3GPP TSG-RAN Working Group 3 Meeting #12Oahu, Hawaii, 22 – 26 May 2000TSGR3#13(00)1326Agenda Item:27bSource:MotorolaTitle:IP-based Iub/Iur User Plane Protocols for R'00Document for:Discussion_________________________________________________________________________________________1IntroductionThe R99 User Plane requires ATM/AAL2 for transporting user traffic on both the Iur and Iubinterfaces. This contribution proposes that for R00 IP transport be introduced as an alternativeto carrying user plane traffic directly over the ATM Layer 2. An objective is to be Layer 2protocol independent, i.e., the standard should optionally allow various Layer 2 protocols inaddition to ATM, which indicates that the transport protocols should be Layer 3 oriented. Thisstudy shows that certain IP based transport protocol alternatives can perform as well as, orbetter than ATM/AAL2 based protocols. In deciding which transport alternatives to choose, the following criteria are considered:Layer 2 should offer services of multiple LAN/WAN technologies and be transparent tothe application layers above.Transport protocols should be Layer 3 (i.e., IP) oriented.An IP over ATM stack option should be included to enable transport infrastructure reuse in transition from ATM oriented protocols.Overhead per user should be minimized, and hence, efficiency should be maximized.Delay and jitter constraints imposed by interface standards must be demonstrably achieveable.QoS services and parametrics must be defined and originate at Layer 3. Support of Layer 3 QoS must be provided by all acceptable Layer 2 services.Options for transporting over point-to-point links, as well as routed networks should beconsidered. (If possible, these two schemes should be "compatible".)2Protocol Stack OptionsHere we explore some possible protocol stacks that may satisfy the objectives above. Ingeneral it is proposed to transport user plane traffic for both the Iub and Iur using IP/UDP asthe layer 3/4 protocols. Different layer 2 protocols may be used in a transparent manner. It isapparent that some type of header compression and multiplexing scheme is required in orderfor IP/UDP to perform efficiently over Iur/Iub interfaces. Two multiplexing alternatives arepresented for use with different layer 2 options.1
2.1PPP Multiplexing SchemesOne possible protocol stack is to use standard HDLC/PPP ,  to carry individual userpackets with compressed IP/UDP headers ,  (see Figure 3.). This is suitable for point-to-point links such as those for the Iub interface. One drawback of this scheme is that there is asizeable (7 bytes) overhead for each user.A standards track IETF draft  proposes to share some of this overhead by multiplexingseveral users within a PPP frame. This reduces the per user overhead to 4 bytes (see Figure 4.),plus 5 bytes which are “amortized” over all the users in the frame. This option is not intendedfor WAN-like routed interfaces such as Iur.
- Spring '13
- Asynchronous Transfer Mode, Internet Protocol Suite, Point-to-Point Protocol