IIR IP Multicast

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IP Multicast Peering

• Karl Jeacle
• kj_at_eircom.net

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Overview

• Overview of multicast peering points
• What, where, who, how?
• Equipment associated costs
• Protocol interaction (PIM/MSDP/MBGP)
• Multicast peering policies
• Operational best common practice

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What is a peering point?

• Peering definition
• Peering is the arrangement of traffic exchange
  between Internet Service Providers, at public
  exchange points, with zero sum financial
  settlement
• Note
• Public exchange points, not private connection
• Zero sum settlement, no transit charges
• Multicast and unicast traffic exchanged

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European exchanges

• DECIX Frankfurt, Germany
• INXS Munich, Germany
• AMSIX Amsterdam, Netherlands
• NDIX Enschede, Netherlands
• NETNOD Stockholm, Sweden
• LINX London, UK
• LoNAP London, UK
• MaNAP Manchester, UK
• XchangePoint - London, UK

• VIX Vienna, Austria
• BNIX Brussels, Belgium
• SFINX Paris, France
• GIGAPIX Lisbon, Portugal
• CATNIX Barcelona, Spain
• SIX Bratislava, Slovakia
• CIXP Geneva, Switzerland

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Future exchange trials

• Most exchanges planning trials in 2003
• INEX Dublin, Ireland
• MIXITA Milan, Italy
• NIX Oslo, Norway
• SWISSIX - Zurich, Switzerland

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Who can join?

• Varies across exchange points
• Network criteria must be met
• Typically ISPs only
• Sometimes content providers
• Rarely end-users
• Depends on MoU and TC

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Exchange equipment

• Desire to isolate multicast traffic from existing
  production unicast traffic
• Separate switch used
• Dedicated connection to multicast switch port
• LINX Extreme Summit 48
• Separate VLAN on same switch
• Dedicated connection to port in multicast VLAN
• AMSIX Foundry BigIron 8000 15000

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Exchange equipment

• Some exchanges do not require an additional
  network connection
• e.g. FICIX, NETNOD, SIX
• OK if point-to-point (e.g. ATM)
• Concern if shared access (e.g. Ethernet)
• Multicast traffic looks like broadcast traffic
• Switch will send data out on all ports
• Bearable if multicast only, unacceptable if
  unicast
• PIM Snooping or equivalent required

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PIM Snooping

• Hosts connected to a switch
• IGMP snooping prevents unwanted traffic
• Routers connected to a switch
• PIM used instead of IGMP
• Switches do not see PIM messages
• Traffic will be flooded on all ports
• Solution
• Enable PIM snooping on switches so they can
  restrict multicast traffic flows to interested
  parties

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RGMP

• Cisco provide RGMP
• RouterPort Group Management Protocol
• Proprietary, but submitted as IETF draft
• Message format resembles IGMP to allow easier
  upgrade of existing switches
• Unlike PIM Snooping, all devices (i.e. switch and
  routers) must run RGMP

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Member costs

• Present for unicast peering already
• New router is unnecessary
• Extra port on existing router sufficient
• Additional rental for multicast port
• Software upgrades may be required
• Main cost
• Staff competence development
• Depends on commitment to multicast

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Steps involved

• Peering agreements
• Are multicast unicast peers equivalent?
• Is a (new) peering agreement necessary?
• Session configuration
• MBGP / MSDP / PIM-SM
• RIPE database
• No specific multicast route entries

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Protocols required

• Protocols required for multicast peering
• MBGP
• Exchange unicast routes to multicast sources
• MSDP
• Exchange Source Active messages (SAs)
• PIM-SM
• Allows branches of multicast distribution tree to
  be built between peers across the exchange

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MBGP

• Multiprotocol Border Gateway Protocol
• Not Multicast BGP
• Multiprotocol extensions allow IPv6 MPLS VPNs
• MBGP exchanges unicast prefixes of multicast
  hosts, it does not exchange group addresses!
• MBGP multicast rationale
• Incongruent routing between unicast multicast
• Force multicast traffic to take alternative path

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Incongruent routes
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MBGP Policies

• Peering policy
• Unicast peering has AS path prefix filters
• Re-use depending on administrative policy
• Can re-announce other peers prefixes a sort of
  pseudo-transit for multicast
• Always agree first with peers concerned!

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MSDP

• Multicast Source Discovery Protocol
• Connects PIM-SM domains
• Allows multicast sources for a group to be known
  across different domains
• Peers exchange multicast Source Active messages
  (MSDP SAs)
• SAs carried to PIM Rendezvous Points

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PIM-SM

• PIM Sparse Mode
• Allow PIM neighbours to be established
• Branches of multicast distribution tree are built
  between peers across the exchange
• Enable on exchange-facing interface
• Ideally run natively back to core of network
• Or tunnel back to multicast-enabled network

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Best Common Practice

• Keep local traffic local!
• Filter traffic SAs with ACLs
• Private source addresses
• Private group destination addresses
• SSM 232/8 space
• PIM BSR and/or Auto-RP
• Misc services (e.g. discovery protocols)

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How active?

• Participants
• Usually numerous interested members
• but typically just 10-20 get up running
• Traffic
• Small percentage of unicast ( 1)
• Efficiency its multicast! ?
• Lack of content ?

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Evangelism!

• If you are an ISP
• Investigate multicast peering options
• Start work on enabling native multicast
• If you are an ISP customer
• Ask your provider for multicast service
• Ask them for details on peering presence

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More information

• Exchange points
• http//www.ep.net/
• http//www.euro-ix.net/ispportal/ixpmatrix.htm
• BCP ACLs
• ftp//ftpeng.cisco.com/ipmulticast/config-notes/ms
  dp-sa-filter.txt
• Sample config
• http//multicast.eircom.net/

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Thank you! Questions?
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