Subject: RE: [Sip] query on draft-rosenberg-sip-entfw-02.txt

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 22 Aug 2001 16:09:27 -0400

> -----Original Message-----
> From: Ranjit K Avasarala [mailto:[email-masked]]
> Sent: Thursday, August 09, 2001 11:47 AM
> To: [email-masked]
> Subject: [Sip] query on draft-rosenberg-sip-entfw-02.txt
> 
> 
> 
> Hi
>      I have a question on a statement in this draft:
> 
> It says  NAT will disappear with the deployment of Ipv6. Why is it so?

I suspect this is going to start a very large flame war, as nat discussions
always do, but I'll bite, since I think this is important.

Some argue that nats exist because address space is limited. My ISP has
limited space, so they give me only a single address, or charge exhorbitant
rates for extra addresses. So, I buy a nat to allow multiple devices to
exist behind a single address. Indeed, I am behind a nat at home right now.
With v6, address space is so plentiful, that the provider will happily give
me 100 addresses for nothing. So, the need for the nat goes away. Thats the
theory, at least.

I am not convinced that this is really actually true. I fear there will
still even be nats with v6. Here is why:

1. some people deploy nats for privacy reasons. That is, they make it so
that no one can know the actual internal addresses of boxes within my
network. In a typical configuration, nats won't actually provide any extra
protection, since mappings are frequently guessable or static. But, when
done right, it can provide a degree of privacy that is not afforded with a
firewall (generally, it requires randomized, dynamic mapping of internal
addresses into a LARGE external address space, larger than the internal
one!). The large external address space required here is expensive in v4,
but becomes cheaper in v6. Arguably, this usage of nats therefore becomes
more attractive with the deployment of v6!

2. People want addresses, so there is demand. Providers control the supply.
Even though they are plentiful, you still must go to an ISP to get one, and
they'll try and charge you money because of they know you want one. The
large supply will certainly drive the price down, but will virtually
unlimited addresses really be free? Not clear. Free is a hard business model
to sustain, as the last year has taught many of us....

3. v4 to v6 transition requires nats of some sort.

So, I hope they do go away ultimately, but I am not so certain. Because of
their pervasiveness today, and because its not clear they'll go away even
with v6, I am a strong advocate of dealing with them in a reasonable fashion
so that new applications can continue to be built and function, even though
there are lots of nats around. 

OK, flame away.

-Jonathan R.

---
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com

_______________________________________________
Sip mailing list  http://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip