Lesson 13: Voice Technology Basics

Convergence of Voice and Data | Voice Technology Basics | Voice over Data Transports | Applications |

Sample Migration

Applications

Now let’s put it all together. How does it actually work? Let’s look at the voice applications on an integrated voice/data network that replace traditional telephony.

Applications for Integrated Voice and Data Networks

Integrated voice and data networks support a variety of applications, all of which are designed to replace leased lines and lower costs. Each of the applications listed above are discussed on the following pages.

   - Inter-office calling
   - Toll bypass
   - On-net to off-net call rerouting
   - PLAR replacement
   - Tie trunk replacement

On-Net Call, Intra-Office

A voice-capable router can function as a local phone system for intra-office calls. In the example, a user dials a phone extension, which is located in the same office. The voice-capable router routes the call to the appropriate destination.

Toll Bypass—On-Net Call, Inter-Office

A voice-capable router can function as a phone system for inter-office calls to route calls within an enterprise network.

In the example, a user dials a phone extension, which is located in another office location. Notice that the extension number begins with a different leading number than the on-net, intra-office call. The voice-capable router routes the call to another voice-capable router over an ATM, Frame Relay, or HDLC network. The receiving router then routes the call to the PBX, which routes the call to the appropriate phone extension.

This solution eliminates the need for tie trunks between office locations, or eliminates long-distance toll charges between locations.

Toll Bypass—On-Net to Off-Net Dialing

A voice-capable router can provide off-net dialing to a location outside the local office, through the PSTN.
In the example, a user dials 9 to indicate an outbound call, then dials the remaining 7-digit number (this is a local phone call). The voice-capable router routes the call to another voice-capable router over a Frame Relay or HDLC network. The receiving router recognizes that this is an outbound call and routes it to the company’s PBX in New York. Finally, the PBX routes the call to the PSTN and the call is routed to the appropriate destination.
This solution places the call on-net as far as possible, allowing a local PBX to place a local call. This saves significantly on toll charges.

On-Net to Off-Net Call Rerouting

1. Call attempted on-net
2. Remote system rejects call
3. Call rerouted off-net

At times, on-net resources within an enterprise may be busy. However, telephone calls must still be routed. Using a voice-capable router that deploys Ear and Mouth (E&M) signaling, a router can route calls to a PBX, and ultimately to the PSTN over a Frame Relay or HDLC network.

Keep in mind that a PBX cannot reroute a call after a line is “seized.” Therefore, a voice-capable router can seize an off-net trunk and route a call. This solution guarantees that a phone call is placed, regardless of the load on the network.

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