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In a VX network, call routing is performed by routing calls between two trunk groups. A trunk group is a collection of channels. The routing between these channels is set by way of the call routing system. This section provides a description of basic call routing with examples.

Example 1: Simple TDM to TDM Call

In this example, we have configured a single VX node with two T1 lines to handle Time-Division Multiplexing (TDM) calls, with trunk group 1 for incoming calls and trunk group 2 for outgoing calls as illustrated below:

Example 1: Simple TDM to TDM Call

For this call routing example, all calls are simply routed from one trunk group to the other. The settings for this call route are shown below:

Example 1: Call Routing Table Entry

In example 1, as the call comes into trunk group 1, it is directed to the call routing system which looks up the Call Routing Table for trunk group #1 and then looks for a matching call route entry. In the example, we have only one call route entry is defined where the Match Rule is set to {+} which matches any called number and Media Class is set to #1 ANY which matches any call media type. These settings mean that any called number using any media class coming into trunk group #1 is routed to the destination defined in the Destination area of this Call Route, specifically TrunkGroup #2.

This call route passes the called number without modification. The entire called number is captured via the Match Rule {+} and passed to the destination trunk with the Translation Rule \1.

In this example, there is only one routing entry defined in a single call routing table, however VX supports multiple call routing entries and multiple call routing tables. When multiple call routing tables are defined, the trunk group of the incoming channel chooses the routing table to use from its configuration. Use of multiple call routing tables for a trunk group is shown in a later example.

A trunk group usually a represent physical line connected to the VX node (as they do in this example). However, in a more complex VoIP configuration, trunk groups can contain virtual channels.

Example 2: TDM to BSP to TDM

For this example, we have connected a set of two VX nodes in the following network configuration:

TDM to BSP to TDM Network Configuration

In this example, VX Node 1 receives inbound ISDN calls on trunk group #1 routes those calls to trunk group #2 which is connected via BSP to VX Node 2, trunk group #2. The calls are then received on VX Node 2, trunk group #2 which routes calls to its trunk group #1, an outbound ISDN line. From a call routing perspective, this scenario requires two call routes: a call route on VX Node 1 for trunk group #1, and a call route on VX Node 2 for trunk group #2, as shown in the illustration below.

BSP Channel Call Flow

VX Node 1 Configuration

For this call routing configuration, VX Node 1 requires two configured trunk groups. Trunk group 1 receives the inbound ISDN calls, and trunk group 2 sends the calls via BSP to VX Node 2. The configuration of these two trunk groups is shown below:

Example 2: VX Node 1, Trunk Group 1 Configuration (ISDN)

Example 2: VX Node 1, Trunk Group 2 Configuration (BSP)

Setting up trunk group 2 as a BSP outbound channel requires several additional steps beyond creating the trunk group configuration shown above:

  1. In the configuration for Node 1, create a peer for Node 2 in the peer table specifying the IP address of the Node 2 and setting the Peer Type to VX Node (BSP).
  2. In the Chassis configuration for Node 1, create a Virtual Slot 15. (A VX Virtual Slot is required to have an slot number of 15.)
  3. In the virtual slot, create virtual port (e.g., Port 1) with a Port Type of BSP, a TrunkGroup value of trunk group #2 shown above and a Channel Profile of Default BSP (if this option is not available, then create a BSP Channel Profile).

Once these two trunk groups are configured on VX Node 1, the following call route can be configured. Since trunk group #1 is mapped to Call Route Table #2, this Call Route entry must be added to that Call Route Table:

Example 2: VX Node 1, Trunk Group 1 Call Route Configuration

This call route tells the system to send calls to trunk group 2, which represents BSP VoIP channels. This route tells the system to keep the called number intact with the Match Rule set to {+} to capture the entire called number and a Translation Rule of \1 to pass the entire number with the call. In the Destination section, notice that the BSP option is selected and VX Node 2 is specified as the destination by selecting a TrunkGroup* of #2, Node ID of 0:0:0:2 and in the Peer IP / IF field, the IP address of VX Node 2 is selected.

If the Node ID and Peer IP / IF values for the VX Node 2 are not available, it means that the node has not been configured in VX Node 1's peer table.

At this point, VX Node 1 will send calls received on its trunk group 1 to trunk group 2, which forwards the calls on to VX Node 2.

