuing block  240 , and an egress driver  250 . 
   Ingress driver  210  receives packets from multimedia network  120  and allocates a message block header for the packet that contains default QoS 3-tuple values which reflect Best Effort (BE) Per Hop Behavior (PHB) treatment. The message block header (MBLK) is used to hold Behavior Aggregate values for internal router mapping. A behavior aggregate is a collection of packets that are treated with the same Quality of Service. 
   Classifier  220  is a multi-field classifier software module configured with a DifServ codepoint (DSCP) to PHB table and a group of specialized algorithmic filters used to select packets based on the content of a configurable number of header fields. Classifier  220  is further described in  FIG. 3 . 
   Meter  230  is an event-based (as opposed to time-based), single-rate, token bucket meter configured to perform an action on a packet based on whether the packet is found to be in-profile or out-of-profile. The configured actions can be one of MARK, DROP or NONE. Meter  230  is further described in  FIG. 4  below. 
   Queuing block  240  generally includes a queuing manager software module configured with queuing precedents, a primary set of queues corresponding to the supported behavior aggregates, and the three prioritized egress queues. Queuing block  240  is further described in  FIG. 5  below. 
   Egress driver  250  provides connection to the differentiated services network and monitors and manages the transmit ring. The egress driver  250  may consist of any of a number of standard implementations. 
     FIG. 3  shows a block diagram of the internal configuration of classifier  220 . Classifier  220  generally includes a DSCP to PHB table  300 , an MBLK marker  310 , and one or more IP filters  320 . For clarity, only one IP filter is shown in  FIG. 3 . 
   The packet is sent to the classifier  220  from the ingress driver  210 . The classifier  220  compares the DSCP field in the packet header to the DSCP to PHB table  300  and the corresponding QoS 3-tuple value is placed in the MBLK message block header by the MBLK marker  310 . The QoS 3-tuple represents a Quality of Service behavior aggregate that is based on the DSCP value of the incoming packet. As an IP packet traverses the system, the values in the MBLK header are used to make handling decisions. 
   The packet is then passed through one or more filters  320 . Filter  320  is an algorithm that is configured as either Behavior Aggregate (BA) or Multi-Field (MF) filter. BA filters only look at the DSCP field in the IP header. MF filters look at a configurable combination of IP header elements (same fields as existing IP filters, plus the DSCP field). The filter compares one or more IP header elements to a set of configurable traffic conditioning rules. If the packet matches a filter and a meter  230  has been assigned it is sent to the corresponding meter  230 . If the packet does not match a filter or the filter does not have a corresponding meter, it is forwarded directly to the differentiated queuing block  240 . 
     FIG. 4  shows a block diagram of meter  230 . Meter  230  generally includes a rate meter  400 , a Drop/Mark/None decision block  410 , a packet dropper  420 , and a packet marker  430 . When a packet matches a filter  320 , it may be passed to a corresponding meter  230 . When packets enter the meter, they are examined by the rate meter  400  to determine if the temporal properties of the data stream are within the rate profile defined for the packets&#39; behavior aggregate. This process is used to ensure the client-user is not exceeding the packet profile determined by the behavior aggregate. The rate meter communicates to the Drop/Mark/None decision block  410  whether the packets are in-profile or out-of-profile. The Drop/Mark/None decision block  410  is configured to examine the rate meter  400  result, the QoS 3-tuple and traffic capacity. 
   If the meter determines that the DS domain  105  contains available capacity, it will attempt to admit “out-of-profile” data packets. If no resources are available, it will drop out-of-profile packets. This process is used to ensure the client-user is not exceeding the packet profile determined by the SLA. 
     FIG. 5  shows a block diagram of the differentiated queuing block  240 . Differentiated queuing block  240  generally includes a queuing manager  510 , an expedited forwarding queue EF queue  520  with associated token bucket meter TB meter  560 , assured forwarding queues AF queue  530  and AFN queue  540  with their associated token bucket meters TB meter  561  and TB meter  562 , a best effort queue BE queue  550  with associated token bucket meter TB meter  563 , and three egress queues, high priority egress queue  570 , medium priority egress queue  575 , and low priority egress queue  579 . 
   Packets are presented to the queuing manager  510  from either the meter  230  or directly from the classifier  220 . Arriving packets will carry in the MBLK information that identifies the primary queue (and indirectly the secondary queue) to which it belongs, drop precedence and a conversation identifier. 
   The queuing manager  510  identifies the primary class queue to which the packet belongs to and if the token bucket (TB) meter associated with that queue has available tokens, the packet is passed straight through to the secondary queue (and possibly straight through to the device driver). The current token count is adjusted based on the number of bytes in the packet. TB token counters are allowed to go negative (borrow from future tokens). If, at the time the queuing manager  510  receives a packet, the token count is negative and the packet is marked for expedited forwarding, the packet will be dropped. Expedited forwarding traffic cannot exceed a maximum rate. Otherwise the queuing manager  510  checks to see if the primary queue is empty. If not empty, the packet is conversation queued. If the queue is empty, queuing manager  510  checks to see if the secondary queue can accommodate this packet. If it can the queuing manager  510  directs the packet through to the secondary queue (this allows AF and BE traffic to consume up to full link bandwidth). If it cannot, queuing manager  510  begins queuing in the primary queue. 
