Too bigs are sacred, was: Re: IPv6 addressing for core network

[iljitsch at muada.com (Iljitsch van Beijnum)]

On 10 feb 2011, at 0:26, David Freedman wrote:

>> Unless every packet you emit is ? the minimum MTU (1280), then, you need
>> to be able to receive TOOBIG messages.

> Can you think of a packet type I will emit from my publically numbered
> backbone interface which may solicit a TOOBIG that I'll have to care about?

What if you're trying to connect to your routers with 1500-byte+ POS, ATM, ethernet jumbo or what have you interfaces from some system with a big fat jumboframe MTU but some 100 Mbps ethernet firewall or office network in the middle?

If you're willing to accept TCP or UDP from somewhere, it's a bad idea to filter ICMP coming in from that same place.