 packet payload. The CIP packet header format includes Context ID (CID) which is to identify the user connection, payload length which indicates the length of one CIP packet payload, and the sequence number which is used to reassemble the segmented packets. The LIPE packet format is given in Figure A.11. Each LIPE packet consists of Multimedia Data Packets (MDP) and their Multiplexing Header (MH). The basic approach of various packets are multiplexed into one UDP/IP packet is similar to CIP scheme. A major difference CIP and LIPE is the header length. CIP has the fixed CIP header length of 4 bytes, while LIPE allows an extension of the MH header, which can vary between 2 and 3 bytes. Even using the extension of the MH header, LIPE still need 1 byte less for the container overhead. In the multiplexing case, the connection identifier cannot be set in the UDP header using the UDP port because in this case several users share the same UDP header, SO we can use the flow ID field in the CIP/LIPE header to identify the user connection. FP PDU FP PDU Header Header Header CIP Payload Header CIP Payload Header CIP Payload CIP Container reserved segmentation payload length sequence number 3 bits 1 bit 1 bit 11 bits 8 bits 1 bit 7 bits Figure A.10: CIP packet format CIP and LIPE are optional multiplexing schemes for the IP-based UTRAN. Both CIP and LIPE are the multiplexing schemes above layer 3, i.e. between FP and UDP/IP. The multiplexing rule is based on the maximum UDP packet size and the multiplexing timer. The multiplexed packet is only sent out if the maximum size of the packet is reached or the multiplexing timer expires. In order to support multiple services with their QoS requirements, different multiplexers can be implemented to support each QoS class. The 3GPP TR 25.933 [3GP04a] defines three basic types of QoS for multiplexers. The first is voice, which has the most stringent delay requirement, the second is delay sensitive data, which has certain delay requirement less than voice, and the last one is the delay 