scope:

This Recommendation focuses on the required functions and procedures necessary for support of narrow-band voice services by MPLS networks. ITU-T Rec. Y.1261 [1] describes the service requirements and architecture for transport of voice services over MPLS networks.

Narrow-band voice services include encoded audio streams, telephony call progress tones, fax, and optionally circuit mode data.

This Recommendation specifies encapsulation of encoded audio in MPLS packets. Algorithms for encoding audio streams are beyond the scope of this Recommendation.

This Recommendation includes three modes:

• voice over IP over MPLS;

• voice over MPLS using AAL type 2 SSCS [2] and [3] for narrow-band services; and

• voice over MPLS using MPLS Forum IA 1.0 [4].