Efficient multicast packet forwarding in a distributed tunnel fabric
A system for efficient multicast control packet forwarding is provided. During operation, the system can maintain a first tunnel between a first switch and a second switch in an overlay tunnel fabric. The encapsulation of a packet sent via the overlay tunnel fabric is initiated and terminated within the overlay tunnel fabric. The system can maintain a second tunnel between the first switch and a third switch, which can be in an external network that excludes the first and second switches. The switch can distinguish the first and second tunnels as intra-fabric and inter-fabric tunnels, respectively. Upon receiving a multicast control packet via the first tunnel, the system can identify the second tunnel as the inter-fabric tunnel and forward the multicast control packet via the second tunnel. Here, a respective multicast control packet received from the first tunnel can be precluded from being forwarded on intra-fabric tunnels.
1. A method comprising:
maintaining, by a first switch, a first tunnel with a second switch in an overlay tunnel fabric that includes the first and second switches, wherein encapsulation of a packet sent via the overlay tunnel fabric is initiated and terminated within the overlay tunnel fabric;
maintaining, by the first switch, a second tunnel with a third switch in an external network that excludes the first and second switches;
distinguishing the first and second tunnels as intra-fabric and inter-fabric tunnels, respectively, of the overlay tunnel fabric; and
in response to receiving a multicast control packet via the first tunnel:
identifying the second tunnel as the inter-fabric tunnel; and
forwarding the multicast control packet via the second tunnel, wherein a respective multicast control packet received from the first tunnel is precluded from being forwarded on intra-fabric tunnels of the overlay tunnel fabric.
2. The method of claim 1 , wherein a first path associated with the first tunnel is determined based on an internal Border Gateway Protocol (IBGP), and wherein a second path associated with the second tunnel is determined based on an external BGP (eBGP).
3. The method of claim 1 , wherein, in response to receiving a second multicast control packet via the second tunnel, the method further comprises:
identifying the first tunnel as an intra-fabric tunnel; and
forwarding the second multicast control packet via the first tunnel, wherein a respective control packet received from the second tunnel is precluded from being forwarded on inter-fabric tunnels coupled to the overlay tunnel fabric.
4. The method of claim 1 , wherein a respective tunnel endpoint in the overlay tunnel fabric is configured as a multicast querier;
wherein the method further comprises:
generating an all-host query (AHQ); and
forwarding the AHQ via a respective local layer-2 port of the first switch without forwarding the AHQ via a tunnel originating at the first switch.
5. The method of claim 4 , further comprising generating the AHQ in response to the first switch recovering from an unavailability event that causes a loss of multicast information at the first switch.
6. The method of claim 4 , further comprising:
receiving a multicast join packet for a multicast group via a local layer-2 port as a response to the AHQ; and
forwarding the multicast join packet via a respective tunnel originating at the first switch.
7. The method of claim 1 , wherein a respective tunnel endpoint in the overlay tunnel fabric is configured as a multicast querier;
wherein the method further comprises:
receiving a leave packet for a multicast group;
generating a group membership query (GSQ) for the multicast group; and
forwarding the GSQ via a respective local layer-2 port of the first switch and a respective tunnel originating at the first switch.
8. The method of claim 1 , wherein the external network includes a second overlay tunnel fabric, and wherein encapsulation of a second packet sent via the second overlay tunnel fabric is initiated and terminated within the second overlay tunnel fabric.
9. The method of claim 1 , wherein a respective intra-fabric tunnel is a dynamic tunnel, wherein a respective inter-fabric tunnel is a static tunnel, and wherein the third switch operates as a gateway for the external network.
10. The method of claim 1 , further comprising:
maintaining, at the first switch, a set of forwarding rules that indicate whether a packet received from an ingress tunnel is allowed to be forwarded to an egress tunnel; and
forwarding the multicast control packet via the second tunnel based on the set of forwarding rules.
