Jumbo frame Question

Mon Nov 29 21:18:24 UTC 2010

On 11/29/2010 1:10 PM, John Kristoff wrote:
> In a nutshell, as I recall, one of the prime motivating factors for not
> standardizing jumbos was interoperability issues with the installed
> base, which penalizes other parts of the network (e.g. routers having
> to perform fragmentation) for the benefit of a select few (e.g. modern
> server to server comms).
>

Given that IPv6 doesn't support routers performing fragmentation, and 
many packets are sent df-bit anyways, standardized jumbos would be nice. 
Just because the Internet as a whole may not support them, and ethernet 
cards themselves may not exceed 1500 by default, doesn't mean that a 
standard should be written for those instances where jumbo frames would 
be desired.

Let's be honestly, there are huge implementations of baby giants out 
there. Verizon for one requires 1600 byte support for cell towers 
(tested at 1600 bytes for them, so slightly larger for transport gear 
depending on what is wrappers are placed over that). None of this 
indicates larger than 1500 byte IP, but it does indicate larger L2 MTU.

There are many in-house setups which use jumbo frames, and having a 
standard for interoperability of those devices would be welcome. I'd 
personally love to see standards across the board for MTU from logical 
to physical supporting even tiered MTU with future proof overheads for 
vlans, mpls, ppp, intermixed in a large number of ways and layers (IP 
MTU support for X sizes, overhead support for Y sizes).

Jack