SIP Federation

How it works

One connection, an eligibility decision, and a controlled media path.

The federation sits between members as a shared peering and policy boundary. It does not replace your existing carrier relationships — it handles the subset of traffic that is eligible for direct delivery between members.

Ordinary path versus federation path

The difference is not price. It is that both ends of an eligible session are known members operating under the same rules.

Ordinary path

Provider A→ Wholesale carrier(s)→ Provider B→ Customer
  1. The dialed destination is treated as ordinary PSTN traffic.
  2. One or more wholesale carriers sit between the two providers.
  3. The terminating provider has limited assurance about who originated the session.
  4. Operating rules differ at every hop.

Federation path

Provider A→ SIP Federation→ Provider B→ Customer
  1. The destination is identified as served by a participating member.
  2. The session crosses one authenticated federation interconnect.
  3. Both members are known, and both have agreed to the same operating rules.
  4. Federation policy is applied, and media is proxied where the deployment requires it.
ORDINARY PATH Provider A Wholesale carrier(s) Provider B Customer originating member one or more hops serving member FEDERATION PATH Provider A SIP Federation Provider B Customer route decision: is this eligible? eligibility directory member policy controlled media serving member registered destination Not eligible → stays on the provider’s ordinary route
The federation is a shared peering and policy boundary between members — not an anonymous termination vendor sitting in a least-cost stack.

The member flow

Five steps from joining to routing an eligible call.

  1. Join and connect once

    A provider joins the federation and establishes one authenticated federation connection. There is no separate bilateral setup per member.

  2. Register eligible destinations

    The member registers the customer destinations or identities it serves and agrees to receive through the federation. Registration is a statement about what you serve, not a published termination route.

  3. Check eligibility at call time

    Another member’s routing environment checks whether a dialed destination is eligible for federation delivery.

  4. Route eligible calls, leave the rest alone

    Eligible calls are routed to the federation. Every other call remains on the provider’s ordinary routes, untouched.

  5. Apply policy and control media

    The federation applies member policy and proxies media where the deployment requires it, producing usage records for both members.

What is routed

  • Sessions to destinations a member has registered and agreed to receive.
  • Traffic between providers that have both completed technical certification.
  • Traffic that meets the federation’s eligibility and fair-use rules.
  • Sessions where the originating member is identifiable and attributable.

What is not routed

  • General PSTN fallback termination. The federation is not a carrier of last resort.
  • Destinations no member has registered.
  • Traffic from providers outside the federation.
  • Anything a member’s own policy or the federation’s abuse rules exclude.

On language. Members do not publish termination routes. They register the customer destinations they serve and agree to receive through the federation — a distinction that matters for how eligibility, policy, and liability are handled.

Want the technical detail?

The technical brief covers the interconnect, the eligibility directory, routing-pattern options for different platform constraints, media handling, and the certification process.

Request the technical brief Apply to become a founding member