Abstract:
Logical ports allow multiple customers to be connected to and to receive different services over a common physical port of a packet forwarding device. Such logical ports allow for customer separation and may be created based on VLAN ID and MPLS labels. In one embodiment, each service provided via a packet forwarding device is associated with a unique logical port. The logical port may span multiple physical ports.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application relates to commonly-assigned U.S. patent application Ser. No. 10/140,234, entitled “System and Method for Providing Transparent LAN Services” filed on even date herewith, the disclosure of which is hereby incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to communication networks, and in particular to a logical port system and method. 
     BACKGROUND 
     Network packet forwarding devices, such as routers, switches, multiplexers, and the like include a limited number of physical ports to which customers may connect. Different customers typically connect to different physical ports of a packet forwarding device. In addition, different services are typically provided to a given customer over different physical ports. 
     For example, a given customer may receive routing services over one physical port of the packet forwarding device and the same customer may receive TDM (time division multiplexing) services over another physical port of the packet forwarding device. Hence, given a limited set of physical ports of a packet forwarding device, the packet forwarding device is limited in the number of different services and/or customers the packet forwarding device may support. 
     Accordingly, a need exists to provide a system and method for increasing port density at a packet forwarding device. Another need exists to provide a system and method for providing an increased number of services or providing services to an increased number of customers over a given set of ports of a packet forwarding device. 
     SUMMARY 
     In general, the present system and method alleviate port density and permit a greater number of services to be provided over a given set of physical ports by creating logical ports. Incoming data packets on a physical port may include a VLAN ID or an MPLS (Multi-Protocol Label Switching) label. The packet forwarding device assigns the incoming data packets to a specific logical port according to the VLAN ID or the MPLS label of the incoming data packet. The packet forwarding device may also assign a specific service to each logical port. Further, different customers may be assigned separate logical ports and be connected to a common physical port. 
     In addition, a given logical port may include more than one physical port and may span multiple physical ports on the same slot, physical ports on different slots, or physical ports on different packet forwarding devices. 
     Further, each logical port may include SLA (Service Level Agreements) or QoS (Quality of Service) associated with the logical port, thereby permitting different QoS to be provided to different logical ports on the same or different physical ports. Accordingly, according to some embodiments of the present invention, each service is associated with a logical port. 
     A logical port is used to identify and manage multiple sets of flows across a single interface. The logical port provides a common set of abstractions that can support delivery of a variety of services, allowing the variety of services to share common lower level mechanisms. In one embodiment, the logical port comprises one of a number of interfaces on a physical interface, such as a physical port. 
     Logical ports may have a one-to-one mapping to services, such that each logical port supports either a different type of service or services for different customers. Thus, a single customer may have multiple logical ports supporting multiple associated services. Higher-level services can use logical ports as a way to gather statistics on a logical port basis. 
     A logical port defines a group of packets according to certain pre-defined criteria. The logical ports behave similar to a physical port in terms of traffic service. The logical ports permit multiple customers to be connected to a single physical port of a node. The logical ports also permit different services to be provided to a customer over a single physical port. Thus, the logical ports help alleviate port density problems. 
     Additional details regarding the present system and method may be understood by reference to the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a communication network in accordance with an embodiment of the present invention. 
         FIG. 2  illustrates details of a  FIG. 1  node in accordance with an embodiment of the present invention. 
         FIG. 3  is a functional diagram illustrating system architecture. 
     
    
    
     Common reference numerals are used throughout the drawings and detailed description to indicate like elements. 
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a network  100  in accordance with one embodiment of the present invention. As shown, the network  100  includes a ring  102 , which interconnects nodes  104 ,  106 ,  108 ,  110 . In one embodiment, the ring  102  may comprise a fiber optic ring having a Resilient Packet Ring (RPR) topology. In some applications, the network  100  may comprise a metro area network (MAN). Each of the nodes  104 - 110  may comprise a high speed routing/multiplexing device. Details of the nodes are described below and in U.S. patent application Ser. No. 09/518,956, the disclosure of which is hereby incorporated by reference in its entirety. 
     The network  100  has locations, or sites, of customer A and customer B connected thereto. As illustrated, customer A has multiple locations  120 ,  122 ,  124 , and  126 . Each of these locations may comprise a LAN. The location  120  is connected to node  110 , the location  122  is connected to node  108 , and locations  124 ,  126  are connected to node  106 . 
     In one embodiment, node  110  provides multiple services to customer A at location  120  over a single physical port of the node  110  using a logical port system and method. The node inspects incoming data packet received by the node over the single physical port and identifies a logical port identifier within data packet. Pursuant to one embodiment, the logical port identifier comprises an MPLS label associated with a logical port. Pursuant to another embodiment, the logical port identifier comprises a VLAN ID (Virtual Local Area Network Identifier). The node then uses a lookup table to identify, or determine, the logical port associated with the packet. The node then assigns a service to the packet based on the logical port to which it is assigned. 
     In another embodiment, nodes  108 ,  110  provide a single service to customer A at locations  120 ,  122  over a physical port of the node  110  and a physical port of the node  108  using a logical port system and method. The nodes  108 ,  110  each inspect incoming data packets received by the nodes  108 ,  110  over respective physical ports and identify the logical port identifier within each data packet. As discussed above, the logical port identifiers may comprise MPLS labels or VLAN IDs. The nodes  108 ,  110  then each use a lookup table to identify, or determine, the logical port associated with the packet. In this embodiment, the incoming data packets include identical logical port identifiers and are thus assigned to the same service for the same customer, namely, customer A. 
