I2 architecture VPC-routed case Henning Schulzrinne

Notes The drawing only reflects VPC-routed case Can also imagine having call server directly contact ESGW –use DNS to determine appropriate ESGW might be several (e.g., several different operators) –assumes business relationship of VSP with one or more ESGW operators

VSP V1 VSP V2 provides in-band location provides out-of- band location looks up location allocates ES* In-band location call server ESGW operator E1 may use MGCP or H.248 internally SR VPC ESGW operator E2 ALI DB E2 ESQK: location SIP handles contingency routing performs URI-to- trunk mapping retrieves location information for call routes all 911 calls to VPC CAMA, SS7 CAMA

VSP V1 VSP V2 provides in-band location provides out-of- band location looks up location allocates ES* Out-of-band location call server ESGW operator E1 may use MGCP or H.248 internally SR VPC ESGW operator E2 ALI DB E2 ESQK: location SIP handles contingency routing performs URI-to- trunk mapping retrieves location information for call inserts location in redirect response

Assumptions on relationship Call server is operated by VSP –it is configured to contact contracted VPC for all emergency calls –each VSP (typically) contracts with one VPC operator –VSPs are often national in their footprint ESGW operators can be regional –similar to SR operators today Thus, each VPC operator contracts with multiple ESGW operators –and a single ESGW can be reached from multiple VPC operators