11. A non-transitory computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method, the method comprising:
maintaining, by a first switch, a first tunnel with a second switch in an overlay tunnel fabric that includes the first and second switches, wherein encapsulation of a packet sent via the overlay tunnel fabric is initiated and terminated within the overlay tunnel fabric;
maintaining, by the first switch, a second tunnel with a third switch in an external network that excludes the first and second switches;
distinguishing the first and second tunnels as intra-fabric and inter-fabric tunnels, respectively, of the overlay tunnel fabric; and
in response to receiving a multicast control packet via the first tunnel:
identifying the second tunnel as the inter-fabric tunnel; and
forwarding the multicast control packet via the second tunnel, wherein a respective multicast control packet received from the first tunnel is precluded from being forwarded on intra-fabric tunnels of the overlay tunnel fabric.
12. The non-transitory computer-readable storage medium of claim 11 , wherein a first path associated with the first tunnel is determined based on an internal Border Gateway Protocol (iBGP), and wherein a second path associated with the second tunnel is determined based on an external BGP (eBGP).
13. The non-transitory computer-readable storage medium of claim 11 , wherein, in response to receiving a second multicast control packet via the second tunnel, the method further comprises:
identifying the first tunnel as an intra-fabric tunnel; and
forwarding the second multicast control packet via the first tunnel, wherein a respective control packet received from the second tunnel is precluded from being forwarded on inter-fabric tunnels coupled to the overlay tunnel fabric.
14. The non-transitory computer-readable storage medium of claim 11 , wherein a respective tunnel endpoint in the overlay tunnel fabric is configured as a multicast querier;
wherein the method further comprises:
generating an all-host query (AHQ); and
forwarding the AHQ via a respective local layer-2 port of the first switch without forwarding the AHQ via a tunnel originating at the first switch.
15. The non-transitory computer-readable storage medium of claim 14 , wherein the method further comprises generating the AHQ in response to the first switch recovering from an unavailability event that causes a loss of multicast information at the first switch.
16. The non-transitory computer-readable storage medium of claim 11 , wherein a respective tunnel endpoint in the overlay tunnel fabric is configured as a multicast querier;
wherein the method further comprises:
receiving a leave packet for a multicast group;
generating a group membership query (GSQ) for the multicast group; and
forwarding the GSQ via a respective local layer-2 port of the first switch and a respective tunnel originating at the first switch.
17. The non-transitory computer-readable storage medium of claim 11 , wherein the external network includes a second overlay tunnel fabric, and wherein encapsulation of a second packet sent via the second overlay tunnel fabric is initiated and terminated within the second overlay tunnel fabric.
18. The non-transitory computer-readable storage medium of claim 11 , wherein a respective intra-fabric tunnel is a dynamic tunnel, wherein a respective inter-fabric tunnel is a static tunnel, and wherein the third switch operates as a gateway for the external network.
19. The non-transitory computer-readable storage medium of claim 11 , wherein the method further comprises:
maintaining, at the first switch, a set of forwarding rules that indicate whether a packet received from an ingress tunnel is allowed to be forwarded to an egress tunnel; and
forwarding the multicast control packet via the second tunnel based on the set of forwarding rules.
20. A computer system, comprising:
a processor;
a memory device;
a tunnel logic block to:
maintain a first tunnel with a second computer system in an overlay tunnel fabric that includes the computer system and the second computer system, wherein encapsulation of a packet sent via the overlay tunnel fabric is initiated and terminated within the overlay tunnel fabric; and
maintain a second tunnel with a third computer system in an external network that excludes the computer system and the second computer system;
a classifier logic block to distinguish the first and second tunnels as intra-fabric and inter-fabric tunnels, respectively, of the overlay tunnel fabric;
a forwarding logic block to receive a multicast control packet via the first tunnel; and
a control logic block to:
identify the second tunnel as the inter-fabric tunnel; and
forward the multicast control packet via the second tunnel using the forwarding logic block, wherein a respective multicast control packet received from the first tunnel is precluded from being forwarded on intra-fabric tunnels of the overlay tunnel fabric.