VX Node 2 Configuration

In order for VX Node 2 to properly receive and route the BSP calls from VX Node 1, the following trunk groups must be configured:

Example 2: VX Node 2, Trunk Group 2 Configuration (BSP)

Setting up trunk group 2 as a BSP outbound channel requires several additional steps beyond creating the trunk group configuration shown above:

  1. In the configuration for Node 2, create a peer for Node 2 in the peer table specifying the IP address of the Node 2 and setting the Peer Type to VX Node (BSP).
  2. In the Chassis configuration for Node 2, create a Virtual Slot 15. (A VX Virtual Slot is required to have an slot number of 15.)
  3. In the virtual slot, create virtual port (e.g., Port 1) with a Port Type of BSP, a TrunkGroup value of trunk group #2 shown above and a Channel Profile of Default BSP (if this option is not available, then create a BSP Channel Profile).
Example 2: VX Node 2, Trunk Group 1 Configuration (ISDN)

In addition, a BSP Inbound Call Route must be defined on VX Node 2 as shown below:

Example 2: VX Node 2 BSP Inbound Call Route

The configuration above tells VX Node 2 that all BSP inbound calls from VX Node 1 are routed through trunk group 2, which is configured to use Route Table #1 for routing.

In order to complete call routing of calls received via BSP from VX Node 1, a call route for trunk group 2 is configured in Route Table #1 to route the call to the outbound ISDN:

Example 2: VX Node 2, Call Route from VX Node 1 (BSP) to ISDN

This call route takes the BSP call and keeps the called number intact with the Match Rule set to {+} and Translation Rule of \1 . The call is routed to trunk group 1, which represents the IDSN outbound (TDM out) line.

Example 3: TDM to H.323 to TDM

Example 3 uses the network configuration shown below. This example describes the operation by following the call flow of the configuration.

TDM to H.323 to TDM Configuration

On each node, H.323 channels are added and assigned to trunk group 2. The call flow is shown below.

TDM to H.323 to TDM Call Flow

VX Node 1 Configuration

The call arrives at the node 1 on trunk group 1.The channels are assigned to trunk group 1 on the port configuration. It is assigned to routing table 1 in the configuration on the trunk group. trunk group 1 contains the configuration shown below.

Example 3: VX Node 1, Trunk Group 1 Configuration (ISDN inbound)

Example 3: VX Node 1, Trunk Group 2 Configuration (H.323 outbound)

Setting up trunk group 2 as an H.323 outbound channel requires additional steps beyond creating the trunk group configuration shown above:

  1. In the Chassis configuration for Node 1, create a Virtual Slot 15. (A VX Virtual Slot is required to have an slot number of 15.)
  2. In the Virtual Slot, create virtual port (e.g., Port 1) with a Port Type of H.323, a TrunkGroup value of trunk group #2 shown above and a Channel Profile of Default H.323 (if this option is not available, then create a H.323 Channel Profile).

Route table 1 has the following entry 1.

Example 3: VX Node 1, Call Route Configuration ISDN to VX Node 2 (H.323)

This setup tells the system to route the call to trunk group 2 which is an H.323 trunk group in this case. The route tells the system to keep the called number intact with the + for an input rule and the \1 as an output rule. The system is set to destination "Other".

H.323 calls that do not involve a gatekeeper require the IP address in the output rule. The IP address after the @ symbol tells VX the IP address to route the H.323 call to. Only the part before the IP address is passed as the called number to the routing table.

Only E.164 numbers are supported before the @ and only IP addresses after it. DNS and alpha numeric numbers are not supported in H.323.

VX Node 2 Configuration

As the call arrives at the second node 192.168.100.20, the system checks which trunk group is assigned to the calls coming from 192.168.100.10 (Node 1) based on H.323 inbound call routing. Once it has determined the trunkgroup from the incoming H.323 table, it then finds the trunk group used.

In the example shown below, it is trunk group 2.

Example 3: VX Node 2, H.323 Inbound Call Route

The configuration for trunk group 2 tells the routing system to use route table 1 on this node.

Example 3: VX Node 2, Trunk Group 2 (H.323 inbound)

Setting up trunk group 2 as an H.323 outbound channel requires additional steps beyond creating the trunk group configuration shown above:

  1. In the Chassis configuration for Node 2, create a Virtual Slot 15. (A VX Virtual Slot is required to have an slot number of 15.)
  2. In the Virtual Slot, create virtual port (e.g., Port 1) with a Port Type of H.323, a TrunkGroup value of trunk group #2 shown above and a Channel Profile of Default H.323 (if this option is not available, then create a H.323 Channel Profile).
Example 3: VX Node 2, Trunk Group 1 (ISDN outbound)

Route table 1 has the following entry in it.

