[ipxe-devel] tftp windowsize RFC 7740

Gene Cumm gene.cumm at gmail.com
Thu Dec 3 11:32:24 UTC 2015

On Thu, Dec 3, 2015 at 5:28 AM, James Harper <james at ejbdigital.com.au> wrote:
> Is anyone working on implementing rfc 7740 tftp windowsize into ipxe?
> https://tools.ietf.org/html/rfc7440
> the rfc includes some observed speedup times which are quite impressive.

I can't say if anyone is looking at implementing such but I could
offer some other information.

Such an option requires both sides to cooperate.  If a tftpd didn't
use it, I believe it would require another attempted option
negotiation, mildly slowing things down.  iPXE would probably need to
default to not using it UNLESS set in a run-time script.  I'm left to
assume the tftpd that Patrick works on is probably the only one that
implements this (yet)

It seems commonplace in the Microsoft WDS realm to use a larger TFTP
blocksize and generate multiple IP fragments in order to accelerate
transfers of large files.  I've seen many PXE clients that can deal
with this.  I'm all but certain all of the systems in our environment
work well this way with a TFTP blocksize of 4096 and 8192.  On the
other hand, I've been dealing with clients recently that can't deal
with the IP fragments being delivered out of order while having some
that can.

The more impressive part that Patrick didn't demonstrate is how using
TFTP windowsize or IP fragments shows greater benefit on links with
higher round trip latencies.


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