Multicast for CATV Distribution

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Multicast for CATV Distribution

• Alan Crosswell
• Columbia University
• Ivy_at_Duke May '05

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Contents

• Overview of IP Multicast
• SD/HD Quality Video Bandwidth Requirements
• Decoders Encoders
• Campus Multicast Routing
• LAN Multicast
• Internet Multicast Routing
• Rights Management
• Licensing Content

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Overview of IP Multicast

• For each channel, only one copy of the stream is
  sent, with routers forking it as needed to
  reach only interested viewers.
• The transmitter sends just one stream no matter
  if it's 1 or 1000 viewers.
• Compare to unicast streaming (e.g. Real,
  Quicktime or Windows Media) where your servers
  and network have to scale up linearly with the
  number of viewers.
• N.B. Live transmission only not VoD.

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Video Bandwidth Requirements

• Standard Definiton D1 720x480
• MPEG-2 about 5 Mbps
• mJPEG (DV) about 30 Mbps
• High Definition 1080p
• MPEG-2 about 270 Mbps
• Typical campus residence network speeds
• Cat 3 Ethernet 10 Mbps
• Cat 5 Ethernet 10/100/1000 Mbps

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Decoders

• Set-top box or PC viewer?
• Northwestern is using Videofurnace PC viewers
• Dartmouth also using Videofurnace.
• Cornell is using PC viewer and Amino STB with
  encryption hardware/software
• Is the TV set obsolete?

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Software Decoders

• Many software viewers available, depending on the
  encoding
• Videofurnace
• Cisco IP/TV Viewer (obsolete?)
• Vbrick Streamplayer
• Videolan Client (VLC MPEG licensing issues)
• Windows Media, Quicktime, etc.

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Encoders

• What is the source?
• Analog Vbrick, Tandberg, Videofurnace, VLC,
  etc.
• DVB
• Minerva http//www.minervanetworks.com
• Skystream http//www.skystream.com
• Tut Systems http//www.tutsys.com
• Bigband Networks http//www.bigbandnet.com
• Stored files (campus TV)
• MPEG-gtAnalog-gtMPEG or directly use the MPEG from
  the DVB?

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Campus Multicast Routing

• Routing protocols to implement
• PIM-SM - router-to-router
• IGMP - host-to-router
• MBGP multicast reachability (used by PIM-SM)
• MSDP multicast source discovery for
  inter-domain multicast
• These are all widely supported today on modern
  campus routers (e.g. Cisco, Juniper)
• There are issues on some other vendors' boxes.

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LAN Multicast

• Today's biggest problem area for high-bandwidth
  stream distribution.
• Old school broadcast LAN model floods multicast
  traffic out all switch ports.
• IGMP snooping switches solve this, but
• Be sure they support IGMP version 3
• Invest the time and effort in evaluating
  competing products.
• See http//www.columbia.edu/acis/networks/advanced
  /igmp

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Internet Multicast Routing

• Not much extra work is required to extend your
  multicast campus to the multicast Internet.
• A good source/sink for non-commercial TV
  programming?
• ResearchChannel - www.researchchannel.org
• Open Student TV Network www.ostn.tv
• See
• http//multicast.internet2.edu

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Rights Management

• IP Multicast does not intrinsically support
  viewer tracking (which is why it scales so
  well!).
• How do you track views of premium channels?
• Encryption
• Application-specific methods for retrieving the
  encryption key
• ?

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Licensing Content

• Cornell Time Warner is peering with the campus
  network and supplying MPEG-2 streams. A fixed
  fee per head was negotiated with TW. This
  service is Cornell-branded.
• Northwestern ?
• Dartmouth Adelphia (120 channels)