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What IP Routing Protocols to Use

When running video networks in an IP metro and core network, you must configure several protocols to function together. These protocols typically include the following protocol types:

A multicast protocol to route multicast traffic
An interior gateway protocol (IGP) to provide topological information to the multicast protocol
An exterior gateway protocol (EGP) to route between different networks (depending on the complexity of your network)

Multicast Protocols to Use—Video networks often use Protocol Independent Multicast sparse mode (PIM SM) when communicating beyond the access side of the network (that is, in the metro or core networks).

PIM is a family of multicast routing protocols that enable one-to-many and many-to-many distribution of data. The term protocol-independent means that PIM is not dependent on any particular unicast routing protocol for topology discovery. However, because it does not have its own method of topology discovery, PIM obtains routing information (such as dynamic endpoints) from other routing protocols, such as Open Shortest Path First (OSPF) or Intermediate System-to-Intermediate System (IS-IS).

Instead of flooding packets throughout the network and then removing (or pruning) paths where no receivers exist, PIM SM uses the information it receives from the other routing protocols to construct a tree from each sender to the receivers in a multicast group.

Interior Gateway Protocols to Use—PIM must use an IGP to obtain current topology information. The two protocols most often used by PIM to obtain topology information are OSPF and IS-IS. As IGPs, OSPF and IS-IS function within a single autonomous system (OSPF) or area (IS-IS).

Both OSPF and IS-IS are link-state routing protocols; they flood topology information throughout a network of routers within the autonomous system or area. After obtaining this information, each router independently builds a picture of the network topology. The routers can then forward packets or datagrams based on the best topological path through the network to the destination.

Exterior Gateway Protocols to Use—Depending on the complexity and size of your network, you might need to configure an exterior gateway protocol (EGP). EGPs such as Border Gateway Protocol (BGP) exchange routing information between networks.

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