neighbor table

[doffins]

Neighbor table- Each router keeps state information about adjacent neighbors. When a newly discovered neighbor is learned on a router interface, the address and interface of that neighbor are recorded, and the information is held in the neighbor table and stored in RAM. Sequence numbers are used to match acknowledgments with update packets. The last sequence number received from the neighbor is recorded so that out-of-order packets can be detected.

So I don't really understand the last two sentences, and the book doesn't explain it either. Can anyone help?

 

[Yami]

"Sequence numbers are used to match acknowledgments with update packets."
Somewhere in every SCTP packet, there is a sequence number; conceptually "This is packet 4 of 9770" (though I'm not sure if it actually has the "of xxxx" in it)

"The last of these sequence numbers is recorded, so that out-of-order packets can be detected"
If the the last packet it receives is 9700 of 9770, then it knows the packets were received out of order. It only does this for the last packet to (presumably) reduce processing delay.


This prevents, for example, a message which says "Yami wants to upgrade his computer this year" being garbled as a result of out-of-order packets into "Yami wants to is computeupgrade hr this year"

 

[doffins]

Ok, I understand, thanks, I really appreciate it.

 

[Yami]

No problem. If you need any more help, feel free to ask.