/mcpthe subsequent incoming call to the SIP phone as the phone does not implement NonPreemptable numbers feature. In order to prevent the phone from preempting a NonPreemptable number, Unified Communications Manager rejects the incoming call to the phone which is higher than the busy trigger. For example, if the busy trigger is 2, then Unified Communications Manager rejects the 3rd call. SIP BPA/488 Error Handling The purpose of this feature is to include a warning header “370 Insufficient Bandwidth” in the 488 Error messages for the following scenarios: • If the Unified Communications Manager receives an inbound precedence call request (for example, with precedence level PRIORITY or above) over the IP network for a served endpoint and the Unified Communications Manager has insufficient bandwidth-related resources (due to call count threshold) to handle the call request, and if there are insufficient existing calls (and/or call requests) of lower precedence where their removal would provide the necessary resources to support the pending call request, then the Unified Communications Manager must reply with a 488 (Not Acceptable Here) response code and must include a Warning header with warning code 370 (Insufficient Bandwidth), and BPA blocked precedence announcement to be played and/or displayed to the user through the calling IP EI. • For an outgoing call when the Unified Communications Manager receives an outbound precedence call request from a served IP endpoint and there are insufficient resources to support the outbound precedence call request (for example bandwidth restriction), the Unified Communications Manager must compare the precedence level of the new precedence call request with the precedence levels of the existing calls and/or call requests to determine whether there are sufficient resources of lesser precedence that can be preempted to accommodate the new precedence call request. This comparison can only occur for calls and call requests having the same value for the precedence-domain subfield in the namespace of the Resource-Priority header field. Sample Message SIP/2.0 488 Not Acceptable Media Via: SIP/2.0/TCP 10.77.46.84:5064;branch=z9hG4bKd47639f069 From: sip:7654@10.77.46.84;tag=1657~c86d348c-200d-4847-ba87-837e294a0ef2-23831059 To: sip:4444@10.77.46.93;tag=1014~785d648c-40a2-4556-b74c-cd3d2402bb56-23829943 Date: Tue, 09 Jul 2013 16:50:09 GMT Call-ID: 9c10fc00-1dc13f41-60-542e4d0a@10.77.46.84 CSeq: 101 INVITE Allow-Events: presence Server: Cisco-CUCM10.0 Warning: 370 10.77.46.93 "Insufficient Bandwidth" Remote-Party-ID: sip:4444@10.77.46.93;user=phone;party=x-cisco-original-called;privacy=off Content-Length: 0 Non-SRTP Call Block All the SIP endpoints (both line and trunk) should not allow any non-secure call to establish if the service parameter "Block Unencrypted Calls" is set to true. Therefore, for any originating/terminating SIP Line device, if the above service parameter is set to true and the device is non-secure, then the call is blocked and is not allowed to proceed further. SIP Line Messaging Guide (Standard Edition) for Cisco Unified Communications Manager 44 SIP Standard Line Interface SIP BPA/488 Error Handling