Subject: [SIP] Informing UA after network initated deregistration?

From: Bernie Hoeneisen <[email-masked]>
Date: Tue, 6 Feb 2001 18:39:37 +0200 (EET)

Hi,

I have some questions concerning informing the UA in case the network 
de-registers the UA, and wants to inform the UA about this.

Let me describe a possible use case:  Supposed the UA normally registers
to only one registrar. Furthermore this registrar needs some maintenance
break. The policy in this registrar/network is, to inform all its
registered UAs, that they have been de-registered (and maybe provide an
address, where it can send a new registration.)
Remark: There can be more reasons, why a network element needs to
de-register a user, maintenance break is just one.

My questions:

- Has this problem area been addressed earlier in IETF?
  If yes, please send me some pointers.

- What do key-people think about such a feature, where a registrar
  informs about de-registration of users? Is it welcome to include it
  into a SIP extension (e.g. defining a method for it e.g. UNREGISTER,
  or re-using other methods such as NOTIFY), or whatever would be
  appropriate?

br,
 Bernie

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---

From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 9 Feb 2001 07:56:54 -0500

> -----Original Message-----
> From: Bernie Hoeneisen [mailto:[email-masked]]
> Sent: Tuesday, February 06, 2001 11:40 AM
> To: [email-masked]
> Subject: [SIP] Informing UA after network initated deregistration?
> 
> 
> Hi,
> 

Yes. The issue has been raised on the list at least three separate times.
Please check the archives.

>   or re-using other methods such as NOTIFY), or whatever would be

My view is the same it was the other three times. Failover and redundancy
for devices contacted by clients is best handled by using things like SRV
records. The SRV record for some registrar would contain a list of ordered
devices to try. When you want to service the main one, you take it out of
service. Clients who re-register will get an ICMP error, and as per
draft-ietf-sip-srv, will then try the next address, which is its backup.

This works not only for registrations, but for outbound proxies, and any
other sip communications, even between servers and servers. SRV is not ideal
for all load balancing and failover needs, as is well known, but I think it
addresses this need perfectly well.

-Jonathan R.
---
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.cs.columbia.edu/~jdrosen         PHONE: (973) 952-5000
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