Local Area Network() Sarawuth Chaimool ศราว ธ ช ยม ล jaounarak@hotmail.com Wireless Communications Research Group (WCR) Department of Electrical Engineering King Mongkut s Institute of Technology North Bangkok,Thailand Objective Understand Basic Devices. Understand the Evolution of Network Devices. Understand the Basics of Data Flow Through s. Understand the Building of s. 1
Outline Basic Network Basic Devices Basics of Data Flow Through s. Building of s. Network Topologies WAN WAN-MAN MAN MAN- PAN -PAN PAN(Personal Area Network) (Local Area Network) MAN(Metro Area Network) WAN(Wide Area Network) 2
Local Area Network Local Area Network 3
Metropolitan Area Network Wide Area Network 4
Internetwork (Internet) 5
Topologies Bus Topologies Single cable connects all computers Each computer has connector to shared cable Computers must synchronize and allow only one computer to transmit at a time 6
Ring Topology Computers connected in a closed loop First passes data to second, second passes data to third, and so on In practice, there is a short connector cable from the computer to the ring Ring connections may run past offices with connector cable to socket in the office: Star Topology Previous diagram is idealized; usually, connecting cables run in parallel to computers: Result is: 7
Multiple Topologies Multiple Topologies Each has advantages and disadvantages: Ring ease synchronization; may be disabled if any cable is cut Star easier to manage and more robust; requires more cables Bus requires fewer cables; may be disable if cable is cut Bucknell has used all three; now almost entirely star topology Industry is settling on star topology as most widely used 8
Networking Media basic functions of media carry a flow of information, in the form of bits and bytes, through a confine network signals to a wire, cable, or fiber Layer 1 components of s Networking Media 9
Wiring ThickNet 10Base5 ; Thick coax cable ThinNet 10Base2 ; Thin coax cable Use BNC connectors, T connectors for bus 10BaseT, 100BaseT ; Twisted Pair Use central hub Typical Media 10
Devices Physical features Functions (on a network) OSI layers on which the devices operate 11
Function of Computers on the provide the user with an almost limitless set of applications 12
Network Interface Cards (NICs) Separate processor, buffers incoming/outgoing data CPU might not be able to keep up network speeds! Distributes processing to avoid overburdening CPU Typically has DMA access NICs Layer 2 devices :MAC address 13
Repeater May want to extend medium Ethernet - timing constraints allow longer medium Signal strength constraints limit length Repeater simplest form is a bidirectional, analog amplifier that retransmits analog signals Simply copy signals between segments; includes noise/collision Do not understand frame formats or addresses Not the case with digital repeaters Hub acts as a repeater One repeater can effectively double the length of an segment, e.g. 100m to 200m Repeater Layer 1 devices REPEATER 14
Limits on Repeaters Can't extend Ethernet with repeaters indefinitely CSMA/CD requires low delay; if medium is too long, CSMA/CD won't work Run into the problem of not being able to detect collisions while transmitting the frame Ethernet standard includes limit of 4 repeaters between any two Ethernet stations Reasons for limitations Ethernet was designed to connect a floor of a building, or a couple floors, but not across wider distances Will need to go to routers to cross larger distances (connect two separate s) Aside from hubs, bridges are used today in favor of repeaters Hub a multi-port repeater purpose amplify and re-time network signals, at the bit level a large number of users (e.g. 4, 8, or even 24) connect to one shared device concentration 15
Hub Layer 1 devices Bridge Copies frames from one network to another Can operate selectively - does not copy all frames (must look at data-link headers). Extends the network beyond physical length limitations. BRIDGE 16
Layer of Bridge Bridges Looks like one to all systems 17
Switch concentrate connectivity, while guaranteeing bandwidth able to combine the connectivity of a hub with the traffic regulation of a bridge on each port switches packets from incoming ports (interfaces) to outgoing ports Layer of Switch 18
Switches Router path selection, and switching of router routes, and packets Each router interface is connected to a different network or network segment it is considered an inter-networking device examine incoming packets, choose the best path for them through the network, and then switch them to the proper outgoing port 19
Layer of Router Gateway Operates as a router Data conversions above the network layer. Conversions: encapsulation - use an intermediate network translation - connect different application protocols encrpyption - could be done by a gateway 20
Encapsulation Example Gateway Gateway Provides service connectivity even though intermediate network does not support protocols. Translation Gateway Translate from green protocol to brown protocol 21
Encryption gateway Secure Network Encryption/Decryption Gateways Secure Network GW??? GW Insecure Network Summary of Network Devices 22