Author: W.Buchanan. Networking elements (3)bill/cnds2003_2004/cnds_unit02_2002_2003.…Author: W.Buchanan. Networking elements (4) Network Classifications • Local area networks (LANs),

Author: W.Buchanan. Networking elements (1)

Unit 2


Network Types (Unit 2)Router

NetworkNetwork

Data LinkData Link

PhysicalPhysical A router routes with the network address (such as the IP address)

Data LinkData Link

PhysicalPhysical A bridge routes withthe MAC address

PhysicalPhysical A repeater boosts thesignal

Repeater

Bridge


Mobile Networks (Unit 10)

Switches/VLANs (Unit 5)

IP Addressing/Subnets (Unit 6) TCP/Socket Programming (Unit 7)

Router Programming (Unit 8) Routing Protocols (Unit 9)

Introduction (Unit 1)

Net Elements (Unit 2) Net Types (Unit 3) Net Design (Unit 4)


Network Classifications

• Local area networks (LANs), which connect over a relatively small geographical area, typically connecting computers within a single office or building. In most cases they connect to a common electronic connection –known as a network backbone. LANs can connect to other networks either directly or through a WAN or MAN.

• Metropolitan area networks (MANs), which normally connect networks around a town or city. They are smaller than a WAN, butlarger than a LAN. An example of a MAN is the EaStMAN (Edinburgh and Stirling MAN) network that connects universities and colleges in Edinburgh and Stirling, UK, as illustrated in Figure 1.

• Wide area networks (WANs), which connect networks over a large geographical area, such as between different buildings, towns or even countries.


Example of a WAN

HeriotWatt(Riccarton Campus)

Napier(Sighthill)

QMC

CrammondWesternGeneralHospital

QMC(Leith)

Napier(Merchiston)

Napier(Craighouse)Napier

(Craiglockhart)

UoE(King’s Buildings)

UoE(Pollock Halls)

UoE(New College)

City of Edinburgh

College ofArt UoE

(Old College)

Moray House(Holyrood)

Connection toUniversity of Stirling

Firth of Forth


NapierNapier

Hub(or switch)

Hub(or switch)

RouterRouter

Hub(or switch)

Hub(or switch)

EaStMANnetwork

EaStMANnetwork

UoEUoE

Stirling University

Stirling University

Heriot-Watt

Heriot-Watt

SuperJANET

SuperJANET

LonMANLonMAN

BWE MAN

BWE MAN AbMANAbMAN InternetInternet

Example connection (UK Universities)

Edinburghand StirlingMAN

Connect toall the Universitiesin the UK


A

A

A

A

A

A

P

P

P

P

P

S

S

S

S

T

T

T

N

ND D

Virtualdata flow

Actual data flow

Sender Receiver

ApplicationApplication

PresentationPresentation

SessionSession

TransportTransport

NetworkNetwork

Data linkData link

PhysicalPhysical



SessionSession

TransportTransport

NetworkNetwork

Data linkData link

PhysicalPhysical

OSI Layers


OSI Protocols


MPEGMPEG GIFGIF AVIAVI

HTTPHTTP FTPFTP TELNETTELNET

TCPTCP SPXSPX

IPIP IPXIPXNetBEUINetBEUI

EthernetEthernet FDDIFDDI ATMATM ISDNISDN


SessionSession

TransportTransport

NetworkNetwork

Data linkData link

PhysicalPhysical


Data linklayer

Networklayer

Data stream

Transportlayer

ApplicationApplicationApplicationApplication


ApplicationApplicationApplicationApplication


MACaddressin NIC

Networkaddress

Socket

Physicallayer

RouterRouter

RouterRouter

Abstraction of Layers


Physical and network addresses

Physical address has only localsignificance

Physical address:Telephone number

Physical address:MAC address

Interconnected networkInterconnected network

Network address:IP address

Network address:IP address

G/W

G/W

Device is refer tousing its network address


OSI Layers

Transport. Provides for reliable end-to-end error and flow control. The network layer does not validate that the data packet has been successfully received, thus it is up to the transport layer to provide for error and flow control.Network. Defines the protocols that are responsible for delivering the data to the required destination.Data link. Provides for the access to the network media and thus builds on the physical layer. It takes data packets from the upper level and frames it so that it can be transmitted from one node to another. Physical. Defines the electrical characteristics of the communications channel and the transmitted signals, such as voltage levels, connector types, cabling, and so on.

Transport. Provides for reliable end-to-end error and flow control. The network layer does not validate that the data packet has been successfully received, thus it is up to the transport layer to provide for error and flow control.Network. Defines the protocols that are responsible for delivering the data to the required destination.Data link. Provides for the access to the network media and thus builds on the physical layer. It takes data packets from the upper level and frames it so that it can be transmitted from one node to another. Physical. Defines the electrical characteristics of the communications channel and the transmitted signals, such as voltage levels, connector types, cabling, and so on.

