Multicast for CATV Distribution

Alan CrosswellColumbia UniversityIvy+@Duke May '05

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

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.

Unicast vs. MulticastMulticastUnicast

from Internet2 Multicast Workshop

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

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?

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.

Set Top Decoders

● Amino http://www.aminocom.com● i3 http://www.i3micro.com/i3web● 2wire http://www.2wire.com● Bast http://www.bastinc.com

Info from Dov Zimring, Occam Networks

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->Analog->MPEG or directly use the

MPEG from the DVB?

Billing, provisioning, etc.

● Myrio http://www.myrio.com● Minerva http://www.minervanetworks.com● Infogate http://www.infogateonline.com/content.asp?id=15

Info from Dov Zimring, Occam Networks

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.

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

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

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– ?

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)