I would be grateful for any info on general routing issues such as algorithms and congestion control?

Answer 1

So first you want to consider static versus dynamic routing. There are cases where static routing might be preferred. There are obvious disadvantages to static routing in most cases, in that it cannot re-route packets around a failed link. That's where dynamic routing protocols come in, and each dynamic routing protocol has it's own algorithm.

A routing algorithm must have (at least) the following properties:
1) Advertise reachability information to others
2) Receive reachability information from others
3) Determine the best route to any destination
4) Maintain a route table with these results
5) React to changes in topology (failed links)

Now, what are some of the issues to consider? This ultimate goal of any routing protocol is that all of the routers have consistent information on the state of the network. We then say that the routing protocol has "converged".

One issue is how will routes be advertised between routers? Will a router only advertise changes in topology, or will it periodically broadcast its entire route table? If it sends the entire route table, and the neighboring routers do the same, then how will the routing protocol avoid routing loops? This is where split horizon and poison reverse come into play.

Another issue is what the metric will be... if a router learns of a route from more than one direction, which one is better? Will it determine this by hop count, or delay, or the load on the link maybe? Another issue related to this is load balancing. What if a router has two EQUAL cost paths to the same destination, can it and will it split the load over both links? And will it do this per destination or per packet?

Another issue is this: suppose there is a link in the network that keeps going up and down. How will the routers address this so you don't end up with route flapping? This is where holddown timers come into play.

A fundamental difference between many of the routing protocols is whether they are distance vector like RIP for example versus link state like OSPF for example. And there's EIGRP that has characteristics of both but is called an advanced distance vector protocol. With distance vector all routers periodically broadcast their entire route table to all directly attached neighbors, and eventually every router knows the distance (hop count) and direction (next hop router) to every network segment. The algorithms behind this were developed by Bellman, Ford and Fulkerson, back in the 1960s before IP and routers even existed. Link state protocols differ in that every router (after convergence) has a complete picture of the network topology. Link state protocols are more robust and efficient but more complex. The algorithms here are Dijkstra's shortest path first algorithm, also developed circa 1960, long before it was applied to IP routing.

Answer 2

Routing protocols like BGP, and smart hardware like Cisco's local director which is like a traffic cop for incoming data packets, load balancing software, non-shared routes. Also there is the shortest path between two computers on a network using Dijkstra’s Algorithm. Just a couple of thoughts before I doze off...

go to How stuff works for some routing explanations including Bellman-Ford Algorithm and the Ford-Fulkerson Algorithms

Answer 3

McCain is a Captain in the USN which is the equivalent of a full colonel in the army. Certainly he has better qualifications than Bill Clinton who was a draft dodger. You probably like John Kennedy who only got to the rank of Lieutenant Junior Grade. How about Carter who never got past Lieutenant in the USN? McCain's Father and Grandfather were both Admirals, his father a four star, and John McCain probably would have gone on to be a four star had he not been so badly injured whikle a prisoner of war in Vietnam. He was injured when tortured, seriously enough to force his retirement from the Navy. He was a jet jockey and is probably for better qualified than either Clinton ior Obama, neither of whom has any military experience.