Leased line

Looking for fast and reliable Net access with zero downtime. A leased line may be the answer to your access woes

When you conduct business on the Internet, your company needs access that is dependable and fast. Time is money, and downtime or slow transfers can cost many times more than what you actually pay for your connections. Leased lines addresses these issues.

Leased lines are dedicated circuits provided by Basic Service Providers (BSPs), which provide permanent connectivity to the Internet. Leased lines provide the last mile access from the user premises to the ISP. They provide permanent connection as compared to the temporary connectivity through dialup access. The quality of the connection is far superior to what is normally available through dialup, thanks to digital signaling, less noise, fewer exchanges etc.

Leased lines provides a scalable access method, important particularly for organizations with large user groups, including corporate, banks and financial institutions, educational and R&D organizations, government, military etc. Starting typically with 64 Kbps, it is possible to deploy a scalable architecture, with multiples of E1 (2 MBPS) pipes, providing the necessary bandwidth. In fact, leased access becomes a must for large organizations in most situations.

Since the access is "always on", it is possible to associate a pool of permanent IP addresses with a particular leased line. Normally, the ISP would provide 16/32 IP addresses for each 64 Kbps chunk of bandwidth. Using these IP addresses it becomes possible to deploy a variety of services such as mail, FTP, WWW, DNS, and proxy, to name the most common requirements of organizations. In other words, leased lines enable hosting of services of all types, and provide a platform for enterprise intranets and extranets, apart from what we may term as "entry level" services such as messaging, which still account for over 70 percent of all Internet access.

We can look at two types of equipment requirements. The first set of hardware is required for establishing the last mile link between the customer premises and the ISP. Currently, 64 Kbps and 2 Mbps leased line modems are commonly deployed for terrestrial leased line access to the Net. The equipment required is one pair of leased line modems (one each with V.35 and G.703 interface) and one G.703/V.35 interface converter, supporting either 64 Kbps or 2 Mbps. Depending on the bandwidth, there are some technical differences between the 2 types of modems as well. This equipment may be provided either by the ISP or the customer can buy it himself.

The other set of equipment required is at the customer premises. This includes a router and various servers as needed in specific sites. The router establishes the link with the ISP. Typically, users need to consider services like DNS, mail, proxy, firewall,FTP, databases, file servers, and security services which can be set up on the available connectivity.

Applications of leased lines

Point-to-point: For Data Only
One of the widely used applications of leased lines is having a secure dedicated data circuit between two locations via a private line, used to transmit data at a constant speed equal to the bandwidth of the circuit.

Point-to-point: For Voice and Data

This kind of application allows transmission of voice and data over the same connection. Here also two separate locations are joined together. This type of configuration is commonly provided on a higher bandwidth circuit. The bandwidth of the circuit is divided into individual voice channels and data channels.

Multiplexing

Multiplexing basically connects multiple remote sites to a single

centralized location. Typically a connection originating at the host location is connected into a multiplexer at a service provider's end. At the multiplexer, the host circuit is split into smaller individual circuits, and those are then delivered to the remote sites.

Mahesh Rathod can be reached at rathodmp@hotmail.com

Advantages

It provides permanent, reliable, high-speed connectivity as compared to the temporary connectivity of dial up access. The quality of the connection is far superior to what is normally available through dialup, because of the digital signaling, less noise, fewer exchanges etc.

Disadvantages

Leased bandwidth prices are quite high, compared to dialup bandwidth of comparable size. Entry level annual port prices are also high at present, so that this access method is only feasible beyond a fairly high threshold level.

Permanent connectivity to the Net exposes the organization to a variety of threats including hacking, malicious code including active vandals, viruses, Trojan Horses, macros, denial of service attacks etc.