Re: Space for Packet Metadata

Michael Tuexen <michael.tuexen@lurchi.franken.de> Wed, 28 February 2018 15:55 UTC

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Subject: Re: Space for Packet Metadata
From: Michael Tuexen <michael.tuexen@lurchi.franken.de>
In-Reply-To: <DM5PR2101MB09010484CA0782C13E43C2C4B3C70@DM5PR2101MB0901.namprd21.prod.outlook.com>
Date: Wed, 28 Feb 2018 16:55:02 +0100
Cc: "Eggert, Lars" <lars@netapp.com>, =?utf-8?Q?Mikkel_Fahn=C3=B8e_J=C3=B8rgensen?= <mikkelfj@gmail.com>, IETF QUIC WG <quic@ietf.org>
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To: Nick Banks <nibanks@microsoft.com>
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> On Feb 28, 2018, at 4:30 PM, Nick Banks <nibanks@microsoft.com> wrote:
> 
> According to spec, QUIC requires at least 1280 (from 9.4):
> 
> "QUIC depends on the network path supporting a MTU of at least 1280 octets. This is the IPv6 minimum MTU and therefore also supported by most modern IPv4 networks. An endpoint MUST NOT reduce its MTU below this number, even if it receives signals that indicate a smaller limit might exist.'
When discussing safe MTU values for WebRTC, 1280 for IPv6 was acceptable, but not for IPv4. After a discussion,
the suggested value for IPv4 was 1200. See
https://tools.ietf.org/html/draft-ietf-rtcweb-data-channel-13#section-5

Not sure what changed in between...

Best regards
Michael
> 
> - Nick
> 
> -----Original Message-----
> From: QUIC <quic-bounces@ietf.org> On Behalf Of Eggert, Lars
> Sent: Wednesday, February 28, 2018 7:12 AM
> To: Mikkel Fahnøe Jørgensen <mikkelfj@gmail.com>
> Cc: IETF QUIC WG <quic@ietf.org>
> Subject: Re: Space for Packet Metadata
> 
> On 2018-2-28, at 16:03, Mikkel Fahnøe Jørgensen <mikkelfj@gmail.com> wrote:
>> Yes, but can it go below 1200? It seems the handshake aims to squeeze up near the minimum guaranteed (required) PMTU and QUIC implementations would probably not expect to maintain a connection that drops below PMTU 1200.
> 
> The minimum IPv4 MTU is 576, so I'd expect QUIC stacks to probe as least that low.
> 
> Lars