Re: [nznog] Cloudflare IPv6 MTU

On 03/02/2015 16:40, Dave Mill wrote:

On Tue, Feb 3, 2015 at 3:40 PM, Simon Allard

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wrote:

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A fair number if you include customers who are tunnelled in PPPoE and have their MTU set to 1492.

I'm a bit of a newbie on this side of things so apologies if this is a stupid question.

So, with a situation like what Simon describes above what tends to fix the issue of the (generally) default TCP MSS of 1460 not fitting inside of this. Does path MTU discovery tend to fix this, or does change TCP MSS on a CPE (or BNG?) tend to fix it instead?

They both tend to break sometimes. Some people filter ICMPv6 too agressively and MSS negotiation seems to fail sometimes (I've never figured out why). And as Tom said, some load balancers screw up on MTUD. Brian