e-business technologies1 chapter 2 networking basics

E-Business Technologies 1

Chapter 2

Networking Basics


Objectives

In this chapter, you will learn to:

• Illustrate the different types of computer networks

• Describe LAN transmission media

• Discuss physical and logical LAN topologies

• Explain the network services provided by LANs

• Identify standards organizations and their role in setting standards

• Describe the Seven-Layer OSI Model


Types of Computer Networks

• A computer network consists of:

– Two or more computers, as well as

– Other devices such as printers or faxes connected by some form of data transmission media such as a cable

• Network Operating Systems provide network services including:

– File management

– Security

– Resource management

• Computers and network devices use a Network Interface Card to connect with the network

Valued Gateway Client:

Valued Gateway Client:


Local Area Networks (LANs)

LANs

• Are limited to a small geographic area, such as an office or a building - will not use the public telephone system

• Have two basic architectures

– Peer-to-peer

– Client/server

• Each computer has its own processing capabilities, but can access files on other computers, network printers, and use network services

• Each computer or destination device on the network is also known as a node - nodes are 'self aware' of the network(s) to which they belong

what's the difference? and why do you care?


Peer-to-Peer Networks• Usually consist of six or fewer general-purpose

personal computers

• Computers communicate with each other and share the same files and devices

• Every computer on a peer-to-peer network is equal, that is, no one computer is in charge of the other computers

• Does not require a special Network Operating System - but note that microcomputer operating systems since Windows 2000 and Windows XP incorporate network capabilities


Peer-to-Peer Network • All computers are connected to one main cable

(also called the backbone)

• Simplest option when connecting two or three devices

what happens if the backbone breaks?


Peer-to-Peer Network with a Hub

• All computers are connected through a common connection point (Hub)

• Can connect more computers and devices to a network than a backbone

• can be 'daisy chained' but this is inefficient


Peer-to-Peer Network with a Hub


Peer-to Peer NetworkAdvantages/Disadvantages

• ADVANTAGES– Simple and

inexpensive network solution

– Does not require special Network Operating System

– Simplicity of administration

• DISADVANTAGES– Not practical for

more than five or six computers

– Limited or no security

– Business may quickly outgrow network


Client/Server Network

• Consists of general-purpose personal computers which are called clients and special high-performance computers called servers - there is no special need for the 'server' to have any more or less power than the clients

• Servers enable clients to:– share data– store data– provide support for network services, such as e-mail

• Requires a special network operating system such as Microsoft Windows 2000 Server, UNIX, or Novel NetWare (Novel has a smaller part of today's market of network operating systems)


Client/Server NetworkArchitecture


Client/Server NetworkAdvantages/Disadvantages

• ADVANTAGES

– Centralizes management of network services in one location

– Increased security

– Support for greater number of computers, devices

• DISADVANTAGES– Requires more

complex setup and management

– Administration requires higher level of technical expertise

– More expensive to implement


Metropolitan Area Network (MAN)

• A high-speed network connecting two or more LANs

• A MAN is usually confined to a single metropolitan area, such as a large city and its suburbs

few people use the term "MAN" anymore, it is just a 'longer' LAN that does note interface with the public telephone system


Wide Area Network (WAN)

• Spans a larger area than a MAN and consists of two or more connected LANs

• The Internet is a very complex and extensive WAN


LAN Transmission Media

• Transmission media are the means for carrying data from one node on a LAN to another node

• Transmission media is divided into two types:

– Cable

– Wireless


Coaxial Cable (coax)

• High-capacity communications and video cable • Has an insulated solid or stranded wire

surrounded by a solid or braided metallic shield, wrapped in a plastic cover

• Carries heavy network traffic at high speeds• Provides resistance to interference called “noise”


Twisted-Pair Cable

• Consists of insulated copper wires twisted around each other in pairs and then enclosed in a plastic covering

• Two most common types are shielded and unshielded

• By far the most prevalent medium today for LANs


Fiber-optic Cable

• Used to carry voice, video, and data signals for very long distances without requiring 'repeaters'

• Contains one or more glass fibers at its core, surrounded by a layer of glass cladding and a protective outer jacket


incorrect representation, should be four groups of twisted pairs for 8 total wires


Infrared (IR) Transmission

• Relies on electromagnetic waves with a frequency range above that of microwave but below the visible spectrum

• solid objects block the transmission• Infrared signals are transmitted through space in the

same way a TV remote control device sends signals across a room


Radio Frequency (RF)Transmission

• Relies on signals sent over a specific frequency, like radio broadcast

• not blocked by solid objects (but a solid object lessens signal strength)

