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Athena Access
Voice-over Frame Relay Applications

Article Number: A010
Article Type: Application
Modified: December 7, 1998

SUMMARY

This article presents a series of applications that are related to the use of Athena Access in a Voice-over Frame Relay network environment. It will provide a beneficial understanding of this product in both typical and advanced voice networking applications.

MORE INFORMATION

Introduction

Leveraging technology for the purposes of extending existing services, adding new services, reducing maintenance activities, and, not to be forgotten, saving money is at the heart of the integration of traditional voice and data technologies. At the junction of these technologies lies Athena Access, providing an extensive set of functionality to fulfill a variety of voice services in a digital data environment.

Before discussing the specific applications of this product, an outline is provided that presents the technology employed in typical business telecommunications applications. This overview will provide an insight into traditional telephony methods, and how Athena Access can provide cost-effective alternatives.

The PBX

It is typical in even the smallest of office environments to use an on-site Private Branch eXchange (more often named by its acronym, PBX) or a simpler key system that connects the in-office telephone handsets of the entire office into a single voice network. The PBX would provide the intra-office voice call services such as call forwarding, call queueing and call contention to the users in the voice network.

Access to both local and long distance services could be extended to the private voice network through the use of one or more discrete trunk-lines connected to the local telephone company. When the number of individual trunk-lines approached 12 (or more), T1 or E1 high-speed services could be employed to help reduce the overall network costs.

Basic PBX Application

In the diagram above, the PBX lies between the user telephone handsets and the public telephone service.

Voice Networking

An Organization with multiple offices may interconnect their PBXs to provide unified dialing plans throughout the corporation and to save on long distance costs. They can achieve additional savings by aggregating multiple trunks onto higher speed links and forwarding calls to other PBXs (tandem calling). In many instances these private voice networks utilize time-division multiplexers that use significant amounts of bandwidth for each voice call.

Traditional Voice Network

With the availability of high-speed public Frame relay services, the improvements in voice compression technology and related algorithms, and the presence of inter-office LAN networking requirements, significant additional savings and operational advantages can be had by merging voice and data onto a single homogenous network. By adding frame relay access devices equipped with anologue voice and LAN interfaces, these same corporations may easily convert to a new merged environment with relative ease and grace.

Frame Relay Voice Network

Athena Access Voice Services

Voice over frame relay is most economical in controlled environments where all voice traffic can be considered to be "on-net." It can then be easily justified for intracorporation communications between sites of a corporate enterprise network, sharing the same facilities that are already in place for the corporate data infrastructure.

The applications presented below do not necessarily depict this merger of voice and data, but rather they have focused on describing the specific voice functionality, assuming that there are other data or LAN connectivity needs present.

Hot Line Service

In the simplest form of application, Athena Access can provide telephone network-like functionality to connect telephones between two sites.

When you connect a telephone to the Athena Access FXS port it will act like a telephone company switch or PBX by providing dial tone when a caller picks up the handset. When it receives calls, the FXS port can also ring the connected telephone. The example below shows one telephone connected to each Athena Access unit, which in turn connects to a frame relay network. The Athena Access allows the user to pick up the phone and connect automatically to the telephone on the opposite end of the network. As the handset goes "off-hook", the local unit sets of a call to the remote unit and rings the telephone.

Hot Line Service

Multi-line Small Office

Expanding the "Hot Line Service", as noted above, to four lines at each site, provides you with a multi-line small office solution. The telephones connect to FXS ports on each Athena Access. Instead of providing the automatic connections between telephones, the Athena Access allows users to select a destination telephone. For example, a caller at Port 5 can call Port 5 on the remote unit by dialing 5, or Port 6 by dialing 6, and so on. The Athena Access will route the calls to the correct destination port on the remote Athena Access.

Multi-line Small Office

Multi-branch Small Network

You can expand the multi-line small office application further to multiple sites and allow any-to-any calling. Instead of a single digit to identify a destination telephone, you can use a two-digit number where the first digit identifies the remote site and the second digit identifies the destination telephone. To call from any telephone at Site 1 to telephone 8 at Site 3, you would call 38. The Athena Access would route the call to the correct remote Athena Access which would ring the correct destination telephone. Even calls within a site are possible. For example, at Site 2 you can call telephone 7 by calling 27. This arrangement is a very minimal dialing plan as used by larger telephone systems. Dialing plans become a very important part of planning a telephone system and integrating with existing PBXs.

Multi-branch Small Network

Public Network Access

It may be necessary to provide connections to a local telephone company to allow calls into the public network. This will allow local users to call local numbers as well as long distance numbers not serviced by the private network. Additionally, remote users can access these lines to access the local calling area, avoiding long distance charges.

