IP forwarding across a link state protocol controlled ethernet network

• US 20090279536A1
• Filed: 05/08/2008
• Published: 11/12/2009
• Est. Priority Date: 12/31/2007
• Status: Active Grant

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Bragg, Nigel, Allan, David, Unbehagen, Paul
• Granted Patent: US 9,432,213 B2
• Time in Patent Office: Days
• US Class Current: 370/352
• CPC Class Codes: H04L 12/462 LAN interconnection over a bridge based backbone
• CPC Class Codes: H04L 12/4625 Single bridge functionality, e.g. connection of two networks over a single bridge
• CPC Class Codes: H04L 45/00 Routing or path finding of packets in data switching networks routing or path finding in wireless networks H04W40/00
• CPC Class Codes: H04L 45/02 Topology update or discovery
• CPC Class Codes: H04L 45/03 by updating link state protocols
• CPC Class Codes: H04L 45/42 Centralised routing
• CPC Class Codes: H04L 45/66 Layer 2 routing, e.g. in Ethernet based MAN's
• CPC Class Codes: H04L 45/742 Route cache; Operation thereof
• CPC Class Codes: H04L 61/103 across network layers, e.g. resolution of network layer into physical layer addresses or address resolution protocol [ARP]

Abstract

Nodes on an Ethernet network run a link state protocol on the control plane and install shortest path forwarding state into their FIBs to allow packets to follow shortest paths through the network without requiring MAC header replacement at each hop through the network. When a node learns an IP address, it will insert the IP address into its link state advertisement to advertise reachability of the IP address to the other nodes on the network. Each node will add this IP address to its link state database. If a packet arrives at an ingress node, the ingress node will read the IP address, determine which node on the link state protocol controlled Ethernet network is aware of the IP address, and construct a MAC header to forward the packet to the correct node. The DA/VID of the MAC header is the nodal MAC of the node that advertised the IP address. Unicast and multicast IP forwarding may be implemented.

Claims

1. A hybrid switching layer (L2)/network layer (L3) network, comprising:

a routing domain comprising a plurality of network layer forwarders and one or more switching domains,

the switching domain interconnecting network layer forwarders and end systems using Virtual Forwarding Entities (VFEs),

the switching domain implementing a plurality of virtual LAN segments, the LAN segments being either addressed or unaddressed, the addressed virtual LAN segments being used to interconnect the VFEs to network layer forwarders or to end systems, and the unaddressed virtual LAN segments being used to interconnect VFEs within the switched domain;

wherein the VFEs in the switching domain interconnect arbitrary subsets of the plurality of virtual LAN segments implemented by the switching domain.

2. The hybrid L2/L3 network of claim 1, wherein the unaddressed virtual LAN segments are further used to interconnect network layer forwarders with other network layer forwarders in the absence of a VFE for a community of interest including the interconnected network layer forwarders.

3. The hybrid L2/L3 network of claim 1, wherein the unaddressed virtual LAN segments are further used to interconnect network layer forwarders and end systems in the absence of a VFE for a community of interest including the network layer forwarders and end systems.

4. The hybrid L2/L3 network of claim 1, wherein the network includes a single unaddressed virtual LAN segment.

5. The hybrid L2/L3 network of claim 1, wherein the network includes a plurality of addressed virtual LAN segments.

6. The hybrid L2/L3 network of claim 1, wherein the unaddressed virtual LAN segment interconnects a subset of all of the VFEs.

7. The hybrid L2/L3 network of claim 1, wherein the addressed virtual LAN segments are realized using virtual bridges or physical LAN segments.

8. The hybrid L2/L3 network of claim 7, wherein the virtual bridges interconnect the switching domain with one of the network layer forwarders or with one of the end systems.

9. The hybrid L2/L3 network of claim 8, wherein the VFEs are used to perform network layer forwarding between the switching domain and the routing domain.

10. The hybrid L2/L3 network of claim 9, wherein the switching domain includes a plurality of switching nodes, at least some of which implement the VFEs, and wherein nodes that implement VFEs within the switching domain will use information associated with routes in the network domain to populate switching node FIBs in the switching domain, so that when a packet arrives at a VFE, the VFE may read the network layer address and determine the appropriate forwarding action to forward the packet on a switched path through the switching domain to the network layer destination in the routing domain.

11. The hybrid L2/L3 network of claim 1, wherein the switching domain comprises a plurality of nodes running a link state routing protocol to control population of forwarding state into forwarding information bases on the nodes in the switching domain, and wherein the link state routing protocol is used to transport network layer addresses between the nodes in the switching domain.

12. The hybrid L2/L3 network of claim 11, wherein transporting network layer addresses between nodes allows the nodes to learn which network layer addressed end systems are reachable via each of the other nodes on the network domain.

13. The hybrid L2/L3 network of claim 12, wherein the nodes store network layer addresses associated with the network layer addressed end systems in link state databases, which may then be used to determine associations between the L2 and L3 network topology.

14. The hybrid L2/L3 network of claim 11, wherein the switching domain is an Ethernet domain.

15. A method of installing forwarding state in a node operating on a link state protocol controlled Ethernet network, the method comprising the steps of:

receiving, by a first node operating in the link state protocol controlled Ethernet network, a Link State Advertisement (LSA) containing a network layer prefix reachable by a second node in the link state protocol controlled Ethernet network, where the path between the first and second node includes a plurality of links in the link state protocol controlled Ethernet network;

updating a routing table to indicate an association between the network layer address and a Ethernet MAC node ID of the second node in the link state protocol controlled Ethernet network.

16. The method of claim 15, further comprising updating a forwarding table entry in the first node to enable the first node to create a MAC header for a packet addressed to the network layer address, the MAC header including a destination MAC address associated with the second node on the link state protocol controlled Ethernet network.

17. The method of claim 16, further comprising the steps of receiving the packet addressed to the network layer address, creating the MAC header, and forwarding the packet on the link state protocol controlled Ethernet network.

18. The method of claim 15, wherein the network layer prefix is an IPv4 or IPv6 network layer address.

19. The method of claim 18, wherein the network layer prefix references a virtualized subnet.

20. The method of claim 19, wherein the virtualized subnet is decoupled from topology of the link state protocol controlled Ethernet network.