Ready for VoIP: Network Management Architectures: Westbay Engineers
Part 19: This British firm has harnessed telecommunications traffic theory to aid in designing and provisioning voice networks.
During the 1990s, the company worked on many major projects for customers throughout Europe in the telecommunication, investment banking, insurance, energy, manufacturing, and government sectors. In 1996, the firm moved into the area of software development, and provided the world's first free, online Erlang traffic calculators (see below) that year, which remain the most popular part of their Web site. Since then, they have launched a number of products to assist in the design and management of voice networks and, in 2001, added voice over IP tools to their portfolio.
Figure 1. The VoIP Lite calculator
In 2003, the firm branched out further and became an ITSP, offering voice over IP calling services to residential customers, internet cafes, calling card companies, and enterprises.
As mentioned, Westbay offers a range of products to assist with the design and analysis of voice communications networks and call centers. These products are based around the Erlang traffic models, which have been used since the first half of the twentieth century for calculating the probability of call blocking. (Agner Erlang was a Danish pioneer of the study of telecommunications traffic. He first published his formulas in 1909, and gained worldwide recognition for his research).
These products offer a simple way of dimensioning voice traffic—via VoIP or traditional switched network paths—to ensure sufficient lines have been provided to meet practical blocking targets.
Figure 2. The VoIP Select calculator
Figure 3. The Westbay Traffic Calculators
The network design and management tools available include:
- VoIP Lite is the most popular VoIP calculation tool (which retails for only $US 99.00 for a single user license). It consists of a single window, with tabs to select between the Lines and IP Bandwidth Calculator and the Erlangs and IP Bandwidth Calculator. The Lines and IP Bandwidth Calculator determines the bandwidth that should be provided through an IP-based network for a given number of voice channels (see Figure 1).
Reverse calculations are also possible to determine the number of voice paths that can be derived from an IP based connection of a known bandwidth. The calculator works up to 100,000 lines and 20,000 Mbps. The Erlangs and IP Bandwidth Calculator determines the bandwidth that should be provided through an IP-based network to transport a known traffic volume in Erlangs or hundred call seconds (or CCS). Reverse calculations are also possible to determine the busy-hour traffic that can be offered to a group of lines derived from an IP link of a known bandwidth. The calculator works up to 25,000 Erlangs and 20,000 Mbps.
- VoIP Select is a more advanced voice over IP calculator, which also takes into account the bandwidth occupied by a number of Data Link (Layer 2) protocols including Ethernet and the Point-to-Point Protocol (PPP). This product includes a number of basic calculator building blocks and allows a user to design, use, and save their own calculators by interconnecting these building blocks (see Figure 2).
- Westbay Traffic Calculators provide a basic Erlang B, Extended Erlang B, and Erlang C calculator. It also includes an add-in for Microsoft Excel, allowing Erlang traffic calculations to easily be included in Excel workbooks (see Figure 3).
- Westplan is an advanced network design tool that allows the designer to experiment with the effects of different network topologies. Westplan's work is organized into projects, which contain collections of defined network nodes, with each project capable of holding an unlimited number of networks (see Figure 4). Each network defines a way of inter-connecting its project's nodes.
Figure 4. The Westplan design tool
By defining new networks using simple point and click techniques, the net manager can investigate the relative merits of different network layouts. The inter-nodal links can be either analog trunks, T1 trunks, E1 trunks, or voice over IP links using PPP, Ethernet, Frame Relay, ATM, or HDLC. Using an integrated spreadsheet table, the inter-nodal traffic levels are defined in either Erlangs of busy-hour traffic or minutes of daily traffic. Call routing through the network can also be specified if the default routing Westplan assumes (based on least hops) is not appropriate. During the optimization process, Westplan calculates the traffic levels offered to each link, and recommends the facilities that should be deployed on each link for the quality of service to remain within the specified constraints.
Further details on the Westbay Engineers architecture and products can be found at http://www.erlang.com. Our next tutorial will continue our examination of vendors' network management architectures.
Mark A. Miller, P.E., is President of DigiNet Corporation, a Denver-based consulting engineering firm. He is the author of many books on networking technologies, including Voice over IP Technologies, and Internet Technologies Handbook, both published by John Wiley & Sons.
Article courtesy of Enterprise VoIP Planet, © 2008 DigiNet Corporation, All Rights Reserved