e media streams (e.g., audio and video), the RTCP is used to monitor transmission statistics and QoS information. When both protocols are used in conjunction, RTP is usually originated and received on even port numbers, whereas RTCP uses the next highest odd port number [6,7]. CHAPTER 5 The IEEE 802. 16m Convergence Sub-Layer 32 bits 32 bits Version Traffic Class Flow Label Source Port Destination Port Payload Length Next Header Hop Limit UDP Length UDP Checksum UDP Header Format 32 bits Source Address (128 bits) Sequence Number Timestamp Synchronization Source (SSRC) Identifier Contributing Source (CSRC) Identifiers (if mixers are used) Header Extension (optional) Destination Address (128 bits) RTP Header Format IPv6 Header Format FIGURE 5-2 IPv6, UDP, and RTP header formats header. This context is formed on the compressor and the decompressor side for each packet flow. The first few packets of a newly identified flow are used to build the context on both sides. These packets are sent without compression. The number of these first few packets, which are initially sent uncompressed, is closely related to link characteristics like bit error rate and round trip time. Once the context is established on both sides, the compressor compresses the payload headers as much as possible. By taking into account the link conditions and feedback from the decompressor, the compressed packet header sizes may vary. At certain intervals and in the case of error recovery, uncompressed packet headers are sent to reconstruct the context and revert back to normal operational mode, which is sending compressed packet headers. The header compression module is a part of the protocol stack on the devices. It is a feature which must be negotiated before it can be used on a link. Both end points must agree if they support header compression, and on the related parameters to be negotiated. Considering the end-to-end connectivity over IP, the header compression does not introduce any changes in the data payload when it compresses and decompres