[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[RRG] Re: [RAM] Tunnelling & GigE jumbo frame size



Hi,

On Wed, Sep 12, 2007 at 04:07:41PM -0400, RJ Atkinson wrote:
o All router-to-router links on the downstream side of an ITR use
either 4470 or 9180 byte MTUs.

Where is this assumption coming from?
As long as there are FastE links, this is not going to happen.

Are you trying to say that you currently have deployed
router-to-router links inside an ISP/IX with less than
4470 bytes of IP MTU ?

We have no single ethernet link in our network that has a MTU *above* 1530
(there are some that could be cranked up, but there was no need yet)

I have a large number of links that have a MTU of *exactly* 1500 (because
there is equipment that cannot handle 1530).

All exchange points that we're connected to run the fabric at 1500 byte
MTU, because they have members that have equipment that cannot handle
more.  There are *some* IXPs that have two different LANs, one with
1500 and one with "Jumbo", but that's not very widespread yet.

So: the answer is "yes".

Btw, at least some 100baseTX/FX switches/routers can
support the 9180 IP MTU.  So it is not necessarily
the case that 100baseTX/FX implies a 1518 byte link MTU.

Switches are easy.  Routers are not.

What good is having a Jumbo-capable switch if there is one peer on the
shared fabric that can only receive 1500-byte (+ Ethernet header) packets?

Gert Doering
        -- NetMaster
--
Total number of prefixes smaller than registry allocations:  122119

SpaceNet AG                        Vorstand: Sebastian v. Bomhard
Joseph-Dollinger-Bogen 14 Aufsichtsratsvors.: A. Grundner- Culemann
D-80807 Muenchen                   HRB: 136055 (AG Muenchen)
Tel: +49 (89) 32356-444            USt-IdNr.: DE813185279
_______________________________________________
RAM mailing list
RAM@iab.org
https://www1.ietf.org/mailman/listinfo/ram

--
to unsubscribe send a message to rrg-request@psg.com with the
word 'unsubscribe' in a single line as the message text body.
archive: <http://psg.com/lists/rrg/> & ftp://psg.com/pub/lists/rrg