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How to provide Inter-domain multicast routing?

How to provide Inter-domain multicast routing?. PIM-SM MSDP MBGP. PIM-SM. Note that PIM-SM is a good candidate Receivers are usually sparsely located What we have seen thus far should work No need to do many changes for the Inter-domain We have only assumed a unicast “next-hop”

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How to provide Inter-domain multicast routing?

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  1. How to provide Inter-domain multicast routing? PIM-SM MSDP MBGP

  2. PIM-SM • Note that PIM-SM is a good candidate • Receivers are usually sparsely located • What we have seen thus far should work • No need to do many changes for the Inter-domain • We have only assumed a unicast “next-hop” • However a single shared-tree is not desirable • What if only one receiver, one sender (in same domain) and RP is many domains away? (expensive!) • ASMs are no longer autonomous (depend on the AS of RP) • Solution: one shared tree in each domain! • Each domain has a RP

  3. RP RP RP RP RP r s One RP per Domain Domain E Domain C Domain B Domain D Domain A

  4. How to find each source • The receiver joins the tree of its local RP as before • Sources send data to their local RP • Note: these two RP could be different! • How can the RP at E (where receiver is) learn about the source at A? • Use the Multicast Source Discovery Protocol (MSDP) • MSDP runs in the RP at each domain • When a new source joins the RP: • MSDP informs all other domain RP’s of the new source in its domain

  5. MSDP Flooding • Each MSDP router (i.e., each RP) maintains a TCP connection with the MSDP router (i.e. the RP) of each neighboring domain. • When the RP detects a new source in its domain, • It sends a “source active” SA message to all its MSDP peers • This message is flooded to all MSDP routers (i.e. to all RP’s) • How is the flooding done? • Use a form of RPF, i.e., use the implicit broadcast tree of unicast • If a RP receives a SA message from its next hop (next domain) to the source of the SA message, then it is accepted and send to all peers.

  6. Broadcast tree of Domain A Domain E MSDP Peers RP Unicast Path Domain C RP Domain B RP RP Domain D RP Domain A

  7. RP RP RP RP RP SA SA SA SA SA SA SA Message192.1.1.1, 224.2.2.2 s Register 192.1.1.1, 224.2.2.2 MSDP Overview Domain E MSDP Peers(TCP Session) Source ActiveMessages SA Domain C Domain B Domain D Domain A

  8. Joining the SPT of the Source • The RP at E, joins the SPT of the source (because it has at least one receiver) • A join is sent along the path to the DR of the source • This causes a path to be built in the SPT of S • Also, the DR of the receiver may join the SPT of the source (if desired)

  9. RP RP RP RP RP Multicast Traffic r SA Join (*, 224.2.2.2) SA SA SA SA SA SA Message192.1.1.1, 224.2.2.2 s Register 192.1.1.1, 224.2.2.2 MSDP Overview Join (S, 224.2.2.2) Domain E MSDP Peers (TCP Session) Source ActiveMessages SA Domain C Domain B Domain D Domain A

  10. RP RP RP RP RP Multicast Traffic r Join (S, 224.2.2.2) s MSDP Overview Domain E MSDP Peers Domain C Domain B Domain D Domain A

  11. Multiprotocol BGP • Not all domains will support multicast • Note that join messages are sent via unicast • What if they traverse a domain where routers don’t support multicast? • We need separate routing for regular unicast messages and multicast join messages • MBGP is the same as BGP, except it provides more than one route • MBGP may support many “protocols” • Provide one route to the destination for each of these protocols • E.g. “multicast” would be one “protocol”

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