Re: [Int-area] Proxy function for PTB messages on the tunnel end

Joseph Touch <touch@strayalpha.com> Wed, 24 March 2021 20:50 UTC

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From: Joseph Touch <touch@strayalpha.com>
In-Reply-To: <348c2c09d1ad4a7dbac4add24bbb5ab8@huawei.com>
Date: Wed, 24 Mar 2021 13:50:18 -0700
Cc: "v6ops@ietf.org" <v6ops@ietf.org>, int-area <int-area@ietf.org>
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To: Vasilenko Eduard <vasilenko.eduard@huawei.com>
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Subject: Re: [Int-area] Proxy function for PTB messages on the tunnel end
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Eduard,

> On Mar 24, 2021, at 1:04 PM, Vasilenko Eduard <vasilenko.eduard@huawei.com> wrote:
> 
> Hi Joseph,
> You have presented below (and in many other messages) a long list of policies (extensive usage of “SHOULD”, “NEVER”, “MUST”)
> That are new – would change how current tunnels operate

Some do, yes. To make them consistent and correct.

> Why virtual link could not send ICMP PTB (like on a physical link)? Just because… it is “unsolicited”. But one moment – any other PTB is unsolicited too - It is an event.

PTBs are only sent when a packet arrives at a router and the router decides to forward that packet to a link whose link MTU is too small.

If the link MTU changes, there would never be an ICMP PTB *until* a new packet is sent.

Go ahead - change the MTU of any interface (tunnel or not) of any router and tell me if you see a PTB being sent *ANYWHERE*.

Nothing happens until the next packet goes to that interface. I.e., PTBs are always in response to an attempt to send a packet - not merely to an interface change.

Joe