Re: NIST and SP800-119

[Steven Bellovin <smb () cs columbia edu>]

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.
> > >
> > > Well, according to this document IPv4 path MTU discovery is,
> > > "optional, not widely used."
> >
> > Optional seems right. Have there been any recent studies on how widely pMTUd is actually used in v4?
>
> Hi Joe,
>
> 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.
All modern TCPs support it; many firewalls are configured to block the necessary ICMPs.


                --Steve Bellovin, http://www.cs.columbia.edu/~smb