Ethernet NAPs (was Re: Miami ...)

Thu Aug 23 15:37:09 UTC 2001

On Thu, 23 Aug 2001, John Kristoff wrote:

>
> Mikael Abrahamsson wrote:
> > If NAPs do not support jumbos, then end systems will never support them.
>
> Many end systems will never support jumbo frames, period.  There are
> lots of 10/100 Mb/s ethernet hosts that will not ever be upgraded.

While not a standard feature, many 100mbit nics support jumbo on
full-duplex links and some 100tx switches do as well.

> Certainly.  In a nutshell, it might be best to take steps to avoid
> fragmentation elsewhere in the network.  Perhaps a rule of thumb that
> should be stressed is to use jumbo frames if you know for sure the other
> end system(s) support it, otherwise default to 1500.

Path MTU discovery works fine. (except for broken firewalls) Your
complaint about end systems never supporting jumbos is a moot point
because if neither end supports them, then PMTU discovery isn't even an
issue.