Frame Relay and Leased Lines
In networking there are many options in having data transferred from one location to another. Two of which include frame relay and leased lines. Frame relay is a communication method that transfers data by dividing information into packets and sending them over a virtual network. Frame relay is a difficult process to understand and to accomplish. Leased lines, however, is the permanent connection between two stations. Leased lines are simpler to understand and do not take a lot of effort to achieve.
According to Computer Networks, frame relay came into existence to overcome the complex protocols caused by slow telephone lines, and expensive computers. Today, telephone lines are fast and inexpensive, which make a good market for frame relay (60). Frame relay is a service in which information can be transmitted in a fast and inexpensive way in either a Local Area Network (LAN) or Wide Area Network (WAN). However, the Frame Relay FAQ Website, refers to frame relay as cost effective because it is not necessarily cheap. The most is made out of the purchaser's money.
Frame relay is often referred to as a cloud because information travels over many different paths; it is not a physical connection between two stations. It is uncertain how exactly the information will get from place to place at any given time. According to the LAN Times Encyclopedia of Networking, the Permanent Virtual Circuit (PVC) is a path in which the frame relay network connects two end points. These PVC's are always active and are guaranteed to provide a certain level of service (384). Today, frame relay is a true fast packet switching network by using switched virtual circuits. Switched virtual circuits can provide any-to-any connectivity by allowing a customer to change the end points of the link to keep up with business changes. Switched virtual circuits also can provide bandwidth-on-demand meaning that when the line is at its peak carrying information more bandwidth can be made available. Also switched virtual circuits allow charges for connection to be made only for what the customer uses, unlike leased lines where you have to pay a flat rate (828-829).
In the May 1999 issue of Computerworld, a trading company decided to change its networking architecture. DCH (Da Chong Hong), in the past, used a multiple leased line architecture consisting of over 50 separate lines (See Figure 1). Figure 1 proves the fact that when transferring data between multiple sites, frame relay decreases the amount of lines that need to be leased. DCH knew it had to change its architecture to keep up with data rate technological advances. DCH decided to switch to a networking architecture that consisted of ATM and frame relay. This venture saved DCH over $129,000 per year. ATM is another form of a packet-switching data communication method.
One problem with transferring information over a frame relay network is the fact at times the network can become congested. The LAN Times Encyclopedia of Networking reports the fact that when a frame relay network becomes congested, frames are arbitrarily discarded. The end nodes are responsible for retransmitting the message frames or either they can be discarded permanently if the customer wants them to (387). Frame relay also offers a security features that help control access to the network: only private lines can access the network, passwords are required to access the network, and a time-out feature logs off inactive stations (388). These delaying tactics help insure the quality of transmission and help prevent hackers from accessing the network resources.
Frame relay use addresses to signify which site or node the message frame is being sent to. In the CCNA Exam Certification Guide, it establishes the fact that frame relay uses a header and a trailer to get the message over the network. The DLCI is the frame relay address; these addresses are used to address the virtual circuits in the network (See Figure 2). As displayed in the figure, if Router A wanted to send
information to Router B it would just need to be sent to the address DLCI 38.
Leased lines provide the permanent connection between nodes that communicate with each other. The LAN Times Encyclopedia of Networking establishes the fact that leased lines