Date: Mon, 02 Dec 1996 14:50:09 GMT Server: NCSA/1.4.2 Content-type: text/html
Message posted the 30th October.
Message posted the 3th November.
Message posted the 14th November.
Are source and destination nodes considered routers? Specifically, in problem #1 we deal with four hops. That implies 5 nodes from which two are source/destination and three are the intermediate routers. As far as the problem #4 is concerned, does the source/destination have to keep the internal table as the intermediate routers? I think so, since the source/destination must know to which neighboring node they must forward their own messages if they want to send it to some destination. Also they could be used as intermediate routers themselves by some other nodes. Am I correct in my assumptions and reasoning?
I am little bit confused about this since you said in class that in some domains only certain nodes may be designed as routers. That would imply that not all source/desination nodes need to have the full tables as routers. Which assumption is correct for problem #1?
The similar problem arises in problem #3. What assumption should we use in figuring out the number of routers?
I would appreciate if you could let me know which assumption is correct (or "better") and if we can use either assumption, as long as we state it, in our homework.
Great question.
So first a general answer. Nodes can be routers. Routers are nodes. Node is a general term used to designate a point where a link ends. Source is a node and may be a router or is only a router to one of the network router node. (Every node has to have a way to inject its informations in the network.) So a node, that is not acting as a router need not keep any routing table except to know where to send the information it has to send out. You may call it routing table where only entry is "for all destination send informatiom to node x." If they have more than one neighboring node (not in the ethernet sense where many nodes are directly connected to the same bus), then they are routers, as they take information from one link and "route" it to another link.
What I said in the class is correct about have designated nodes as routers for external traffic. Subdomains may have other routers for internal routing only.
Numbers of routers on a path are the number of intermediate nodes. Remember a destination for a particular packet may also be a router (for other packets) but it is not a router for that packet.
Hope this helps in clarifying the concept.
Arun
Message posted the 18th November.
5.1
5.2
5.3 (omit 3.3.9)
5.4
5.5 (omit 5.5.5 - 5.5.9)