     A management console  130  may also be connected to the ring  102  by a node  132 . The management console  130  is used to permit network management and provisioning of the devices connected to the ring  102  as described in more detail below. In particular, the management console  130  may be used to access individual nodes  104 - 110  to establish logical ports thereon. 
     Several applications exist for the present system and method. For example, with respect to the provision of layer  1  services, the logical port may be used to setup cross connects for wire mode transports. This allows multipoint to point physical port aggregation and de-aggregation based on logical ports. Services such as Ethernet private lines (EPL), virtual leased lines (VLL), and circuit emulation services (CES), are examples of this type of service. In wire mode, MPLS label based logical ports provide layer  1  services. 
     With respect to the provision of layer  2  services, the logical support functions as if a physical port were set in a TLS (Transparent LAN Services) mode. Packets incoming on the logical port interface would be switched based on the layer  2  destination MAC Address. This provides aggregation and de-aggregation service at layer  2 . Thus, traffic may be aggregated using logical ports for each domain. Additional details regarding TLS mode are disclosed in U.S. Patent Application entitled “System and Method for Providing Transparent LAN Services” filed on even date herewith and incorporated herein by reference above. 
     With respect to the provision of layer  2 . 5  services, the logical port functions to support aggregation and de-aggregation services using MPLS labels. The MPLS label of an incoming packet is examined to forward the data packet. It is to be noted that the MPLS label ranges may also be used to specify logical ports for offering layer  1  services. The mode of the logical port determines whether it forwards using layer  1  or layer  2 . 5 . 
     With respect to layer  3  services, a logical port would support aggregation and de-aggregation using layer  3  header information. In this mode, also referred to as routing mode, incoming packets are routed based on the destination IP address of each incoming packet. 
       FIG. 2  illustrates details of one of the nodes of  FIG. 1 , which may be similarly configured. Node  108  is shown as an example. As illustrated, the node  108  includes ring interface cards  230  and  232 , a switching card  238 , line cards  252 , and a system controller  262 . The ring interface cards  230  and  232  convert the incoming optical signals on fiber optic cables  234  and  236  to electrical digital signals for application to switching card  238 . In one embodiment, the ring interface cards  230 ,  232  may be implemented as a single card. Additional details regarding the ring interface cards  230  and  232  and the node  108  are disclosed in U.S. patent application Ser. No. 09/519,442, entitled “Dynamically Allocated Ring Protection and Restoration Technique” filed Mar. 3, 2000, the disclosure of which is hereby incorporated by reference in its entirety. 
       FIG. 3  is a functional diagram  300  illustrating system architecture. The functional diagram  300  includes system controller applications  302 , a control plane framework  304 , and line card applications  306 . The system controller applications  302  may run on the system controller  262  of  FIG. 2  and include the following modules: a management interface  310 , a shelf manager  312 , a system port manager  314 , a policy manager  316 , and a classifier  318 . 
     In general, the classifier  318  verifies the configuration of the newly-created logical port and downloads necessary information (e.g., vlan_id or mpls label, port mode, actions to be taken for incoming/outgoing packets on the specified logical port) to the associated line card(s). 
     The management interface  310  may comprise a graphical user interface (GUI) based interface that permits a user at the management console  130  ( FIG. 1 ) to remotely configure, monitor, and manage the associated node. The shelf manager  312  receives data from the management interface  310 , stores the information for persistency, and forwards the information to the system port manager  314 . The system port manager  314  handles the creation and the management of a logical port. The system port manager  314  specifies the mode, the administrative state, the IP address, and the MAC address of the logical port and communicates with the classifier  318 . 
     The shelf manager  312  provides the interface to management of the system or node resources. The resources may include the cards, ports and configuration information. 
     The system port manager  314  provides a uniform abstraction for managing port behavior across various line card interfaces. 
     The classifier  318  and policy manager  316  manage the information related to creation of logical ports and the actions associated with them. The policy manager  316  in addition also handles the communication between the switching card  238  and the line cards  252 . 
     The shelf manager  312  on receipt of a request for creation/deletion of a logical port from the management interface  310 , initiates actions to interact with the classifier  318  and port manager  314  to create/delete the logical port. The shelf manager  312  also stores/deletes the information related to the logical port in a persistent database (not shown). 
     The policy manager  316  in turn initiates a set of actions that get communicated to the line card port manager  320  of each line card  252  ( FIG. 2 ) to provision the logical port at the ingress of the physical ports. The policy manager  316  also handles the policy rules applied on a logical port. The policy manager  316  is responsible for storing/restoring policy rules from the database (not shown) and interacts with the classifier  318  to download policy applied on a logical port. 
     Accordingly, a logical port may be established by a user at the management console  130  ( FIG. 1 ) by accessing the management interface  310  ( FIG. 3 ). Then, using the management interface  310  the user may request a new logical port. In establishing a new logical port, the management interface  310  receives a request for a new logical port from the user. The request may include specification of whether the logical port is to be MPLS label based, or VLAN ID based, and may specify the physical port over which the logical port will be provided. The request may also include specification of data rate limits associated with the logical port. The management interface  310  then forwards this information to the shelf manager  312 , which provides this information to other of the system controller modules. Lastly, this information is downloaded to a line card manager  320  for control of the associated line card. 
     The new logical port is then provisioned via the management interface  310 . To provision the new logical port, a user at the management console  130  ( FIG. 1 ) then specifies a customer, a service, and a quality of service (QoS) for the new logical port. At this point, the new logical port is established and provisioned. 
     The above-described embodiments of the present invention are meant to be merely illustrative and not limiting. Thus, those skilled in the art will appreciate that various changes and modifications may be made without departing from this invention in its broader aspects. Therefore, the appended claims encompass all such changes and modifications as fall within the scope of this invention.