[whatwg] UDP size (Re: Peer-to-peer communication, video conferencing, and related topics (2))

Harald Alvestrand harald at alvestrand.no
Tue Mar 29 04:30:53 PDT 2011

On 03/29/11 03:00, Ian Hickson wrote:
>> >  It is stated that the data size can be up to 65467 bytes in "send()".
>> >  Our network guys tell us that this is unrealistic to get over such big
>> >  chunks using UDP.
> Is that true? I thought they'd just get fragmented at the IP level, but
> would still make it through eventually, am I wrong?
> Obviously you want to avoid fragmentation too if possible, but limiting
> all packets to a few bytes seems a bit extreme...
A lot of firewalls (including Google's, I believe) drop the subsequent 
part of fragmented UDP packets, because it's impossible to apply 
firewall rules to fragments without keeping track of all fragmented UDP 
packets that are in the process of being transmitted (and keeping track 
would open the firewalls to an obvious resource exhaustion attack).

This has made UDP packets larger than the MTU pretty useless.


More information about the whatwg mailing list