Assured Services - Session Initiation Protocol (AS-SIP)

The Assured Services-Session Initiation Protocol (AS-SIP) feature provides the mechanism that allows outgoing precedence (priority) calls to be created.

Use dialplan.digitmap parameter to configure an outgoing call's precedence. You can create Multi-Level Precedence and Preemption (MLPP) for outgoing calls. The precedence levels are automatically assigned to the calls in the initial outgoing signaling. You can configure a call’s precedence level to be changed by the Session Initiation Protocol (SIP) server in subsequent signaling.

When all call appearances are occupied for a line and a new incoming call having a higher priority than the other calls in the same line is in place, the call appearance with the lowest priority is removed for the new call. When the calls are of the same precedence level, the calls in progress are selected for preemption in the following order: alerting, held then active. For calls of the same precedence level and the same state, more recently created alerting calls held for shorter or longer duration are selected first. The conference calls are treated as a single call for the purposes of preemption as they occupy only one call appearance until they are split.

The precedence level assigned to an incoming call alters the following behavior:
  • Ring Type: The Resource-Priority header contents map to one or more custom ring types which may in turn map to a unique ringer sound effect pattern. When the Resource-Priority header is present, the feature by which the ring type assignment is mapped to Alert-Info header content will be disabled. The default behavior for precedence calls will be the normal ringer pattern with an accelerated tone. The ring type and subsequent ring pattern assigned to precedence calls via the Resource-Priority header mapping has higher priority than other types of distinctive incoming call. This includes per-line ring pattern assignment and local contact directory-based treatment such as auto-divert or auto-reject.
  • Call Waiting: When the call.callWaiting.ring parameter is set to beep, a beep tone plays through the selected audio output mode on the active call. If the parameter is set to ring, the call waiting tone pattern is derived from the ring type assigned to the alerting call ( and plays through the speaker. The default behavior for precedence calls will be the normal call waiting pattern with three short busts rather than one 300 ms.
  • Precedence Handling: When a user receives multiple precedence calls, they are displayed on the call alerting list according to their precedence level. The high precedence calls are listed at the top and the low precedence calls are listed at the bottom of the call alerting list.
  • Visual Indication: The priority string displays as follows on the call screen of the phone for priority calls:
    • VVX 101, VVX 201, VVX 3xx business media phones: P-1,P-2,P-3
    • VVX 4xx, VVX 5xx, VVX 6xx, VVX 15xx business media phones: Priority-1,Priority-2,Priority-3
    • VVX 150 business IP phone: P-1,P-2,P-3
    • VVX 250, 350, 450 business IP phones: Priority-1,Priority-2,Priority-3