NETWORKING FUNDAMENTALS. Network+ Guide to Networks, 4e2

NETWORKING FUNDAMENTALS

Network+ Guide to Networks, 4e 2


Why Use Networks?

• Network: group of computers and other devices that are connected by some type of transmission media

• Advantages of using networks over standalone computers:– Networks enable multiple users to share the

network’s resources (devices and data)– Networks allow you to manage, or administer,

resources on multiple computers from a central location


NETWORK ARCHITECTUREPeer-to-peer Networks

• Every computer can communicate directly with every other computer

• By default, no computer has more authority than another

• Every computer is capable of sending and receiving information to and from every other computer


Peer-to-peer Networks

Figure 1-1: Resource sharing on a simple peer-to-peer network


Client/Server Networks

• Server: central computer used to facilitate communication and resource sharing between other computers on the network (called clients)

• Client/server network: uses a server to enable clients to share data, data storage space, and devices

• To function as a server, a computer must be running a network operating system (NOS)


Client/Server Networks (continued)

Figure 1-2: Resource sharing on a client/server network



• Advantages of using client/server networks over peer-to-peer networks:– User logon accounts and passwords can be

assigned in one place– Access to multiple shared resources can be centrally

granted to a single user or groups of users– Problems can be tracked, diagnosed, and often fixed

from one location



• Advantages of using client/server networks over peer-to-peer networks (continued):– Servers are optimized to handle heavy processing

loads and dedicated to handling requests from clients, enabling faster response time

– Because of their efficient processing and larger disk storage, servers can connect more than a handful of computers on a network


TYPES OF NETWORKS

• Local area network (LAN): confined to a relatively small space, such as a building or an office

• Metropolitan area network (MAN): larger than a LAN; connects clients and servers from multiple buildings

• Wide area network (WAN): connects two or more geographically distinct LANs or MANs


LANs, MANs, and WANs (continued)

Figure 1-4: A simple WAN

BENEFITS OF A NETWORK

• Information sharing: Authorized users can use other computers on the network to access and share information and data. This could include special group projects, databases, etc.

• Hardware sharing: One device connected to a network, such as a printer or scanner, can be shared by many users.

• Software sharing: Instead of purchasing and installing a software program on each computer, it can be installed on the server. All of the users can then access the program from a single location.

• Collaborative environment: Users can work together on group projects by combining the power and capabilities of diverse equipment.


HOW ARE NETWORKS CATEGORIZED?

• Networks are usually classified using three properties:

• Topology• Protocol• Architecture


NETWORK TOPOLOGIES

• Network Topology (or layout) – refers to the way computers and peripherals are configured to form networks– Bus topology – all computers are linked by a single

line of cable– Star topology – multiple computers and peripheral

devices are linked to a central computer, called a host

– Ring topology – each computer or workstation is connected to two other computers, with the entire network forming a circle

– Hybrid topology – combine network layout types to meet their needs


NETWORK/COMMUNICATION PROTOCOLS

• A protocol is simply an agreed-on set of rules and procedures for transmitting data between two or more devices.

• Features determined by the protocol are:– How the sending device indicates it has finished

sending the message.– How the receiving device indicates it has received

the message.– The type of error checking to be used.


Signals and Protocols

• A data network is a group of computers connected by a network medium.

• The network medium carries signals between computers.

• Signals reduce complex information to the simplest possible form.

• Computers communicate by using a language called a protocol.


Protocol Services

• Packet acknowledgment

• Segmentation

• Flow control

• Error detection

• Error correction

• Data compression

• Data encryption


The OSI Reference Model


Data Encapsulation


The OSI Reference Model


NETWORKING HARDWARE AND SOFTWARE

• Hub – electronic device (with a number of ports) used in a LAN to link groups of computers

• Repeaters (also called amplifiers) – electronic devices that receive signals and amplify and send them along the network

• Routers - electronic devices used to ensure messages are sent to their intended destinations

• Gateway – consists of hardware and/or software that allows communications between dissimilar networks

• Bridge – consists of hardware and/or software that allows communication between two similar networks


REPEATERS• A common problem in the networking world is that of weakening electrical

signals. Electrical signals traveling through wires (such as copper wires used in most networks) This effect limits the lengths of the cable that can be used. when there is a need to connect two computers at a larger distance.

• A repeater is connected to two cable segments. Any electrical signal reaching the repeater from one segment, will be amplified and retransmitted to the other segment.

An illustration of a repeater at workThe electrical signal entering the repeater at one end is weakened.The repeater amplifies the electrical signals and resends the data.

22

ROUTERS


• Routers connect two or more networks and forward data packets between them. When data arrives from one of the segments, the router decides, according to it's routing table, to which segment to forward that data.

MODEMS

24

A modem is a device that converts digital data originating from a terminal or computer, to analog signals used by voice communication networks such as the telephone system. At one end, modems convert the digital pulses to audible tones and convert audio tones back to digital pulses at the other.

• An illustration of data sent using a modem and a regular telephone line.

• A modem is a device that converts digital data originating from a terminal or computer, to analog signals used by voice communication networks such as the telephone system. At one end, modems convert the digital pulses to audible tones and convert audio tones back to digital pulses at the other.

EXAMPLE OF FIREWALL

Firewalls are systems that establish access control policies among networks. They can block information from entering a network or from getting out of that network, they can permit different users to perform different kinds of operations, according to the user's authorizations.



Elements Common to Client/Server Networks


Elements Common to Client/Server Networks

Figure 1-8: Examples of network transmission media


How Networks Are Used

• Network services: functions provided by a network

• File services– Capability of a server to share data files,

applications, and disk storage space– File server

• Print services: used to share printers across a network



• Communications services– Allow remote users to connect to the network– Remote access server (also known as

communications server or access server)

• Mail services– Coordinate the storage and transfer of e-mail

between users on a network– Mail server



• Internet services– Supplying Web pages, file transfer capabilities,

Internet addressing schemes, security filters, and a means for directly logging on to other computers on the Internet

– Web server

• Management services: centrally administer management tasks on the network– Traffic monitoring and control– Load balancing

Documents

NETWORKING FUNDAMENTALS. Network+ Guide to Networks, 4e2