Yesterday's Windows update causes IPv4 to be default

Dan Wing dwing at
Thu Nov 15 18:04:40 CET 2012

> -----Original Message-----
> From: at [mailto:ipv6-
> at] On Behalf Of Steinar H.
> Gunderson
> Sent: Thursday, November 15, 2012 5:04 AM
> To: Lorenzo Colitti
> Cc: IPv6 Ops list; Erik Kline; Mike Jones; Nick Hilliard
> Subject: Re: Yesterday's Windows update causes IPv4 to be default
> 2012/11/15 Lorenzo Colitti <lorenzo at>:
> > 3. It imposes twice the connection load on server operators.
> Only twice the SYN load, no? (Which, in many cases, is much cheaper than
> a full new socket.)

At minimum, Apple's existing algorithm needs to see a SYNACK (to determine
round trip time over that address family).  That doesn't cost much on
most servers or load balancers, which take pains to avoid creating TCP 
state that early (to combat SYN flood attacks), or have good algorithms
to discard SYN floods and create as little state as possible.

The traces I remember taking had a full TCP 3-way handshake, though,
which was then reset.


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