Subject: Re:

From: Michael Teroerde <[email-masked]>
Date: Tue, 1 Feb 2000 09:28:37 +0100 (MET)

Hello !!

I have searched your Email-list for Questions like mine, but there
wasn't
a posting which answerd all my questions.

I would know something about the REGISTER- Request in the SIP-Language.

1. Could a Server send me an De-Register message if he want (e.g. if he
wants to reboot)??
2. Could a Server change the "Expires"- Header field (and therefore
 change the Register- Time)??
3. Did the Server send somthing as "Keep Alive" to the registerd
 UserAgent??(or did he make a "ping" to the IP or something else to
determine that my UA is still active)
4. What happens if my UserAgent hangs up??
5. Is there a generelly timout when the Server delets the
register-entry   (e.g. after 48 hours) ??
6. Did the server MUST send a "200 OK"- Response if the UserAgent send a
 De-register(REGISTER with Expires=0) ??

Please help me !!!
If you know an interesting Paper about generelly Sever behavior, please
tell it to me.

Thanks for your effort

Michael Teroerde

(instead of posting it on the List , you can also send it to my
NEC-Email-Adress)
----------------------------------------------------------------
Michael Teroerde
Student at NEC- Heidelberg
[email-masked]

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From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 01 Feb 2000 14:45:58 -0500

To add a few comments to what has been said already:

> 1. Could a Server send me an De-Register message if he want (e.g. if he

The decision was made not to include such a function as it can be
accomplished in many other ways. For example, by changing the DNS
entries for the server, or by mandating multicast for registrations. The
latter makes reboot handling really easy. Adding a de-register message
has other problems. To what clients is it sent? What about clients that
aren't registered right now but are going to do so after the server
reboots? You need to tell them to try a different server also.

>  change the Register- Time)??

This has been answered by others.

> determine that my UA is still active)

Registrations are kept alive through refresh. The server can reduce the
refresh interval by placing it in the 200 response to the registration,
as has been mentioned.

SIP sessions, right now, have no keepalive. It is done at the moment
through the media session itself. However, a specification is in
development for a keepalive within SIP itself:

http://www.ietf.org/internet-drafts/draft-ietf-sip-session-timer-00.txt

Note that the call is always up so long as the end systems believe it
is. If a proxy uses the session timer, and the call times out, the call
may still be up if the end systems think it is.

> 4. What happens if my UserAgent hangs up??

Like others, I don't understand this question.

> register-entry   (e.g. after 48 hours) ??

Been answered by others.

>  De-register(REGISTER with Expires=0) ??

All requests generate responses. 

-Jonathan R.
-- 
Jonathan D. Rosenberg                       200 Executive Drive
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dynamicsoft                                 West Orange, NJ 07052
[email-masked]                     FAX:   (732) 741-4778
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