Outstanding document.  Very specific on what changes need to be made, why the change needs to be made and the draw backs of each solution.  Great Great write up...............

 This is a common problem with phones that have an older  firmware trying to register with CUCM that contains a newer device default  version. A conflict comes into play and the phone is ultimately rejected.  You would first need to verify the phone ...

Good Documentation.  Just add the verification command of Show credentials to validate your gateway has pulled its SRST configs from CUCM.  #show credentials

   Your correct. Jabber revisions come out more frequently as they do for  CUCM updates.  So when you upload the latest version of Jabber its not compatible with the current CUCM version your on. Hence is why I down graded my Jabber Client to 8.6.5 a...

  Hi Rajesh, I just had the same issue that you are having and resolved it, but being that now Cisco has new phone models of 6900, 8900, or 9900 series along with a new Jabber client version its sometimes hard to determine what the problem is if your...