FREE online courses on Information Technology - Chapter 8 NETWORK &
COMMUNICATIONS IN I T - THE ADVANTAGES OF NETWORKS FOR BUSINESS
There are large numbers of sources for communications
services. As examples, we have discussed the public switched network, in which
telephone lines on the local level connect with AT&T, Sprint, or MCI. We can
also pay to lease a line or pay according to the time a line is in use. The
actual communications path may be through land lines, microwave links,
satellites, or some combination of the three. A firm may develop a private
network and/or use services offered by common carriers.
A type of network known as packet switching is now a standard for transmitting digital data. A
circuit-switched network establishes a connection between every pair of points
that wants to transmit data, just as the telephone network does. There is
considerable overhead in making the connection between the two parties. In
packet switching, the network does not make connections for individuals. It
routes bunches of data called packets. Network hardware and software break data
into packets with each packet having an address. Each node on the network looks
at the address and determines the best path to send it on toward its final
destination. Network hardware and software reassemble the packets on the
receiving end. Packet switching has proven very popular for transmitting data
over large distance. There is an international packet-switching standard called
x.25, and a number of networks use this protocol, including the French Transpac
network. You may hear the term
asynchronous transfer mode (ATM), which refers to a standard for high-speed
packet switching. It includes the packet size, speed, and format. With such a
standard, transmission services, around the world should be compatible. ATM
features high bandwidth (high capacity) and low delay. It is capable of carrying
voice, data, image, and video communications.
Frame relay is a
promising service offered by some of the common carriers to win data
transmission business for wide area networks. The user chooses a data rate and
connects to the common carrier's frame real system through a router. The common
carrier maintains a packet-switched “public” frame relay network which offers
higher speeds than some private network alternatives. This common carrier
network also features extensive backup and rerouting capabilities, making an
outage of service less likely. Speeds with frame relay and lower than ATM,
ranging from 56,000 to 1,544 million bits per second.
