Networka set of nodes connected by media links for resource sharing.A node: computer, server, printer, etc.A link: telephone line, leased line, fiber cable, etc.Resource: printer, files, programs, database, etc.

Technology Paradigm Shift1960-1970’s: Mainframe 1970-1980’s: Mini PCs/WAN1980-1990’s: PCS/LAN/NOS1990-2000’s: Networking

Networking: A brief history1972- Ethernet local area network specifications formulated.1972- IBM’s synchronous data link control protocol announced.1974- IBM announces its systems network architecture (SNA).1975- Personal Computers were introduced, the Altair 8800 replaced terminals in many cases.1981- IBM PC introduced.1985- Cellular Radio Telephones are introduced.1990- World Wide Web is introduced.1993- Web search engines are introduced.1995- The internet grows to over 4 million host computers.1999- The internet grows into a 10 million host computers.

ARPANET Developed by the Advanced Research Project Agency of the US Department of Defense.A small network started in the mid-1960s for connecting mainframe computers.In 1969, four nodes are connected; UCLA,UCSB, Stanford Research Institute, and University in Utah.Used NCP, then TCP/IP protocol suites.MILNET: Military Users.ARPANET: non-military users.

CSNETNetwork for Universities and companies that connected through TCP/IP, and TELNET; sponsored by the National Science Foundation, 1981-1986.

NSFNETA backbone that connected five supercomputer centers by a T1 (1.50044 Mbps) line; 1990-1995.

EUROPECERN, RIPE, 1989.

AUSTRALIAAAR Net, 1989.

JAPANJUNET, 1984.

SINGAPORETECHNET, 1990.

Networking : InternetThe internet is a big collection of computers linked by cables. Some links are as small as your phone line. Some are huge undersea cables, capable of carrying thousands of telephone calls and data “conversations” simultaneously. The internet is just a huge computer network.

Networking : Intra and ExtraIntranet is “an infrastructure based on internet standards and technologies that supports sharing of content within a limited and well-defined group.”Extranet is a private network that uses internet protocol network connectivity, and possibly the public telecommunication system to securely share part of a business’s information or operations with suppliers, vendors, partners, customers, or other businesses.

Internet Working ConceptsOSI Model OverviewApplication Layers

- Application Layer- Presentation Layer- Session Layer

Data flow Layers- Transport Layer- Network Layer- Data Link Layer- Physical Layer

Role of Application LayerThe application layer specifies the communication interface with the user and manages

communication between computer applications.

Role of Application Layer:

-Select network application to support users application-Inter network application extends beyond the enterprises

APPLICATION LAYER EXAMPLES Telnet - A program that lets you connect to remote computers as if you are working

locally. File Transfer Protocol (FTP) - A service that supports file transfer between local and

remote computers. Hypertext Transfer Protocol (HTTP) - The standard way of transferring information

across the internet. Domain Name Service (DNS) - A mechanism used in global and public networks for

translating computer games to IP addresses. Simple Network Management Protocol (SMP) - The most common method by which

network management applications can query a management information base (MIB) Simple mail transfer protocol (SMTP) - A protocol used for transferring emails

between servers.

Computer applicationsWord processingPresentation graphicsSpreadsheetsDatabaseDesign/manufacturingProject planning

Network applicationE-mailFile transferRemote accessClient/server processInformation locationNetwork management

Inter network applicationsElectronic data interchangeWWWE-mail gatewaysSpecial-interest bulletin boardFinancial transaction servicesInternet navigation utilitiesConferencing

Others

ROLE OF PRESENTATION LAYER

The presentation layer transforms data into a mutually agreed-upon format (transfer syntax) that can be understood by each application and the computers they run on. The presentation layer may also compress, expand, encrypt and decrypt data.

-ensures that information sent from the application layer of one system will be readable by the application layer of other systems

-provides code formatting and conversion for applications

PRESENTATION LAYER EXAMPLES

TIFF - the tagged image file format is a standard graphics format for high-resolution, bitmapped images.

JPEG - the joint photographic experts group bring these photo standards to us. MIDI - the musical instrument digital interface is used for digitized music. MPEG - the moving picture experts group standard for the compression and coding of

motion video for CDs is increasingly popular. It provides digital storage and bit rate up to 1.5Mbps.