   EF queue  520  controls all traffic having low latency requirements. The system includes multiple AF queues, AF 1   530  through AFN  540 . In the preferred embodiment, the system includes four AF queues implementing three different drop precedents, (AF 1 - 1 , or a higher drop AF 1 - 2  or AF 1 - 3 ). The BE queue  550  controls all unmarked traffic. EF, AF, and BE queues are considered primary queues and are “fair” queues in the present invention. A fair queue is a queue having multiple FIFO queues configured in parallel. 
   In the preferred embodiment, there are six primary queues: an expedited forwarding queue, four assured forwarding queues, and a best effort queue. The expedited forwarding queue (EF queue)  520  is token bucket metered by TB meter  560  to a maximum configured rate. The assured forwarding queues (represented by AF 1  queue  530  and AFN queue  540 ) are also token bucket metered (by TB Meter  561  and TB Meter  562 ) to a minimum configured rate but allowed to consume unused bandwidth up to full line rate. The best effort queue BE queue  550  is token bucket metered by TB Meter  563  to the rate which is calculated by subtracting the sum of the EF and AF configured rates from the total link bandwidth. Configured rates must not total more than the maximum link rate. Best effort traffic may end up with no minimum guaranteed bandwidth, but it can still contend for unused bandwidth. 
   The secondary queue generally includes three priority based FIFO queues: high priority egress queue  570 , medium priority egress queue  575 , and low priority egress queue  579 . 
   High priority egress queue  570  is a FIFO queue that transmits data packets received from a forwarding queue as directed by the queuing manager  510  to a device driver transmit ring egress driver  250 . If the device driver transmit ring, through software logic, is recognized as full, data packets are queued into the high priority egress queue  570 . Data packets propagating through the HP queue  310  are typically EF queue  520  data packets. 
   Medium priority egress queue  575  is a FIFO queue that transmits data packets received from a forwarding queue as directed by the queuing manager  510  to a device driver transmit ring egress driver  250 . If the device driver transmit ring, through software logic, is recognized as full, data packets are queued into the medium priority egress queue  575 . Data packets propagating through the MP queue are typically from one of the assured forwarding queues (e.g. AF 1  queue  530 ) data packets. 
   Low priority egress queue  579  is a FIFO queue that transmits data packets derived from a forwarding queue as directed by the queuing manager  510  onto a device driver transmit ring egress driver  250 . If the device driver transmit ring, through software logic, is recognized as full, data packets are queued into the low priority egress queue  579 . Data packets propagating through the LP queue are typically BE queue  550  data packets. 
     FIG. 6  illustrates the IP packet flow through differentiated services edge router  110 . In operation, IP packet signal traffic is processed through ingress driver  210  which associates a default MBLK data descriptor DMBLK  610  with the IP packet  600 . IP packet  600  then propagates to a point incident with the classifier  220 . The classifier  220  includes a configurable database that assigns the QoS 3-tuple based on the traffic profile using fields contained in the data packet header information, including the DiffServ codepoint DSCP  605  field. If the QoS 3-tuple is different than the default MBLK value, the classifier  220  may overwrite the default MBLK DMBLK  610  with the new QoS 3-tuple based on configurable rules. The resulting classifier-processed MBLK is CMBLK  630 . 
   The system passes IP packet  600  with processed MBLK field through a series of filters. If IP packet  600  matches a filter, it is sent to the corresponding meter. If an IP packet  600  does not match any filters resident in classifier  220 , it is sent directly to the differentiated queuing block  240 . If the system sends the IP packet to meter  230 , the system examines the packet to see if the temporal properties of the aggregate flow to which IP packet  600  belongs is in-profile or out-of-profile. 
   Meter  230  interrogates the DS domain  105  available capacity and uses a configurable set of rules to determine if IP packet  600  disposition should be DROP, MARK or NONE. If the decision is to DROP the packet, the system forwards IP packet  600  to meter dropped packet protocol  615 . If the decision is to MARK the packet, the system updates MBLK and/or the DSCP fields and forwards the packet to differentiated queuing block  240 . The resulting meter-processed fields are MDSCP  635  and MMBLK  640 . If the decision is NONE, the packet is sent unmodified to differentiated queuing block  240 . 
   Differentiated queuing block  240  receives IP packet  600 , examines the MBLK field and places the packet in the appropriate queue. If the IP packet is identified as EF and the EF token bucket meter TB meter  560  reads negative, the packet is dropped. EF traffic cannot exceed a maximum pre-determined rate. If the packet is dropped, IP packet  600  is forwarded to DQB dropped packet protocol  620 . If IP packet  600  is not dropped, queuing manager  510  checks to see if the associated primary queue is empty. If not empty, the packet is conversation queued. If the primary queue is empty, the queuing manager  510  checks to see if the secondary queue can accommodate the packet. If the secondary queue can accommodate the packet, the packet is passed through to the secondary queue. This arrangement allows AF and BE traffic to consume up to full link bandwidth. If the secondary queue cannot accommodate the packet, the queuing manager  510  begins queuing in the primary queue. 
   As space in the egress device driver transmit ring becomes available, packets are transferred to egress driver  250  based on priority queuing precedents. Egress driver  250  strips The MBLK field from the IP packet  600 . The IP packet  600  retains egress DiffServ codepoint EDSCP  645 . The DiffServ codepoint may or may not have been modified through the routing process. 
   The many features and advantages of the invention are apparent from the detailed specification. Numerous modifications and changes will readily occur to those of ordinary skill in the art; consequently, the invention is not limited to the embodiments described herein. All suitable modifications and equivalents should be considered as falling within the spirit and scope of the invention.