Subject: [SIP] Basic Question

From: Aseem Agarwal <[email-masked]>
Date: Thu, 1 Jun 2000 15:59:11 -0700

Hi All,
  I have a few basic questions about SIP Registrar functionality.

 - Can a User Agent also act as a Registrar ? Assuming that a UA 
   can act as a Registrar as well, is it expected to NOT respond 
   to any REGISTER requests ?
 
 - Need some clarity on the following para in Section 4.2.6 [2543bis]. 
   "It is recommended that the UA registers via multicast and send a 
   registration to it's home address"

   Does this mean that registry database is maintained at two places,
   one at the registrar listening on the well known multicast address
   and another at the server at the home address ?

   To my understanding, there should be a local SIP Registrar server
   for any network. All UA's should register with this server when they
   come up. However, is it possible for UA's to also cache the registrations
   and use the cached entries for subsequent calls with out going to the
   location services or the registrar in the network ? 

thanks,
aseem

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From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 02 Jun 2000 00:53:21 -0400

>    to any REGISTER requests ?

Being a UA is a logical role, as is a registrar. If an entity accepts
REGISTERs and stores location information, its a registrar. So, you can
write a piece of code that is both a UA and a registrar if you want.

>    and another at the server at the home address ?

Maybe, maybe not. You can have a single server listening to both
multicast and unicast.

>    location services or the registrar in the network ?

Sure, its possible. Seems a bit more work than its worth, since the UA
basically needs to be a registrar. Also, this only works for multicast,
as that is the only case where other UAs can see the registrations. 

-Jonathan R.

-- 
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
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