RTF - rich text format is a file format that lets you exchange text files between different word processors even in different operation systems.

ROLE OF SESSION LAYER

-Establishes, manages and terminates communication session between presentation layer entities.-Establishes end connections between two nodes.-Monitor of flow control-Coordinates applications as they interact on different hosts.

SESSION LAYER EXAMPLES

Network File System (NFS)Developed by Sun Microsystems and used with TCP/IP and Unix workstations to allow transparent access to remote resources.

Structured query language (SQL)Developed by IBM to provide users with a simpler way to define their information requirements on both local and remote systems.

Remote procedure call (RPC)A broad client/server redirection tool used to disparate service environments. Its procedures are created on clients and performed on servers.

ROLE OF TRANSPORT LAYER

The transport layer acts as the interface between the higher layers and the lower three layers. It provides the session layer with a message transfer facility that is independent of the underlying network type. It specifies connection oriented or connectionless protocol, full or half duplex, flow control and error recovery services. Data is grouped into segments in this layer.

TRANSPORT LAYER EXAMPLES

UDP (User datagram protocol)-connectionless-Regardless of the acknowledgement

TCP (Transmission control protocol)-Connection oriented method of transporting data to the destination which requires acknowledgement from the destination.-distinguishes between upper layer applications-establishes end to end connectivity between applications-defines flow control-provides reliable or unreliable services for data transfer

ROLE OF NETWORK LAYER

The objective of the network layer is to move or route information across a network made up of multiple network segments. The network layer does this by examining the destination network layer address (different from the physical layer address) and sending the packet to the next transit point in the inter network.

-defines logical source and destination addresses associated with specific protocol-defines path through network-interconnects multiple data links

ROLE OF DATA LINK LAYER

The data link layer organizes the physical layers bit into frames (logical groupings of information). A frame is a contiguous series of data with independent logical meaning. The data link layer also detects (and sometimes corrects) errors, controls data flow and identifies particular computer on the network.

-defines physical source and destination addresses-defines higher layer protocol (service access point) associated with frame.-defines network topology-defines frame sequencing-define flow control-define error detection, not correction

ROLE OF PHYSICAL LAYER

The physical layer defines the mechanical and electrical specifications of the network medium and the network interface hardware, how they connect to one another, and how data (in form of bits) is placed on and retrieved from the network medium.

-defines media types-define connector type-define signaling type

LAN STANDARDSStandard name Definition Speed

Ethernet IEEE802.3 10MbpsFast Ethernet IEEE802.3u 100MbpsGigabit Ethernet IEEE802.3z 1GbpsToken Ring 802.5 4/16MbpsFDDI ANSI Standard 100Mbps

WAN STANDARDSStandard name DefinitionRS 232,RS449,EIA530 EIA/TIAX.21, V.35, V.24 ITU-TISDN BRI, ISDN PRI ITU-T

CATEGORIES OF A NETWORK

By Size-Wide Area Network (WAN)-Metropolitan Area Network (MAN)-Local Area Networks (LAN)

By capability-client/server-peer-to-peer

3 MAJOR TYPES OF NETWORK

Local Area Network (LAN)Serves user within a confined geographical area (usually within a mile).

Metropolitan Area Network (MAN)Covers a geographic area the size of a city or suburb. The purpose of a MAN is often to bypass local telephone companies when accessing long distance service.

Wide Area Network (WAN)Covers a wide geographical area, such as a state or a country.

NETWORK MODELS: Client/Server ModelMicrocomputer users, or clients, share services of a centralized computer called a server.

Server software generally, but not always, runs on powerful computers dedicated for exclusive use to running the business application.

Client software on the other hand generally runs on common PCs or workstations.

Properties of a server-passive (Slave)-waiting for requests

-on requests serves them and send a reply

Properties of a client-active (master)-sending requests-waiting until reply arrives

NETWORK MODELS: Client/Server model

Pros -Security -centralized servers are easy to manage -physically centralized -secure operating system-Performance-Centralized backups-Reliability

Cons-requires professional administration-more hardware intensive

Ex.-E-mail system-database system-Web browsing-File Transfer Protocol (FTP)-Windows domain-Network games

NETWORK MODELS: Peer to Peer Model

Peer-to-Peer modelComputer share equally with one another without having to rely on a central server.

