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Old 09-29-2014, 10:58 PM
sunilkumarv sunilkumarv is offline
Join Date: Mar 2010
Location: India
Posts: 124
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u => uri
p => phase

Phase header is used for origination based routing. below is more info about this

Origination based routing vs. regular (R-URI based) routing
  • Origination based routing is a construct that SRE employs to route the incoming requests based on call phase to originator of the request or to destination of the request.
  • By default, SRE routes the requests based on origination (PAI) unless asked for termination based routing. It takes care of incoming requests, say EC-500, that SRE must route to the URE belonging to the originator of the call.
  • There are going to be cases, where the requesting elements (say URE) may want SRE to route requests based on termination rather than origination. In such instances, the requesting elements fill 'phase=term' tag in route header while forwarding request to SRE. On detecting such request, SRE shall route request to a URE associated with the user specified in R-URI.
  • Summary:
    • If the incoming request contains phase tag, SRE routes requests based on tag.
    • If there is no tag, SRE routes incoming requests based on origination.
    • For outbound calls, SRE reads the phase from route header belong to itself. SRE inserts same phase tag in the route header it inserts for the destination.
    • SRE never creates or flips the phase tag.
While routing calls to and from external network, SRE can also enforce additional policies while making routing decision. The policies include least-cost routing, time based routing (time of day, day of week), media preferences, logging requests with particular origination/destination. In case of network (interface or n/w element) failure detection, SRE routes the requests based on alternate routing rule


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Last edited by sunilkumarv; 09-29-2014 at 11:19 PM. Reason: adding more info
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