Networking System Having Multiple Components with Multiple Loci of Control

20210273891

16/886417

May 28, 2020

Each switch unit in a networking system shares its local state information among other switch units in the networking system, collectively referred to as the shared forwarding state. Each switch unit creates a respective set of output queues that correspond to ports on other switch unites based on the shared forwarding state. A received packet on an ingress switch unit operating in accordance with a first routing protocol instance can be enqueued on an output queue in the ingress switch; the packet is subsequently processed by the egress switch unit, operating in accordance with a second routing protocol instance that corresponds to the output queue.

1. A method among a plurality of switch units including a first switch unit and a second switch unit, the method comprising: the first switch unit receiving a packet; the first switch unit performing a forwarding lookup operation using addressing information in the received packet to identify an egress port and a next hop address; in response to the egress port being on the second switch unit, the first switch unit using shared forwarding information to: identify a virtual output queue (VOQ) that corresponds to the egress port on the second switch unit; and identify a rewrite index based on the next hop address; the first switch unit enqueueing a packet block on the VOQ, the packet block comprising the received packet and the rewrite index; the second switch unit dequeuing the packet block; the second switch unit modifying the received packet contained in the dequeued packet block according to the rewrite index contained in the dequeued packet block; the second switch unit transmitting the modified packet on the port that is associated with the VOQ without performing a forwarding lookup operation in the second switch unit, wherein the first switch unit processes packets in accordance with a first routing protocol instance and the second switch unit processes packets in accordance with a second routing protocol instance different from the first routing protocol instance.

2. The method of claim 1, wherein the shared forwarding information comprises: rewrite indices generated by each of the plurality of switch units, each rewrite index identifying a set of rewrite actions in one of the plurality of switch units; and a plurality of VOQ identifiers, each VOQ identifier uniquely identifying a port on one of the plurality of switch units.

3. The method of claim 1, further comprising each of the plurality of switch units receiving the shared forwarding information from a central source and storing a respective local copy of the received shared forwarding information.

4. The method of claim 3, further comprising each of the plurality of switch units providing its respective local forwarding information to the central source, wherein the central source aggregates the respective local forwarding information received from each of the plurality of switch units to generate the shared forwarding information.

5. The method of claim 1, the method further comprising the second switch unit: identifying a set of rewrite actions using the rewrite index contained in the dequeued packet block; and modifying the packet contained in the dequeued packet block using the identified set of rewrite actions.

6. The method of claim 5, wherein the rewrite actions are stored in the second switch unit.

7. The method of claim 1, wherein the egress port is a member port of a link aggregate group (LAG) defined on the second switch unit, the method further comprising the first switch unit: using the shared forwarding information to identify all member ports of the LAG; and selecting one of the member ports of the LAG as a new egress port.

8. The method of claim 7, wherein the shared forwarding information includes LAG information that identifies LAGs defined among the plurality of switch units and identifies member ports for each identified LAG.

9. A modular chassis comprising: a plurality of switch units including at least a first switch unit and a second switch unit; the first switch unit and the second switch unit, each, configured to receive and process packets in accordance with a routing protocol instance different from the other; the first switch unit configured to: receive packets in accordance with the first routing protocol instance; perform a forwarding lookup operation using addressing information contained in a packet received on a port of the first switch unit to determine an egress port on which to egress the packet and a next hop address; and when the egress port is a port on the second switch unit: identify a rewrite index and a virtual output queue (VOQ) that is associated with the next hop address; and enqueue the packet and the rewrite index on the VOQ; the second switch unit configured to: dequeue the packet and rewrite index from the VOQ; modify the packet according to the rewrite index; and transmit the modified packet on a port on the second switch unit that is associated with the VOQ in accordance with the second routing protocol instance, without performing a forwarding lookup operation in the second switch unit.

10. The modular chassis of claim 9, wherein when the egress port is a port on the first switch unit, then egress the packet using the first routing protocol instance.

11. The modular chassis of claim 9, wherein when the egress port is a member port of a LAG defined on the second switch unit, then the first switch unit identifies all member ports of the LAG and selects as a new egress port one of the member ports of the LAG.

12. The modular chassis of claim 9, wherein the first switch unit has stored therein a local copy of shared forwarding information that is used to identify the virtual output queue (VOQ) and the rewrite index.

13. The modular chassis of claim 12, wherein the shared forwarding information comprises: rewrite indices generated by each of the plurality of switch units, each rewrite index identifying a set of rewrite actions in one of the plurality of switch units; and a plurality of VOQ identifiers, each VOQ identifier uniquely identifying a port on one of the plurality of switch units.

14. The modular chassis of claim 12, wherein each of the plurality of switch units is configured to provide its respective forwarding information to a central server, wherein the shared forwarding information is an aggregation of the respective forwarding information received from the plurality of switch units, wherein each of the plurality of switch units stores a local copy of the shared forwarding information.

15. A distributed switch fabric comprising: a plurality of switch units including at least a first switch unit and a second switch unit; the first switch unit and the second switch unit each configured to receive and process packets in accordance with a routing protocol instance different from the other; the first switch unit configured to process a first packet received on a port of the first switch unit in accordance with a first routing protocol instance when the first packet is destined for egress on another port of the first switch unit; the first switch unit configured to enqueue a second packet and a rewrite index on a virtual output queue (VOQ) associated with the second switch unit when the second packet is destined for egress on a port of the second switch unit, wherein the second switch unit: dequeues the second packet and rewrite index from the virtual output queue; modifies the second packet in accordance with rewrite actions identified by the rewrite index; and transmits the modified second packet on a port on the second switch unit that corresponds to the virtual output queue in accordance with a second routing protocol instance different from the first routing protocol instance.

16. The distributed switch fabric of claim 15, wherein the modified second packet is transmitted by the second switch unit without performing a forwarding lookup operation.

17. The distributed switch fabric of claim 15, wherein the first switch unit stores a local copy of shared forwarding information and uses the shared forwarding information to identify the virtual output queue and the rewrite index.

18. The distributed switch fabric of claim 17, wherein the shared forwarding information comprises: rewrite indices generated by each of the plurality of switch units, each rewrite index identifying a set of rewrite actions in one of the plurality of switch units; and a plurality of VOQ identifiers, each VOQ identifier uniquely identifying a port on one of the plurality of switch units.

19. The distributed switch fabric of claim 15, further comprising a modular chassis wherein the plurality of switch units is installed in the modular chassis and interconnected by a communication fabric, wherein the modular chassis is configurable to add switch units and to remove switch units.

20. The distributed switch fabric of claim 15, further comprising a plurality modular chassis interconnected by a communication fabric, each modular chassis comprising at least some of the plurality of switch units installed therein, each modular chassis being configurable to add switch units and to remove switch units.

21. The distributed switch fabric of claim 15, further comprising a plurality of fixed-configuration chassis, each fixed-configuration chassis comprising a fixed number of the plurality of switches.

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edspap.20210273891