Test your connectivity for World IPv6 Day

[Rémi Després]

Le 7 juin 2011 à 14:29, Mark Smith a écrit :

> On Tue, 7 Jun 2011 12:30:08 +0200
> Rémi Després <remi.despres at free.fr> wrote:
> 
>> 
>> Le 6 juin 2011 à 21:41, Daniel Roesen a écrit :
>> 
>>> On Mon, Jun 06, 2011 at 05:58:43PM +0200, Rémi Després wrote:
>>>> Unless there are good reasons to know that a longer PMTU applies to all
>>>> their connections, all servers SHOULD send IPv6 packets to off-link
>>>> destinations with 1280 octets as default PMTU.

I agree that this sentence I wrote is too restrictive.
Longer PMTU's can be discovered on a per connection basis.
Yet 1280 remains AFAIK a good value to start with.


>>> 
>>> So you advocate making 1280 effectively the maximum MTU, not the minimum?
>> 
>> The "default" MTU, not the "maximum".
>> 
>> If some PMTUD permits to detect that a larger PMTU is possible on a specific path, it can then be used.
> 
> Conventional PMTUD only works downwards, so if you start at a
> default MTU 1280, you'll never discover a larger PMTU than 1280. MSS
> also works to constrain that, as it tells the other end the maximum
> segment size to send. 

This being so, which size do you recommend to start with in IPv6?
- 1500?
- 9000 to get a chance to reach jumbo-frame sizes?

RD

 


> 
>> Also, on-link connections can use the link MTU.
>> Regards,
>> RD
>> 
>>> 
>>> I'm with Fred here. Fix broken paths, not work around the problems.
>>> 
>>> Best regards,
>>> Daniel
>>> 
>>> -- 
>>> CLUE-RIPE -- Jabber: dr at cluenet.de -- dr at IRCnet -- PGP: 0xA85C8AA0
>>