EMCC Call Routing

VC Phone CSS

HC Builds the following CSSes for VC Phone (priority order as listed):

1. Adjunct CSS: Configured in Roaming DP to support country specific emergency dialing plan (e.g., UK phone remotely registers back to US cluster; user dials 9.999 (UK emergency#) that US cluster will normally not recognize). May skip Adjunct CSS configuration if HC and VC share the same emergency pattern and Local Route Groups are implemented.
2. Line CSS: Configured under the DN of EMCC UDP
3. EMCC CSS: Configured under UDP as 'Extension Mobility Cross Cluster CSS'. Note that UDP doesn't have CSS option for EM. It is available only for EMCC

VC Phone Call Flow

1. Call from VC Phone to HC Phone
• Signaling will take place between VC Phone <=> HC <=> HC Phone
• Media will flow directly between VC Phone <=> HC Phone
2. Call from VC Phone to VC Phone
• Signaling will take place between EMCC VC Phone <=> HC <=> SIP/H323 ICT (not EMCC SIP Trunk) <=> VC <=> Local VC Phone
• Media will flow directly between VC Phones
• The users will dial the phone next to them as if they were in the Home cluster, Home Cluster Dialing Habits should be Maintained
3. Call from VC to PSTN (No SLRG)
• Signaling will take place between VC Phone <=> HC <=> HC GW
• Media will take place between VC Phone <=> HC GW
• Incoming calls for this DID will always be received on the HC GW
4. Call from VC to PSTN (SLRG)
• In EMCC, RP with SLRG doesn't point to LRG configured in Roaming DP. Instead, it sends the call over EMCC SIP Trunk to VC
• VC Cluster checks its own dialplan to route the call. EMCC SIP Trunk needs a CSS to access the dialplan. The selection of the CSS can be defined under 'Advanced Features > EMCC > EMCC Feature Configuration':
• Use Trunk CSS
• Use Phone's Original Device CSS
• VC will use original VC Phone DP to determine the LRG and get the exit gateway (not EMCC SIP Trunk DP LRG). If VC Phone original DP doesn't have LRG configured, call will fail
• Signaling will take place between VC Phone <=> HC <=> EMCC SIP Trunk <=> VC <=> VC GW
• Media will take place between VC Phone <=> VC GW
• Dialing habits should be maintained for HC
5. Emergency Calls
• Emergency Calls require SLRG to route the calls out of the local gateway for proper call handling
• VC Phone will use 'Adjunct CSS' assigned to Roaming DP to match the emergency RP. This RP shouldn't be accessible to HC Phones
• Signaling will take place between VC Phone <=> HC <=> EMCC SIP Trunk <=> VC <=> VC GW
• Media will take place between VC Phone <=> VC GW

Note: If LRGs are already deployed for the Emergency route pattern AND a home and visiting cluster pair have the same Emergency dial string, use of the Adjunct CSS is not required

Calling Party Presentation

• The Calling Party number leaving the VC gateway should be the HC +E164 format
• Calling number transformation can take place on incoming EMCC SIP Trunk, on Route Patterns, or egress on the VC Gateway