Abstract: A method and apparatus in a gateway node of a telecommunications network for receiving frames from a source node such as a Radio Network Controller (RNC) and forwarding the frames with correct sequencing and timing to a destination node in an IP Multimedia Subsystem (IMS) network. Upon determining that a potential or actual discontinuity in frame numbering has occurred, the apparatus sends a discontinuity indication toward the destination node. The indication may be included in the first frame subsequent to the discontinuity. The destination node is thus made aware that the frame numbering may not be reliable.