Local Area Networks

Andres, Wen-Yuan Liao

Department of Computer Science and Engineering

De Lin Institute of Technology

andres@dlit.edu.tw

http://www.cse.dlit.edu.tw/~andres

OverviewLocal area network (LAN) devices High-speed, low-error data

networks that cover a relatively small geographic area

Connect workstations, peripherals, terminals, and other devices

Basic LAN Devices

The topology LAN devices in a topology NICs,Media Repeaters , Hubs, Bridges, Switches Routers Clouds , Network segments

Topology

Defines the structure of the network Physical topologyThe actual layout of the wire (media)

Logical topologyDefines how the media is accessed

by the hosts.

Physical topology

BusUses a single backbone segmentAll the hosts connect to it directly

Ring Connects one host to the next and the last

host to the first

StarConnects all cables to a central point

Physical topology

Extended star Links individual stars together by linking the

hubs/switches.

hierarchical Similar to an extended star The system is linked to a computer The computer controls the traffic on the topology

Mesh Each host is connected to all other hosts Internet

Logical topologiesBroadcastEach host sends its data to all other

hosts on the network medium (no order)

Token-passingControls network access by passing an

electronic token sequentially to each hostWhen a host receives the token, that

means that that host can send data on the network

LAN devices in a topology

Devices that connect directly to a network segment are referred to as hosts Operate at all 7 layers

NICsAn NIC card is a printed circuit board

Layer 2 device

Media Access Control (MAC) address

AUI (Attachment Unit Interface)

RJ-45

BNC

AUI

Media

Carry a flow of information

Be considered Layer 1 components Cable length Cost Ease of installation

Repeaters

One of the disadvantages of the type of cable that we primarily use (CAT5 UTP) is cable length Repeaters: strengthen their signals over long distancesThe purpose of a repeater is regenerate and retime network signals

Repeaters

5-4-3 Rule: you can connect five network segments end-to-end using four repeaters but only three segments can have hosts (computers) on them

Hubs

Multi-port repeater

Create a central connection point for the wiring media

Increase the reliability of the network

Classifications I

ActiveThey take energy from a power

supply to regenerate network signals

Passive They merely split the signal for

multiple users

Classifications IIIntelligent hubsHave console ports, which means

they can be programmed to manage network traffic

Dumb hubsTake an incoming networking signal

and repeat it to every port without the ability to do any management

Repeaters

Token-ring network : Media Access Unit (MAU)

FDDIs: the MAU is called a concentrator.

Bridges

Layer 2 device

To filter traffic on a LAN

To keep local traffic local

Allow connectivity to other segments

Every networking device has a unique MAC address on the NIC

Switches

Layer 2 deviceMulti-port bridge Make decisions based on MAC addresses The purpose of a switch is to concentrate connectivity, while making data transmission more efficient.

Routers Layer 3 device (IP address)Connect different Layer 2 technologiesEthernet, Token-ring, and FDDI.

To examine incoming packets (Layer 3 data), choose the best path for them through the network, and then switch them to the proper outgoing port

Clouds

There is a way to connect to that other network (the Internet), but does not supply all the details of either the connection or the network

A collection of devices that operate at all levels of the OSI model, it is classified as a Layer 1-7 device

Network segments

Layer 1 segmentA segment identifies the Layer 1

media that is the common path for data transmission in a LAN

Repeater is the separator

Layer 2 segment

Segments

A segment as a collision domain

Segment: a Layer 4 PDU

Evolution of Network Devices 

Evolution of network devices

Milestones in the history of networking

Evolution of networking devices and the OSI layers

Devices and the OSI layers

Hosts & servers operate at Layers 2-7

Layer 1Transceivers, repeaters, and hubs Patch cables, patch panels, and other

interconnection components

Layer 1,2: NIC, Bridge, Switch

Layer 1,2,3: Router

Basics of Data Flow Through LANs

Encapsulation and packets review Packet flow through Layer 1 devices Packet flow through Layer 2 devices Packet flow through Layer 3 devices Packet flow through clouds and through Layer 1-7 devices A data packet's path through all seven layers of a LAN

Encapsulation & packets review

Transport layer: segmentsSequence numbers (order)

Network layer: packet Destination & source address

Data Link layer: frameAdd the source/destination(MAC)

address

Encapsulation & packets review

The bottom three layers (Network, Data Link, Physical) The primary movers of data

across an Intranet or Internet.

The gateway uses all seven of the OSI layers

Layer 1 devices are passive (e.g. plugs, connectors, jacks, patch panels, physical media)

AUI port to RJ-45

RJ-45 electrical toST Optical

selection of best path and actual switching

Gateway

SNALAN

Building LANs

Summary

LAN devices, such as routers, switches and hubs

Evolution of networking devices

basics of data flowbasics related to building LANs