Practical Number 6
Network Protocol - Types of Network Protocols
Network Protocol is a set of rules that governs the communications
between computers on a network.
What is a Network Protocol
Rules
of Network Protocol include guidelines that regulate the following
characteristics of a network: access method, allowed physical topologies, types
of cabling, and speed of data transfer.
Types of Network Protocols
The
most common network protocols are:
·
Ethernet
·
Local Talk
·
Token Ring
·
FDDI
·
ATM
The
followings are some commonly used network symbols to draw different kinds of
network protocols.
Ethernet
The Ethernet protocol is by far the most widely
used one. Ethernet uses an access method called CSMA/CD (Carrier Sense Multiple
Access/Collision Detection). This is a system where each computer listens to
the cable before sending anything through the network. If the network is clear,
the computer will transmit. If some other nodes have already transmitted on the
cable, the computer will wait and try again when the line is clear. Sometimes,
two computers attempt to transmit at the same instant. A collision occurs when this
happens. Each computer then backs off and waits a random amount of time before
attempting to retransmit. With this access method, it is normal to have
collisions. However, the delay caused by collisions and retransmitting is very
small and does not normally effect the speed of transmission on the network.
The Ethernet protocol allows for linear bus, star, or tree topologies.
Data can be transmitted over wireless access points, twisted pair, coaxial, or
fiber optic cable at a speed of 10 Mbps up to 1000 Mbps.
Fast Ethernet
To allow for an increased speed of transmission, the Ethernet protocol
has developed a new standard that supports 100 Mbps. This is commonly called
Fast Ethernet. Fast Ethernet requires the application of different, more
expensive network concentrators/hubs and network interface cards. In addition,
category 5 twisted pair or fiber optic cable is necessary. Fast Ethernet is
becoming common in schools that have been recently wired.
TCP - Transmission Control Protocol
TCP
is one of the main protocols in TCP/IP networks. Whereas the IP protocol
deals only with packets, TCP enables two hosts to
establish a connection and exchange streams of data. TCP guarantees delivery of
data and also guarantees that packets will be delivered in the same order in
which they were sent.
Local Talk
Local Talk is a network protocol that was developed by Apple Computer,
Inc. for Macintosh computers. The method used by Local Talk is called CSMA/CA
(Carrier Sense Multiple Access with Collision Avoidance). It is similar to
CSMA/CD except that a computer signals its intent to transmit before it actually
does so. Local Talk adapters and special twisted pair cable can be used to
connect a series of computers through the serial port. The Macintosh operating
system allows the establishment of a peer-to-peer network without the need for
additional software. With the addition of the server version of AppleShare
software, a client/server network can be established.
The Local Talk protocol allows for linear bus, star, or tree topologies
using twisted pair cable. A primary disadvantage of Local Talk is low speed. Its
speed of transmission is only 230 Kbps.
Token Ring
The Token Ring protocol was developed by IBM in the mid-1980s. The
access method used involves token-passing. In Token Ring, the computers are
connected so that the signal travels around the network from one computer to
another in a logical ring. A single electronic token moves around the ring from
one computer to the next. If a computer does not have information to transmit,
it simply passes the token on to the next workstation. If a computer wishes to
transmit and receives an empty token, it attaches data to the token. The token
then proceeds around the ring until it comes to the computer for which the data
is meant. At this point, the data is captured by the receiving computer. The
Token Ring protocol requires a star-wired ring using twisted pair or fiber
optic cable. It can operate at transmission speeds of 4 Mbps or 16 Mbps. Due to
the increasing popularity of Ethernet, the use of Token Ring in school
environments has decreased.
FDDI
Fiber Distributed Data Interface (FDDI) is a network protocol that is
used primarily to interconnect two or more local area networks, often over
large distances. The access method used by FDDI involves token-passing. FDDI
uses a dual ring physical topology. Transmission normally occurs on one of the
rings; however, if a break occurs, the system keeps information moving by
automatically using portions of the second ring to create a new complete ring.
A major advantage of FDDI is high speed. It operates over fiber optic cable at
100 Mbps.
ATM
Asynchronous Transfer Mode (ATM) is a network protocol that transmits
data at a speed of 155 Mbps and higher. ATM works by transmitting all data in
small packets of a fixed size; whereas, other protocols transfer variable
length packets. ATM supports a variety of media such as video, CD-quality
audio, and imaging. ATM employs a star topology, which can work with fiber
optic as well as twisted pair cable.
ATM is most often used to interconnect two or more local area networks.
It is also frequently used by Internet Service Providers to utilize high-speed
access to the Internet for their clients. As ATM technology becomes more
cost-effective, it will provide another solution for constructing faster local
area networks.
