Subject: [Sipping] [Sip] Anonymization of To & revisiting tags alone for dialog ID

From: Juha Heinanen <[email-masked]>
Date: Sat, 9 Feb 2002 10:41:38 +0200

Jonathan Rosenberg writes:

 > The spec has generally assumed that the r-uri equals the To field for
 > new requests. The exceptions are register, and pre-loaded routes, both
 > of which are mentioned in bis-07. 

moved to sipping, this reminds me of one thing regarding register that i
have never remembered to ask.

bis-07 says that in the register mmessage

  The Request-URI names the domain of the location service for which the
  registration is meant (for example, sip:chicago.com ). 1514

and figure 2 in bis-07 shows the register message going *directly* from
the UA to the registrar without going through any proxies.

now my questions are: 

1) how does the UA know which host in the domain, in
the example above, within chicago.com, acts as the registrar of that
domain?  

2) is there an srv record that points the UA to the correct host and if
not, why?

3) why can't the UA simply send also the register message to its
outbound proxy that would them handle the dns lookup and find the host
acting as the registrar?

what i'm after here is making the UA as simple as possible.

-- juha

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---

From: "Bob Penfield" <[email-masked]>
Date: Mon, 11 Feb 2002 10:13:22 -0500

----- Original Message -----
From: "Juha Heinanen" <[email-masked]>
<snip>
> the example above, within chicago.com, acts as the registrar of that

If the UA can do DNS, it follows the procedures in:
http://bdsl.greycouncil.com/sipwg/drafts/draft-ietf-sip-srv-04.txt

> 2) is there an srv record that points the UA to the correct host and if

yes. see above draft

> outbound proxy that would them handle the dns lookup and find the host

The UA IS allowed to send the register request to its outbound proxy. The
proxy will locate the registrar and send it on when it sees that it is not
the target of the Request_URI in accordance with section 16.4 of bis-07.

---

From: Juha Heinanen <[email-masked]>
Date: Mon, 11 Feb 2002 17:29:59 +0200

> http://bdsl.greycouncil.com/sipwg/drafts/draft-ietf-sip-srv-04.txt

from that i-d i have found how a sip ua finds a proxy server of domain
chicago.com, not how a sip ua finds a registrar of domain chicago.com.
what if the proxy server of a domain is a different host than the
registrar?

-- juha

---

From: Aki Niemi <[email-masked]>
Date: 11 Feb 2002 18:50:36 +0200

I would argue, that this depends on the configuration of chicago.com's
network. The server at that domain receiving the request may accept and
process it by itself, or may forward it to a server that does. 

Similarly, I do not have to know the exact Presence Server address at
chicago.com, when I SUBSCRIBE to [email-masked]'s presence.

Br,
Aki

---

From: Juha Heinanen <[email-masked]>
Date: Mon, 11 Feb 2002 17:56:13 +0200

> process it by itself, or may forward it to a server that does. 

yes, that is what i thought too, i.e., that the proxy serving
chicago.com would know who is the registrar of chicago.com.  

it would be nice though if i would not need to manually configure in the
proxy, who is the registrar of that domain.  that would be possible if
there would be a separate srv entry for registars.

-- juha

---

From: Aki Niemi <[email-masked]>
Date: 11 Feb 2002 19:14:46 +0200

> there would be a separate srv entry for registars.

However, I would consider announcing the SRV records of all of my
network servers to the rest of the Internet more expensive than the
configuration of the domain's authority proxy.

Br,
Aki

---

From: "Dean Willis" <[email-masked]>
Date: Mon, 11 Feb 2002 11:03:57 -0600

----- Original Message -----
From: "Juha Heinanen" <[email-masked]>
To: "Bob Penfield" <[email-masked]>
Cc: <[email-masked]>
Sent: Monday, February 11, 2002 9:29 AM
Subject: Re: [Sipping] Register question (was [Sip] Anonymization of To &
revisiting tags alone for dialog ID)

> what if the proxy server of a domain is a different host than the

That's chicago.com's problem. The most likely configuration is that their
externally visible proxy either IS a registrar, or has message-specific
routing to send REGISTER messages on to a registrar. This configuration,
however, is not required. Some phones allow their registrar to be configured
seperately from their home proxy, so one could build a diffeent
configuration.

How does you mail client know where your POP server is, or where your SMTP
server is? You tell it. Personally, I use nine of each, depending on which
of my multiple personalities is in control at the moment, but most people
just have one.

--
Dean

---

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 11 Feb 2002 14:31:14 -0500

> there would be a separate srv entry for registars.

Where do you draw the line for demux? Should we have separate SRV
entries for presence servers? What about specific packages for
SUBSCRIBE, so that presence goes to one server, conferencing models to
another, and so on? I think all of this is best hidden within the
providers network, with a front proxy either processing things locally,
or sending them to the server(s) its been configured to talk to. That
provides for a much richer set of security. I see little gained from
exposing this to clients trying to reach that domain.

-Jonathan R.

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

---

From: Juha Heinanen <[email-masked]>
Date: Mon, 11 Feb 2002 21:56:24 +0200

Jonathan Rosenberg writes:

 > entries for presence servers? 

ok, it is fine with me for the proxy of the domain to know where the
different servers of the domain are.  my question was in the first place
prompted by figure 2 of bis-07 that shows the ua sending the register
message directly to the registrar without having no automatic means to
find out who the registrar is.

-- juha

---

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 11 Feb 2002 15:29:25 -0500

> find out who the registrar is.

Ah, now that is a good point. Interestingly, the text never even refers
to the figure. The figure is OK if the text would say that this is a
logical model. However, that will probably confuse people, so I will
enter a bug to make it represent physical reality (REG also goes to
proxy first), and also make sure the figure is discussed in the text.

THanks,
Jonathan R.