Re: [v6ops] [Last-Call] Tsvart last call review of draft-ietf-v6ops-ipv6-ehs-packet-drops-05

Fernando Gont <> Mon, 22 February 2021 18:14 UTC

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To: Tom Herbert <>, Nick Hilliard <>
Cc: Brian E Carpenter <>, Gorry Fairhurst <>,,,, IPv6 Operations <>
References: <> <> <> <> <> <> <> <> <> <> <>
From: Fernando Gont <>
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Date: Mon, 22 Feb 2021 14:33:29 -0300
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Subject: Re: [v6ops] [Last-Call] Tsvart last call review of draft-ietf-v6ops-ipv6-ehs-packet-drops-05
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On 22/2/21 13:29, Tom Herbert wrote:
> On Mon, Feb 22, 2021 at 8:23 AM Nick Hilliard <> wrote:
> I understand the purpose of the draft, however, IMO, for the problems
> that are described there is insufficient detail and scope to draw any
> meaningful conclusions or take away any new insights.

Then I guess we disagree. One of the most commonly questions asked in 
this contact is "But... why do routers look inside packets?" -- and this 
document answers that question, along with the challenges it represents.

Note: in a thread on specific transports you also asked what information 
routers process. And this document also answers such question.

> When the draft
> mentions that routers might drop packets because packets are too long,
> then the obvious question is what exactly is too long.

And the obvious answer is that that depends on a vendor/model basis. If 
the router only copies the mandatory header to a buffer, then "too long" 
might be "1 EH".

> Since this
> draft is discussing real implementation and not theory, it seems like
> measuring the extent and determining the real operational parameters
> of the problems, like what a useful minimum length of header chains
> is, seems straightforward either by experimentation or simply polling
> router vendors to see what they support.

It performs a qualitative analysis of the problem.

What you ask seems to be either RFC7872bis, or a document that would 
complement RFC7872.

... but certainly out of the scope of this document.

Fernando Gont
SI6 Networks
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