Computer on the network communicate with each other as equals and each computer is responsible for making its own resources available to other computers on the network.

Pros-Uses less expensive computer networks-easy to administer-No NOS (Network operating system) requires-More built-in redundancy-Shared resources-some machine will have what you need

Cons-Individual user performance easily affected-Not very secure

-Hard to back up

EX.-Napster-Gnutella-eDonkey-Peercast-KaZaa-Limewire-uTorrent

CHARACTERISTICS THAT DIFFERENTIATE ONE NETWORK FROM ANOTHER

Topology-the geometric arrangement of devices on the network. For example, devices can be arranged in a ring or in a bus or in a star topology.

Protocols-The rules and encoding specification for sending data. The protocols also determine whether the network uses a peer-to-peer or client/server model.

MediaDevices can be connected by twisted-pair wire, coaxial cable, or fiber optic cables. Wireless networks are connected via radio waves.

Medium Access ControlScheme to allow sharing of the media.

NETWORK TOPOLOGIES: BUSIn a bus topology, all nodes are attached directly to the same piece of cable. The bus terminates at both ends of the medium.

Features-Network maintained by a single cable-Bus ends with terminators-Can be daisy chained-Uses coaxial cable

Advantage-easy to install-easy to add stations-uses less cabling than other topologies

Disadvantage-Difficult to troubleshoot-a break in the main cable shuts the network-limited number if stations

EX.Thin Ethernet (10Base2)

-IEEE 802.3 Standard

-Maximum segment length of 200m-Maximum of 30 stations per segment-Maximum of 5 segments using 4 repeaters

Thick Ethernet (10Base5)-IEEE 802.3 Standard-Maximum segment length of 500m-Maximum of 100 stations per segment-Maximum of 5 segments using 4 repeaters

NETWORK TOPOLOGIES: STARIn a star topology, each device is connected via point to point link to a central point or node. This central node is commonly referred to as hub, wiring concentrator or multi port repeater.

Features-Segments meet at the hub-each station needs its own cable to the hub-easy to maintain and expand

Advantages-Easy to troubleshoot-Terminals can be added and removed easily-Lots of support due to its popularity

Disadvantages-longer cable requirement than bus-concentrator(hub) as a single point of failure-Higher costs than most bus networks.

NETWORK TOPOLOGIES: RINGA ring is a closed loop of point-to-point links between repeaters (station). The repeaters duplicate signals, so degradation is minimal.

Features-Equal access for all stations-A station has to wait for its turn for transmission-Data travels in one direction

Advantages-Data travels at great speed-No collisions-Easy to troubleshoot

Disadvantage-Longer cable requirement than bus-A break in the ring shuts the network-Not common as the bus-less devices available

DATA COMMUNICATION

Data can exist in two forms…

Digital Transmission – 1’s and 0’s On and Off computer-speakAnalog Transmission – wires or wireless. Audio tones into conveyed through signal amptitude, frequency and phase.

Analog data is converted to digital because electronic computers process data in digital form.

Digital data is converted to analog because most existing transmission facilities make use of analog signals.

ANALOG ENCODINGAmplitude shift keying encodes digital data by modulating the carrier’s amplitude between two or more levels.

COMMUNICATION MODES

Simplex

TX RXOnly one interface is a transmitter and every other interface is a receiver, the channels full bandwidth is always available for signals traveling from transmitter to receiver(s).

Half-Duplex

TX RXRX TXEach interface servers as both transmitter and receiver, but only one interface can transmit at a time. The channels full bandwidth is available to the transmitting interface (which cannot receive while it is transmitting).

Full-Duplex

TX RX

A full duplex channel has two ends, each serving as both transmitter and receiver. Each interface can both transmit and receive at the same time.

TRANSMISSION TYPES

Asynchronous transmission- calls for each character to be transmitted separately, with separate synchronization information.

