IP Fragmentation - Not reliable over the Internet?

• Subject: IP Fragmentation - Not reliable over the Internet?
• From: kris at kriskinc.com (Kristian Kielhofner)
• Date: Fri, 20 Sep 2013 08:54:51 -0400
• In-reply-to: <[email protected]>
• References: <6e53114d968f40f097a83640d90f9acf@BN1PR03MB171.namprd03.prod.outlook.com> <[email protected]> <[email protected]> <[email protected]> <[email protected]> <[email protected]> <m2ob8fjspp.wl%[email protected]> <[email protected]> <[email protected]> <m2bo4ei045.wl%[email protected]> <[email protected]>

I know I'm digging up an old thread here but I've spent some time
analyzing some of the significant changes that Apple has made to the
Facetime protocol, apparently with a huge focus on IP packet size to
avoid fragmentation issues:

http://blog.krisk.org/2013/09/apples-new-facetime-sip-perspective.html

I'm betting they've had HUGE issues with IP+UDP MTU issues over the
last three years...

On Sun, Sep 1, 2013 at 4:34 PM, Emile Aben <emile.aben at ripe.net> wrote:
> On 31/08/2013 13:13, Randy Bush wrote:
>> could you please test with ipv6?
>
> This is what I see for various IPv6 payloads (large ICMPv6 echo
> requests) from all RIPE Atlas probes that where available at the time to
> a single "known good" MTU 1500 destination:
>
> plen    fail%   nr_probes
> 100     9.64    1266
> 500     9.34    1039
> 1000    9.94    1298
> 1240    9.94    1308
> 1241    11.62   1300
> 1440    12.70   890
> 1441    14.70   1306
> 1460    15.18   1304
> 1461    19.84   1290
> 1462    22.02   1294
>
> plen: IPv6 payload length (ie. not including 40byte IPv6 header)
> fail%: percentage of probes that didn't get any of the 5 pkts that were
> sent. Note that there is a large baseline failure rate in IPv6 on RIPE
> Atlas probes [1], which would explain the ~10% failure rate for the
> smaller packets.
>
> I plan to do more analysis and start writing this up on RIPE Labs over
> the next few days.
>
> cheers,
> Emile Aben
> RIPE NCC
>
>
> [1]
> https://labs.ripe.net/Members/stephane_bortzmeyer/how-many-atlas-probes-believe-they-have-ipv6-but-are-wrong
>



-- 
Kristian Kielhofner

• References:
  • IP Fragmentation - Not reliable over the Internet?
    • From: emile.aben at ripe.net (Emile Aben)

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