One of the principal reasons jumbo frames have not been standardized is due
to latency concerns. I assume this group can appreciate the IEEE holding
ground on this. For a short time, servers with gigabit NICs suffered but
smarter NICs were developed (TSO, LRO, other TLAs) and OSs upgraded to
support them and I believe it is no longer a significant issue.

Kevin Gross

On Thu, May 12, 2011 at 10:31 AM, Fred Baker <fred@cisco.com> wrote:

>
> On May 9, 2011, at 11:06 AM, Rick Jones wrote:
>
> > GSO/TSO can be thought of as a symptom of standards bodies (eg the IEEE)
> > refusing to standardize an increase in frame sizes.  Put another way,
> > they are a "poor man's jumbo frames."
>
> I'll agree, but only half; once the packets are transferred on the local
> wire, any jumbo-ness is lost. GSO/TSO mostly squeezes interframe gaps out of
> the wire and perhaps limits the amount of work the driver has to do. The
> real value of an end to end (IP) jumbo frame is that the receiving system
> experiences less interrupt load - a 9K frame replaces half a dozen 1500 byte
> frames, and as a result the receiver experiences 1/5 or 1/6 of the
> interrupts. Given that it has to save state, activate the kernel thread, and
> at least enqueue and perhaps acknowledge the received message, reducing
> interrupt load on the receiver makes it far more effective. This has the
> greatest effect on multi-gigabit file transfers.
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