DN Reservation [Draft]
Agent reservation feature (for cluster deployment better to be named DN reservation feature) provides the ability to reserve particular DN for particular time. When DN becomes reserved any attempt to reserve it again within reservation time period will be rejected. Agent reservation feature is independent of other agent or DN related functionality. That means neither agent nor DN states will be taken into consideration during reservation. Fact of reservation does not affect any SIP/T-lib (1pcc/3pcc) activities. While describing this feature we will operate with three important parameters:
- Request collection time. This time period starts at the moment when first reservation request regarding unreserved DN arrives. During that time DN reservation is in pending state. Higher priority request may substitute previous request. As soon as collection time expires, reservation of that DN is granted according to the request with highest priority.
- Reservation time. This time period starts at the moment reservation is granted. Any attempt to reserve the same DN again by the same or different client will be rejected within this timeframe.
- Reservation priority. This is the number. Higher number means higher priority. Request with higher priority, which arrives during collection time, substitutes low priority request and that low priority request becomes rejected. But this substitution does not reset collection timer. Request with the same or lower priority request arriving within collection time is rejected immediately.
Explicit Reservation
Client (URS) invokes explicit reservation by TReserveAgent request. Here is list of user level attributes for this request:
- AgentDN. This is directory number (DN) for which reservation is requested.
- AgentID. For cluster deployment this attributes is not taken into consideration.
- AgentPlace. For cluster deployment this attributes may be used for information purpose only and does not provide any special meaning for this design.
- Duration. Defines reservation time in seconds.
- Priority. Defines the priority of this request regarding this DN.
- Attribute reasons and Attribute extensions does not provide any special meaning in this design.
SIP Server grants reservation of the DN by responding with EventAgentReserved event. If for some reasons reservation is not possible SIP Server reject the request with EventError. Error code is 1700 (TERR_AGENT_ALREADY_RESERVED).
Implicit Reservation
Client (URS) may invoke implicit reservation as part of TRouteCall request. To trigger implicit reservation that request has set of pairs inside AttributeExtensions. Keys in these pairs starts with prefix “iscc-ar” and resemble attributes of TReserveAgent request with the same meaning:
- iscc-ar-agent-dn
- iscc-ar-agent-id
- iscc-ar-place
- iscc-ar-duration
- iscc-ar-priority
Let us not be confused with names. For cluster deployment that feature does not need any ISCC involvement.
The rules of reservation are the same as for explicit reservation. But there is no special event distributed regarding agent reservation. SIP Server does not start routing till agent reservation is confirmed. If agent reservation is rejected RequestRouteCall is rejected as well with error code 1700 TERR_AGENT_ALREADY_RESERVED.
Feature Configuration
DN Registration uses the native Agent Registration feature of SIP Server to provide similar funcationality to the cluster. To configure DN Registration, use the same configuration options as for the Agent Registration feature. For a full description of Agent Reservation, see the Framework 8.1 SIP Server Deployment Guide
Complete the following configuration steps to enable DN Registration in the cluster.
Enabling DN Registration in the Cluster
Note from Val: For Agent Reservation to work properly in the cluster, the SIP Server application option ‘extrouter/cluster-role’ must be set to a value of ‘iscc-node’, or ‘iscc-proxy’.