Thoughts on increasing MTUs on the internet

Fri Apr 13 07:35:03 UTC 2007

Saku Ytti wrote:

> IXP peeps, why are you not offering high MTU VLAN option?
> From my point of view, this is biggest reason why we today
> generally don't have higher end-to-end MTU.
> I know that some IXPs do, eg. NetNOD but generally it's
> not offered even though many users would opt to use it.

Larger MTU size was something I did some work on back in the FDDI days and the benefits are significant. More than just CPU improvements. Throughput and server performance increased substantially also. But  FDDI and the like didn't come cheap so little interest at the time. At the LINX a few providers did run larger MTUs during those FDDI days. We did some testing with SRP/DPT in Stockholm and London also and again it worked well but again not cheap. (we were looking at this for storage and exchange of cached content at the time)

Unfortunately I think the time where IXPs could make a difference might be past - and to make this happen tere needs to be more of a demand  from the members of tose exchanges, its not just a case of turning on a vlan either the impact to the main fabric needs to be understood. Also atleast here in Europe many of the circuits into exchanges are Ethernet based also and I suspect many circuits into exchanges would require a lot of work to support Jumbos.  And then again lots of circuits into customer premise are Ethernet based now also some on GFP based SDH systems, some ATM and other whacko technologies with dubious support for jumbo or larger frames.

Then there is the actual interface card support of large amounts of jumbos which in my experience is questionable  based on a limitedl amount of testing though - Come back POS all is forgiven!

Regards,
Neil