This type of transmission is often used in situations where characters may be generates at random intervals, such as when a user types at a terminal.

With asynchronous transmission, all of the bits that comprise a character are framed and then sent as a single transmission string.

Synchronous transmission – can send both character-oriented and bit-oriented information.The data are usually buffered and transmitted as a entire message or frame, unlike asynchronous, which transmits one character at a time.

The transmitting and receiving clocks maintain synchronization which is accomplished in two ways:

a separate synchronizing signal, a clock, can be constantly transmittedclocking can be included in a the data signal

Baseband- a type o data transmission in which digital or analog data is sent over a single unmultiplexed channel

Broadband- a type of data transmission in which a single medium (wire) can carry several channels at once.

COMPONENTS OF A NETWORK

Hardware:-computer-network interface card-hub, switches, routers-modems

Software-network operating system-programs and utilities

Transmission medium-Copper cable-fiber optic cables-space (wireless)

BASIC NETWORKING ELEMENTS

-PCs and Servers-NIC – Network Interface Card-Cables and Connectors-Switches, hubs, routers (other networking devices i.e. bridge, router, etc.)-Network software-users

SERVER-a computer that provides services to other networked computers-e.g. file server and print server

File server-controls users and their privileges-control remote access services-control file use

Print server-a system that provides a printer for use by other members of the network permitted to do so

Workstations (Client/workstation)-machines that use services provided by other machines in the network.-a client may or may not provide services to other machines, therefore a client can perform server functions.

NETWORK INTERFACE CARD (NIC)A “NIC”, or network interface card, is a broad-level product that fits into a PC, workstation, or

server that allows the computer to talk to the rest of the network. A server NIC provides increased reliability, reduced CPU overhead, and better overall performance.

Cable(Transmission media)-unshielded twisted pair-coax cable-fiber optic cable

Physical media that connects all network nodes (i.e devices attached to the network such as printers, servers, computers etc.) The cable serves as the conduit along which data is sent between devices. LAN cables carry only one signal at a time.WAN Cables can carry multiple signals simultaneously.

There are three main cabling standards:

EIA/TIA 568 A/B - this is the American standard and was the first to be published (1991).

ISO/IEC 11801 – the international standard for structured cabling systems. CENELEC EN 50173- the European cabling standard (the British version is BS EN

50173).

UNSHIELDED TWISTED PAIR-Unshielded twisted pair (UTP) is the most popular and is generally the best option for most

networks.-the cable has four pairs of wires inside the jacket. Each pair is twisted with a different number

of twists per inch to help eliminate interference from adjacent pairs and other electrical devices.-shielded twisted pair (STP) is suitable for environments with electrical interference. However,

the extra shielding can make the cables quite bulky.

UTP cable categories

Type Uses

Category 1 Voice only (telephone wire)Category 2 Data of up to 4Mbps (LocalTalk)Category 3 Data of up to 10Mbps (Ethernet)Category 4 Data of up to 20Mbps (16Mbps token ring)Category 5 Data of up to 100Mbps (Fast Ethernet)Category 5e Data of up to 1Gbps (Gigabit Ethernet)Category 6 Data of up to 1Gbps (Gigabit Ethernet)

COAXIAL CABLE-has a single copper conductor at its center.-a plastic layer provides insulation between the center conductor and a braided metal shield.

-the metal shield helps to block any outside interference from fluorescent lights, motors and other computers.

FIBER OPTIC CABLE-consist of a glass core surrounded by several layers of protective materials-transmits light rather than electronic signals eliminating the problem of electrical interference.

This makes it ideal for certain environments that contain a large amount of electrical interference.-it has also made it the standard for connecting networks between buildings, dues to its

immunity to the effects of moisture and lighting.-has the ability to transmit signals over much longer distances than coaxial and twisted pair-has the capability to carry information at vastly greater speeds.-cost of fiber optic cabling is comparable to copper cabling; however, it is more difficult to

install and modify.

FIBER OPTIC CABLE MODEMultimode

-designed to carry multiple, concurrent light waves or modes.-used for relatively short distances because the modes tend to disperse over longer lengths.

Single mode-designed to carry a single light wave or mode.-used for long distance signal transmission.

