----- Original Message -----
> From: Fred Baker (fred) <f...@cisco.com>
> To: Randy Bush <ra...@psg.com>
> Cc: IPv6 Deployment Prevention <ipv6@ietf.org>
> Sent: Wednesday, 26 June 2013 1:30 PM
> Subject: Re: New Version Notification for
draft-bonica-6man-frag-deprecate-00.txt
>
>
> On Jun 25, 2013, at 12:42 PM, Randy Bush <ra...@psg.com> wrote:
>
>> in reality, you can not count on pmtud working
>
> One of these days, I'll understand why Linux/FreeBSD/Windows/Apple don't
> implement RFC 4821.
Actually, Linux does, it just needs to be switched on in /proc/sys/net/ipv4/
tcp_mtu_probing - INTEGER Controls TCP Packetization-Layer Path MTU Discovery.
Takes three values: 0 - Disabled 1 - Disabled by default, enabled when an ICMP
black hole detected 2 - Always enabled, use initial MSS of tcp_base_mss.
I think Windows also implements something similar:
"
Troubleshooting PMTU Black Hole Routers"
http://technet.microsoft.com/en-us/library/cc958871.aspx
One of the issues with conventional ICMP PTB based PMTUD is the default rate
limits on ICMP messages on broadband routers with PPPoE subscribers i.e.
dumbell [1500][1492][1500] MTUs, slowing down PMTUD. Upping the limit on ICMP
PTBs is an obscure parameter to have to remember to change, and it isn't clear
exactly what to change it to - IIRC, the value I've used in the past is 1000/s
up from 10/s. RFC4821 would be nice because it would avoid control plane
processing that ICMP based PMTUD causes.
Regards,
Mark.
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