[96036] in North American Network Operators' Group
Re: Thoughts on increasing MTUs on the internet
daemon@ATHENA.MIT.EDU (Douglas Otis)
Sat Apr 14 13:23:07 2007
In-Reply-To: <D86C7EA3-D603-41FC-9524-5FA12BA47B74@cisco.com>
Cc: NANOG list <nanog@merit.edu>
From: Douglas Otis <dotis@mail-abuse.org>
Date: Sat, 14 Apr 2007 10:22:16 -0700
To: Fred Baker <fred@cisco.com>
Errors-To: owner-nanog@merit.edu
On Apr 13, 2007, at 4:55 PM, Fred Baker wrote:
> The biggest value in real practice is IMHO that the end systems
> deal with a lower interrupt rate when moving the same amount of
> data. That said, some who are asking about larger MTUs are asking
> for values so large that CRC schemes lose their value in error
> detection, and they find themselves looking at higher layer FEC
> technologies to make up for the issue. Given that there is an
> equipment cost related to larger MTUs, I believe that there is such
> a thing as an MTU that is impractical.
>
> 1500 byte MTUs in fact work. I'm all for 9K MTUs, and would
> recommend them. I don't see the point of 65K MTUs.
Keep in mind that a 9KB MTU still reduces the Ethernet CRC
effectiveness by a fair amount. Adoption of CRC32c by SCTP and iSCSI
has a larger Hamming distance restoring the detection rates for Jumbo
packets.
-Doug