• RF transmissions are regulated by the Federal Communications Commission (FCC) which licenses frequencies by geographic location to ensure that multiple transmitters do not interfere with each others’ transmissions


Traveling at the Speed of Data

• Throughput – Amount of data that can be transmitted within a specific time period– Measured in units of bits per second (bps)– 1 Kbps = 1,000 bits per second

– 1 Mbps = 1,000,000 bits per second = 1,000Kbps

– 1 Gbps = 1,000,000,000 bits per second = 1,000 Mbps

• Throughput for most (Ethernet) networks is between 10 Mbps and 100 Mbps

• Current media (category 7 twisted pair) runs 1Gbps (i.e. 1,000Mbps) with 10Gbps available but network interface cards of 10/100Mbps are the most common


Physical Topologiesof Local Area Networks

• Physical topology refers to a network’s physical layout or the pattern in which its devices and cabling are organized

• Three basic physical topologies: – Bus

– Ring

– Star

• Modern LANs generally combine these topologies into a hybrid topology


Bus Topology

• Used on peer-to-peer LANs

• Consists of a single coaxial cable called a trunk (or backbone) to which all devices are connected

• Because the cable is shared, it carries only one transmission at a time


Data Transmissions

• Data transmissions involving one sending and receiving node are called point-to-point transmissions

• Transmissions that involve one sending node and multiple receiving nodes are called broadcast transmissions


Ring Topology

• Each node is connected to the next node via a single circle of twisted-pair or fiber-optic cable

• Data transmissions travel around the circle in a clockwise direction, passing through each node

• When a node receives a transmission, it accepts the data addressed to it and then forwards the transmission on to the next node


Star Topology

• Each node is connected to a central hub by a separate twisted-pair or fiber-optic cable

• Data is transmitted from one node, through the hub, and out again to the destination node


Hybrid Topology

• Contains elements of two or more physical topologies

• Star-wired ring topology is the most common hybrid

• Data travels in a circle, from one node to the next, but each transmission passes through the hub


Logical Topologiesof Local Area Networks

• Logical topology defines the way in which the data is transmitted between computers

• Specifies several network characteristics including:

– The access methods, or rules, the nodes follow to access the transmission media

– The network’s physical topology

– The network’s transmission media

– The data throughput rate

• Logical topologies commonly used on LANs are Ethernet and Token Ring (actually, token ring is much less common)


Ethernet

• Uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD) access method, which directs transmission traffic over the network

• All stations attached to the Ethernet are "listening" and the station with the matching destination address accepts the frame and checks for errors

• Collisions:– If two nodes simultaneously check and then transmit,

their two transmissions collide– In this case, both nodes immediately stop transmitting,

wait a random interval, recheck, and then rebroadcast


Token Ring

• A network access method that uses a continuously repeating 3-byte frame (the token) that is transmitted onto the network by the controlling computer

• The token moves clockwise in a circle from node to node

• When a node wants to send a message, it waits for an empty token; then fills it with the address of the destination node and some or all of its message

• Every node on the network constantly monitors passing tokens to determine if it is the recipient of a message, in which case it "grabs" the message and resets the token status to empty


Network Services

• Programs that manage data and operations on a network, and provide services to multiple users

• Network services include:

– File services

– Print services

– Mail services

– Communications services

– Internet services

– Management services


File Services

• Permit centralized storage of data files• A high-speed computer in a network

stores the programs and data files shared by users

• A file server acts like a remote disk drive• Data stored on a file server can be

accessed by authorized users around the network


Print Services

• Enable employees to share printers across a network

• Print services include storing print-image output from all users of the system and feeding it to the printer one job at a time

• A print server provides this service for one or more printers in a network

• The print server function may be software that is part of the network operating system or an add-on utility


Using NetworkFile and Print Services

1. Document is created and stored on the file server

2. Second user can retrieve document from file server then edits and saves file on the file server

3. Remote user can retrieve document from file server

4. Sends document to network printer


Mail Services

• Manages the sending, receiving, routing, and storage of e-mail

• Controlled by a mail server, usually a computer in a network that provides "post office" facilities

• Mail services include storing incoming mail for distribution to users and forwarding outgoing mail through the appropriate channel

• The software that performs this service may reside on a computer providing other services


Communications Services

• Enables traveling employees (remote users) to connect to the network and access their data files and e-mail messages

• Company LAN is accessed using POTS (plain, old telephone system) or ISDN modem, or broadband connection through a remote access server, or wireless, or any other communications medium


Using NetworkMail and Communications Services

1. User e-mails a document to a co-worker for editing

2. Second user edits the document, then e-mails copy to the remote user

3. Remote user connects to network, then retrieves document from e-mail

4. Remote user edits document, then e-mails document to the original user


Internet Services

• Provides external Internet access, internal intranet services, and management of Internet-related technologies such as Web servers, Web browsers, and Internet-based e-mail

