PBB-EVPN MAC Learning via BGP Control Messages
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Solution Overview
Problem
In PBB-EVPN networks, asymmetric MAC learning leads to inefficiencies and resource wastage due to unnecessary Broadcast, Unknown Unicast, and Multicast (BUM) traffic flooding, especially in multi-homed configurations where remote PE routers do not learn C-MAC addresses, resulting in inefficient network resource utilization.
Innovation Solution
A method where a PE router in an Ethernet segment sends an extended community for a B-MAC route via BGP to inform remote PE routers about the reachability of C-MAC addresses, allowing them to learn and forward unicast traffic instead of BUM traffic, thereby reducing flooding and optimizing resource use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If remote PE routers perform data-plane learning for C-MAC addresses in PBB-EVPN, then MAC address visibility is improved, but unnecessary BUM traffic flooding increases due to asymmetric learning
Solution Approach 1:
The patent applies preliminary action by having the local PE router proactively send L2 control messages containing C-MAC addresses to remote PE routers before BUM traffic flooding occurs. This pre-population of MAC address information in remote PE routers' routing tables prevents the need for subsequent flooding, as remote routers can directly forward traffic using the pre-learned addresses.
Solution Approach 2:
The patent uses L2 control messages as an intermediary mechanism to transfer C-MAC address information from the local PE router to remote PE routers. This control plane communication serves as a mediator that enables remote routers to learn MAC addresses without requiring data-plane flooding, thus resolving the contradiction between address visibility and resource utilization.
2Loss of information
If all PE routers store all C-MAC addresses in EVPN, then complete MAC address information is available, but PE router memory resources are wasted
Solution Approach 1:
The patent applies local quality by enabling each PE router to selectively store and process C-MAC addresses relevant to its specific forwarding needs. Remote PE routers receive and store only the C-MAC addresses of interest through L2 control messages, rather than maintaining complete MAC address tables of all connected devices. This selective approach optimizes memory utilization while preserving necessary forwarding information.
3Quantity of substance
If remote PE routers do not learn C-MAC addresses, then memory resources are saved, but BUM traffic flooding increases due to unknown unicast forwarding
Solution Approach 1:
The patent resolves this contradiction by performing preliminary action where the local PE router sends L2 control messages to remote PE routers to pre-populate their routing tables with C-MAC addresses before traffic forwarding begins. This allows remote routers to have just enough MAC address information to avoid flooding, optimizing both memory usage and network efficiency simultaneously.
Solution Approach 2:
The system implements feedback through BGP route advertisements that carry C-MAC address information from local to remote PE routers. This feedback mechanism ensures that remote routers receive updated MAC address information dynamically, allowing them to make informed forwarding decisions without storing excessive address data, thus balancing memory resources and network efficiency.
Data Source
AI summary
In one example, a method includes performing L2 learning of a C-MAC address included in a first L2 data message by a first provider edge (PE) router included in an Ethernet Segment of a Provider-Backbone Bridging Ethernet Virtual Private Network (PBB-EVPN); sending to a second PE router within the Ethernet Segment an L2 control message comprising the C-MAC address and a B-MAC address corresponding to the Ethernet Segment of the PBB-EVPN, wherein the L2 control message informs the second PE router of the reachability of the C-MAC address through the first PE router; receiving, by the first PE router and from the second PE router, a second L2 data message as unicast traffic destined for the C-MAC address; and forwarding the second L2 data message to the first CE router.