The lines from the telephone company connect to FXO ports on the Athena Access. These ports simulate a telephone, as far as the telephone network is concerned. The FXO ports will go off-hook to start a call, will detect the dial tone from the telephone company, and then send the DTMF dialing digits to the network. For incoming calls, the FXO ports detect ringing, and will then go off-hook to accept the call.

In this application, the dialing plan can be very simple or integrated with the public network. In the simplest form, the callers could use the same plan as in the Multi-branch Small Network example. By dialing 37, a user connect to the trunk line on Port 7. Once connected, the user would hear a new dial tone from the telephone company and enter another number to get to the public network destination.

Public Network Access

You can configure Athena Access to streamline this process, make it easier for the users, and become nearly transparent.

If the destination port is busy, Athena Access can automatically place the call to Port 8, in this example. Port 7 and 8 become a trunk group and Athena Access can use either one at any time using a single destination number.

You can use automatic call routing in the Athena Access so that a user only enters the local public telephone number of the destination instead of dialing 37 and the destination number. The Athena Access will examine the incoming digits, check a routing table, determine the correct Athena Access site and trunk ports, get a dial tone from the public network, and send the number. For example, if a user at Site 3 enters 416-555-1390 the Athena Access would direct all 416 calls to Port 7 or Port 8. The Athena Access ignores the 416 digits, as the public network does not need them.

Public Network Access

PBX Integration

As the number of employees in an office grows, the telephone communications requirements do also. Not only do the employees need to call one another but they also need to call outside the office. Instead of relying on the telephone company to supply lines to each individual employee, you can use an on-premise telephone switch such as a PBX (Private Branch Exchange) or key system. An on-site system also allows for simple and easy moving, and adding extensions without involving any telephone company changes.

All the extensions in the office connect to the switch as well as the lines or trunks to the telephone company. The switch allows the users to call each other without connecting to the public telephone network.

The PBX provides incoming and outgoing access to the public telephone network for both local and long distance calls. The PBX also provides a level of concentration where a small number of trunk lines can service a large number of extensions. This provides cost savings in trunk line costs while still providing the required level of service to the users.

You can connect a PBX in one office to another remote office PBX to allow direct office-to-office calling. Not only does this provide you with a level of convenience by simplifying the dialing sequence for users calling between offices, but it can also be more efficient by reducing the number of trunk lines. The distance between the offices, and the amount of voice traffic, will affect the economic justification for these tie trunks. In some instances, the equivalent long distance costs will be higher than the trunk line costs.

PBXs also apply a level of intelligence to automatically route calls to selected trunk groups based on the digits dialed. For example, any number preceded by a 9 will route the call to the public telephone network, or any number preceded by an 8 will route the call to the tie trunk group to a remote office PBX.

Athena Access integrates with PBXs and key systems by replacing tie trunks and local trunk lines to the public telephone network. The most common interface for PBX inter-connection is E&M and to a lesser degree, FXS. Athena Access supports both of these types of interfaces.

Since the Athena Access simulates the telephone network or another PBX, the use of the system is exactly the same after installing the Athena Access. For a local outside line, the users still dial 9 and the PBX routes the call to the public network trunk lines. Users dial 8 for office-to-office calls and the PBX routes the call to the trunk lines connected to the Athena Access.

You can minimize call routing changes in the PBX by using the power of the Athena Access. Athena Access can route the calls to any other Athena Access in the network using the destination call digits passed to it from the PBX. The call routing features allow you to add or drop digits, and partially or completely translate them into new destination digits.

In the example below, Toronto is in area code 416, Los Angeles is in area code 213, and Paris is 01133. When a user in Toronto calls Los Angeles, the number would be 1-213-555-1212. The PBX examines the number and, based on the 1-213, forwards the call to the trunk lines terminating on the Athena Access. The Athena Access then decides which remote Athena Access on the frame relay network should receive the call. Based on the 1-213 digits, the Athena Access routes the call to the frame relay DLCI that connects to the Los Angeles Athena Access. The receiving node examines the called digits and determines that the call should be sent to the E&M ports connected to the PBX.

Toronto, LA, and Paris Network with PBXs

In the PBX network above, you achieve significant savings in long distance calling by avoiding the public telephone network for calls between the three offices. You can achieve even more savings by using each office for out-bound gateways for calls within the regions of each office.

Each PBX examines the dialed digits it receives from a local extension to determine if it should pass the call to another individual office extension or send it to the public telephone network.

REFERENCES

This article is an excerpt from the Athena Access Operations Guide - Document number A.40300.§

Copyright © 1998 Develcon Electronics Ltd.  All Rights Reserved.