mes seek to reduce the overhead to payload ratio by including multiple payloads within the same IP packet. 3GPP TR 25.933 [3GP04a] and [MWIF01] propose several multiplexing schemes for the IP-based UTRAN with different protocol stacks. The four main proposed schemes are briefly described below. Their corresponding protocol stacks are shown in Figure 2.2. Composite IP (CIP), originally proposed by Alcatel, adopts the aggregation of small packets into one IP packet and the segmentation of large packets into smaller chunks in order to keep transmission delays low and avoid blocking of small time-critical packets by large packets. Several CIP packets are transported into one UDP/IP packet. 2) Lightweight IP Encapsulation (LIPE), proposed as a draft document at the IETF Audio/Video Transport working group, multiplexes various packets of low bit rate in one UDP/IP packet. 3) AAL2 over IP, proposes to apply AAL2 user plane protocol over UDP/IP to achieve multiplexing. The protocol stack is then AAL2/UDP/IP. This solution has the 2 UMTS Evolution advantages of simplifying interoperability between IP and AAL2/ATM nodes and reusing already existing fragmentation and multiplexing standards. 4) Multiplexing with Point-to-Point Protocol (PPP): PPP Multiplexing (PPPmux), proposed by RFC 3153, provides a method to reduce the PPP framing overhead used to transport small packets, e.g. voice frames, over slow links. PPPmux sends multiple PPP encapsulated packets in a single PPP frame. As a result, the PPP overhead per packet is reduced. When combined with a link layer protocol, such as High Level Link Control (HDLC), this offers an efficient transport for point-to-point links. In the above proposed multiplexing schemes, PPPMux is a Layer 2 multiplexing proposal, where the multiplexing gain is mainly achieved from multiplexing multiple PPP frames (each PPP frame encapsulates one IP packet) into a single PPP multiplexed frame. While LIPE and CIP are two proposals that apply multiplexing above Layer 3. They propose to create containe