NAT444 or ?

Thu Sep 8 17:10:24 UTC 2011

> -----Original Message-----
> From: Simon Perreault [mailto:simon.perreault at viagenie.ca]
> Sent: Wednesday, September 07, 2011 2:29 PM
> To: nanog at nanog.org
> Subject: Re: NAT444 or ?
> 
> David Israel wrote, on 09/07/2011 04:21 PM:
> > In theory, this
> > particular performance problem should only arise when the NAT gear
> insists on a
> > unique port per session (which is common, but unnecessary)
> 
> What you're describing is known as "endpoint-independent mapping"
> behaviour. It
> is good for not breaking applications, not so good for scalability. RFC
> 4787 section 4.1 makes it a MUST.

There are two dimensions of that scalability, of course:

Endpoint-independent mapping means better scaling of the NAT itself, 
because it stores less state (slightly less memory for each active 
mapping and slightly less per-packet processing).  This savings
is exchanged for worse IPv4 utilization -- which I agree is not so
good for scalability.

-d