Still Using Statistical Multiplexers?
Marcio Saito - Revision 1.1 April 2000

About this document
    This paper shows how to save money and simplify the communication infrastructure by eliminating dedicated leased lines used by statistical multiplexers and consolidate serial data in the IP network.

Executive Summary
    There are still a lot of statistical multiplexers (muxes) being used in the corporate market to connect serial devices over remote sites. These muxes support legacy applications over expensive dedicated lines while LAN internetworking is being handled in parallel router networks running over other physical circuits or frame-relay. By replacing the multiplexers by the IP-enabled Cyclades-PR3000/TS, you can consolidate traffic, eliminate leased lines and, at the same time, make the change transparent to the mission-critical legacy applications.

What are Statistical Multiplexers?
    Statistical multiplexers allow multiple serial devices connected over two remote sites to share a single data line. This way, a pair of statistical multiplexers connected by a leased line is equivalent to multiple individual serial connections between the two sites.
    The term "statistical" refers to their ability to use the "pauses" in the communication of each serial pair to allow the sum of the baud rates of the individual lines to be larger than the bandwidth of the communication line.
    Typical uses of multiplexers include:

• Connection of remote serial terminals, point-of-sale, printers, etc to a host system.
• Remote data-entry or terminal applications.
• Communication with remote monitoring devices.
• Remote process control equipment.

What is the Cyclades-PR3000?
    The Cyclades-PR3000 is a powerful, flexible, cost-effective, multi-protocol router. It has one Ethernet interface for a LAN connection and 3 slots where combinations of several possible WAN interfaces can be installed.
    It supports IP, IPX and SNA networks over PPP, Frame Relay and X.25 connections. The WAN interfaces supported include Serial WAN (RS-232, V.35, X.21), ISDN BRI, T1/FT1, E1/FE1.
    It also supports terminal server functionality. Using a special interface card in one of the expansion slots, the PR3000 can support up to 64 serial RS-232 ports. This is one of the features that allow it to work in this mux replacement application.

How to Eliminate the Muxes and Leased Line
    The Cyclades-PR3000 is a powerful, flexible, cost-effective, multi-protocol router. It has one Ethernet interface for a LAN connection and 3 slots where combinations of several possible WAN interfaces can be installed. It supports IP, IPX and SNA networks over PPP, Frame Relay and X.25 connections. The WAN interfaces supported include Serial WAN (RS-232, V.35, X.21), ISDN BRI, T1/FT1, E1/FE1. It also supports terminal server functionality. Using a special interface card in one of the expansion slots, the PR3000 can support up to 64 serial RS-232 ports. This is one of the features that allow it to work in this mux replacement application.

With the PR3000 solution you get:

• Cost savings, there is no more need for expensive statistical multiplexers and leased lines. The investment in the PR3000 is recovered in a few of months.
• Management and administration benefits. There is only one box and one network to manage.
• Flexibility and efficiency. While statistical multiplexers usually connect serial ports between two fixed sites, the PR3000 can connect any serial port individually to any other site connected to the network. Before the serial traffic is consolidated into the IP network, idle communication lines are eliminated.
• The first step towards a client-server implementation. Using the PR3000, you can first replace the hardware and communication infrastructure without changing the application. That gives you more control and security in the migration process.

Conclusion
    Whether you use statistical multiplexers or not, we invite you to consider our Serial Boards, Routers and Remote Access Servers every time there is the need for remote connectivity product.
    This paper illustrates only one example of application where the flexibility of the PR3000 allows you to save money and have a better networking solution. For more information, look at the PR3000 and PR3000/TS literature or contact us at Cyclades. We will be more than happy to analyze you specific needs and propose a Cyclades Solution.

    Comments or suggestions to this document can be sent to Marcio Saito marcio@cyclades.com