Network service providers commonly utilize aggregation and core networks in large scale networks, such as metropolitan area networks (MANs) and wide area networks (WANs). Aggregation networks, often found at the edge of a service provider's network, aggregate traffic for transmission via a core network, which is the central part of the network. Aggregation networks are sometimes referred to as access aggregation networks because they provide customers with access to the service provider's network, including the core network.
Various communications protocols are used in aggregation and core networks. G.8032 is a ring protocol standardized by the Telecommunication Standardization Sector of the International Telecommunication Union (ITU-T) and is a candidate for use in aggregation networks. Multi-Protocol Label Switching (MPLS) is a technology that has gained favor for use in edge and core networks.
An embodiment of the invention is a method, or corresponding apparatus, of internetworking. The method includes monitoring a status of a link between an interworking node and at least one peer node in a first network that includes a first plurality of nodes at an interface between the first network and a second network. The second network includes a second plurality of nodes including the interworking node and other interworking node(s). Connectivity is maintained between the interworking node and the other interworking node(s) via the second network. The method further includes supporting communications between the first and second networks via at least one of the interworking nodes and supporting ring communications among the interworking node, the other interworking node(s), and the peer node(s).
Another embodiment of the invention is a method of internetworking at an interworking node. The method includes monitoring a status of a link between the interworking node and at least one peer node in a first network including a first plurality of nodes at an interface between the first network and a second network. The second network includes a second plurality of nodes including the interworking node and at least one other interworking node. Connectivity is maintained between the interworking node and the other interworking node(s) via the second network. The method further includes supporting communications between the first and second networks via at least one of the interworking nodes.
In a corresponding apparatus embodiment, an interworking node has a link status module configured to monitor a status of a link between the interworking node and a peer node in a first network. The interworking node also has a connection status module configured to monitor a connectivity status between the interworking node and another interworking node. The interworking nodes are configured to support interworking activities at an interface between the first network and a second network including the interworking nodes. The interworking node further includes an internetworking information storage unit to store information to enable traffic to flow via the interworking node between the first network and the second network. The interworking node also includes a traffic support module to enable traffic to flow in a ring among the interworking node, the other interworking node, and at least the peer node in the first network.
Another embodiment of the invention is a method, or corresponding apparatus, that includes employing a ring protocol at multiple ring nodes and employing a second protocol different from the ring protocol at an interworking node in a plurality of interworking nodes. The method further includes monitoring a status of a link between the interworking node and a peer node among the ring nodes and a connectivity state with another interworking node. Ring communications are supported among at least the interworking node, the peer node, and the other interworking node.
The foregoing will be apparent from the following more particular description of example 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 embodiments of the present invention.
A description of example embodiments of the invention follows.
Traditionally, attempts to provide interworking between access ring aggregation networks, such as G.8032, and core networks, such as Multi-Protocol Label Switching (MPLS), have been unsuccessful. Typically, efforts to interconnect access ring aggregation networks and core networks have required keeping the two networks separate and providing a network-to-network interface connecting the two networks. Such a technique is inefficient and does not provide end-to-end protection of network traffic.
Embodiments of the invention provide end-to-end integration with protection for seamlessly combining an access ring aggregation network, such as G.8032, and a core network, such as MPLS. Such an end-to-end integration of two disparate networks provides network designers and customers with flexibility in designing, operating, and maintaining networks. MPLS in the guise of Virtual Private LAN Service (VPLS) provides multipoint bridging capabilities complementing Provider Backbone Bridges (PBB) over G.8032 in a ring configuration. MPLS supports standards-based PBB encapsulation/decapsulation, and PBB/G.8032 switches treat MPLS “interworking” nodes as normal G.8032 ring nodes. MPLS has gained favor for use in edge and core networks.
G.8032 is a ring protocol that provides a mechanism, known as Ring Protection Link or RPL, to prevent looping on a bridged ring. G.8032 also provides for transmission of Ring Automatic Protection Switching (RAPS) messages in the event of a link outage to inform nodes to flush Media Access Control (MAC) forwarding databases in order to relearn MAC addresses at Layer 2 of the Open Systems Interconnection (OSI) networking stack.