WIRELESS LANWireless LANs use high frequency radio signals, infrared light beams, or lasers to

communicate between the workstations and the file server or hubs. Each workstation and file server on a wireless network has some sort of transceiver/antenna to send and receive the data. Information is relayed between transceivers as if they were physically connected. For longer distance, wireless communication can also take place through cellular telephone technology, microwave transmission or by satellite.

TRANSMISSION MEDIUMS

Comparing transmission mediums

Cable type Speed Distance Cost Other RemarksUTP 100-1000Mbps 100meters Low Widely AvailableCoaxial 100Mbps 500meters Medium Difficult to installFiber 622Mbps 2Km High Interference-freeWireless (LAN) 11Mbps 50meters High Offers mobility

Other transmission media

Satellite communication-high reliability-long distance advantage-high data capacity

Microwave communication-line-of-site-high speed

-cost effective-easy to implement-weather can cause interference-physical characteristics-data signals sent through atmosphere-Signals cannot bend or follow curvature of the earth-relay stations required

NETWORKING DEVICES

Hubs -device that serves as the center of a star-topology network, sometimes referred to as a

multiport repeater, or in Ethernet, a concentrator; not intelligent-a hub is a box that is used to gather groups of PCs together at a central location with

10BaseT cabling.-Like network cards, hubs are available in both standard (10Mbps) and fast ethernet

(100Mbps) versions.

Disadvantage of using hubs-bandwidth is shared by all hosts i.e. 10Mbps shared by 25ports/users.-can create bottlenecks when used with switches.-have no layer 3 switching capability.

Bridge-device that connects and passes packets between two network segments more intelligent

than hub--- analyzes incoming packets and forwards (or drops) based on addressing information.

-more intelligent than a hub--- can analyze incoming packets and forward (or drop) based on addressing information.

-collect and pass packets between two network segments-control broadcast to the network-maintain address tables-different types of bridges

Switch - the switching hub, sometimes called a switch is a more advance unit over the basic hub, this

hub treats each network card independently and in the matter of the 10 100Mbps network with the one 10Mbps network card. The switching hub allows all of the faster connections to remain at the higher speed and still interact with the 10Mbps system.

Router- path determination using metrics, forward packets from one network to another

Device Purpose Complexity, Cost SpeedModem Point to Point Low 56kbpsHub Creates LAN segment Low 10MbpsLAN Switch Creates bigger LANs Medium 10-1000MbpsRouter Network to Network High 64kbps to 155Mbps

OPERATING SYSTEMS

An operating system is a collection of programs that manages the activities of the computer.

-Provides an interface between the computer hardware and application programs.-acts as an intermediary between the user and applications-provides a user interface into computer hardware and application programs-manages peripheral devices such as printers, monitor, keyboard, and modems.-manages memory and central processor use

Two types of operating system are:

Personal Operating System-the operating system of a terminal-the program that controls the operation of the computer-it allows applications and peripherals to communicate and share resources.

Network Operating System (NOS)-the software side of a LAN.-the program that controls the operation of the network-it allows users to communicate and share resources-NOS and NIC are not the same

Personal Operating SystemMS-DOS and PC-DOSOS/2Windows 3.xWindows 9xWindows MEWindows 2000Mac OS

Network Operating SystemSolaris UNIXRedhat LinuxNovell NetwareWindows NTWindows 2000Windows 2003

Database- a database management system (DBMS) is a sophisticated software system for storing data

and providing easy access to them.-the most common database for PCs is the relational database-data in a relational database are set up in tables; tables are related by common fields.-any type of data--- text, graphics, voice or video—can exist in a database.

Electronic mail and modem sharing

Electronic Mail

Email allows users to communicate quickly an easily with internal employees, customers and supplier via electronic messages.

Modem sharingModem-sharing software allows multiple users to share modems for dial-out or connection to

the internet. It also facilities fax-sharing services, which allow users to compose and send faxes over the network.

Web sharing and publishingWith the popularity of the internet, many businesses are either establishing an online presence

or setting up shop in cyberspace. Web servers allow you to do both, bringing your business to millions of customer worldwide.