Subject: [Int-area] Packing in draft-touch-intarea-tunnels-00.txt

From: George Tsirtsis <[email-masked]>
Date: Mon, 23 Mar 2009 13:37:17 -0700

Was just looking at draft-touch-intarea-tunnels-00.txt

The section on "Packing (ala GigE bursting)" in this draft is a bit strange.
Although this is under a section listing known "issues" with
tunnels/fragmentation, it is not clear what the authors think about
it.
It is almost written as if the authors believe that tunnel packing is
a "good thing", is that true or am I mis-interpretatiing?

Thanks
George

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From: Joe Touch <[email-masked]>
Date: Mon, 23 Mar 2009 13:51:17 -0700

Hi, George,

> a "good thing", is that true or am I mis-interpretatiing?

The point of the doc is to be objective. That means pros, cons, and
caveats. The doc isn't fully matured, though, and some sections have
more detail than others. This probably needs development, e.g.:

It you're sending lots of 40-byte packets over a tunnel that can support
500-byte packets, then you can do so more efficiently by using packing.
However, you do run the risk of introducing timing artifacts (bursts)
into the traffic that goes through the tunnel, and this assumes that
enough packets arrive at the tunnel ingress to be useful to pack - a
tunnel ingress shouldn't delay packets just to pack them.

I.e., there are pros (efficiency), cons (timing effects), and caveats
(no additional queuing delay just to aggregate).

Is that what you were looking for? is that reasonable?

Joe

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From: George Tsirtsis <[email-masked]>
Date: Mon, 23 Mar 2009 14:11:29 -0700

Yes Joe, this is exactly what I am looking for, thanks.

I am somewhat concerned with taking something that is done over a
single hop technology (GigE) and applying it blindly to the multi-hop
Internet. e.g., one should think what this would do to packet
fate-sharing and what it would mean for end nodes if/when the tunnel
terminates on them etc.

George

On Mon, Mar 23, 2009 at 1:51 PM, Joe Touch <[email-masked]> wrote:
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From: Joe Touch <[email-masked]>
Date: Mon, 23 Mar 2009 14:16:33 -0700

> fate-sharing and what it would mean for end nodes if/when the tunnel

Agreed. It also impacts packet fate sharing over lossy tunnels.

Thanks - I'll put that in the update.

Joe