1. 1 Extensions to CRTP RTP Multiplexing using Tunnels Bruce Thompson Tmima Koren Cisco Systems Inc

2. 2 Status RTP Multiplexing using TunnelsRTP Multiplexing using Tunnels –draft-wing-avt-tcrtp-00.txt –Submitted in Oslo –Broken into distinct parts: IP Tunneling, PPP Multiplexing, CRTP enhancementsIP Tunneling, PPP Multiplexing, CRTP enhancements –Draft to be updated to reflect changes Extensions to CRTPExtensions to CRTP –draft-koren-avt-crtp-enhance-00.txt –Three enhancements to RFC 2508 –Can be considered separately

3. 3 COMPRESSED_UDP "T bit” Currently only the I bit may be setCurrently only the I bit may be set A COMPRESSED_UDP packet that includes the deltaT can fully restore the state at the decompressorA COMPRESSED_UDP packet that includes the deltaT can fully restore the state at the decompressor No need to include the deltaT in the following COMPRESSED_RTP packetNo need to include the deltaT in the following COMPRESSED_RTP packet Used for decompressor state refresh without CONTEXT_STATEUsed for decompressor state refresh without CONTEXT_STATE

4. 4 COMPRESSED_UDP packet format lsb of context ID UDP Checksum “RANDOM” fields Delta IPv4 ID UDP data (uncompressed RTP header) CRTP seq # I000 lsb of context ID UDP Checksum “RANDOM” fields Delta IPv4 ID UDP data (uncompressed RTP header) delta RTP timestamp CRTP seq # I00T msb of context ID

5. 5 NON-RTP stream flag Notifies the decompressor that this stream is not an RTP streamNotifies the decompressor that this stream is not an RTP stream Decompressor can enter flow in negative cache without RTP compression attemptsDecompressor can enter flow in negative cache without RTP compression attempts Less CID thrashingLess CID thrashing Useful for application nodes where compressor has hints from application layer.Useful for application nodes where compressor has hints from application layer.

6. 6 NON-RTP stream flag in the FULL_HEADER packet CID 0 Generation 01 U New FULL_HEADER length fields format: For 8-bit context ID: For 16-bit context ID: Seq # CID Generation 11U 0 Set U = 1 to indicate a non-RTP stream

7. 7 Rejecting a new compressed stream Decompressor implementations may share resources across multiple linksDecompressor implementations may share resources across multiple links Decompressor may over commit decompression resources in RFC 2509 negotiationDecompressor may over commit decompression resources in RFC 2509 negotiation Decompressor may REJECT a compressed steam when out of resourcesDecompressor may REJECT a compressed steam when out of resources

8. 8 session context ID Reject packet (Using CONTEXT_STATE opcode ) context count CRTP seq# 0110 1 =Reject 8-bit CID session context ID generation 00 context count CRTP seq # 0110 2 =Reject 16-bit CID generation 00 CID, CRTP sequence# and generation are taken from the FULL_HEADER

9. 9 Tunneled CRTP Encapsulation for end to end multiplexing Consists of: Compression - RFC 2508 Multiplexing - PPP layer multiplexing IP tunneling for PPP - L2TP CRTP negotiation - RFC 2509 Application runs with RTP encapsulation CRTP, multiplexing at layer 2 Tunnel adds destination IP header

10. 10 Compression CRTP - RFC2508CRTP - RFC2508 –Compressed UDP T-bit extension Allows drops in tunnel without CONTEXT_STATEAllows drops in tunnel without CONTEXT_STATE draft-koren-avt-crtp-enhance-00.txtdraft-koren-avt-crtp-enhance-00.txt –Multiplexed sessions don’t share context CRTP sessions can be distributedCRTP sessions can be distributed

11. 11 Multiplexing PPP MultiplexingPPP Multiplexing –draft-ietf-pppext-pppmux-00.txt –New payload type for multiplexed payloads Payload Length 1 Byte Payload Type 1-2 Byte PayloadLength 1 Byte Payload Type 0-2 Byte Payload Type MUXED_PPP_FRAME 1-2 Byte

12. 12 Tunneling Efficient tunnel header requiredEfficient tunnel header required L2TP with Header Compression (L2TPHC)L2TP with Header Compression (L2TPHC) –draft-ietf-l2tpext-l2tphc-03.txt –Removes session ID, tunnel ID from L2TP –Removes UDP header Negotiated IP protocol IDNegotiated IP protocol ID Other tunneling encapsulations possibleOther tunneling encapsulations possible L2TPHC encapsulation: 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 +---+---+-+-+---+---+---+-+-+-+-+-+-+-+-+-+-+-+ |T=0|L=0|x|x|S=0|I=0|O=0|P| PPP packet... +---+---+-+-+---+---+---+-+-+-+-+-+-+-+-+-+-+-+

13. 13 Tunneled CRTP Encapsulation PPP 1 Byte VOIP G.729A, AAL-5, IP, Tunneled CRTP, 1 Audio Sample / 1 Cell Payload Cell Header 5 Bytes AAL-5 Trailer 8 Bytes PAD AAL-5 Voice Payload 10 bytes CRTP 2 Bytes L2TP 1 Byte IP (L2TP payload type) 20 Bytes PPP Mux 1 Byte Length 1 Byte 4 Bytes IP HDLC 20 Bytes VOIP G.729A, HDLC, IP, Tunneled CRTP, 3 Audio Samples / Packet RTP G.729a, 10 bytes 4 Bytes Voice Payload G.729a, 10 bytes PPP/ CRTP 3 Bytes Voice Payload PPP/ CRTP Voice Payload PPP/ CRTP 4 BytesG.729a, 10 bytes CRC 4 Bytes L2TP/ PPP Mux 2 Bytes

14. 14 TCRTP vs. RTP / CRTP Bandwidth 10 msec packetization