1 MASH: A Multimedia Architecture that Scales Across Heterogeneous Environments Steven McCanne, Randy H. Katz, Eric Brewer Computer Science Division University of California, Berkeley Berkeley, CA ©

2 The Challenge: Heterogeneous Collaboration Environments 326 Soda UC-Net / UC-MBone CAIRN UCLA UCB PARC LBL MIT DARPA NIMA ISDN Internet (MBone) UCL T1 OC-3c POTS ISDN Pen-Based PCs Collaboration q in the face of heterogeneity q at large scale

3 Approach Build on q MBone Tools q LWS q BARWAN Proxies Create core mash software system q reusable, scripted components q Web-based “platform”

4 Problem Existing Media Tools q Monolithic and non- integrated q No building blocks exist for composing new tools

5 Solution Media “components” q vic, vat, wb abstracted into media processors q shared, “pluggable” user interface The MASH Toolkit q leverage Ousterhout’s vision for Tk (USENIX ‘91): –build large, complex apps by composing small tools –glue together tools with Tk send primitive –we simply replace Tk send with Coordination Bus

6 MASH Toolkit Enhanced Tennenhouse’s VuSystem with “split objects”: Object implementation split across compiled/scripting languages Command/callback API replaced by “seamless” method Sink Filter Source Data Methods Data Otcl Obj C++ OTcl

7 The MASH Platform Beyond a simple toolkit... q MASH as a “platform” q MASH + browser = platform

8 The MASH Platform (cont’d) Monolithic model q configure browser to launch MASH app for an SDP announcement –i.e., MIME type x-sd Platform model q configure browser to launch MASH interpreter (or plug- in) for mashlet (MASH script) –i.e., MIME type x-mash/x-script

9 NASA Server NASA Server SDP URL Launch Tools Example: Monolithic Model

10 Example: Monolithic Model UCB Server UCB Server SDP URL Launch Tools

11 UCB Server UCB Server mashlet Launch Interpreter Tailored for CSCW Class! Example: Platform Model

12 UCB Server UCB Server mashlet Hand to Plugin mashlet MARS Server MARS Server RTSP Example: Platform Model

13 Research Directions MASH Platform Scalable Reliable Multicast (SRM) Large User Community Scalable Multicast Protocols Protocol Scalability & Heterogeneity Problems Useful Collab Tools (web) Media Gateways Layered Video Novel Coding Schemes Coordination Protocols

14 MASH Colab Remote participants Local Participants

15 Research Directions MASH Platform Scalable Reliable Multicast (SRM) Large User Community Scalable Multicast Protocols Protocol Scalability & Heterogeneity Problems Useful Collab Tools (web) Media Gateways Layered Video Novel Coding Schemes Coordination Protocols

16 Heterogeneous Multimedia Communication Offices Cafe Nefelli Cafe Nefelli Home Seminar Room Seminar Room Metricom MBone ISDN Campus Backbone 100Mb/s 128kb/s 30kb/s64kb/s

17 The Problem Offices Cafe Nefelli Cafe Nefelli Home Seminar Room Seminar Room Metricom MBone ISDN Campus Backbone 1Mb/s 100Mb/s 128kb/s 30kb/s64kb/s

18 The Problem Offices Cafe Nefelli Cafe Nefelli Home Seminar Room Seminar Room Metricom MBone ISDN Campus Backbone 1Mb/s 100Mb/s 128kb/s 30kb/s64kb/s

19 The Problem Offices Cafe Nefelli Cafe Nefelli Home Seminar Room Seminar Room Metricom MBone ISDN Campus Backbone 30kb/s 100Mb/s 128kb/s 30kb/s64kb/s

20 The Problem Offices Cafe Nefelli Cafe Nefelli Home Seminar Room Seminar Room Metricom MBone ISDN Campus Backbone 100Mb/s 128kb/s 30kb/s64kb/s 30kb/s

21 An “End to End” Solution Can we avoid changing the net? Layered media + layered transmission layered codec layered codec video +++

22 The Problem Offices Cafe Nefelli Cafe Nefelli Home Seminar Room Seminar Room Metricom MBone ISDN Campus Backbone 1Mb/s 100Mb/s 128kb/s 30kb/s64kb/s

23 Layered Transmission Offices Cafe Nefelli Cafe Nefelli Home Seminar Room Seminar Room Metricom MBone ISDN Campus Backbone

24 Problems with Layered Model Format conversion Local application of FEC Multicast (un)availability Fundamental issues: semantically q decisions at source not semantically scalable across heterogeneous receivers q It’s not just a bandwidth problem...

25 Research Directions MASH Platform Scalable Reliable Multicast (SRM) Large User Community Scalable Multicast Protocols Protocol Scalability & Heterogeneity Problems Useful Collab Tools (web) Media Gateways Layered Video Novel Coding Schemes Coordination Protocols

26 Solution: Media Gateways Mitigate bandwidth heterogeneity with explicit computation inside the network q Fine-grain control over bandwidth allocation –transcoding lifts restriction of layered granularity q Format conversion –gateway can convert to any form you’d like q Provisions for backward compatibility –bridge multicast islands with unicast “tunnels”

27 LocallyCustomizedControl GWGW GWGW Solution: Media Gateways S S R1R1 R1R1 R2R2 R2R2 R3R3 R3R3 128kb/s 1.5Mb/s 10Mb/s 10Mb/s 10Mb/s

28 “MeGa” Specialization of AS1 for media gateways q AS1/MeGa implemented and deployed on NOW q Video, audio, whiteboard, and SDP q Used regularly at UCB for home ISDN, low bandwidth wireless MBone connectivity, CSCW course participation. MBONE GWGW GWGW GWGW ISDN Berkeley NOW HomeUsers

29 Active Services Leave IP service model alone q Preserve its scalability, robustness Move “activation” from network- to application- layer q Don’t reprogram the routers! services q Instead program services within the network q Adequate for many applications (e.g., transcoders)

30 Active Services Umbrella Media gateways Reliable Multicast Proxies Archival as an active service q MBone transcoding service q Demo: Yatin Chawathe & Angie Schuett

31

32

33 Publications System building yields concrete contributions: q Four papers in ACM MM98! –including Best Student Paper (Swan) q INFOCOMM-98 q SIGCOMM-98 q NOSSDAV-98 q SIGMETRICS-98 q Half dozen or so more in the pipeline...