hgs/sip2001 Conferencing 1 SIP Conferencing

Transcription

1 hgs/sip2001 onferencing 1 SIP onferencing Henning Schulzrinne ept. of omputer Science olumbia University New York, New York (sip:)schulzrinne@cs.columbia.edu onference International SIP Paris, France February 21, 2001 Joint work with Gautam Nair, Jonathan Rosenberg and Kundan Singh

2 hgs/sip2001 onferencing 2 Overview conferencing models full-mesh conferencing implementation of a conferencing server open issues

3 hgs/sip2001 onferencing 3 onference models: end system mixing

4 hgs/sip2001 onferencing 4 onference models: multicast transmit & receive May be suitable for small-scale multicast proposals ( xcast )

5 hgs/sip2001 onferencing 5 onference models: multicast receive, unicast transmit RTP translator

6 hgs/sip2001 onferencing 6 onference models: central server can be call-out or dial-in + + SIP + RTP

7 hgs/sip2001 onferencing 7 onference models: central server conference identified by SIP URL, e.g., sip2001@upperside.fr ad-hoc conferences useful for three-party calls can create ad-hoc conference by using random URL, e.g., sip:a7hytaskp09878a@a.servers.com,userefer to get others to add themselves to that conference for ad-hoc, conference lasts until last one leaves

8 hgs/sip2001 onferencing 8 onference models: decentralized entral signaling server, mesh media c= c= conference signaling server c=,, c=,,

9 hgs/sip2001 onferencing 9 onference models: full mesh 1 2 invites invites invites invites invites,

10 hgs/sip2001 onferencing 10 Full mesh +: all participants are equal +: easy to control media distribution need to deal with simultaneous call-outs of two parties departures while other party joins U and US send membership list in request and 200 if either learns about a new member, send INVITE allows joining of separated clouds departing member sends YE to everyone may need to refuse INVITEs from new arrivals (partitions!)

11 hgs/sip2001 onferencing 11 onference models: full mesh invites and invites simultaneously:,,,,,,,,,,,,,,,,,,,,,,,

12 hgs/sip2001 onferencing 12 Full mesh: open issues conference identification? how to identify that call legs are related (should be mixed) call-in for mesh? refresh mechanism to heal network partitions

13 hgs/sip2001 onferencing 13 onference models acomparison Name SIP media adding joining members scale End-Mixing tree tree normal normal RTP small INVITE INVITE Multicast pairs mcast normal mcast RTP large INVITE join ial-in star star REFER normal RTP medium INVITE d-hoc star star REFER normal RTP medium INVITE ial-out star star REFER normal RTP medium INVITE ecentral star mesh refer + normal RTP medium Mesh mesh mesh INVITE? SIP medium

14 hgs/sip2001 onferencing 14 onference models complexity M active senders, N participants O(M + N ) O(M + N ) O(1) O(M ) O(M ) O(1) O(M + N ) O(M ) O(1) O(M ) O(1) O(1) Properties central full mesh mcast uni rx, mcast tx end mixing Topology Star full mesh m-cast tree star + mcast tree ad-hoc Server proc. n/a n/a n/a Endpoint proc. variable Server bw n/a n/a n/a Endpoint bw variable Scaling medium medium large large medium Heterogen. U yes yes no no yes (partially) Own media? no no no yes no

15 hgs/sip2001 onferencing 15 olumbia sipconf conferencing server central-server model for mixing commodity hardware, easily scalable to rack full (conferences: avg. 5, 45 minute duration) mixes audio streams, replicates RTP (and UP) streams works for video and text chat (RF 2793)

16 hgs/sip2001 onferencing 16 Mixing heterogeneous streams Play out delay Periodic timer interrupt G.711 Mu Linear VI GSM Linear Linear X = + X = ++ X Mixed Linear Stream X E E E Send to G.711 Mu Send to VI Send to G.711 Mu E = udio Encoder = udio ecoder

17 hgs/sip2001 onferencing 17 Example: olumbia software conference server

18 hgs/sip2001 onferencing 18 Performance for single conference < < SPR Ultra 10 with 350 MHz PU: Participants PU memory bandwidth (Mb/s) (%) (M) inbound outbound

19 hgs/sip2001 onferencing 19 Performance for three-party conferences < < Good quality up to 15 conferences onfer- partici- PU memory bandwidth (Mb/s) ences pants (%) (M) inbound outbound

20 hgs/sip2001 onferencing 20 onclusion need many different models of conferencing trade-off infrastructure vs. complexity vs. scaling mostly, can be handled by existing SIP mechanisms full mesh requires further work transition between conferencing models?