I'm unsure how to answer this question Given that Data Link Layer protocols already employ sequence numbers, provide 2 distinct motivations for Network Layer protocols also employing sequence numbers.

Hi, Not sure if this is correct but my answer would have been something like this: Reason 1: The network layer primarily deals with packets so the sequencing numbers can be used to sequence the packets whereas in the data link layer, the packets are broken up into frames which are then seperately numbered. Reason 2: The sequence number also helps with flooding protocols. It prevents the same packet from being sent out again by the same router. When the router detects a sequence number that has appeared before, it just discards the packet. Thanks, would love some feedback too!

not sure if your answer already covers this but, like you said the network layer deals with routing of packets. Since packets may take different routes to reach a destination (through different routers) the packets need to be numbered so that at the destination they can be re-assembled

ANONYMOUS wrote: This is the strongest answer of all the points made, above. Consider *who* the sequence numbers are for: - in a DataLink Layer protocol, they're for 2 directly connected node - in a Network Layer protocol, they're for 2 nodes possibly many hops apart. If a single physical link (wire) is on the path between multiple pairs of remote nodes, then the traffic crossing that wire will use sequence numbers to control/manage/describe each frame crossing the wire, and each frame will be carrying (in its payload) the NL sequence numbers for each of the many pairs of remote nodee.