FREE ESSAY ON FRAME RELAY

FRAME RELAY

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
are guaranteed to operate at certain speeds and provide a quality service. Leased lines
are used to build private networks, where a company connects sites by using their own
switching equipment (518). Conditioning is also a service provided by carriers who supply
leased lines, which include repairing or replacing damaged lines.
Two types of leased lines are available: analog and digital lines. Analog lines require
modems to be at each end of the line. Digital lines, however, do not require any extra
equipment. They have higher data transmission rates and signals are represented by 1's or
0's. Digital lines can beT1 or T3 lines. According to the Frame Relay Webopaedia Website,
T1 lines can reach speeds up to 1.544 Mbps and T3 lines reach speeds up to 45 Mbps. The
LAN Times Encyclopedia of Networking also states that when determining whether or not to
use a leased line or not there are 4 points to take into consideration: the cost of
leased lines increase with distance (may only work in certain geographical areas); may
want to use leased line if two sites have four or more hours of traffic per day; leased
lines are feasible if only connecting a few sites; leased lines can be used if a lot of
voice and data traffic exists between two sites (920).
There are other means of leased lines. Leased lines do not always have to be T1 or T3
lines. A customer can lease fiber optic cable and coaxial cable. Fiber optic cables are
very fast, provide security, and noise is minimal. Fiber optic cable can reach data
speeds around 1 Gbps, but the bandwidth can be increased to provide speeds even higher.
Coaxial cable run about 400 Mbps and is fairly inexpensive. Fiber is often compared to
coaxial cable, however fiber has many advantages over coaxial cable. Fiber optic cable
operates at more than twice the rate as coaxial cable. So, depending on whether speed is
necessary or cost is an option there are other alternatives when leasing a line from a
common carrier.
Usually leased lines are referred to as dedicated lines but they also can be nondedicated
which means the customer only makes connections when needed. These can also be referred
to as fractional lines. For example a fractional T1 line, allows a customer to use the T1
line only when needed. This saves money for companies who only need partial connection
time. Another alternative to these methods if only a portion of the line needs to be used
is just using a dialup line. In the LAN Times Encyclopedia of Networking, it states that
a good example of using a dialup line is when the only thing being transferred is e-mail.
The e-mail accumulates until it has enough to make a call (519).
An example where leased lines may be more beneficial than using frame relay could be an
instance of a central company in Atlanta, GA needing to communicate with another site in
Athens, GA (approximately 5 miles). This communication needs to be established throughout
the day and it needs to be speeds at least 1.2 Mbps. The reason why a leased line would
be most beneficial for this situation is the fact that the connection has to be
established throughout the day, forcing a leased (dedicated) line to be used.
Frame relay and leased lines interconnect with each other to transmit data from one
station to another. Leased lines provide some of the physical connections while using
frame relay. Data in frame relay is transmitted through a cloud and data over a leased
line is transmitted over a physical connection that actually connects the computers.
According to a picture found in the July issue of PC Magazine, LAN's are connected by
using a leased line connection between routers. The router then uses a frame relay
connection to access the frame relay service, and then it is able to send information to
the other LAN (176). In the CCNA Exam Certification Guide, it states that the main
difference between frame relay and leased lines is the fact that frame relay is a
multi-access network, meaning that more than two devices can be attached to the medium
(390). It also states that leased lines are the access link between the router and the
Frame Relay switch (391).
In the LAN Times Encyclopedia of Networking, it states that in order to obtain frame
relay or leased line services a user must use a common carrier such as AT&T, MCI, Sprint,
and the Regional Bell Operating Companies (RBOCs). These companies provide the physical
connections to the frame relay network, which are usually in the form of leased lines
(384). When setting up a frame relay network it is necessary to choose which common
carrier will be used. After choosing which carrier a service needs to be chosen that best
suits the customers' needs. The customer can choose between a variety of access speeds
ranging between 56 Kbits to 1,544 Mbits. The customer then needs to plan on how to link
from one site to the frame relay service provider by placing routers and other access
devices at the site. These devices connect to the service provider's frame relay port
which connect to the PVC's (386). 
Frame relay and leased lines are good ways to have data transferred in a fast and
predictable manner. Frame relay would be used in a situation where there are many sites
and communication needs to be established throughout the day. A leased line is used to
keep a communication link established between 2 locations and usually also is needed
throughout the day. Each data communication need depends on the situation at hand and the
communication circuit used would vary accordingly to that situation. 
Bibliography
Baasch, Dennis. Frame Relay FAQ. Emerging Technologies, Inc.
http://www.etinc.com/frmain.htm.
Frame Relay. PC Webopaedia Definition and Links.
http://webopedia.internet.com/Networks/Frame_Relay.html.
Lemon, Sumner. Trading Firm Chooses ATM, Frame Relay. Computerworld. May 31, 1999.
Metz, Cade. The Techncial Pro User. PC Magazine. July 1999.
Odom, Wendell. CCNA Exam Certification Guide. Indianapolis, Indiana: Cisco Press, 1999. 
Tanenbaum, Andrew S. Computer Networks. 3rd Edition. Upper Saddle River, New Jersey:
Prentice Hall, 1996.
Sheldon, Tom. LAN Times Encyclopedia of Networking. Berkeley, California: McGraw-Hill,
1994.