Layer2 Bridge support in Multi POP Deployments
This feature is available from Release 1.0.1 onwards.
This feature is applicable to Layer 2 bridging and when Deterministic Prefix Allocation (DPA) is configured on the e2e controller.
In terragraph network, CNs and DNs are allocated prefixes from a seed prefix. There are various way of prefix allocation. In DPA, controller assigns prefixes to nodes based on the network topology to allow POP nodes to take advantage of route summarization and help load balance ingress traffic.
CNs & DNs see multiple POP node in mesh, they select POP to form GRE tunnel, by matching there lo ipv6 address with POPs lo ipv6 address. The longest prefix match is selected as best POP for L2 GRE Tunnel establishment.
Multi-POP setup gives the advantage that user data traffic can take alternate routes if the best route is unavailable for some reason. Open/R make this selection to route the traffic.
If due to some reason best pop is unavailable, CNs & DNs switch to next best POP. They however keep track of their primary POP availability and switch to it once it become online