Keep confederation-internal AS paths from leaking beyond the confederation

Use this document to resolve one bounded operational decision: Keep confederation-internal AS paths from leaking beyond the confederation. Only the official source and traced locations below supply facts. Confirm applicability before acting.

Source fact:

The official RFC 5065 — Autonomous System Confederations for BGP from RFC Editor / Internet Engineering Task Force supports the following bounded statements:

• A confederation member uses its confederation identifier with outside peers and its Member-AS number with peers inside the same confederation. The research record locates this support at Section 4 (Operation).
• Before advertising outside the confederation, a speaker must remove AS_CONFED_SEQUENCE and AS_CONFED_SET segments and prepend its confederation identifier under the external AS_PATH rules. The research record locates this support at Section 4.1 (AS_PATH Modification Rules), rule c.
• A speaker must not transmit confederation path segments to an outside peer, and receiving them from an outside neighbor is a malformed AS_PATH error. The research record locates this support at Section 5 (Error Handling).

These statements are the factual basis for this document. Do not extend them into a broader assurance. Review address plans, interfaces, routes, peers, protocol roles, timers, middleboxes, and intended failure domains only where the source and recorded environment align.

What the source does not establish

This RFC evidence supports only the named network-protocol decision; it does not select vendor settings, topology, capacity, or an acceptable failure mode. A correct source interpretation can still be inapplicable to a particular design. Confirm DNS, Active Directory authentication, PKI, time, routing policy, transport reachability, and monitoring, ownership, and change authority instead of treating documented behavior as a deployment guarantee.

Applicability questions

• For source statement 1 at Section 4 (Operation), which observable configuration, record, or test can confirm applicability here?
• For source statement 2 at Section 4.1 (AS_PATH Modification Rules), rule c, which observable configuration, record, or test can confirm applicability here?
• For source statement 3 at Section 5 (Error Handling), which observable configuration, record, or test can confirm applicability here?
• Within address plans, interfaces, routes, peers, protocol roles, timers, middleboxes, and intended failure domains, which versions, roles, and configuration states define the review population?
• Could DNS, Active Directory authentication, PKI, time, routing policy, transport reachability, and monitoring invalidate the test, hide a failure, or change applicability?
• Who owns the decision, and which observation requires stopping, escalation, or rollback?

DSE recommendation:

DSE recommends using the cited source as the evidence anchor for this decision. Start with applicability, then compare the observed state with the cited source. Record the source location, examined part of address plans, interfaces, routes, peers, protocol roles, timers, middleboxes, and intended failure domains, observed and expected states, owner, and reason for deviation.

Do not move from citation to production in one step. Pilot the decision where practical, observe agreed signals, retain a reversal point, and verify DNS, Active Directory authentication, PKI, time, routing policy, transport reachability, and monitoring. Handle credentials, keys, recovery data, and personal information through approved secure channels.

Verification and evidence

Evidence should let another reviewer reproduce this decision. Retain observations beside the traced locations Section 4 (Operation); Section 4.1 (AS_PATH Modification Rules), rule c; Section 5 (Error Handling). Favor configuration snapshots, route or neighbor state, packet captures, counters, topology records, and controlled failover results, linked to stable identifiers, time, and operator.

Record the decision even when no change is made, including uncertainty and the next trigger. Use safe testing conditions for disruptive work, preserve rollback proof, and revisit the conclusion after relevant platform, dependency, vendor, or ownership changes.

Official references

• RFC 5065 — Autonomous System Confederations for BGP — RFC Editor / Internet Engineering Task Force