In an MPLS network, routers do not need to consult Internet Protocol (IP) routing tables, which may impose memory limitations, to determine where to forward incoming traffic. Rather, MPLS establishes fixed paths known as label-switched paths (LSPs) from one end of the network to another. Routers in the MPLS network check a label and destination associated with the packet and send the packet to the next router on the fixed path (including the present router) corresponding to the label.
MPLS may be used to implement Virtual Private LAN Service (VPLS), which is a Layer 2 service that emulates LAN service across a large region such as a WAN or a MAN. MPLS enables construction of label switched paths (LSPs), and VPLS makes it possible to interconnect LAN segments over a packet switched network using LSPs and makes the remote LAN segments behave as a single LAN. A VPLS includes Virtual Switching Instances (VSIs), which serve as nodes, and pseudowire (PW) tunnels, which serve as edges. Ethernet packets are forwarded by a VSI to the appropriate PW tunnel for transport across the VPLS network. PBB framing is added on customer frames sent on PW tunnels towards the MPLS core, increasing MAC scalability within the VPLs network towards the core.
Prior to embodiments illustrating the present invention, the networking industry used various Ethernet Ring Protection mechanisms, either standards-based or proprietary, which lacked proper integration into MPLS networks. Traditional 802.1ah PBB networks lack granularity control of user traffic at core and transit nodes. Embodiments of the invention provide granular control over end user traffic quality of service (QoS), bandwidth, and forwarding policies by re-surfacing customer MAC addresses at MPLS networks. Traditional IEEE 802.1ad (Provider Bridge) networks lack scalability protection against an increase in customer MAC addresses; embodiments of the invention address this problem by hiding customer MAC addresses in a G.8032 domain and providing solutions for re-learning MAC addresses in case of path switchovers. Thus, embodiments of the invention address several deficiencies of the prior art, as will be shown below with reference to the figures.
PBB tunnels 150a through 150f (generally 150a-f) are used as edges in the access ring aggregation network 110. The PBB tunnels 150a-f provide dual homing connectivity to the core network 120 via interworking node A 160a and interworking node B 160b, which may be configured as a primary node and a backup node, respectively. Dual homing refers to a configuration in which two access points are provided for security and reliability, thereby avoiding a single point of failure.
In a normal mode of operation, as shown in
The RPL break 158 is shown in
Link status messages 152a and 152b (generally 152a,b) are exchanged between PBB 4140-4 and PBB-5140-5, which are said to be in a peering relationship with one another. Link status messages 152a,b are also exchanged between other pairs of adjacent peer ring nodes and between the interworking nodes 160a and 160b and their respective peer nodes PBB 4140-4 and PBB 3140-3. Link status messages may also be exchanged between non-adjacent peer nodes, e.g., via an intermediate node that serves as a proxy, as will be described below in the context of
The interworking nodes 160a and 160b maintain connectivity with each other by exchanging connectivity status messages 176a and 176b (generally 176a,b). The connectivity status messages 176a,b may utilize a Fast Re-route (FRR) mechanism, e.g., in the case of the core network 120 being an MPLS network, to ensure connectivity within 50 ms, for example. The connectivity status messages 176a,b establish a logical connection (which may also be a physical connection) 175 between the interworking nodes 160a and 160b, i.e., the interworking nodes 160a and 160b are logically adjacent to each other. The logical connection may utilize intermediate nodes (not shown) in the core network 120. In some embodiments, CCM signaling is maintained over the logical connection 175.
The interworking nodes 160a and 160b include virtual switching instances (VSIs) 170-1a, 170-2a, 170-3a (at 160a) and 170-1b, 170-2b, 170-3b (at 160b) (VSIs generally denoted as 170-1 . . . 3a,b). For illustration, at each interworking node 160a,b, the VSIs 170-1 . . . 3a,b are labeled VSI 1, VSI 2, and VSI 3, and are shown to connect to ISID 1162-1, ISID 2162-2, and ISID 3162-3, respectively (generally 162-1 . . . 3), although VSIs 170-1 . . . 3a,b need not connect to same-numbered ISIDs 162-1 . . . 3. Different numbers of VSIs 170-1 . . . 3a,b may be used at the primary and backup interworking nodes 160a and 160b, respectively. The interworking nodes 160a and 160b terminate PBB tunnels 150c and 150f, respectively, and extract instance service identifier (ISID) information (shown as 162-1 . . . 3 generally at each tunnel). At each interworking node 160a, 160b, Ethernet packets are forwarded by a VSI 170-1 . . . 3a,b to the appropriate pseudowire 174 for transport across the core network 120. Thus, ISID fields (tyically 24 bits in length) are used as service delimiters and identifiers to be associated into virtual private network (VPN) instances.
