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LAN - WANLAN - WAN

ARCHITECTUREARCHITECTURE

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NETWORKNETWORK Set of devices connected by communication Set of devices connected by communication

links.links. No specific taxonomy available in which all No specific taxonomy available in which all

computer networks fit, still two are of vital computer networks fit, still two are of vital importance:importance:

Network Technologies

Transmission Technology Geographical Span

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Classification on transmission technologyClassification on transmission technology

Broadcast Network

Point-to-point Network

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Network topology based on areaNetwork topology based on area

Bus topology: Ring Topology :

Star topology: Mesh topology:

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Categories of NetworkCategories of Network

LANLAN-Privately owned and links the devices in a -Privately owned and links the devices in a single office, building or campus.single office, building or campus.

MANMAN-Designed to extend over an entire city -Designed to extend over an entire city either by cable television network or connecting either by cable television network or connecting many LANs into a larger network.many LANs into a larger network.

WANWAN-Provides long-distance transmission of -Provides long-distance transmission of data, voice, image etc. over large geographic data, voice, image etc. over large geographic outline may be country or continent or the outline may be country or continent or the world. world.

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Components of LANComponents of LAN A Local Area Network, LAN is a combination of A Local Area Network, LAN is a combination of

hardware and software.hardware and software. The physical component of the network system The physical component of the network system

is hardware. The invisible part, that is programs is hardware. The invisible part, that is programs enabling the network to function properly is the enabling the network to function properly is the software.software.

Ethernet is the most dominant LAN in the Ethernet is the most dominant LAN in the market.market.

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LAN Protocol ArchitectureLAN Protocol Architecture

Lower layers of OSI modelLower layers of OSI model IEEE 802 reference model, is a standardized IEEE 802 reference model, is a standardized

protocol architecture for LANs, which describes:protocol architecture for LANs, which describes: Physical layer.Physical layer. Logical link control (LLC) sub-layer,Logical link control (LLC) sub-layer, Media access control (MAC) sub-layer.Media access control (MAC) sub-layer.

Data Link Layer

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OSI ModelOSI Model

ApplicationApplication

PresentationPresentation

SessionSession

TransportTransport

NetworkNetwork

Data LinkData Link

PhysicalPhysical

• Provides for reliable transfer of information across the physical link• Sends blocks (frames) with necessary synchronization• Error control, flow control

• Concerned with transmission of bit stream• Deal with mechanical, electrical functionality• Procedural characteristics to access physical medium

IEEE 802 Reference ModelIEEE 802 Reference Model

IEEE 802 committee developed, revises, and IEEE 802 committee developed, revises, and extends standardsextends standards

Use a three-layer protocol hierarchy: physical,Use a three-layer protocol hierarchy: physical,medium access control (MAC), and logical link medium access control (MAC), and logical link control (LLC)control (LLC)

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ETHERNETETHERNET

Most widely used data communication standardMost widely used data communication standard Physical Medium – Carry signal between Physical Medium – Carry signal between

computers.computers. MAC rules embedded in each interface that MAC rules embedded in each interface that

allow multiple computers to access shared allow multiple computers to access shared channel.channel.

Ethernet frame of standardized set of bits used Ethernet frame of standardized set of bits used to carry data over the system. to carry data over the system.

Uses Star topology and 1-persistent CSMA/CD Uses Star topology and 1-persistent CSMA/CD access method.access method.

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Logical Link ControlLogical Link Control

Acts as interface between MAC and upper Acts as interface between MAC and upper layer.layer.

Accountable for flow control.Accountable for flow control. Manages error control and error detection.Manages error control and error detection. Independent of topology and medium.Independent of topology and medium. Specifies method of addressing whether Specifies method of addressing whether

unicast multicast or broadcast.unicast multicast or broadcast.

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MAC SublayerMAC Sublayer

Governs the operation of access method and Governs the operation of access method and frames data from upper layer and passes them frames data from upper layer and passes them for encoding. Access method is 1-persistent for encoding. Access method is 1-persistent CSMA/CD. CSMA/CD.

Frame formatFrame format

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Physical LayerPhysical Layer

Encoding/decoding of signals mostly using Encoding/decoding of signals mostly using Manchester coding.Manchester coding.

Bit transmission/receptionBit transmission/reception Specification of the transmission medium.Specification of the transmission medium. Preamble generation/removalPreamble generation/removal Transmission medium and topologyTransmission medium and topology

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Data Transfer through Ethernet Data Transfer through Ethernet LANLAN

Twisted pair or fiber optics with RJ-45 plug or sockets.Twisted pair or fiber optics with RJ-45 plug or sockets. Data rate range from 100Mbits/s to 1000Mbits/sData rate range from 100Mbits/s to 1000Mbits/s To network multiple devices, switch is required where To network multiple devices, switch is required where

devices are connected to it using regular network devices are connected to it using regular network cable.cable.

Registers MAC address of each devices connected to Registers MAC address of each devices connected to it. When switch receives data, it forwards it only to the it. When switch receives data, it forwards it only to the port that is connected to the device with appropriate port that is connected to the device with appropriate destination MAC address.destination MAC address.