Application. Provides application programs, such as file transfer, print access and electronic mail.Presentation. Transforms the data into a form which the session layer and the application layer expect. It can perform encryption, translating character sets (such as converting binary values into text for transmitting a binary program over a text-based system), data compression and network redirections.Session. Setting up, maintaining and closing down of a session. It should not depend on any specific transport or network layer, and should be able to communicate as if the session was created on a stand-alone computer (that is, the network is transparent to the session layer).

Application. Provides application programs, such as file transfer, print access and electronic mail.Presentation. Transforms the data into a form which the session layer and the application layer expect. It can perform encryption, translating character sets (such as converting binary values into text for transmitting a binary program over a text-based system), data compression and network redirections.Session. Setting up, maintaining and closing down of a session. It should not depend on any specific transport or network layer, and should be able to communicate as if the session was created on a stand-alone computer (that is, the network is transparent to the session layer).

PhysicalPhysical

Data linkData link

NetworkNetwork

TransportTransport

SessionSession

Data linkEthernet/ATM/FDDI

NetworkIP/IPX

TransportTCP/SPX

SessionHTTP/FTP


Session Layer

Do you want to connect?

Here’s the details of my connection.

Yes. Here’s the details of my connection.

Initiator Recipient

Data transfer

Acknowledgement of data

Close connection

Connection details•Unique connection number (socket).

•Starting number ofsegment sent.

•Number of packets to be received before an acknowledgement is required.

Connection details•Unique connection number (socket).

•Starting number ofsegment sent.

•Number of packets to be received before an acknowledgement is required.

Connection creation


Internetworking

Router

NetworkNetwork

Data LinkData Link

PhysicalPhysical A router routes with the network address (such as the IP address)

Data LinkData Link

PhysicalPhysical A bridge routes withthe MAC address

PhysicalPhysical A repeater boosts thesignal

Repeater

Bridge


Broadcasts and ARP

3. Updated ARP table: All the hosts update their ARP table with the correct IP and MAC address for the host.

1. Broadcast: What is the MAC address of this network address?

2. Requested host: All the hosts read the broadcast and checks if it relates to them. If it does then they respond back with their MAC address.


Broadcasts

BridgeBridge

RouterRouter

Broadcast

Repeaters: Forward broadcastsBridges: Forward broadcastsRouters: Block broadcasts


Collisions

BridgeBridge

RouterRouter

Collision

Repeaters: Forward collisionsBridges: Block collisionsRouters: Block collisions


Repeaters, bridges and routers

RepeaterRepeater BridgeBridge

RouterRouter

Network segment (repeater extends the network segment)

Bridge only forwards if theMAC address is not on the current segment.

Router only forwards if thenetwork address is not on the current segment.


Data definitions



SessionSession

TransportTransport

NetworkNetwork

Data linkData link

PhysicalPhysical



SessionSession

TransportTransport

NetworkNetwork

Data linkData link

PhysicalPhysicalBitsBits

Data framesData frames

Data packetsData packets

Data SegmentsData Segments

MessagesMessages


Repeaters, bridges and routers

Router only forwards if the network address is on anothernetwork. It does not forward broadcasts.Network segment (repeater

extends the network segment)

RepeaterRepeater RouterRouter

BridgeBridge

Bridge only forwards if thestation (or MAC) address is not on the connected network segment that it originated from. Broadcasts are also passed over.

Network segment bounded by a router or a bridge


Broadcasts and collisions

RouterRouter

RouterRouter

BridgeBridge

BridgeBridge

CollisionDomain(bounded bybridges)

Broadcastdomain(bounded by routers)


Typical Network Devices

Network Routers: Block broadcastsBlock collisions

Data Link Bridges/switches: Forward broadcastsBlock collisions

Physical Hub/repeaters: Forward broadcastsForward collisions


Broadcast domain

Switch Switch Switch RepeaterRepeater

A

B

C

D

RepeaterHub

E F

G

H

RepeaterBridge

I

J

K

RepeaterSwitch


Broadcast domain


A

B

C

D

RepeaterHub

E F

G

H

RepeaterBridge

I

J

K

RepeaterSwitch


Broadcast domain


A

B

C

D

RepeaterHub

E F

G

H

RepeaterBridge

I

J

K

RepeaterSwitch


Broadcast domain


A

B

C

D

RepeaterHub

E F

G

H

RepeaterBridge

I

J

K

RepeaterSwitch


Collision domains


A

B

C

D

RepeaterHub

E F

G

H

RepeaterBridge

I

J

K

RepeaterSwitch

Documents

Author: W.Buchanan. Networking elements (3)bill/cnds2003_2004/cnds_unit02_2002_2003.…Author: W.Buchanan. Networking elements (4) Network Classifications • Local area networks (LANs),