IP-Multicast and its Companions An Introduction

1. IP-Multicast and its Companions An Introduction How to solve the “many to many” communication problem? Peter Parnes LTU-CDT/Marratech AB Enator - 990416

2. Overview • Multicasting • MBone • Applications • Conferencing Tools - MBone and mPro • Protocols • MBone and the Internet • Usage • “Smörgåsbordet”

3. Many to Many • How to implement “many-to-many” traffic? 1. Central server: Have a central server that duplicates packets to all other members. 2. (Fully) connected mesh: Let every member have a connection to all/some other members. 3. Multicasting: Let the network duplicate the packet when needed. 1 and 2 wastes bandwidth!!!!

4. IP Addressing • The TCP/IP family includes four types of distribution of a packet from a single host: • Unicast: To one host • “Normal” IP-traffic • The packet is “seen” only by the receiving host • Broadcast: To all hosts on a network • When trying to find another host • The packet is seen by all hosts on the local network

5. IP Addressing • Anycast: To one host of a group of hosts • To access a resource that is served by several computers • IP6 • The packet is “seen” by one off the receiving hosts • Multicast: To a group of hosts • The packet is seen by all hosts in the group • The packet is only duplicated when needed

6. Multicast vs. Unicast

7. Multicasting • Multicast traffic uses a special range of IP-addresses: • 224.0.0.0 - 239.255.255.255 • A host much join a specific group to receive the traffic in that group but can send to a group without joining. • Membership is controlled by the IGMP protocol.

8. MBone? • The MBone is both a network-technology and a suite of tools. • The network part is today deployed as a virtual network on the Internet. Sites need to have special MBone-feeds. The setup is handled manually (but only once for each site) • The tools consists today primarily of conferencing tools but more is coming...

9. Applications • The MBone is today used for: • “Broadcasting”: conferences, meetings, seminars, concerts and radio-stations are multicasted daily. • Conferencing: The MBone is used for traditional video-conferencing (but MUCH cheaper!!) • News: Distribution of Usenet-News • M-FTP: Multi-user File Transfer

10. Applications Tomorrow • Applications tomorrow include: • Software-distribution: Forget the very costly procedure of new software CDs for each new release and bug-fix! Just supply the latest version in a known multicast-group. • Mirroring: Instead of letting each client fetch all new files from a server, send out the changed files using multicast!

11. Applications Tomorrow • Real News: All news is transmitted on the net. Indexed and ready. (Reuters have this since 1996!) • TV: Why not watch your favourite TV-channel over the network? • File-Caches: If all file-requests are issued using multicasting it’s much easier to cache them locally! • And much much much.......

12. Conferencing tools • The MBone tools today consists of: • SDR: The session directory, “the channel-guide” • WB: A distributed white-board (postscript and text) • VIC: A video-tool • VAT/RAT: Two audio-tools • Marratech Product Suite

13. The mPro Family • A family of tools for scalable distributed electronic teamwork. • It supports a number of different conferencing media: • audio/video • shared whiteboard, chatting, voting • Web based electronic presentations

14. The mFamily history • mStar was developed by CDT since 1995 (CDT created Jan-95) • Today about 30 persons • Was used in a number of different scenarios over the years • Marratech AB spring 98 • m* -> mStar -> mPro (mFamily) • mStar trademarked by Motorola

15. multicast Media Server: mMS • As all traffic is network and multicast based, it is very easy to record it. • mMS is another member of mFamily that support recording and later playback. • Web based control (work in progress)

16. multicast Tunnel: mTunnel • Some links do not support multicast • ISDN, analog modem • mTunnel allows for easy tunnelling of multicast traffic over non-multicast links. • It also allows for traffic transformation: • recoding, mixing, switching, scaling • This allows users to join into high bandwidth sessions even if they do not have the needed bandwidth.

17. mFamily Design Issues • Scalable: The environment should scale to a very large number of users - IP-Multicast is the solution! • Robust: The environment should survive network failures and not be dependent on any central services • Accessible: Users should be able to participate from their desktop • Network based: No need for any special ISDN connections, just the standard local network and the Internet.

18. Protocols MANY different protocols involved with Multicasting - UDP, RTP, SRM, MTP-2, MTCP • UDP: User Datagram Protocol • Unreliable == Packets can be lost • The applications has to take care of reliability

19. RTP RTP - Real-Time Transfer Protocol • Developed by the IETF (RFC1889/90) and later copied into ITU/H.225. • End-to-End transport functionality for real-time data • Designed for multicasting • Completely network layer independent

20. Reliable Multicasting • No standard today (IETF/ITU are not working on this problem although several other groups are) • Multicast Transport Protocol 2 - MTP2 • NACK based • Fanout TCP - MTCP • Star-topology with a TCP connection to each receiver

21. Reliable Multicast - SRRTP • Scalable Reliable Multicasting - SRM • NACK based - every member participates in repairs and not only the original sender of a packet • Originally used in the MBone WB • I have designed a RTP-extension to include SRM - SRRTP • This is today implemented and used in the mPro family.

22. More Protocols • Session Description Protocol - SDP • Session Announcement Protocol - SAP • Real-time Streaming Protocol - RTSP • Session Initiation Protocol - SIP • Receiver-based Layered Multicast - RLM • Plus many more….

23. MBone and the Internet • To simplify the development process of the MBone-network, it was first deployed as a virtual network using IP-tunnels • but is now changed into a standard IP-service == all routers need to know about multicasting • Multicasting is both an Internet and an Intranet technology

24. Usage Scenarios of the mFamily • Electronic Meetings • Meeting using your desktop computer • Distance Education • Distribution of lectures over the Internet where participants can ask questions and be active • Electronic Corridor • Daily work where users run the tools 24 hours a day

25. Usage Examples • Education Direct • Distribution of lectures to the county of Norrbotten • Ericsson Erisoft • Electronic meetings and teamwork between their offices and Ericsson in Stockholm and other countries • Daily work at CDT • mFamily is used for electronic meetings, the electronic corridor, multicast of seminars and courses

26. “Smörgåsbordet” • Mcast routing, real-time traffic, security, session announcement, session invitation, H.323, mcast address allocation, stream control, better service, codecs and media packetization, congestion control for multimedia • mManagement, mTunnel, scalable media, advanced audio • (The education scenario)

27. Questions? peppar@cdt.luth.se http://www.cdt.luth.se/~peppar/ http://www.cdt.luth.se/mStar/ http://www.marratech.com/

28. Multicasting and FireWalls • Political question NOT technical • There is nothing special about multicasting in comparison to other IP-traffic. There are four solutions to the FireWall problem: 1 Open the wall for all multicast-traffic. Simple and a router can control which networks within a company should have MBone access.

29. Multicasting and FireWalls 2 Set up a tunnel through the wall 3 Rent a dedicated line that isn’t connected to the rest of the companies network and is only used for Multicasting 4 Stay behind the rest and don’t use multicasting at all! :-)