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Multicast
Colin Whittaker
INEX Members Meeting
Tuesday 6th February 2007
All About Me
•Senior Network Engineer in Network Development
•Previously with HEAnet & Internet Ireland
•Responsible for all areas of Network Design and Planning
•Responsible for fixing it when the plan doesn’t come together
•All opinions are my own and not Magnet Networks
Magnet Networks
•Magnet Networks part of Columbia Ventures Corporation
•Private Investment Company
•Telecoms Assets in UK / USA / Australia
Columbia Ventures Corporation –
(Ireland)
(Australia)
(Ireland)
(UK)
(United States)
(United States)
(United States)(United States)
(United States)
(United States)
(United States)
Privately held investment company
CVC – Investments
Hibernia Atlantic Network
Magnet Networks
•Magnet Networks started September 2004
•FTTH launched December 2004
•Acquired LEAP in mid 2005
•LLU launch in September 2005
•Acquired Netsource in 2006
•Two Brands – Magnet Entertainment = Residential – Magnet Business = Corporate
Agenda
•Tech Primer
•Drivers
•Challenges
Agenda
•Drivers
•Tech Primer
•Challenges
IPTV Key Driver
•NRENs have deployed already
•Large Internal deployments:Financial and Content Provider segments.
•Business Users will demand support in VPN offerings.
•IPTV is driving Multicast to the end user
•Walled Garden - Magnet / Vodafone & Sky
•Public - BBC
IPTV key driver
•How much bandwidth:
•Sky Digital via satellite: MPEG2 4 – 10Mbit/s
•SD MPEG 2 @ 4Mbit/s is a tight fit
•SD MPEG 4 @ 2 – 3Mbit/s is expected to be the norm
•HD MPEG 4 @ 10 – 20Mbit/s is required to maintain quality
IPTV Key Driver
IPTV Key Driver
Agenda
•Drivers
•Tech Primer
•Challenges
Unicast
•One to One communications
•Got us where we are today
•Has scaling challenges as number of sessions grows
•10x increase in Users means 10x the traffic volume
Unicast
Broadcast
•One to All
•Just like a sprinkler system
•Data goes to all Nodes if they want it or not.
•Wasted capacity
Multicast
•Some to Some
•One to Many
•The Middle ground between Unicast and Broadcast
•Replicate as close to the User as possible
•Bandwidth only used once and only when needed.
Multicast
Multicast - ASM
•Any Source Mulitcast (1990)
•Sources send to multicast groups
•Receivers join group and receive from any source
•Supports Some to Some and One to Many
•Group ID’s are global (limited addresses)
•Anyone can DOS your group
Multicast - SSM
•Source Specific Mulitcast (2000)
•Sources send to multicast groups
•Receivers join group and source
•Group ID’s are based on the source as well as the group
•Receivers only see traffic from specific source
Multicast - Protocols
•PIM-SM (sparse mode – forward on request)
•MSDP / Anycast-RP for redundancy•AutoRP & BSR have too many moving parts
•MSDP for interdomain support
•Multiprotocol BGP for interdomain RPF selection
•Well understood toolbox
Multicast - Protocols
•That’s the Router to Router stuff, now for the LAN
•IGMP•v2 and v3
•v3 needed for SSM
•IGMP snooping required in switches
•IGMP v3 not widely deployed
Multicast – Group ID
•224.0.0.0/4
•224.0.0.0/24 – link local (OSPF)
•239.0.0.0/8 – admin scoped
•233.0.0.0/8 – GLOP – encode as into middle two octets
•232.0.00/8 – SSM range
Multicast – MAC addr
•Half an OUI reserved for multicast
•Steve Deering requested 16 OUIs but only given half of one
•23bits of MAC to contain 28bit of group ID
•Leads to 32:1 overlap
•Be careful not to overlap with special group id’s
Multicast – Tricks
•Static Joins
•Fast Leave
•Bidir
•PIM Snooping
Channel Zapping
•Perceived slowness when changing channel
•Single channel join <100msec
•For common channels number of hops required is low
•GOP much bigger impact. •WM9 GOP = 3sec•Sky / Magnet = .5sec
•Iframe caching if >.5sec
Agenda
•Drivers
•Tech Primer
•Challenges
Access Networks
•Easy enough to deploy in Backbone and Data centre
•How about to end users
DSL
•Most DSL users reached via PPPoE / L2TP
•Have to replicate at BRAS
•Need to send multiple copies into the access network
•Cost of bitstream access a concern
•Do get benefit of bandwidth saving in the backbone
•UK ISPs found this helpful in BBC deployments
DSL
•Two Solutions
•Multiple PVC’s to the customer•One for PPPoE•Second for Video
•Run IP all the way to the DSLAM and let it do the replication
•Both require Control of the Access Network
Wireless
•Many wireless devices do not understand multicast.
•In many cases a separate copy is sent to each reciever
•Video suffers from timing issues
Wireless @home
•Customers have come to love WiFi
•Customers do not want to have to run new cabling
•Some solutions available for home networking
•99% of them cannot do multicast
•CPE vendors slowly moving to support Multicast
Agenda
•Drivers
•Tech Primer
•Challenges
P2P
•Working around the lack of efficient distribution
•Bitorrent
•20GBtye HD movie via Bitorrent
•Joost
•TV on demand via P2P
VOD
•TV is our killer app but …
•TV is moving to on demand
•Sky Plus / Tivo …
•VOD traffic will dwarf current traffic
Support
•It is backwards to “normal” IP
•In multicast trouble shooting starts at the receiver•Step by Step back to source
•Not as field hardened as unicast
•“All Customers TVs stop working after 3 minutes”
Further Reading
•John Lyons – IP Multicast “The Good, the Bad & the Ugly”
•Toerless Eckert – “IP Multicast/Multipoint for IPTV (and beyond)”
•Developing IP Multicast – Beau Williamson
•Inter-domain IP Multicast – Edwards, Guiliano, Wright
•Internet 2
Questions
?