Intersite Connectivity (WAN)

Why connect sites together? As the market trends reverse, away from the distributed and "power to the desktops" type situations seen with the advent of the PC, but back towards centralised computing power, as in the old mainframe days, Wide Area Networks (WAN's) are becoming increasingly useful, if not necessary. Companies trying to establish a broader presence also find a need to access company data held at the head office from several regional offices. The use of so-called "Thin Clients" such as Citrix Winframe and Windows Terminal Server clients, as well as web based Java, Perl and CGI software used on Intranets and the Internet means that the network needs to reach and further. More and more your key customers need and expect access to your systems for electronic ordering and MRP systems. Increasing customer expectation drives the requirement for information systems to extend towards the customer.

What is required to build my company WAN?

Before any solution to a WAN can be designed it is important to ensure the requirements of the WAN are fully understood. Factors including bandwidth requirement, usage, resilience, scalability should be considered. If a connection to a branch office is only used occasionally a "cost based on time" solution may be more cost-effective than a "fixed cost solution". If the company depends on IT systems for operation then clearly resilience is an important factor.

Bandwidth requirements are an important factor, if a database is to be used over a WAN, an SQL server client based system will function well in comparison to a file based database system because of the smaller amounts of data to be transferred. Web based systems will function well over WANs because little bandwidth is required to pass the web pages of information.

The traffic and protocols to be passed over the WAN should be fully understood and considered. Some protocols cannot be spoofed meaning the protocol should not be used over ISDN without special consideration.

Scalability is important since most companies underestimate the growth of their WAN, particularly where no existing systems exist. Use of branch wide email and database systems grows fast and it is important that the WAN can scale to keep up response times and handle increasing demand. 

On a simplistic level, to connect two sites over a leased line, or ISDN (depending on bandwidth and usage requirements) a router at each site. This will need, as a minimum, one interface matched to the LAN topology, be that Ethernet or token-ring, and one matched to the WAN, generally an X.21 interface to a leased line, or ISDN.

Can I send voice traffic over the same lines to reduce telephone call costs?

Yes, many products allow you to transmit voice traffic over data networks as IP (Voice over IP, or VoIP). Since many companies are connecting their voice networks together for the same reasons they want to connect their data networks together, it make sense to combine the two systems.

By combining wide area voice and data cost savings can be made, for this reason the IT manager/director is becoming increasingly responsible for voice within companies.

The transport of voice needs careful network design since with voice bandwidth and delay is more critical. 

Am I limited to UK only for a WAN using leased lines?

No, although the price of a leased line from London to New York will be of the order of tens of thousands of pounds as a minimum which may not be realistic for many companies. There are, however, alternatives including Frame Relay which is a public switched network which you purchase connections to from your local telecomms provider. This is especially useful for a hub and spoke topology where only one connection is necessary at the central site.

Talk to GGR about your Intersite connectivity needs to find the best solution for your company.