----- Original Message -----
From: "Joe Touch" <to...@isi.edu>
Sent: Monday, October 10, 2016 7:15 PM

> HI, Fred (et al.),
>
> ...
> > IMHO, your draft is getting wrapped up with too many new acronyms
for no
> > good reason when simple English-language text would make things
easier to
> > understand.
> We're dealing with legacy use of the term MTU and path MTU too,
though.
>
> > In 'draft-templin-aerolink', there are only five acronyms:
> >
> >   MTU - the MTU of the tunnel as seen by the IP layer
>
> That's the term we need to specify in more detail - to some, it's
> one-hop IP MTU, to others it means path MTU, to others it means what
we
> would call egress reassembly MTU.
>
> We need to either avoid the term MTU in our definitions or provide an
> adjective to specify each type (as I have done).
>
> >   MFU - the maximum fragment size within the tunnel
> This is confusing because the fragment could refer to the payload or
the
> entire IP datagram.
>
> >   MRU - the maximum reassembly size supported by the egress
> Sure.
>
> >   ENCAPS - the size of the encapsulation headers inserted by the
ingress
> Sure.
>
> >   PTB - an IP Packet Too Big message
> ICMPv4 or IPv6...
>
> You have omitted the concept of a transit MTU, which is only the ERU
> when the ingress supports fragmentation and reassembly (which not all
> tunnels or links do).
>
> Therein lies the problem with "simple" English, IMO.

Joe

I echo Fred's point about acronyms; yes you need adjectives to qualify
MTU but when I read
' The TMTU (d) is not limited by TIMTU (e), but by ERMTU (f), the
   tunnel equivalent of RMTU (c). '
I have to pause, expand and think.  Spelling out the adjectives every
time would make it easier.

Likewise, when 'MTU' or 'protocol' or some such is unqualified, I have
to stop and think which is meant.  I think that most uses of MTU should
have an adjective or two in front of them.

I would say the same of protocol.  At times, the I-D seems specific,
that this is IP in IP and so protocol is IP but other usages seem more
generic.  After all, you can tunnel Ethernet in ATM and while I think
that most of this I-D does not cater for that, I think there are some
places where 'protocol' is not limited to IP so if IP protocol (or IPv4
protocol or IPv6 protocol) is intended, then I would write that
explicitly.

Tom Petch


> Joe

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