Transcript IP-Multicast and its Companions An Introduction communication problem?

IP-Multicast and its Companions
An Introduction
How to solve the “many to many”
communication problem?
Peter Parnes
LTU-CDT/Marratech AB
Enator - 990416
Peter Parnes, Marratech/CDT
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Overview
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Multicasting
MBone
Applications
Conferencing Tools - MBone and mPro
Protocols
MBone and the Internet
Usage
“Smörgåsbordet”
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Many to Many
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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!!!!
Peter Parnes, Marratech/CDT
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IP Addressing
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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
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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
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Multicast vs. Unicast
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Multicasting
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Multicast traffic uses a special range of
IP-addresses:
 224.0.0.0 - 239.255.255.255
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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.
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MBone?
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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...
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Applications
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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
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Applications Tomorrow
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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 multicastgroup.
 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 TVchannel 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.......
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Conferencing tools
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The MBone tools today consists of:
 SDR: The session directory, “the channelguide”
 WB: A distributed white-board (postscript
and text)
 VIC: A video-tool
 VAT/RAT: Two audio-tools
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Marratech Product Suite
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The mPro Family
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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
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The mFamily history
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mStar was developed by CDT since 1995
(CDT created Jan-95)
 Today about 30 persons
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Was used in a number of different
scenarios over the years
Marratech AB spring 98
m* -> mStar -> mPro (mFamily)
 mStar trademarked by Motorola
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multicast Media Server: mMS
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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)
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multicast Tunnel: mTunnel
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Some links do not support multicast
 ISDN, analog modem
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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.
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mFamily Design Issues
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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.
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Protocols
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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
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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
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Reliable Multicasting
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No standard today (IETF/ITU are not
working on this problem although several
other groups are)
Multicast Transport Protocol 2 - MTP2
 NACK based
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Fanout TCP - MTCP
 Star-topology with a TCP connection to each
receiver
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Reliable Multicast - SRRTP
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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.
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More Protocols
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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….
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MBone and the Internet
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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 IPservice == all routers need to know about
multicasting
Multicasting is both an Internet and an
Intranet technology
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Usage Scenarios of the mFamily
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Electronic Meetings
 Meeting using your desktop computer
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Distance Education
 Distribution of lectures over the Internet
where participants can ask questions and be
active
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Electronic Corridor
 Daily work where users run the tools 24
hours a day
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Usage Examples
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Education Direct
 Distribution of lectures to the county of
Norrbotten
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Ericsson Erisoft
 Electronic meetings and teamwork between their
offices and Ericsson in Stockholm and other
countries
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Daily work at CDT
 mFamily is used for electronic meetings, the
electronic corridor, multicast of seminars and
courses
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“Smörgåsbordet”
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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)
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Questions?
[email protected]
http://www.cdt.luth.se/~peppar/
http://www.cdt.luth.se/mStar/
http://www.marratech.com/
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Multicasting and FireWalls
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Political question NOT technical
There is nothing special about
multicasting in comparison to other IPtraffic. 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 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! :-)
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