Re: [v4tov6transition] Any Experience with Using Behave's StatelessNAT-PT for IMS-SIP VoIP Application...

["Mosley, Leonard" <[e-mail]>]

Tks Cameron, I concur with your comments below and was just curious if the Behave's IP/ICMP Algorithm/Stateful NAT64 had been evaluated in an SBC (IMS VoIP) environment yet and any "unexpected" impacts.  Maybe Xing Li can shed some light as Fred indicated.

Tks again,

Len...

-----Original Message-----
From: Cameron Byrne [mailto:[e-mail]]
Sent: Wednesday, September 22, 2010 12:23 PM
To: Hui Deng
Cc: Mosley, Leonard; [e-mail]; [e-mail]; [e-mail]
Subject: Re: [v4tov6transition] Any Experience with Using Behave's StatelessNAT-PT for IMS-SIP VoIP Application...

On Wed, Sep 22, 2010 at 9:01 AM, Hui Deng <[e-mail]> wrote:
> I guess that NATPT and B2BUA are different story?

Right, B2BUA is a proxy that terminates and re-initiates the call leg.
 B2BUA are very specific to SIP and therefore can be very robust in
their handling of SIP traffic.

As where any form of NAT is fundamentally just a "network layer"
function with some ALG to support.  And, ALGs are notoriously poorly
implemented and seldom standardized.

> What about ur opinion about performance of deprecated NAT-PT regarding to
> SIP-SDP-RTP?
>

I do not recommend anyone to have a going forward network strategy
based on a deprecated protocol, if it can be avoided.

VoIP is generally considered very important traffic (billable minutes,
emergency services, branded services) while Internet is considered not
very important (best effort,  ...).  That said, i believe most network
operators feel more comfortable keeping the protocol translation
infrastructure for VoIP / IMS separate (use a B2BUA or P-CSCF
functions) from the general use protocol translation (NAT64).  The
basic logic is that the NAT64, like NAT44 today, will have a lot of
entropy from the various different types of protocols and
interactions, as where the B2BUA will be much more focused functions
with stricter rules and less entropy that can trigger "unforeseen
feature interactions", aka bugs.

Also, given my limited scope, i have not seen a strong use case, IMHO,
for stateless translation since it requires 1 to 1 mapping of IPv4 to
IPv6, and thus does not solve the address exhaustion issue .... which
is why folks are doing IPv6 in the first place.

Generally about NAT64 performance, we expect it to be approximately
consistent with NAT44 CGN performance, slightly less on some
platforms.  ALGs generally decrease performance since they require
more complex logic deeper in the packet.

Cameron

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