Subject: [Sip] SIP AoR, tel and ENUM - Second Try

From: "Stastny Richard" <[email-masked]>
Date: Wed, 7 Dec 2005 13:01:28 +0100

Hi folks,

thanks for the statements sofar, but I am still confused
(maybe even more ;-)

It seems also that my first post was not too well formulated

The basic question was:
Should Infrastructure ENUM contain a routing information
to the next hop only (the ingress border element of Provider B
(or administrative domain B) 
or simply a mapping from an E.164 number to an AoR?

I will try to give another example and start from
within the scope of SPEERMINT (I hope this is the
last iteration before the name gets too lomg ;-)

I subscribe with provider B and get a default public
user identity (AoR) from this provider:
e.g. sip:[email-masked]

This "foo" can be anything the provider chooses it to be:
e.g. an alphanumeric string such as ywzabcd,
a numeric string such as 16241 (my FWD number)
or 019793321 or 4319793321

Any other provider A having a peering agreement
with Provider B must be able to route a SIP call
given this SIP AoR to provider B, either to the
SIP proxy hosting this account or at least to
the ingress proxy(s) in provider B network.

On way to do so is to use SRV records within
the zone of provB.net pointing to e.g

ingress14.provB.net
and
ingress21.provB.net

Question: is this correct?

Note: after the ingress proxy provider B
may use another mapping mechanism to find
the real hosting server e.g. srv21.provB.net

Now I as a user are not happy with this default
public user identity, I want to have some aliases

eg: 
1)sip:[email-masked] and
2) +43 1 9793321

In case 1) I assume that provider B needs
to provide me with redirect server(s), and I
need to enter in stastny.com SRV records
to point to these redirect servers
e.g. redirect.provB.net

sip:richard.stastny.com is redirected to
sip:[email-masked]

Question: is this correct?

In case 2) we need Infrastructure ENUM
[Side note; in my user ENUM I would either enter
sip:[email-masked] or sip:[email-masked]
this is my choice]

Now the question is: what goes into Infrastructure
ENUM for say +4319793321?

Is it:
Sip:[email-masked] (if plain sip:[email-masked] works
this must also work)
OR
sip:[email-masked];user=phone (correct?)
OR
sip:[email-masked] (wrong?)
OR
sip:[email-masked] (valid only if 4319793321 = foo)

OR is it
sip:[email-masked];user=phone (and the above variants)
AND
sip:[email-masked];user=phone

In this last case one would not need to query the
SRV records in provB.net

I hope I did not confuse the issue even more

Richard

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---

From: Klaus Darilion <[email-masked]>
Date: Wed, 07 Dec 2005 13:39:35 +0100

Hi Richard!

comments inline

> or simply a mapping from an E.164 number to an AoR?

IMHO it should be a mapping to an AoR as in user ENUM.

> I will try to give another example and start from
...
> Question: is this correct?

IMO yes. Thus, A sends "INVITE sip:[email-masked]" to ingress14.provB.net

> 1)sip:[email-masked] and

This is a working scenario. But a redirect server is not mandatory. It 
may also be a proxy which forwards the request "INVITE 
sip:richard.stastny.com" to "INVITE sip:[email-masked]".

It is also possbile that SRV for stastny.com points directly to 
ingress12.provB.net and ingress12 knows about all hosted SIP domains and 
knows how to forward the request to the end user.

But this is a design decision of the provB and IMO should be out of 
scope of SPEERMINT. provB may use redirect server, provC may accept all 
hosted SIP domains directly on their ingress points, .....

I personally prefer relaying instead of redirect. E.g. redirect raises 
questions like: How should intercept the redirect response and forward 
to the new URI? The UA client or the SIP proxy of provA or the egress proxy?

The important thing is that the originator (provA) should not have to 
take care how provB implemented the hosting of SIP domains.

> sip:[email-masked];user=phone

IMO all of these are valid. It's up to the choice of provB. provB can 
put anything into ENUM as long as provB is able to map from the URI in 
I-ENUM to the end user.

If I would design the network for provB, I would use version 2 (without 
user=phone as the user are not limited to phones).

> In this last case one would not need to query the

Also in the last case (if beeing conform with RFC3263), the egress proxy 
has to perform NAPTR and SRV lookups. If you want to avoid them, just 
put the IP address or the port into the host part, e.g.

sip:[email-masked]:5060;user=phone

regards
klaus

---

From: Paul Kyzivat <[email-masked]>
Date: Wed, 07 Dec 2005 22:56:23 -0500

Richard - this second try is much more successful than the first!

	Paul

Klaus Darilion wrote:
>> (or administrative domain B) or simply a mapping from an E.164 number 
>> to an AoR?
> 

I think Richard has some specific ideas about what form of sip URI may 
be an AOR ans which may not. I am not entirely sure what those are, but 
suspect I disagree at least somewhat.

For this application, it should be something known to be stable by 
whoever is making the entry. Beyond that I don't see there is a need to 
be very specific.

If the user "owning" this number also has an "email-style" AOR that is 
intended to be fully equivalent to the phone number then that is 
probably one good choice. But it may be that a provider would rather set 
up the ENUM to simply route the numbers to itself using the user=phone 
form. I see nothing wrong with that either.

>> or 019793321 or 4319793321

If it is a telephony-oriented provider, there may be no reason to assign 
such an AOR. It might prefer simply to assign an AOR of the form: 
sip:[email-masked];user=phone.

>> eg: 1)sip:[email-masked] and
>> 2) +43 1 9793321

I guess (2) is really: tel:+4319793321

> hosted SIP domains directly on their ingress points, .....

I agree with the above. It also depends on how you got stastny.com as 
your own domain. Is it hosted by somebody that can provide the 
forwarding service for you? Do they manage the DNS for you? Perhaps 
provB provides this service for you. If so there are many things it can do.

>> In case 2) we need Infrastructure ENUM

You need for than that! You need for the number +43 1 9793321 to be 
assigned to you and set up so that pstn calls are routed to provB.

>> sip:[email-masked] or sip:[email-masked]

You only get to do this if *you* have control over your entry in the 
user ENUM. Will that always be the case, or will the provider manage it 
on your behalf?

One way to get the number would be for provB to get it for you. It might 
do as you suggest. Or it might consider this to be a separate AOR. In 
that case it might use something like IMS implicit registration sets to 
ensure that your same UA gets calls to both address forms.

>> sip:[email-masked] (wrong?)

This is ok I guess. I think this is a provider option. I like it less 
because it is less explicit about what it means.

> user=phone as the user are not limited to phones).

(Isn't the one without user=phone option 3?)

I would use use sip:[email-masked];user=phone

The presence of user=phone in no way prevents use for things other than 
phones. Of course it is not very convenient to type for those that enter 
URIs from a keyboard. If use for purposes like IM on a PC is expected, 
then sip:[email-masked] may be preferred. Or else sip:[email-masked] can 
just be supported also on the same device.

I also hope that as we go forward, pc apps will allow either sip URIs 
phone numbers (entered as a dial string and represented as a tel uri) to 
be used. So the "caller" would be using tel:+4319793321 and that will be 
appropriately routed.