Virtual IP Channels

Licensing of Virtual IP Channels

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

Important! 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.

The following licensing options are available by model number:

Initial license for 2,000 virtual IP channels

Incremental 2,000 virtual IP channels

Incremental 4,000 virtual IP channels

Incremental 6,000 virtual IP channels

Incremental 8,000 virtual IP channels

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 Cards

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.

0x80 Virtual VDAC, 32-span

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.

Table 6-1 Virtual VDAC Cards and Spans

Channels Licensed

Virtual VDAC Cards

Virtual Channels

Virtual Spans





















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

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.


Exnet® Ring

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).

Host-Based Control of Channel Allocation

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

This coupling can be achieved in two ways:

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:

• Call Agent Mode Physical Channel ID TLV (0x011A)

PPL Component - L4 CH PPL (0x0061)

PPL Event Request - Modify Bearer Service (0x00CC)

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.

1. The host sends the CSP either of the following messages:

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.

Refer to the following:

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.