Twisted Pair Cabling Twisted pair is a transmission medium consisting of two insulated wires that are twisted together to create a double helix that reduces noise levels and eliminates crosstalk between the wires. Unshielded twisted pair (UTP) Shielded twisted pair (STP) has an extra layer of insulation
Twisted Pair Cabling Twisted-pair cabling is broken into categories. CAT 5 means category 5. The wires terminate in an RJ-45 connector.
Coaxial Cabling Coaxial cable, also known as coax, consists of a cylindrically braided outer conductor that surrounds and shields a single solid inner copper wire conductor.
Coaxial Cabling Coaxial cable comes in two forms: Thinnet Thicknet Thin coaxial cable Thick coaxial cable Used in 10Base2 Used in 10Base5 Ethernet networks Ethernet networks Cable segments up to Cable segments up to 185 meters in length 500 meters in length
Fiber Optic Cabling Fiber optics is a transmission method that transmits light-modulated video, voice, or data signals through hair-thin strands of glass called fibers. These strands are encased by a layer of Kevlar-reinforced reflective material called cladding, which keeps the light inside the fiber.
Wireless Media Includes cellular, radio, microwave, satellite, and infrared signals. Network nodes that use wireless connections must have a wireless NIC, which connects to a transceiver known as a wireless access point (WAP). Defined by the 802.11 standards. For more information, go to www.microsoft.com/windowsxp/mediacenter
Computer Network is a system of data terminal equipment(Exp.mainframe system, workstation,PC’s, terminals, other device) whichcommunication with one another overmedia(Exp.electronic conductor, fibreoptic conductor) and are linked togetherby transmission equipment(modems,multiplexer) or subnetworks(LAN’s,MAN’s,WAN’s)
Characteristics of a Network All networks require: A physical connection (or wireless connection). A set of communication rules called protocols. One or more network services that will receive the communication.
Mainframe/Terminal Model The mainframe/terminal model A mainframe is a centralized computer to which users connect to obtain network services. The terminal is a device with a keyboard, which you use to type commands or enter data to communicate with the mainframe computer.
Client-Server Model Client-server refers to the manner in which computers exchange information by sending it (as servers) and receiving it (as clients). Computers can serve dual roles as both servers and clients.
Multi-Tier Large organizations may subdivide complex applications into multiple stages called tiers. Multi-tier computing typically includes three tiers consisting of the user interface tier, the business tier, and the database tier.
การเชื่อมตอแบบ LANแบง การออกแบบเปน 2 วิธี Server Based : แต ล ะ Workstation พึ่ ง พา Central Computer ที่ จะให บริการ File, Printing Peer-to-peer (P2P) is a network architecture in which each workstation has equal responsibilities.
รูป แบบก ารเชื่ อมต อ Network แบบ Server Based LAN WorkstationHarddisk IBM PS/2 IBM PS/2 IBM PS/2 IBM PS/2 Mainframe Gateway File Server Print Server Modem IBM printer IBM PS/2 IBM PS/2 IBM PS/2 Printer Communication Server
Network Topologies A network’s geographical shape is referred to as the network’s topology. The five kinds of network topologies are: Bus topology Ring topology Star topology Hybrid topology Mesh topology
Bus Topology The bus topology has a single cable, called the bus or the trunk, to which every device on the network connects. All of the messages on the bus pass by each device, or node, on the bus. It uses inexpensive coaxial cable that is easy to install. A break anywhere along the cable causes all network traffic to stop.
Ring Topology A ring topology forms when you connect a network’s nodes in a circle. Messages flow in a single direction. A small packet called a token circulates the ring – a device must have the token to use the network.
Star Topology In a star topology, each device in the network connects to a central hub, which distributes messages from one node to another. Provides centralized control Easy expansion Fault tolerance
Hybrid Topology A hybrid topology in a network employs more than one topology to connect devices.
Mesh Topology In a mesh topology, multiple connections are made. In mission-critical operations, you want as much redundancy as possible so that if one part of the network goes down, the packets can find an alternate path to their destination.
