Cisco Systems The Session Description Protocol (SDP) supports grouping media lines. SDP also has semantics defined for grouping the associated source and Forward Error Correction (FEC)-based repair flows. However, the semantics that were defined in RFC 4756 generally fail to provide the specific grouping relationships between the source and repair flows when there are more than one source and/or repair flows in the same group. Furthermore, the existing semantics also do not support additive repair flows and prioritization among the repair flows protecting one or more source flows. This document addresses these issues by introducing new FEC grouping semantics.