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IGP exchanges "inter-domain" info: contradiction in review slides with Lec 5 and PS2?


Hi - the final review slides define IGP as the following:

“The protocol used to exchange inter-domain routing
information among routers in the same domain.”

However, slide 32 on Lec 5 - Internet topology state that RIP and OSPF are types of IGP, which are used for routing within an AS.

This also contradicts PS2, Q10. In all four cases, the info was learned via some form of BGP, not RIP/OSPF - because they were all examples of learning about routing info for a node outside the AS in question.

I figured the point of the question was to drive home the idea that iBGP is the protocol to transmit inter-domain routing info (as in, info about a node outside the domain), when such info is being passed around within the domain.

In this case, isn’t it inaccurate to call IGP={RIP, OSPF} a inter-domain routing protocol?

Does domain = AS?

Does “inter-domain routing” mean “info about a node outside my current domain”, even if that info is being bounced around within my domain?



Update - asked Joe in office hours. Calling IGP an interdomain routing protocol is incorrect, he says the slide is wrong.

Would love confirmation from Sajad - thank you!


“Interior gateway protocols can be divided into two categories: distance-vector routing protocols and link-state routing protocols. Specific examples of IGPs include Open Shortest Path First (OSPF), Routing Information Protocol (RIP), Intermediate System to Intermediate System (IS-IS) and Enhanced Interior Gateway Routing Protocol (EIGRP).”
Book page 323:
"At the same time, all the routers in the AS are also running some intradomain routing protocol such as Routing Information Protocol (RIP) or Open Shortest Path First (OSPF). (A generic term for intradomain protocols is an interior gateway protocol, or IGP.) "

The problem set had an inconsistency there. I think IGP={RIP, OSPF} as you stated.


The final review slide is not correct. It should be intra-domain. In other words, IGP (Interior Gateway Protocol) is to exchange information inside an AS about links that are inside it.