Suppose a router, routerA received an IPv4 packet of size, say 1500 bytes. The packet is addressed to one of its interfaces, say interface5, so routerA itself is the destination of the packet. Further suppose that the MTU of the network on interface5 is 500 bytes-- too small for the packet as is. In this case, who fragments the packet?
- routerA does-- just fragments the packet as specified in RFC791 and relays the fragments on interface5. The receiving host then reassembles them. Link layer has no part in this.
- Link layer does. routerA just passes the packet as is to link layer to be delivered within network interface5.
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In another line, suppose routerA is receiving packets with itself as the ultimate router on the IP path, i.e., the destination network is one of its interfaces. The packets are frames and need to be assembled. Are there any cases in this scenario that routerA itself reassembles the frames before delivering them to the host? Everywhich way I look at it, it is the host machine that does this reassembly. Just looking to make sure whether there are any exceptional cases.
TIA.
