IP-Multicast and its Companions

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

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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!

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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 its 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 -gt mStar -gt 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

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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

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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_at_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.

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Multicasting and FireWalls

• 2 Set up a tunnel through the wall
• 3 Rent a dedicated line that isnt connected to
  the rest of the companies network and is only
  used for Multicasting
• 4 Stay behind the rest and dont use multicasting
  at all! -)