What protocol does OSPF use for routing table updates? Is it TCP based, UDP, or ICMP?

We're having a problem here where a fiber link appears to be overpowered (lack of attenuation in the line) and dropping off. Connection oriented protocols like SMTP won't go through; however, the OSPF routing tables continue to show the link as good. We suspect OSPF uses a connectionless protocol which does make it through, but connection oriented protocols, which require a better connection, don't.

OSPF does not use either TCP or UDP; it has its own value in the protocol field of the IP header.

On a related matter: Your theory that a noisy line will yield better results with a connection oriented protocol vs. and connectionless protocol is a slippery slope. The entire reason for a connection oriented protocol is to insure packets make it in very lossy environments. TCP does this quite well with state timers, etc. , hence there must be a more direct problem, perhaps below the IP layer.

If a fiber link is lossy and IP data is being dropped, one must look at the entire protocol stack. What is running on top of the fiber? ATM? Ethernet? Serialized point-to-point? The problem as I read the statement appears to be coupled to the protocols below the IP stack and I would look there as well.

Routing tables are hard to judge, BTW. OSPF will still show good values in a lossy environment, results can stay in the tables for weeks, months. If you do a 'show IP protocol' in the cisco routers and post the results, we can help further.