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Agent Availability for Routing

Handling how DNs become available for routing is unique to SIP Cluster. It is different from how DN or agent availability is handled in the regular architecture. There are two different use cases:

  • SIP Phone Agents
  • PSTN Phone Agents

DN State for SIP Phone Agents

Consider the following sample diagram:

DNStateSIPPhoneAgents1.png

In the above sample diagram, the phones are not registered in the initial state and the DNs are out of service (OOS).

  • DN ownership for agents SIP phones is defined by SIP REGISTER
  • If phone is not registered, DN is Out Of Service (OOS)

There are several ports on the SIP Server and each port is dedicated to a specific functionality.

  • SIP port - for handling SIP traffic.
  • Default port - is the T-Library port and unlike in the regular architecture, only local activity passes through this port. No events about calls on other SIP Servers are sent through the default port (as a result, URS is only aware of call on that particular SIP Server).
  • T-Controller port - the Stat Server is connected to this port (all calls in the SIP Cluster is passed through this port and as a result, the Stat Server is aware of all calls in different SIP servers in the SIP Cluster).

For more information on SIP Server's internal modules used to provide cluster functionality, refer to the SIP Server section in this document.

The following sample diagram illustrates the flow when one of the SIP phones registers:

DNStateSIPPhoneAgents2.png

  • SIP phone 1 registers to DC1.
  • SIP Server 1 becomes an owner of DN1.
  • DN1 is set to In Service (InSrv) on SIP Server 1.
  • DN state is passed to local routing Stat Server through TCport.
  • DN state is passed to the remote SIP Server 2 through TC layer.
  • SIP Server 2 distributes DN state to the Stat Server 2 through the TCport.

DN State for PSTN Agents

PSTN agents are treated differently compared to SIP agents.The difference is in how ownerhsip is defined. For PSTN agents, ownership is defined by the T-Library registration received from the WWE dekstop application. The desktop application is physically configured in the SIP Server and is recognized as a client by the SIP Server. Then, when the client registers for a certain extension DN, the node where the registration comes from becomes the owner.

When GWS is not registered on Agent DN:

DNStatePSTNAgents1.png

  • DN ownership for PSTN agents is defined by TRegisterAddress received from GWS .
  • SIP Server recognizes GWS by client name (configurable).
  • GWS doesn’t register DN if WWE is not connected.
  • If GWS is not registered on a DN, DN is Out Of Service (OOS).

When WWE1 connects to GWS:

DNStatePSTNAgents2.png

  • Agent 1 logs in to WWE and GWS registers on DN1.
  • SIP Server 1 becomes an owner of DN1.
  • DN1 is set to In Service (InSrv) on SIP Server 1.
  • New DN state is distributed the same way as for the SIP phone agents.

Other Scenarios

The following sample diagram illustrates how an inbound call is routed to an agent when the cluster nodes are connected and both the DNs are registered:

[File:DNAvailability1.png]

  • Both DNs are in service.
  • Global Routing: Call can be routed from any node to any agent.

The following sample diagram illustrates the flow when the connection between the two SIP Cluster nodes is lost:

[File:DNAvailability2.png]

  • The SIP Cluster nodes are not connected through the T-Controller layer.
  • As soon as connection is lost, both SIP servers understand that the owner of the DN is not connected any more and events for that particular DN cannot be received.
  • SIP Cluster node moves DN to OOS state, if connection to DN owner is lost.
  • Local Routing: each SIP Cluster node can continue routing to the locally owned DNs.
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