ISID information 162-1 . . . 3 identified as control messaging is routed at each interworking node 160a, 160b to a control VSI (designated as 172a, 172b, respectively; generally 172a,b), which outputs the control information on the logical connection 175 to the other interworking node. In this way, a ring network is formed using the access ring aggregation network 110 and the core network 120 to transmit control information according to G.8032. Since the interworking nodes 160a,b monitor link status with peer nodes 140-3, 140-4 in the access ring aggregation network 110, the interworking nodes 160a,b can be said to emulate functionality of the ring nodes 150. Thus, the interworking nodes 160a,b can be said to be part of both the access ring aggregation network 110 and the core network 120.
Upon detection of the link failure 180, a ring automatic protection switching (RAPS) message is propagated from the ring node PBB 5140-5 towards the interworking node A 160a. Another RAPS message 182b is propagated from the ring node PBB 1140-1 towards the interworking node B 160b. Each ring node 140-1, . . . , 140-5 has a forwarding database 141-1, . . . , 141-5 (generally 141-1 . . . 5) containing media access control (MAC) address information that is learned at Layer 2 according to the principles of bridging (switching). The RAPS messages 182a and 182b (generally 182a,b) inform each ring node 140-1 . . . 5 along the dual paths to the interworking nodes 160a,b to flush their respective forwarding databases 141 to force MAC re-learning. The interworking nodes 160a,b, upon receiving the RAPS messages 182, flush their own respective forwarding databases 192a and 192b (generally 192a,b) and propagate respective RAPS messages 183a, 183b (generally 183a,b) to other nodes in the core network 120 in order to force MAC re-learning in the core network 120. MAC flushing and convergence is typically achieved in less than one second. Flushing MAC forwarding databases helps achieve fast convergence for MAC bridging instead of waiting for an aging timer (e.g., a timeout) to expire.
Also upon detection of the link failure 180, the RPL segment 158 is cleared (unblocked, as indicated by a double dashed line in
An embodiment of the invention is a method, or corresponding apparatus, of internetworking. The method includes monitoring a status of a link between an interworking node and at least one peer node in a first network that includes a first plurality of nodes at an interface between the first network and a second network. The second network includes a second plurality of nodes including the interworking node and other interworking node(s). Connectivity is maintained between the interworking node and the other interworking node(s) via the second network. The method further includes supporting communications between the first and second networks via at least one of the interworking nodes and supporting ring communications among the interworking node, the other interworking node(s), and the peer node(s).
The method may further include including supporting network traffic and operational characteristics according to G.8032 on the first network and multi-protocol label switching (MPLS) on the second network.
The method may further include enabling a user network interface (UNI) at a node among first plurality of nodes and supporting primary and backup interworking node activities by way of interworking nodes designated as a primary and a backup interworking node, respectively.
The method may further include blocking a segment between a selected interworking node and a corresponding peer node to disable user traffic flow.
The method may further include detecting a failure in the link by checking for a lost continuity check messaging (CCM) signal. Based on detecting the failure, the segment may be blocked, a media access control (MAC) forwarding database at a node in the first network may be flushed, a ring automatic protection switching (RAPS) signal may be propagated towards at least one of the interworking nodes, and switching to the backup interworking node may be performed for traffic between the first and second networks.
Another embodiment of the invention is a method of internetworking at an interworking node. The method includes monitoring a status of a link between the interworking node and at least one peer node in a first network including a first plurality of nodes at an interface between the first network and a second network. The second network includes a second plurality of nodes including the interworking node and at least one other interworking node. Connectivity is maintained between the interworking node and the other interworking node(s) via the second network. The method further includes supporting communications between the first and second networks via at least one of the interworking nodes.
The method may further include supporting network traffic and operational characteristics according to G.8032 on the first network and multi-protocol label switching (MPLS) on the second network.
The method may further include blocking a segment between the interworking node and the peer node(s) in the first network to disable user traffic flow.
