Activities in the field of header compression
Center for TeleInFrastructure 2 ROHC working group RFC 3095 ROHC (Framework + RTP. UDP, ESP, uncompressed) RFC 3242: LLA profile - ”0 byte” RFC 3408: 0-byte for R-mode RFC 3241: ROHC over PPP RFC 3816: ROHC MIB RFC 3843: ROHC for IP RFC 3220: SigComp
Center for TeleInFrastructure 3 Link-layer Assisted ROHC (0-byte) Purpose is to efficiently match existing applications to existing link technologies Air interfaces, as GSM and IS-95, will be used in all-IP networks, but their radio bearers are optimized for specific payload size. Adding even 1 byte of ROHC header is costly Header-free packet format
Center for TeleInFrastructure 4 LLA ROHC Lower layers provide the necessary information Care should be taken of Packet type identifier Sequence number CRC 1 byte Smallest header in ROHC RTP Smallest header in LLA NHP (No Header Packet) Header field functionality provided by other means
Center for TeleInFrastructure 5 LLA ROHC Zero-byte operation for U/O modes (RFC 3242) Zero-byte operation for R-mode (RFC 3408) Periodic context verification is performed CSP (Context Synchronization Packet) contains only header information, no payload
Center for TeleInFrastructure 6 Interfaces towards the Assisting Layer ROHC RTP LLA profile Interface ROHC to AL Link technology ROHC RTP LLA profile Interface ROHC to AL Link technology channel
Center for TeleInFrastructure 7 Signaling Compression (SigComp) Motivation 3GPP R5 introduces IP Multimedia subsystem (IMS) that uses Session Initiation Protocol (SIP) for call signaling and session setup SIP is text-based. SIP message is from a few hundreds bytes up to two thousand bytes. On average 500 bytes For cellular networks large message size is problematic introduce delays Compression of signaling messages is desirable
Center for TeleInFrastructure 8 Signaling Compression (SigComp) SigComp RFC 3320 Requirements for Signaling Compression Efficient compression 1:8 – 1:15 Compress any text based protocol For bidirectional application protocol, the choice to use SigComp is independent in both directions Transport independent
Center for TeleInFrastructure 9 SigComp Architecture Local application Transport layer Compressor dispatcher Compressor dispatcher Decompressor dispatcher Decompressor dispatcher Compressor 1 Compressor 2 State handler State 1 State 2 Decompressor (UDVM) Decompressor (UDVM) SigComp layer SigComp message SigComp message Application message and Compartment identifier Compartment identifier Decompressed message