Re: Last Call: <draft-ietf-6man-rfc1981bis-04.txt> (Path MTU Discovery for IP version 6) to Internet Standard

"Eggert, Lars" <lars@netapp.com> Thu, 02 February 2017 10:22 UTC

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From: "Eggert, Lars" <lars@netapp.com>
To: Fernando Gont <fgont@si6networks.com>
Subject: Re: Last Call: <draft-ietf-6man-rfc1981bis-04.txt> (Path MTU Discovery for IP version 6) to Internet Standard
Thread-Topic: Last Call: <draft-ietf-6man-rfc1981bis-04.txt> (Path MTU Discovery for IP version 6) to Internet Standard
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Date: Thu, 2 Feb 2017 10:21:35 +0000
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On 2017-2-2, at 10:54, Fernando Gont <fgont@si6networks.com> wrote:
> On 02/02/2017 06:37 AM, Eggert, Lars wrote:
>> Also, even if ICMP delivery is assured, there are additional
>> complications for UDP, which has been seeing a lot of interest both
>> as a tunneling encapsulation and for applications (e.g., QUIC). Many
>> platforms do not provide UDP-sending applications any information
>> about arriving ICMP messages that were triggered by their
>> transmissions. So even if the path delivers ICMP, the OS makes
>> ICMP-based PMTUD for UDP often impossible. Another reason to
>> recommend 4821?
> 
> Agreed... although in this case this would be more of an app-layer
> implementation than one at the transport layer?

There are two dimensions here, one is in kernel vs. in userspace, the other which "layer" something is at. It used to be that "transport layer" (or "network layer" always implied "in kernel", but those days are past.

Lars