17. IAB Considerations

The IAB has studied the problem of Unilateral Self-Address Fixing (UNSAF), which is the general process by which a client attempts to determine its address in another realm on the other side of a NAT through a collaborative protocol reflection mechanism (RFC 3424 [RFC3424]). STUN can be used to perform this function using the Binding request/response transaction if one agent is behind a NAT and the other agent is on the public side of the NAT.

The IAB has mandated that protocols developed for this purpose document a specific set of considerations. Since some STUN usages provide UNSAF functions (such as ICE [MMUSIC-ICE]) and others do not (such as SIP Outbound [SIP-OUTBOUND]), the answers to these considerations need to be addressed by the usage itself.