Re: [Int-area] Multi-MTU subnet draft

[Iljitsch van Beijnum <iljitsch at muada.com>]

On 28 feb 2008, at 21:08, Templin, Fred L wrote:

> Apologies on being slow to coming around to reading this.
> Still have to read further, but one question for now: is
> this useful for router-to-router, or is it only used for
> host-to-router (and maybe also host-to-host). For that
> matter, perhaps the definition of what is meant by "host"
> and "router" is somewhat soft?

It's meant for each of the following cases:

router-router
router-host
host-host

I've tried to be careful with using the words "node" and "host". Most  
stuff applies both to routers and hosts, but there are a few things  
that only hosts can do because they get to determine the size of  
packets that are sent, routers have no choice in the matter. I.e., the  
TCP MSS option makes sure a jumbo-capable host doesn't send TCP  
segments larger than the standard MTU to a non-jumbo-capable host, and  
RFC 4821 also only works on hosts.

So should implementers want to keep their life simple and omit the  
neighbor discovery options and jumbo ARP, they can take care of the  
difference through RFC 4821. But routers can't send larger packets  
unless this is administratively configured OR the neighbor discovery /  
jumbo ARP probing takes place.
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