Extended header for use in ATM adaptation layer type 2 packets

摘要

A packet voice system includes an ATM Adaptation Layer Type 2 (AAL-2) and Service Specific Convergence Sublayer (SSCS) System comprising a transmitter and a receiver. A portion of the 32 codepoints of the five bit RES (or UUI) field of the AAL-2 header are predefined to indicate an extended header. This a prior definition is stored in tables in both the transmitter and the receiver. The extended header itself comprises an additional octet appended to the AAL-2 header. A sequence number is normally carried in the RES field for the packet stream of voice calls that require sequence numbers. When the extended header is used, the sequence number is part of the extended header and thus messages are conveyed from the transmitter to the receiver without causing an interruption to sequence number assignment messages The transmitter dynamically uses the extended header and discontinues use of the extended header after a predefined duration of time or upon receiving an acknowledgment from the receiver.