[Serusers] Access control on PSTN gateways

[Jiri Kuthan]

At 01:03 AM 1/11/2003, Michael Graff wrote:
[...]
>That said, I'm new to telephone stuff, so I may be asking the wrong
>questions or using the wrong words.

Don't worry, that's mostly me where confusion comes from. 

I understand now -- you wish that requests From: sip:graff at isc.org
will appear to the destination as From: sip:65077970xx at isc.org so
that a gateway can propagate the number down to PSTN and use it
for accounting.

I think the right way to do this thing is to have a proxy server
attaching a "network asserted identity" (NAI) to the request. The
NAI piece of data includes then the desired number. This has
been recently discussed on the IETF/SIPPING mailing list, thread
"URIs for Gateways". The major drawback of this method is it is
still under discussion, it will take quite long to complete
(if ever, you never know in IETF).

Changing content of From header field by proxy is imho too risky and 
could result in interoperability problems. Pre-3261 implementations use
from to identify transactions and dialogs. 3261 implementations only
use from-tag, but it is hard to tell which currently available
implementations really do that. Some people might be concerned too
about a possible damage to transparency, which -- similarly to
how NAT's rewrite packets and cause confusion -- might result in
confusion.

So I may be too pesimistic or ignorant, but I unfortunately only
see these imperfect options:
- account from a proxy server and use some local translation
  (graff->65077970xx) during the accounting process; ignore the issue
  of displaying 65077970xx down in PSTN
- use 65077970xx as SIP user id and 'graff' as an alias for incoming
  request
- wait until NAI is standardized in IETF and deployed in SIP products
- rewriting From at a quite high risk of interoperability problems

What do you think?

-Jiri