ขอดีของ PC local Network การใชอปกรณตาง ๆ รวมกัน (Device Sharing) ุ การใช ไฟล หรือ โปรแกรม รวมกัน (Shared File Access) การสื่อสารภายในองคกร (Communication Within Organization) การนําเอาโปรแกรมใหม ๆ มาใชงานไดงายขึ้น การจัดการบริหารที่งายขึ้น (Management)
ขอเสียของระบบเครือขาย ไมสามารถแทนการทํางานบนเครื่องขนาดใหญไดแทจริง การดูแลระบบตองการคนที่มีความรู เพระเปนเรื่องที่ยุงยากสลับซับซอน ความปลอดภัยของขอมูลนอยกวาแบบ Stand Alone
What is a ServerA Server คือ Computer ที่ ใ ห บริก าร Computer ตัวอื่ นบนเครือ ข าย ชนิดของ Server ส วนใหญใ น เครือ ข าย คื อ File Server และ Print Server
ชนิด ของ Server File Server Print Server Communication Server Database Servers
ข อ ดี Server Based เร็ว การทํางานบน Server จะทําไดเร็วกวา การทํางานแบบ Peer-to-Peer Full Featured มีมาตรฐานอุตสาหกรรม สนับสนุนการทํางานกับเครือขายใหญ ๆ การรักษาความปลอดภัยของขอมูลทําไดดีกวา
ข อ เสีย Server Based ราคาคอนขางแพง การติดตั้งระบบทําไดยาก จําเปนตองคนดูแลระบบ
ข อ ดี Peer to Peer ราคาไมแพง การติดตั้งทําไดงาย การใชงานทําไดงาย ไมจําเปนจะตองมี Stand-alone server
Network Operating System A network operating system is the software that adds to a computer the functions required for connecting computers together for networking. Microsoft Windows (peer to peer) Windows 2003, Windows NT UNIX and Linux Mac OS Novell NetWare
Microsoft Windows Microsoft Windows is the most wide spread network operating system. Every version of Windows contains networking capability, but some versions do not support all network services. For a history of Windows server products, visit www.microsoft.com/windows/winhistoryserver. mspx
UNIX and Linux The UNIX and Linux operating systems support the full range of networking services, including both client- and server- side components. The Open Group holds the trademark and defines the official version of UNIX at www.unix-systems.org Linux is an open source version of UNIX To learn more, go to www.linux.org
Mac OS The Macintosh OS X operating system has networking built in. Behind the Macintosh user interface is a UNIX-based operating system. To learn more, go to www.apple.com/macosx/features/unix
Novell NetWare NetWare is a PC-based local area networking product that was one of the most dominant network operating systems during the decade following its invention in 1983. However, when Microsoft marketed Windows NT in 1993, Novell NetWare’s market share dropped. For more information, go to www.novell.com/products/netware
หนา ที่ พ้ื นฐานของ NetworkOperating System File Server Print Service Back up Security
Extending Network WAN (Wide Area Network) MAN (Metropolitan area Network) Internetworks Big LANs
MANA metropolitan area network(MAN) connects local networksacross a larger geographical region. The term metropolitan implies that MANs cover an area the size of a city.
WAN A wide area network (WAN) uses high-speed transmission lines to connect MANs and LANs over large geographical areas.
Big Network Hardware Repeaters Bridges Routers Gateways
Network Components A repeater interconnects two network cables so they can be treated as a single cable. Allows one to extend the length of the cable. A switch filters, forwards, and floods frames based on the destination MAC address of each frame. To flood is to pass traffic out all of the switch’s connections except for the incoming interface through which the traffic was received.
Network Components A bridge is used to connect two network segments and pass packets between them based on the destination MAC address of each frame. A switch is a multiport bridge. A router forwards network traffic along the optimal path based on information in the packet’s Network Layer header.
Bridges LAN LAN Desktop System Desktop System Desktop System Desktop System Bridge Bridge Desktop System Desktop System Bridge Bridge
Routers Desktop System Desktop System Desktop System Desktop System Router Router Desktop System Desktop System Router Desktop System Desktop System Desktop System
Network Components A bridge router (brouter) is a relay that functions as both a router and a bridge. A gateway is a computer that routes traffic from a workstation on an internal network to an external network such as the Internet.
Gateway Desktop System Desktop System Desktop System Desktop System GATEWAY GATEWAY Desktop System Desktop System GATEWAY GATEWAY Desktop System Desktop System Desktop System Desktop System Desktop System Desktop System
Protocol A protocol is a set of rules that define how computers communicate with each other. The International Standards Organization (ISO) developed an international standard called the Open System Interconnection (OSI) Reference Model (OSI/RM).
OSI Reference Model This model comprises of seven layers that describe the way data is shared on a network. Suppose you just clicked on a link on a Web page. The following slides describe the process from one layer to another. Data is passed down from Layer 7 to Layer 1, is then transmitted over the medium, and then goes back up from Layer 1 to Layer 7 in the receiving device. Headers are added at each layer.
Layer 7: Application Through an Application Programming Interface (API), the browser informs the Application Layer of your request. The Application Layer begins to form the packet that will eventually travel across the network.
Layer 6: Presentation The Presentation Layer translates the data into a standard network data format. It can use data compression to streamline the packet so it does not consume unnecessary bandwidth on the network. It can also encrypt the data for sensitive data transmissions.
Layer 5: Session The Session Layer negotiates the connection that will be made between the two computers exchanging data. It inserts a checkpoint, which is a marker used to signal that a certain amount of the data has arrived all right.
Layer 4: Transport The Transport Layer works to ensure that the data arrives reliably at its destination. If the amount of data is large, the data is split into fragments that are numbered sequentially.
Layer 3: Network The Network Layer organizes data into datagrams consisting of the data from the Transport Layer and routing information such as the source and destination addresses.
Layer 2: Datalink The Data Link Layer transforms the data into data frames. It consists of two sublayers: Logical Link Control (LLC) Performs error checking and regulates the flow of data. Media Access Control (MAC) Handles the actual placement of the packets onto the Physical Layer.
CRCThe Data Link layer also calculates acyclic redundancy check (CRC) basedon the information in the frame. The receiving machine calculates its own CRC and compares it to the value in the frame. If they do not match, the frame is corrupt and discarded.
Layer 1: Physical The Physical Layer transforms the 0’s and 1’s into signals that flow over the transmission media. At the receiving end, the Physical Layer converts these signals back into 0’s and 1’s and passes them up to the Data Link Layer.