Summary

  • A 28 October individual Internet-Draft proposes a BGP extended community carrying a four-byte Router ID and a two-byte egress Group ID. The advertising router sets both; a supporting ingress router maps the remote group to one of its own ECMP subgroups.
  • The draft's diagram fixes the type octet at 0x83 and leaves the subtype TBD. IANA's current transitive-type registry reserves 0x83–0x8f for experimental use. The draft's IANA section does not explain a permanent type allocation.

A traffic plan with a borrowed badge

Ordinary per-flow ECMP hashes flows onto equal-cost links. A small number of enormous flows can land together and crowd one path. The Group ID draft names AI training networks as its target: a handful of heavy flows can hash onto the same link and leave equal-cost capacity idle. Sending packets individually across paths would add a different headache: reordering. The companion enhanced-ECMP draft proposes dividing an ingress router's outgoing links into local subgroups, then hashing within the selected subgroup. Its link counts are an example, not a performance result.

The new Group ID draft provides the route-carried hint for that arrangement. An egress device advertises a route with its own Router ID and locally assigned group index. At the other end, an ingress device reads the index and decides which of its local subgroups should handle flows to that destination. One party names a remote group; another controls the actual local lanes. The badge is an input to a local forwarding decision, not proof of where packets went.

The proposed eight-byte extended community has one more authority problem. Its first octet is shown as 0x83. IANA's public registry marks that entire high-order type range experimental. The document asks for a GroupID subtype, still TBD, under a newly named transitive registry, but it gives no path from the experimental type in its diagram to a lasting allocation. An experimental value can serve a trial; a standard intended for shared interpretation needs its registered identity settled.

The IETF status page calls this an individual Internet-Draft, not adopted IDR work. A router without the enhanced mechanism may ignore the new community and run normal ECMP. The security section is also TBD. No measured cluster gain, interoperation result or deployed use of 0x83 appears in these records. A revised type/subtype request and a two-router trace showing the received badge, local mapping and resulting link choice would change the operating case. Until then, the route label has a job description and an experimental visitor pass.

Sources: Group ID draft; enhanced ECMP draft; IETF status; IANA BGP registry.