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Token Ring NetworkToken Ring Network

Originally developed by IBM in 1970’sOriginally developed by IBM in 1970’s Still IBM’s primary LAN technologyStill IBM’s primary LAN technology In cases of heavy traffic, the token ring In cases of heavy traffic, the token ring

network has higher throughput than network has higher throughput than Ethernet due to the deterministic (non-Ethernet due to the deterministic (non-random) nature of the medium accessrandom) nature of the medium access

Is used in applications in which delay Is used in applications in which delay when sending data must be predictablewhen sending data must be predictable

Is a robust network i.e. it is fault Is a robust network i.e. it is fault tolerant through fault management tolerant through fault management mechanismsmechanisms

Can support data rates of around 16 Can support data rates of around 16 MbpsMbps

Typically uses twisted pair Typically uses twisted pair

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FDDI (Fiber Distributed Data FDDI (Fiber Distributed Data Interface)Interface) FDDIFDDI is a standard is a standard developed by the developed by the

American National Standards Institute American National Standards Institute (ANSI) for (ANSI) for transmitting data on optical transmitting data on optical fibersfibers

Supports transmission rates of up to 200 Supports transmission rates of up to 200 MbpsMbps

Uses a dual ring Uses a dual ring First ring used to carry data at 100 First ring used to carry data at 100

Mbps. Second ring used for primary Mbps. Second ring used for primary backup in case first ring failsbackup in case first ring fails

If no backup is needed, second ring If no backup is needed, second ring can also carry data, increasing the data can also carry data, increasing the data rate up to 200 Mbps rate up to 200 Mbps

Supports up to 1000 nodesSupports up to 1000 nodes Has a range of up to 200 kmHas a range of up to 200 km

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Wide Area NetworkWide Area Network Contains collection of machines called hosts running Contains collection of machines called hosts running

user program and the host are connected by subnet user program and the host are connected by subnet which carries message from host to host.which carries message from host to host.

Host owned by customers and subnet by ISP.Host owned by customers and subnet by ISP. Subnet consists of transmission lines and switching Subnet consists of transmission lines and switching

element.element. Switching computers are called routersSwitching computers are called routers

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Wide Area Network (Contd.)Wide Area Network (Contd.) Packets sent from receiver to sender may be stored at Packets sent from receiver to sender may be stored at

intermediate router till the required output line is busy.intermediate router till the required output line is busy. This principle is known as “Store-n-Forward” which is This principle is known as “Store-n-Forward” which is

implemented by almost all WAN except using Satellite.implemented by almost all WAN except using Satellite. Sender cuts the data into packets bearing a number Sender cuts the data into packets bearing a number

and injected into network one at a time and at the and injected into network one at a time and at the receiver they are reassembled into original message. receiver they are reassembled into original message.

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WAN TECHNOLOGYWAN TECHNOLOGY Devices on subscriber premises are calledDevices on subscriber premises are called Customer Customer

Premises Equipment owned by the subscriber.Premises Equipment owned by the subscriber. Copper or fiber cable connects CPE to Central Copper or fiber cable connects CPE to Central

Office (CO) which is known as local loop.Office (CO) which is known as local loop.

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WAN Link OptionsWAN Link Options

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Circuit SwitchedCircuit Switched When a subscriber makes a telephone call, the dialed When a subscriber makes a telephone call, the dialed

number is used to set switches in the exchanges number is used to set switches in the exchanges along the route of the call so that there is a continuous along the route of the call so that there is a continuous circuit from the originating caller to that of the called circuit from the originating caller to that of the called party where the internal path is shared by a number of party where the internal path is shared by a number of conversations.conversations.

Time division multiplexing (TDM) is used to give each Time division multiplexing (TDM) is used to give each conversation a share of the connection in turn. conversation a share of the connection in turn.

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PACKET SWITCHINGPACKET SWITCHING

An alternative is to allocate the capacity to the traffic An alternative is to allocate the capacity to the traffic only when it is needed. Share the available capacity only when it is needed. Share the available capacity between many usersbetween many users

Huge data converted into packets which passes from Huge data converted into packets which passes from exchange to exchange through network.exchange to exchange through network.

Allows same data path to be shared between various Allows same data path to be shared between various users in the network.users in the network.

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Leased LinesLeased Lines A point-to-point link provides a pre-established WAN A point-to-point link provides a pre-established WAN

communications path from the customer premises communications path from the customer premises through the provider network to a remote destination.through the provider network to a remote destination.

Point-to-point lines are usually leased from a carrier Point-to-point lines are usually leased from a carrier and are called leased lines.and are called leased lines.

Leased lines provide direct point-to-point connections Leased lines provide direct point-to-point connections between LANs and connect individual branches to a between LANs and connect individual branches to a packet-switched network.packet-switched network.

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WAN ConsiderationsWAN Considerations

Many WANs are connected to the Internet to provide Many WANs are connected to the Internet to provide alternative for inter-branch connections.alternative for inter-branch connections.

Since the Internet probably exists everywhere that the Since the Internet probably exists everywhere that the enterprise has LANs, there are two principal ways that enterprise has LANs, there are two principal ways that this traffic can be carried. this traffic can be carried.

Each LAN can have a connection to its local ISP, or Each LAN can have a connection to its local ISP, or there can be a single connection from one of the core there can be a single connection from one of the core routers to an ISP.routers to an ISP.

The advantage is that traffic is carried on the Internet The advantage is that traffic is carried on the Internet rather than on the enterprise network, possibly leading rather than on the enterprise network, possibly leading to smaller WAN links.to smaller WAN links.

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Thank You!!Thank You!!