Transcript here. - Colin

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
CVC – Investments
Columbia Ventures Corporation
–
Privately held investment company
(Ireland)
(United States)
(Ireland)
(United States)
(United States)
(United States)
(United States)
(Australia)
(UK)
(United States)
(United States)
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