Example 3: VX Node 2, Call Route Configuration H.323 to ISDN

This route takes the VoIP call and once again keeps the called number intact with the {+} for an input rule and the \1 as an output rule. In H.323 only the E.164 part of the number is fed to the input rule. The call is routed to trunk group 1 which is "out TDM" line.

Gatekeeper routed calls are easier to configure. The gatekeeper is configured on the trunk group on both nodes and only the E.164 number is specified in the rule on the outgoing node. On the incoming node, the H.323 incoming route does not need to be filled out since being registered with the gatekeeper is enough to tell which trunk to go to.

Example 4: TDM to SIP to TDM

For this example, we have connected a set of two VX nodes in the following network configuration.

TDM to SIP to TDM Network Configuration

On each node, SIP channels are added to trunk group 2 on each node and used to . The call flow is shown below.

Call Routing Table Entries

VX Node 1 Configuration

The call arrives at the node on trunk group 1. The channels are assigned to trunk group 1 on the port configuration. It is assigned to routing table 1 in the configuration on the trunk group.

Example 4: VX Node 1, Trunk Group 1 (ISDN inbound)

Example 4: VX Node 1, Trunk Group 2 (SIP outbound)

Setting up trunk group 2 as an SIP outbound channel requires additional steps beyond creating the trunk group configuration shown above:

  1. In the Chassis configuration for Node 1, create a Virtual Slot 15. (A VX Virtual Slot is required to have an slot number of 15.)
  2. In the Virtual Slot, create virtual port (e.g., Port 1) with a Port Type of SIP, a TrunkGroup value of trunk group #2 shown above and a Channel Profile of Default SIP (if this option is not available, then create a SIP Channel Profile).

This setup tells the system to route the call to trunk group 2, the SIP VoIP channels in this case. The route tells the system to keep the called number in act with the + for an input rule and the \1 as an output rule. The system is set to "other "destination and the CODEC is chosen. The IP address or DNS name after the @ symbol tell VX the IP address to route the SIP call to. Unlike H.323 the entire output rule is passed to the remote device.

Route table 1 has the following entry in it.

Example 4: VX Node 1, Call Route ISDN to SIP

This entry tells the system to route the call to trunk group 2, the SIP VoIP channels in this case. The route tells the system to keep the called number in tact with the + for an input rule and the \1 as an output rule. The system is set to "other" destination. The IP address or DNS name after the @ symbol tells VX the IP address to route the SIP call to. Unlike H.323 the entire output rule is passed to the remote device.

VX Node 2 Configuration

As the call arrives at the second node the system checks which trunk group is assigned to the calls coming from 192.168.100.10 (Node 1). Once it has determined the trunk group from the incoming SIP table, it then finds the trunk group used. In the example below it is trunk group 2. A subnet mask can be used to match a range of IP addresses.

The configuration for trunk group 2 asks the routing system to use route table 1 on this node.

Example 4: VX Node 2, Trunk Group 2 (SIP inbound)

Setting up trunk group 2 as an SIP inbound channel requires additional steps beyond creating the trunk group configuration shown above:

  1. In the Chassis configuration for Node 2, create a Virtual Slot 15. (A VX Virtual Slot is required to have an slot number of 15.)
  2. In the Virtual Slot, create virtual port (e.g., Port 1) with a Port Type of SIP, a TrunkGroup value of trunk group #2 shown above and a Channel Profile of Default SIP (if this option is not available, then create a SIP Channel Profile).
Example 4: VX Node 2, Trunk Group 1 (ISDN outbound)

In order to map the incoming SIP call to trunk group 2, a SIP Inbound Call Route must be defined on VX Node 2 as shown below:

Example 4: VX Node 2, SIP Inbound Call Route

Route table 1 has the following entry in it.

Example 4: VX Node 2, Call Route SIP to ISDN

This route takes the VoIP call and keeps the called number intact with the {+}@192.168.100.20 for an input rule and the \1 as an output rule. The @192.168.100.20 is outside the brackets so it is not fed to the ISDN line. The call is routed to trunk group 1, which is the ISDN outbound or "out TDM" line.

This Call Route requires that the Match Rule Advanced SIP Matching option is enabled, in order to properly handle the "@xxx.xxx.xxx.xxx" suffix of the incoming call. If this option was not enabled, the call would fail with a NO ROUTE error.