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
Types of Network Protocols
The most common network protocols are:
- Local Talk
- Token Ring
The followings are some commonly used network
symbols to draw different kinds of network protocols.
The Ethernet protocol is by far the most widely used
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.
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.
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
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.
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.
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.
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.
The most latest development in the Ethernet standard is a
protocol that has a transmission speed of 1 Gbps. Gigabit Ethernet
is primarily used for backbones on a network at this time. In the
future, it will probably also be used for workstation and server
connections. It can be used with both fiber optic cabling and
copper. The 1000BaseTX, the copper cable used for Gigabit Ethernet,
became the formal standard in 1999.
Compare the Network Protocols
||Twisted Pair, Coaxial, Fiber
||Linear Bus, Star, Tree
||Twisted Pair, Fiber
||Linear Bus or Star
||4 Mbps - 16 Mbps
||Twisted Pair, Fiber
||Linear Bus, Star, Tree
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Network Protocol Overview
The OSI model, and any other network communication
model, provides only a conceptual framework for communication between computers,
but the model itself does not provide specific methods of communication. Actual
communication is defined by various communication protocols. In the context of
data communication, a protocol is a formal set of rules, conventions and data
structure that governs how computers and other network devices exchange
information over a network. In other words, a protocol is a standard procedure
and format that two data communication devices must understand, accept and use
to be able to talk to each other.
In modern protocol design, protocols are "layered"
according to the OSI 7 layer model or a similar layered model. Layering is a
design principle which divides the protocol design into a number of smaller
parts, each part accomplishing a particular sub-task and interacting with the
other parts of the protocol only in a small number of well-defined ways.
Layering allows the parts of a protocol to be designed and tested without a
combinatorial explosion of cases, keeping each design relatively simple.
Layering also permits familiar protocols to be adapted to unusual circumstances.
The header and/or trailer at each layer reflect the
structure of the protocol. Detailed rules and procedures of a protocol or
protocol group are often defined by a lengthy document. For example, IETF uses
RFCs (Request for Comments) to define protocols and updates to the protocols.
A wide variety of communication protocols exists. These
protocols were defined by many different standard organizations throughout the
world and by technology vendors over years of technology evolution and
development. One of the most popular protocol suites is TCP/IP, which is the
heart of Internetworking communications. The IP, the Internet Protocol, is
responsible for exchanging information between routers so that the routers can
select the proper path for network traffic, while TCP is responsible for
ensuring the data packets are transmitted across the network reliably and error
free. LAN and WAN protocols are also critical protocols in network
communications. The LAN protocols suite is for the physical and data link layers
of communications over various LAN media such as Ethernet wires and wireless
radio waves. The WAN protocol suite is for the lowest three layers and defines
communication over various wide-area media, such as fiber optic and copper
Network communication has slowly evolved. Today's new
technologies are based on the accumulation over years of technologies, which may
be either still existing or obsolete. Because of this, the protocols which
define the network communication are highly inter-related. Many protocols rely
on others for operation. For example, many routing protocols use other network
protocols to exchange information between routers.
In addition to standards for individual protocols in
transmission, there are now also interface standards for different layers to
talk to the ones above or below (usually operating system specific). For
example: Winsock and Berkeley sockets between layers 4 and 5; NDIS and ODI
between layers 2 and 3.
The protocols for data communication cover all areas as
defined in the OSI model. However, the OSI model is only loosely defined. A
protocol may perform the functions of one or more of the OSI layers, which
introduces complexity to understanding protocols relevant to the OSI 7 layer
model. In real-world protocols, there is some argument as to where the
distinctions between layers are drawn; there is no one black and white answer.
To develop a complete technology that is useful for the
industry, very often a group of protocols is required in the same layer or
across many different layers. Different protocols often describe different
aspects of a single communication; taken together, these form a protocol suite.
For example, Voice over IP (VOIP), a group of protocols developed by many
vendors and standard organizations, has many protocols across the 4 top layers
in the OSI model.
Protocols can be implemented either in hardware or
software or a mixture of both. Typically, the lower layers are implemented in
hardware, with the higher layers being implemented in software.
Protocols could be grouped into suites (or families, or
stacks) by their technical functions, or origin of the protocol introduction, or
both. A protocol may belong to one or multiple protocol suites, depending on how
you categorize it. For example, the Gigabit Ethernet protocol IEEE 802.3z is a
LAN (Local Area Network) protocol and it can also be used in MAN (Metropolitan
Area Network) communications.
Most recent protocols are designed by the IETF for
Internetworking communications and by the IEEE for local area networking (LAN)
and metropolitan area networking (MAN). The ITU-T contributes mostly to wide
area networking (WAN) and telecommunications protocols. ISO has its own suite of
protocols for internetworking communications, which is mainly deployed in
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