Re: FW: Why?

inline.

Tony Hain wrote:

> Joel M. Halpern wrote:
>
> > This discussion seems to take as a premise the view that if we define
> > applications only on IPv6, even though they could be defined on IPv4, that
> > this will give people a reason to use IPv6.
> > It also seems to take as a premise that if we don't define ways to work
> > around NATs, people won't use the applications with NATs.
>
> I suffer from no such disillusions as those are not the premise for the
> initial note, though without having the background in the original note it
> is easy to see why someone might come to that conclusion. 
>
> My assumption is that the market will not ignore the opportunity to develop
> NAT traversal technologies. That does not equate to a need for the IETF to
> waste valuable resources standardizing hacks that attempt to mask previous
> hacks. In particular the IAB needs to be looking forward and helping the
> application community understand that there are approaches today that allow
> them to ignore the nonsense that has grown in the network by using IPv6
> tunneling as a NAT traversal tool. This approach completely avoids the need
> for complex and error prone ALGs.
I agree that ALGs are not the answer, and I believe the reasons for that 
are treated in:
http://www.ietf.org/internet-drafts/draft-iab-nat-traversal-considerations-00.txt

As I mentioned during the plenary, the document above makes a case that 
the right answer in many situations are vpn-ish technologies that 
include v6 tunnels. However, different applications have different 
needs, and there are real differences between the various vpn-ish 
solutions (TURN, STUN, teredo, etc.) that are driving their development 
and adoption. For VoIP, where the nat traversal issue has been 
especially painful, the increase in voice latency, packet loss, and 
substantial cost increase of relaying traffic through the tunnel 
servers, has driven people to solutions like STUN. Thus, I cannot agree 
that there only needs to be a single solution here.
That said, I agree that the IAB nat traversal consideration document 
lacks adequate consideration of how evolution plays into this, and I'll 
endeavor to improve the document on that front.
Another concern I have is that, in an IPv6-only world, even if you 
eliminate NAT, there will still be firewalls, and those firewalls will 
frequently have the property that they block traffic coming from the 
outside to a particular IP/port on the inside unless an outbound packet 
has been generated from the inside from that IP/port. This means that IP 
addresses are not globally reachable. You'd still need most of the same 
solutions we have on the table today to deal with this problem. Indeed, 
in the VoIP space, I believe you'd need pretty much everything, 
excepting you'd be able to remove a single attribute from a few of the 
protocols (STUN and TURN in particular), which tell the endpoint its 
address on the other side of the NAT. The endpoint knows its address, 
but all of the protocol machinery is still needed to rendezvous with the 
other participant in the call.

-Jonathan R.
--
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Director, Service Provider VoIP Architecture   Parsippany, NJ 07054-2711
Cisco Systems
jdrosen(_at_)cisco(_dot_)com                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com

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