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

?