• Used to establish and manage external business Web sites to sell products and services, provide customer support, and gather information about potential customers and the marketspace

• Internet-based e-mail allows businesses to maintain contact with customers and suppliers


Network Management Services

• Enables administrator to monitor network activity, manage user access and network resources

• Includes diagnostic and management tools for troubleshooting problems and gathering statistics for administration and fine tuning

• Centralized installation of software and backup of stored data


The Role of Standards Organizations

• A standard is a rule, description, or design approved by an established organization or accepted by an industry through common usage

• Networking standards that cover the formatting and transmission of data are set by third-party organizations that include government agencies, scientists, research institutions, consumer groups, engineers, manufacturers, vendors, and other interested parties


International Organization for Standardization (ISO)

• A global alliance drawn from approximately 140 countries

• Establishes and publishes standards that help make possible the international trade of goods and services

• Standards govern areas such as: photographic equipment and film speed, quality management, environmental management, freight container, and paper size


International Electrotechnical Commission (IEC)

• Promote international standards in fields of electronics, magnetics and electromagnetics, electroacoustics, multimedia, and telecommunications

• Works with ISO to develop standards for the IT industry

ANSI - American National Standards Institute

• Non-profit organization that represents the U.S. to international organizations such as ISO and IEC

• Promotes adoption of U.S. and international standards that make U.S. businesses more competitive in global markets


Additional Standards Organizations

• Electronic Industries Alliance (EIA)

– Develops standards for electronic components, consumer electronics, and telecommunications

• Institute of Electrical and Electronics Engineers, Inc. (IEEE)– Internal authority on biomedical technology,

consumer electronics, computer engineering, electric power, aerospace, and telecommunications


Additional StandardsOrganizations

• International Telecommunications Union (ITU)

– International forum for government agencies and industry representatives

– Develops standards for telecommunications

• European Telecommunications Standards Institute (ETSI)– European standards organization in the areas

of telecommunications, broadcasting, and information technology


Open Systems Interconnection(OSI) Model

• An ISO standard for worldwide communications that defines a framework for implementing protocols in seven layers

• Control is passed from one layer to the next, starting at the application layer in one station, proceeding to the bottom layer, over the channel to the next station and back up the hierarchy


Open Systems Interconnection(OSI) Model

7

6

5

4

3

2

1

7

6

5

4

3

2

1

hubs are at level 1, routers act at level 3, switches act

at levels 2 & 3


Physical Layer (1)

• SENDING NODE– Passes bits onto the

connecting medium

• RECEIVING NODE– Receives bits from the

connecting medium

• Defines the physical and electrical characteristics of a system


Data Link Layer (2)

• SENDING NODE– Subdivides data into

frames, and then transfers without errors

– Retransmits frames if acknowledgement is not received

• RECEIVING NODE– Reassembles the

frames, performs error checking, then acknowledges receipt of the data

• Ethernet technologies work at the Data Link layer


Network Layer (3)

• SENDING NODE

– Determines best route to receiving node

– Translates IP addresses to MAC addresses

– Segments frames into smaller units

• RECEIVING NODE

– Reassembles the segmented frames


Transport Layer (4)

• SENDING NODE– Breaks long frames

into smaller units– Assigns sequence

numbers to each unit

• RECEIVING NODE– Uses the sequence

numbers to reassemble units in correct order

– Acknowledges error-free receipt of frames

• Ensures frames traveling between nodes arrive without error


Session Layer (5)

• SENDING NODE– Sets up session with

the receiving node– Decides which nodes

can communicate and for how long

– Restarts terminated sessions when necessary

• RECEIVING NODE– Acknowledges session

request from sending node

– Maintains communications with sending node

• Establishes and maintains communications between the sending and receiving node


Presentation Layer (6)

• SENDING NODE– Formats data sent to

receiving node for network use

– Compresses data into the smallest number of bits

– Can also encrypt data

• RECEIVING NODE– Formats data received

from the sending node for application use

– Decompresses data received from the network

– Also decrypts encrypted data

• Formats data for network and application use


Application Layer (7)

• SENDING NODE– Translates data

received from the application into a format recognized by the Presentation layer

• RECEIVING NODE– Translates data

received from the Presentation layer into a format recognized by the Application layer

• Enables the user applications to access network services such as: e-mail, file services

e-business technologies1 chapter 2 networking basics

Documents

network devices

network printers

network capabilitiesplanning

network serviceseach

network interface card

peerclientservereach

peer networksusually

devicesevery computer