|
|
|
|
|
|
by beneater
4056 days ago
|
|
|
The reason is because you never want routers to have to fragment your packets ever. Fragmentation is really inefficient. So any modern stack will always set DF and listen for ICMP unreachables. In other words, PMTU discovery. None of the other reasons you mention are really relevant. |
|
|
Alternative idea: when router needs to fragment a packet, router passes the fragmented packet through, but sends an ICMP to the source - "fragmentation happened". (Or the party which re-assembles the fragmented packet, maybe receiver, sends this "fragmentation happened" message).
So this IP packet does not need to be resent, the source can optimize packet size for future, and the network doesn't break if ICMP is disabled somewhere.
We don't want to constantly send these "fragmentation happened" ICMP messages (if they don't reach the source and it keeps sending large packets), so the router sends ICMP not always, but only for first 3 fragmented packets of that source in each 10 minutes.
[I am just thinking, it's not a real proposal.]