[SIPForum-discussion] Registrar forcer re-registration

[Tyler Parkin]

Hi Mark,

Thanks for your quick reply.  Let me see if I can re-phrase what I'm trying to resolve.

We have multiple SBC's on our network, with an active and standby in each location, and our users targeted to an SBC node based on market.  If the UA is set to register via a DNS SRV record, they will register with the proper SBC for their region.  On failure, we can updated the DNS record to reflect a standby node and new invites originating from the UA will be directed to the standby node, then to the feature server/registrar, and from there out one of our gateways.  In a failure situation, SIP -> PSTN is not an issue at all due to DNS records an authenticated INVITE messages.

On register a UA REGISTER message is delivered to the SBC, which caches the origin IP and call-id information, NAT's the IP, and then forwards the registration to a Registrar/Feature Server.  The Registrar/Feature server at that point has the user telno record pointing to the IP of the SBC's private/internal side.  

In an outage situation where we lose an SBC node, we change the DNS SVR record to a standby SBC node which does not have the cached NAT/IP/Call-ID records and therefore the call fails.  Situation is Gateway -> Feature Server -> Standby SBC which fails to find the entry for the destination because that entry was created in an SBC node that would be down.

To get around that situation we would have to re-register the endpoints to reestablish the cached entry (endpoint IP) in the standby SBC and Registrar.

To be clear, our current configuration includes an active and standby SBC which share cached information.  The situation we're looking at is where we lose an entire colo facility (active & standby).

Thanks,

Tyler
  ----- Original Message ----- 
  From: Mark Holloway 
  To: 'Tyler Parkin' ; discussion at sipforum.org 
  Sent: Wednesday, January 16, 2008 8:43 PM
  Subject: RE: [SIPForum-discussion] Registrar forcer re-registration


  Depending on where the outage resides and whether you have geographically diverse SBC's, your gateways should have the ability to point to two different geographically located SBC's as primary/secondary or use DNS SRV's with multiple A records.  If you only have one geographic location with an SBC, the SBC should be configured to monitor your routing and application server clusters on the protected side of the network so it can forward the SIP invites to the active servers in the cluster where the users' SIP registration lives.   

    

   

  From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Tyler Parkin
  Sent: Wednesday, January 16, 2008 5:40 PM
  To: discussion at sipforum.org
  Subject: [SIPForum-discussion] Registrar forcer re-registration

   

  Good evening,

   

  I'm curious to know if there is a SIP method for a registrar to force (an early) re-registration. 

   

  Our network is pretty standard:

   

  SIP UA -> SBC -> REGISTRAR

   

  In an effort to minimize the effects of an outage event, identifying a solution for SIP -> PSTN calls is easy.  However, PSTN to SIP calls is more difficult unless the registration cache in both the SBC and the Registrar/feature server are updated (due to endpoint IP NAT'ing).  To date, our only solution has been to re-register the UA's, either via a SIP method (preferred) or a script that logs into each UA and tears down the endpoint and rebuilds it.

   

  In reading the RFC's, I've been unable to find a SIP method that will force a UA to re-register prior to reaching the normal expires value and thought I'd bounce it off the community.

   

  Thanks,

   

  Tyler

   

   
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