On Jan 27, 2014, at 4:25 PM, Edward Crabbe <edc(_at_)google(_dot_)com> wrote:
I assume we're talking about the chksum issue here. If this is the case,
please go fix IPv6 by adding a hop by hop checksum extension header and
getting it implemented by vendors. ^_^
Please don't use UDP as a network layer.
See how easy that works?
If by 'this' we mean stateful congestion control of multiple terabits of
tunnel traffic, then it is *most certainly* not a solved problem, and
definitely not something I'm interested in paying for.
Oh, nobody wants to pay for anything, including (and especially) following
standards. Fortunately, the IETF isn't an extension of an industrial company's
marketing department (or isn't yet, I should say).
Joe
cheers,
-ed
On Mon, Jan 27, 2014 at 11:24 AM, Joe Touch <touch(_at_)isi(_dot_)edu> wrote:
On 1/27/2014 11:19 AM, Joel M. Halpern wrote:
Yes Joe, routers could ahve been built to do those calcualtions at that
performance scale.
There are however two major problems:
1) That is not how routers are built.
2) The target performance scale is rather higher.
So could someone build an ASIC to do what you want?
Has. It's already part of nearly every DMA ASIC in a network interface
already.
Probably. Is there
any reason in the world to expect operators to pay the significant extra
cost for such?Not that I can see.
We're talking about a ring of full adders, the specs for which are given in
an RFC that's 18 years old, and that is already implemented in nearly every
host interface, including 10Gps NICs.
And we're talking about "routers", many variants of which operate at very
high speeds and transparently proxy TCP already. So this is a solved problem.
And even if we could and they would, that is not the world into which we
are deploying these tunnels.
We're back to "that's not what they do now", at least in some devices.
Well, they don't use MPLS in UDP (since no spec exists), so clearly if
they're limited to doing what they already do, this is an exercise in
futility.
Joe
Yours,
Joel
On 1/27/14 1:53 PM, Joe Touch wrote:
On 1/27/2014 10:48 AM, joel jaeggli wrote:
On 1/27/14, 8:48 AM, Joe Touch wrote:
Those same mechanisms have provided hardware checksum support for a
very long time.
The new header and the payload are actually in different parts of the
forwarding complex until they hit the output queue, you can't checksum
data you don't have.
You can (and some do) the checksum component parts when things go into
memory; the partial sums can be added as the parts are combined in the
output queue.
I appreciate that we're all taking about what might be done, but the
reality is that there are many 'transparent TCP proxies' that have to do
this, so there's clearly a solution, and it clearly runs fast enough.
Joe
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