Re: DISCUSS's on rfc1981bis - MK Comments

[Gorry Fairhurst <[e-mail]>]

On 19/05/2017, 15:51, Mirja Kuehlewind (IETF) wrote:
> Hi Gorry, hi all,
>
> thanks for the work and the update. All comments from Gorry seemed fine to me and I will try to review the changes in the updated doc soon. One more minor comment on this:
>
>> Am 09.05.2017 um 08:07 schrieb Gorry Fairhurst<[e-mail]>:
>>
>>> I don't understand the following paragraph. Can this be removed?
>>> "Note: A packetization layer must not retransmit in response to
>>> every Packet Too Big message, since a burst of several oversized
>>> segments will give rise to several such messages and hence several
>>> retransmissions of the same data. If the new estimated PMTU is
>>> still wrong, the process repeats, and there is an exponential
>>> growth in the number of superfluous segments sent."
>>>
>> GF: I think the example is important. I'm not sure why that would be removed.
> The problem is I don’t understand this example. Is there an assumption that all mtu probe packets have been ‚generated‘ on the same packet? If so that makes sense but must the spelled out somewhere!
>
> Mirja
>
>
I think the wording is maybe jumbled, but the point is OK. Perhaps 
something like this would be clearer?

"Note: A packetization layer ought to avoid retransmitting the data in a probe packet
using the size reported in the last Packet Too Big message.
This is to avoid an exponential growth in the number of superfluous segments
that would be sent when a path encounters several successive smaller PMTU limits.
(Each new estimated PMTU would result in retransmission of the data in a smaller
packet that may itself fail if it encounters a still smaller PMTU in a device further
along the same path)."

Gorry