Answers to your Questions

How many protocols does an edge router typically support?

At a very minimum, edge routers are required to support the ubiquitous external routing protocol, eBGP-4, and an internal routing protocol (IGP), such as iBGP-4, OSPF, IS-IS, or RIPv2. If the device is a dual-stack router, it must also support IPv6 flavors for the above protocols. With MPLS now deployed at the edge as well as the core, MPLS protocols (including the MPLS signaling protocols, LDP/CR-LDP and RSVP-TE) plus traffic engineering extensions to existing IGPs are also required. The number of other protocols depends on the number of services and applications a router supports. If it is IP multicast-enabled, it must support IGMPv3 and a multicast routing protocol, such as PIM-SM. VPN services add further complexity. For example, to implement BGP/MPLS VPNs, a router must support the routing and MPLS protocols discussed above, as well as multi-protocol extensions to BGP-4 (MP-iBGP) so it can exchange VPN reachability information between provider edge (PE) routers. The device may also need to support other VPN services. such as L2TP. With broadband access technologies and services continuing to proliferate at the edge, it's no wonder that multi-protocol performance and scalability are key test issues facing engineers who are developing and deploying edge routers today.