Re: How to find a sick router with 2.6.17+ and tcp_window_scaling enabled

From: Willy Tarreau
Date: Tue Aug 15 2006 - 14:47:09 EST

On Tue, Aug 15, 2006 at 02:33:00PM -0400, alex@xxxxxxxxxx wrote:
> On Tue, Aug 15, 2006 at 08:19:39PM +0200, Willy Tarreau wrote:
> > > This is absolutely not correct. Routers forward packets. They do not mangle
> > > the data in them.
> >
> > Believe it or not, there are a lot of routers nowadays that can do NAT.
> > And even for very basic NAT, you have to recompute the TCP checksum, which
> > means that you mangle data within the packet. Even worse, some of them are
> > able to NAT complex protocols such as FTP and for this, they need to mangle
> > the application payload. OK, this should not be the router's job, but it's
> > often the best placed to do the job, and there is customer demand for this.
> Just because you are using a Linksys/Netgear or god else knows what to
> mangle your packets and call that device a router

That's not what I call a router !

> does not mean that normal service providers have NAT enabled on
> their GSRs and Junipers.

not on the PE, but offen on the CE.

> The issue is not in a router running IOS somewhere. The issue is in the
> broken code/broken driver/broken something on the end-point.

He may very well have an IOS based 1600 or equivalent doing a very dirty NAT.

> Alex


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