Virtual IP Channels

To use the Call Agent feature, you must configure virtual IP channels in the CSP.

To enable more than 2,000 virtual channels you require at least two licenses, one to enable the initial virtual 2,000 channels, and a second license to incrementally increase to greater than 2,000 virtual channels. You also must license SIP software to use the Call Agent feature.

Refer to Downloading License Keys to the CSP in the Licensing Overview chapter in the Developer’s Guide: Overview and the Product License Download message (0x0079) in the API Reference.

Virtual IP channels function on virtual cards. Virtual cards function the same way as physical cards in all respects. You logically insert and remove virtual cards for the CSP without interruption to service using the Virtual Card Configure (0x00E0) message.

Important! The same messages that reset a physical card’s tag configuration also reset the equivalent virtual card. You must send the Tag Configuration (0x00D0) message to retag the virtual card. Refer to the Tag Configuration (0x00D0) message in the API Reference for a list of configuration messages that reset the tag configuration of physical cards.

The host receives the Card Status Report (0x00A6) as if the virtual card actually existed. The Virtual Span Control (0x00E2) message supervises the actual spans that the virtual card controls.

The following card type represents the 32-span version of the Virtual VDAC card.

To support the expanded number of channels, you must extend the range of slots using the Virtual Card Configure (0x00E0) message.

The following table breaks down the number of virtual cards required for the additional virtual spans.

* Nine virtual VDAC cards have 32 spans. The tenth card has 27 spans to get to the maximum 315 virtual VDAC spans.

Channels Licensed	Virtual VDAC Cards	Virtual Channels	Virtual Spans
2,000	2	2,048	64
4,000	4	4,096	128
6,000	6	6,144	192
8,000	8	8,192	256
10,000	10*	10,080	315

Important! When you configure any virtual card, the resources are allocated for the maximum configuration. For example, when you configure a 32-span VDAC virtual card, the resources are reserved for all 32 spans even if you configure only one span.

Refer to the section, Configuring SS7 10K Virtual Channels in the Developer’s Guide: Common Channel Signaling for a full explanation.

You cannot connect virtual IP channels over the Exnet Ring. In order for a call to be connected over the Exnet Ring, the channels must be terminated locally (that is, on the CSP or Exnet Connect card).

Application developers can have the host application hunt and allocate the coupled physical VoIP channel in a Call Agent Mode call.

• The host can send the Call Agent Mode Physical Channel ID TLV (0x011A) in the Connect with Data message. By doing so, the host conveys the physical VoIP span/channel identifier to the CSP.

• The host can send the CSP a PPL Event Request message that includes the following:

Important! This message is used when a request for DSP media services is involved.

Conversely, this PPL Event Request message can decouple the physical span/channel from a virtual span/channel in Call Agent Mode. By doing so, the PPL Event Request allows the host application developers to toggle the bearer nature of a virtual VoIP channel. When a physical channel is coupled with the virtual channel, service is modified to bearer-switched. When the physical channel is decoupled from the virtual channel, service is modified to bearer-free.

With this feature, the virtual channel does not need to request a physical channel from the L4 Router. Instead, the virtual channel busys-out the physical channel and removes it from the free pool of L4 Router channels.

The reverse happens when the call is torn down or when the virtual channel transitions from bearer-switched to bearer-free mode.

The following summarizes how the host can hunt and allocate the coupled physical VoIP channel on the inbound side of a Call Agent Mode call received by the CSP.

• Connect with Data message, with the Call Agent Physical Channel ID TLV (0x011A). This TLV contains the physical span/channel to use for the call.

• PPL Event Request message, with the Modify Bearer Service Event. This message contains the PPL Generic ICB to carry the Physical Channel ID TLV and an NPDI Universal ICB to carry the physical VoIP channel parameters (Source IP 0x2792 and Source RTP 0x2793). The CSP must be in Answer State because this message causes SIP RE-INVITE messages.

2. The virtual channel requests the L4 Router to busy-out the physical channel in the pool of free channels.

3. The virtual channel busys-out the physical channel, essentially coupling the virtual channel and the physical channel.

4. The CSP takes the appropriate signaling action, such as sending a SIP RE-INVITE message to the caller.

• Call Agent Mode Physical Channel ID TLV (0x011A) in the Tag Length Value Blocks chapter in the API Reference.

• CH - Channel Management (0x0061) in the Layer 4 Call Control PPL Information chapter in the Developer’s Guide: Overview.

Internet Protocol. Part of the TCP/IP family of protocols used to route messages and tracks the addresses of nodes.

Session-Initiation Protocol. A signaling protocol used for establishing sessions in an IP network. A session could be a simple, two-way telephone call, or it could be a collaborative multi-media conference session.

Range of channels provided by T1 or E1 transmission service. A physical span is a group of channels taking up a single physical wire. A logical span is a group of channels taking up less than a single logical wire, or carried over more than one physical wire.

See Signaling System Number Seven.

CCS. Network architecture using SS7 protocol for the exchange of information between telecommunications nodes and networks on an out-of-band basis.

A computer, attached to the Excel platform through an RS-232 or Ethernet link, from which you run the telecommunications application that controls the Excel platform.

Voice over Internet Protocol. The delivery of voice information in digital form in discrete packets rather than in the traditional circuit-committed protocols of the public-switched telephone network (PSTN).

Tag-Length-Value block. A standardized block that allows data to inserted in a standard way into API messages.

See Programmable Protocol Language.

A programmable software component that uses PPL state machines that can be modified with the PPL Tool.

A condition that, when met, drives a state machine from one state to another. A condition that drives a Component out of its current state by invoking an associated primitive.

Digital Signal Processor

See Information Control Block.

Network Protocol Data Intelligence. Also called “Interworking,” it is a software product that operates within Excel’s Call Control (Layer 4) and Services (Layer 5) call processing layers. NPDI is meant to enhance Excel’s call processing product offering by allowing call processing layers (specifically Layers 4 and 5) to perform advanced analysis, generation, and conversion of Network Signaling (NS) Layer 3 information.

Real-Time Transport Protocol. Supports transport of real-time data like interactive voice and video over packet-switched networks.

The condition of a component at a given instant. The current "context" of a PPL object, such as Idle, Seizing, Answered. In PPL files, a State is represented by a circle.