Efficient multicast traffic forwarding in EVPN-based multi-homed networks
Embodiments of the present disclosure relate to assisting forwarding of multicast traffic over Ethernet Virtual Private Network (EVPN) from a multicast source to a host multi-homed to multiple provider edge (PE) devices. Embodiments are based on the inclusion of an Ethernet Segment Identification (ESI) to EVPN type-6 routes advertised by PE devices which received a multicast Join message. Other PE devices receiving such routes are able to determine whether they belong to the ES identified by the ESI and to determine whether they are designated forwarders (DFs) for the host. Furthermore, PE devices which are the DFs are configured to re-originate the EVPN type-6 routes, i.e. re-send the advertisements, indicating themselves as DFs. This ensures that a remote PE device associated with the multicast source will also send multicast traffic to such DF PE devices, which, in turn, would allow the multicast traffic to successfully reach the host.
1. A method for assisting forwarding of multicast traffic over an Ethernet Virtual Private Network (EVPN) fabric from a multicast source to a host device multi-homed to a plurality of provider edge devices, the method comprising:
obtaining, at a provider edge device elected, out of the plurality of provider edge devices, to be a designated forwarder provider edge device for the host device, a first route advertisement message;
determining, by the designated forwarder provider edge device, that the route advertisement message includes an Ethernet Segment-Import Route Target;
determining, by the designated forwarder provider edge device, that the Ethernet Segment-Import Route Target matches an Ethernet Segment Identification for an Ethernet communication link between the host device and the designated forwarder provider edge device; and
providing, by the designated forwarder provider edge device, a second route advertisement message, wherein the second route advertisement message includes the Ethernet Segment-Import Route Target and an EVPN Instance Route Target.
2. The method of claim 1 , wherein the first route advertisement message is a Selective Multicast Ethernet Tag route message of the Border Gateway Protocol.
3. The method of claim 2 , further comprising:
after determining that the Ethernet Segment-Import Route Target matches an Ethernet Segment Identification for an Ethernet communication link between the host device and the designated forwarder provider edge device, adding data contained in the Ethernet Segment-Import Route Target to an Internet Group Management Protocol synchronization listing of the designated forwarder provider edge device.
4. The method of claim 3 , further comprising:
when the designated forwarder provider edge device is no longer elected to be the designated forwarder for the host device, withdrawing routes included in the second route advertisement message, based on the Internet Group Management Protocol synchronization listing.
5. The method of claim 3 , further comprising:
receiving the multicast traffic for the host device; and
forwarding the multicast traffic to the host device based on the Internet Group Management Protocol synchronization listing.
6. The method of claim 2 , wherein when the route advertisement message includes an EVPN Instance Route Target, the method further comprises the designated forwarder provider edge device accepting a route specified by the EVPN Instance Route Target.
7. The method of claim 6 , wherein the EVPN Instance Route Target is a Route-Import Route Target based on a Virtual Network Instance or a Route-Import Route Target based on Multi-Protocol Label Switching.
8. A system for assisting forwarding of multicast traffic over an Ethernet Virtual Private Network (EVPN) fabric from a multicast source to a host device multi-homed to a plurality of provider edge devices, the system comprising:
at least one memory element configured to store computer executable instructions, and
at least one processor coupled to the at least one memory element and configured, when executing the instructions, to:
obtain, at a provider edge device elected, out of the plurality of provider edge devices, to be a designated forwarder provider edge device for the host device, a first route advertisement message;
determine, by the designated forwarder provider edge device, that the route advertisement message includes an Ethernet Segment-Import Route Target;
determine, by the designated forwarder provider edge device, that the Ethernet Segment-Import Route Target matches an Ethernet Segment Identification for an Ethernet communication link between the host device and the designated forwarder provider edge device; and
provide, by the designated forwarder provider edge device, a second route advertisement message, wherein the second route advertisement message includes the Ethernet Segment-Import Route Target and an EVPN Instance Route Target.
9. The system of claim 8 , wherein the first route advertisement message is a Selective Multicast Ethernet Tag route message of the Border Gateway Protocol.
10. The system of claim 9 , wherein the processor is configured to:
after determining that the Ethernet Segment-Import Route Target matches an Ethernet Segment Identification for an Ethernet communication link between the host device and the designated forwarder provider edge device, add data contained in the Ethernet Segment-Import Route Target to an Internet Group Management Protocol synchronization listing of the designated forwarder provider edge device.
11. The system of claim 10 , wherein the processor is configured to:
when the designated forwarder provider edge device is no longer elected to be the designated forwarder for the host device, withdraw routes included in the second route advertisement message, based on the Internet Group Management Protocol synchronization listing.
12. The system of claim 10 , wherein the processor is configured to:
receive the multicast traffic for the host device; and
forward the multicast traffic to the host device based on the Internet Group Management Protocol synchronization listing.
13. The system of claim 9 , wherein when the route advertisement message includes an EVPN Instance Route Target, the processor is configured to accept a route specified by the EVPN Instance Route Target.
14. The system of claim 13 , wherein the EVPN Instance Route Target is a Route-Import Route Target based on a Virtual Network Instance or a Route-Import Route Target based on Multi-Protocol Label Switching.
15. One or more non-transitory computer-readable storage media encoded with software comprising computer executable instructions for forwarding of multicast traffic over an Ethernet Virtual Private Network (EVPN) fabric from a multicast source to a host device multi-homed to a plurality of provider edge devices, the instructions when executed by a processor cause the processor to:
obtain, at a provider edge device elected, out of the plurality of provider edge devices, to be a designated forwarder provider edge device for the host device, a first route advertisement message;
determine, by the designated forwarder provider edge device, that the route advertisement message includes an Ethernet Segment-Import Route Target;
determine, by the designated forwarder provider edge device, that the Ethernet Segment-Import Route Target matches an Ethernet Segment Identification for an Ethernet communication link between the host device and the designated forwarder provider edge device; and
provide, by the designated forwarder provider edge device, a second route advertisement message, wherein the second route advertisement message includes the Ethernet Segment-Import Route Target and an EVPN Instance Route Target.
16. The one or more non-transitory computer-readable storage media of claim 15 , wherein the first route advertisement message is a Selective Multicast Ethernet Tag route message of the Border Gateway Protocol.
17. The one or more non-transitory computer-readable storage media of claim 16 , wherein the instructions cause the processor to:
after determining that the Ethernet Segment-Import Route Target matches an Ethernet Segment Identification for an Ethernet communication link between the host device and the designated forwarder provider edge device, add data contained in the Ethernet Segment-Import Route Target to an Internet Group Management Protocol synchronization listing of the designated forwarder provider edge device.
18. The one or more non-transitory computer-readable storage media of claim 17 , wherein the instructions cause the processor to:
when the designated forwarder provider edge device is no longer elected to be the designated forwarder for the host device, withdraw routes included in the second route advertisement message, based on the Internet Group Management Protocol synchronization listing.
19. The one or more non-transitory computer-readable storage media of claim 17 , wherein the instructions cause the processor to:
receive the multicast traffic for the host device; and
forward the multicast traffic to the host device based on the Internet Group Management Protocol synchronization listing.
20. The one or more non-transitory computer-readable storage media of claim 15 , wherein when the route advertisement message includes an EVPN Instance Route Target, wherein the instructions cause the processor to accept a route specified by the EVPN Instance Route Target.