Re: [Int-area] I-D Action: draft-ietf-intarea-tunnels-05.txt

"Templin, Fred L" <Fred.L.Templin@boeing.com> Thu, 04 May 2017 17:28 UTC

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From: "Templin, Fred L" <Fred.L.Templin@boeing.com>
To: Joe Touch <touch@isi.edu>
CC: "int-area@ietf.org" <int-area@ietf.org>
Thread-Topic: [Int-area] I-D Action: draft-ietf-intarea-tunnels-05.txt
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Date: Thu, 4 May 2017 17:28:24 +0000
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Subject: Re: [Int-area] I-D Action: draft-ietf-intarea-tunnels-05.txt
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Hi Joe,

> -----Original Message-----
> From: Joe Touch [mailto:touch@isi.edu]
> Sent: Wednesday, May 03, 2017 3:04 PM
> To: Templin, Fred L <Fred.L.Templin@boeing.com>
> Cc: int-area@ietf.org
> Subject: Re: [Int-area] I-D Action: draft-ietf-intarea-tunnels-05.txt
> 
> Winding down to the last part:
> 
> (I agree that encryption or mimicry is useful only when it works, but
> not much more can be said than that)
> 
> 
> On 5/3/2017 2:59 PM, Templin, Fred L wrote:
> > The problem is that if there are N paths in the multipath the ingress has
> > no way of knowing that it has probed all N of them. And, if a transit
> > packet arrives that would be tunneled over a path that has not been
> > probed, it could black hole if the MTU is too small.
> 
> That's correct - PLPMTUD can fail at any time if the PMTU changes and
> becomes smaller (for any reason, including link reconfiguration, path
> changes, multipath selection).
> 
> That's why it keeps retrying. Again, this isn't new or unique to tunnels.

What is different about tunnels is that they are the sources of the tunnel
packets but are not the sources of the transit packets. And, except for
some tunnel-inserted obfuscation such as encryption, there is no way
for the tunnel to act like it is the source of the transit packets.

That said, it sounds like you may have some ideas on how to re-formulate
some of the text. If you want to do that and then have me re-review it
I could do that.

Thanks - Fred 

> Joe
>