[137519] in North American Network Operators' Group
Re: NIST and SP800-119
daemon@ATHENA.MIT.EDU (Steven Bellovin)
Tue Feb 15 11:23:26 2011
From: Steven Bellovin <smb@cs.columbia.edu>
In-Reply-To: <AANLkTimY3JNVW7CEJxkEWZ5=7J6Mm20VMspUfZC0aduy@mail.gmail.com>
Date: Tue, 15 Feb 2011 11:22:20 -0500
To: William Herrin <bill@herrin.us>
Cc: NANOG list <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Feb 15, 2011, at 10:36 54AM, William Herrin wrote:
> On Tue, Feb 15, 2011 at 10:09 AM, Joe Abley <jabley@hopcount.ca> =
wrote:
>> On 2011-02-14, at 21:41, William Herrin wrote:
>>> On Mon, Feb 14, 2011 at 7:24 PM, TR Shaw <tshaw@oitc.com> wrote:
>>>> Just wondering what this community thinks of NIST in
>>>> general and their SP800-119 (
>>>> http://csrc.nist.gov/publications/nistpubs/800-119/sp800-119.pdf )
>>>> writeup about IPv6 in particular.
>>>=20
>>> Well, according to this document IPv4 path MTU discovery is,
>>> "optional, not widely used."
>>=20
>> Optional seems right. Have there been any recent studies on how =
widely pMTUd is actually used in v4?
>=20
> Hi Joe,
>=20
> Are you aware of a TCP implementation in an OS that shipped within the
> last decade but doesn't enable IPv4 pMTUd by default? Each version of
> Windows and all the major unixes use it on every TCP connection unless
> you explicitly turn it off.
>=20
All modern TCPs support it; many firewalls are configured to block the =
necessary ICMPs.
--Steve Bellovin, http://www.cs.columbia.edu/~smb