The method may further include detecting a failure in the link by checking for a lost connectivity check message (CCM) signal. Based on detecting the failure, a media access control (MAC) database of the interworking node may be flushed, and a ring automatic protection switching (RAPS) message may be sent to a third node in the second network to relearn MAC addresses in the second network.
The method may further include receiving a ring automatic protection switching (RAPS) signal, flushing a media access control (MAC) database of the interworking node based on receiving the RAPS signal, and sending a ring automatic protection switching (RAPS) message to a third node in the second network based on receiving the RAPS signal to relearn MAC addresses in the second network.
In a corresponding apparatus embodiment, an interworking node has a link status module configured to monitor a status of a link between the interworking node and a peer node in a first network. The interworking node also has a connection status module configured to monitor a connectivity status between the interworking node and another interworking node. The interworking nodes are configured to support interworking activities at an interface between the first network and a second network including the interworking nodes. The interworking node further includes an internetworking information storage unit to store information to enable traffic to flow via the interworking node between the first network and the second network. The interworking node also includes a traffic support module to enable traffic to flow in a ring among the interworking node, the other interworking node, and at least the peer node in the first network.
The link status module may employ a ring protocol, the other interworking node may include a corresponding link status module, and the interworking nodes may be configured, based on their respective link status modules, to emulate functionality of a node in the first network.
Another embodiment of the invention is a method, or corresponding apparatus, that includes employing a ring protocol at multiple ring nodes and employing a second protocol different from the ring protocol at an interworking node in a plurality of interworking nodes. The method further includes monitoring a status of a link between the interworking node and a peer node among the ring nodes and a connectivity state with another interworking node. Ring communications are supported among at least the interworking node, the peer node, and the other interworking node.
The method may further include supporting network traffic and operational characteristics according to G.8032 as the ring protocol and multi-protocol label switching (MPLS) as the second protocol.
The method may further include enabling a user network interface (UNI) at a ring node and supporting primary and backup interworking node activities by way of interworking nodes designated as a primary and a backup interworking node, respectively.
The method may further include blocking a segment between a selected interworking node and a corresponding peer node to disable user traffic flow.
The method may further include detecting a failure in the link by checking for a lost continuity check messaging (CCM) signal. Based on detecting the failure, the segment may be unblocked, a media access control (MAC) forwarding database at a ring node may be flushed, a ring automatic protection switching (RAPS) signal may be propagated towards at least one of the interworking nodes, and switching to the backup interworking node may be performed for traffic between the ring network and another network employing the second protocol.
Although three G.8032 ring networks 210a-210c (generally 210a-c) are shown, it should be understood that other numbers may be present, and more than one MPLS core network 220 may be present. Each UPE node 260a-260d (generally 260a-d) has an associated VSI 270a-270d (generally 270a-d) to connect the associated G.8032 ring network 210 and the associated MPLS core network 220. Aggregation services are provided by 802.1ah in each G.8032 ring network 210. Core services are provided by 802.1ah in the MPLS core network 220.
A link status module 420 in interworking node A 460a monitors link status with peer nodes, e.g., using a connectivity check message (CCM) 452, over the PBB interfaces 450-1 . . . 4.
A connection status module 430 monitors connectivity status between interworking node A 460a and an interworking node B 460b. Interworking node A 460a and interworking node B 460b form an interface between the first network including the peer nodes (not shown) and a second network including the interworking nodes 460a and 460b.
An internetworking information storage unit 435 stores information to enable a message 480 to flow between the first and second networks; such traffic flow is bidirectional in some embodiments. The internetworking information storage unit 435 maps ISIDs to VSIs. Although
A traffic support module 440 enables traffic (e.g., CCMs 476a and 476b) to flow in a ring among the interworking node A 460a, the interworking node B 460b, and at least one peer node (not shown). Incoming control packets, e.g., a RAPS messages 482, are sent to a control VSI 472 (labeled VSI X in
While this invention has been particularly shown and described with references to example 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 scope of the invention encompassed by the appended claims.
Embodiments or aspects of the invention may be implemented in hardware, firmware, or software, if implemented in software, the software may be implemented in any software language capable of performing the embodiment(s) of the invention. The software may be stored on any computer-readable medium, such as RAM, ROM, CD-ROM, and so forth. The software includes instructions that can be loaded and executed by a general purpose or application specific processor capable of supporting embodiment(s) of the invention.