Basic Data Networks

July 2001 Copyright 2001 Global Wireless Education Consortium S-BDN Switch - Basic Data Networks 1

Switch - Basic Data Switch - Basic Data NetworksNetworks

(S-BDN)(S-BDN)


S-BDNS-BDN

© Copyright 2001 Global Wireless Education Consortium

All rights reserved. This module, comprising presentation slides with notes, exercises, projects and Instructor Guide, may not be duplicated in any way without the express written permission of the Global Wireless Education Consortium. The information contained herein is for the personal use of the reader and may not be incorporated in any commercial training materials or for-profit education programs, books, databases, or any kind of software without the written permission of the Global Wireless Education Consortium. Making copies of this module, or any portion, for any purpose other than your own, is a violation of United States copyright laws.

Trademarked names appear throughout this module. All trademarked names have been used with the permission of their owners.


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Partial support for this curriculum material was provided by the National Science Foundation's Course, Curriculum, and Laboratory Improvement Program under grant DUE-9972380 and Advanced Technological Education Program under grant DUE‑9950039.

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Table of ContentsTable of Contents

Overview 5

Learning Objectives 6

Data Networks 7

Backbone Networks 17

Error Detection And Correction 50

Summary 61

Contributors 62


OverviewOverview

In this module, you will learn about local area networks, access networks, and backbone networks.

Layered protocols, packet structure, addressing, and error detection and correction within the Public Switched Telephone Network are also discussed.


Learning ObjectivesLearning Objectives

After completing this module, you will be able to: Compare and contrast the alternative topologies of

networks made up of hubs, routers, switches and gateways that exist in the basic Public Switched Telephone Network (PSTN).

Explain how errors are detected and how to correct them.


Data NetworksData Networks


Bandwidth

Narrowband0 - 64 Kbps

Wideband64 Kbps - 45 Mbps

Broadband45 Mbps and Beyond

X.25 Frame Relay ATMSMDS

Token Ring

x xT-1,PRI

T- 3

SONET

LAN

Backbone

Network Access

IP

Ethernet

Network Hierarchy and Network Hierarchy and ProtocolsProtocols

Source: KnowledgeLink,Inc


Topology Definition:

The physical and logical way thenetwork elements are connected

Network TopologyNetwork Topology



Legend

Device on LAN=

Bus Star Ring

Local Area Network (LAN) Local Area Network (LAN) TopologiesTopologies



Legend

Device on LAN=

BusExample: Ethernet

CSMA/CD: Carrier Sense Multiple Access/Collision Detection

Sends Data Units out unless you

detect another data unit. already in progress on the bus.

Bus TopologyBus Topology



RingExample: Token Ring

Send data units when youpossess the token..

Token: Special Type of Data Unit

Ring TopologyRing Topology



IEEE 802.1 INTERNETWORKING

lOG

ICA

LL

INK

CO

NT

RO

(LL

C)

OSILAYERS3-7

OSILAYER 2

OSILAYER 1

PH

YS

ICA

L

ME

DIU

MA

CC

ES

SC

ON

TR

OL

(MA

C)

IEEE 802.2TYPE 1 - UNACKNOWLEDGED CONNECTIONLESS SERVICETYPE 2 - CONNECTION MODE SERVICETYPE 3 - ACKNOWLEDGED CONNECTIONLESS SERVICE

802.3CSMA/CD(ETHERNET)

802.4TOKEN BUS

802.5 TOKEN RING

802.6DQDB(MAN)

BASEBANDCOAXIALAND UNSHIELDEDTWISTED PAIR

BROADBANDCOAXIAL

BROADBANDCOAXIAL

OPTICALFIBER

SHIELDED OR UNSHIELDEDTWISTED PAIR

OPTICALFIBERORCOAXIALCABLE

LAN StandardsLAN Standards



Entry to Wide Area Network (WAN)

CustomerPremises

[Bridge-]Router

Access NetworkEnter via port on LAN router

Access NetworksAccess Networks



Protocol LayersInvolvedin DataTransfer

3

2

1

Switch A Switch CX.25 Network

Switch B

Data Flow in an X.25 Data Flow in an X.25 NetworkNetwork



Frame Relay Network

Protocol LayersInvolvedin DataTransfer

3

2

1

Switch A Switch CSwitch B

Data Flow in a Frame Data Flow in a Frame Relay NetworkRelay Network



Backbone Backbone NetworksNetworks


ATM Cell StructureATM Cell Structure

Header Payload

48 Octets5 Octets

Backbone Example: Backbone Example: Asynchronous Transfer Asynchronous Transfer Mode (ATM)Mode (ATM)



ATM users receive as much ATM users receive as much bandwidth as they requirebandwidth as they require

Python with expandableskin (bandwidth)

Asynchronous Transfer Asynchronous Transfer Mode (ATM)Mode (ATM)



User 1

User 2

User 3

125 sec 250 sec 375 sec 500 sec

Asynchronous means data units (cells) areplaced on the network as the application requires

User 1 User 1 User 1

User 2 User 2User 2

User 3

Bandwidth on DemandBandwidth on Demand



Open Systems Open Systems Interconnection (OSI) ModelInterconnection (OSI) Model

Application

Presentation

Session

Transport

Network

Data Link

Physical

Application

Presentation

Session

Transport

Network

Data Link

Physical

Network

Data Link Data Link

NetworkNode

77

66

55

44

33

22

11

77

66

55

44

33

22

11


Wireless OSI ModelWireless OSI Model

Application

Presentation

Session

Transport

Network

Data Link

Physical

Application

Presentation

Session

Transport

Network

Data Link

Physical

Network

Data Link Data Link

NetworkNode

77

66

55

44

33

22

11

77

66

55

44

33

22

11

MESSAGES USE

BOTTOM 3 LAYERS


OSI Protocol “Stack”

What are We Doing?7

Are We Speaking the Same Language (Code)?6

How Long Can Both Sides Talk?

How do We Control Info Flows andand Keep Messages in the Right Order?

5

4

How do We Put Together and Move Chunks of InformationAcross a Whole Network?

3

What Signals and Timing Are We Using?How Are We Going to Recognize Errors between Two Points?2

What Hardware Are We Using?1

The OSI Seven-Layer The OSI Seven-Layer ModelModel

(E-Mail)?



The OSI Model

Application

Presentation

Session

Transport

Network

Data Link

Physical Header

User Info

1

7

6

5

4

3

2

A Set of RulesA Set of Rules



Layer 1 DetailsLayer 1 Details

Network

Data Link

Physical

Application

Presentation

Session

Transport

Transmits bits received from the Data Link Layer across the transmission medium



Data Link

Physical

Sequences messages and checks for errors between adjacent link stations


Network

Application

Presentation

Session

Transport



Network

Data Link

Physical

Fragments or “packetizes” messages and routes them to the proper destination



Application

Presentation

Session

Transport



Network

Data Link

Physical

Transport

Fragments or “packetizes” messages and routes them to the proper destination



Provides multiplexing, network connection management, quality of service, etc.

Application

Presentation

Session


Header Information

Packet FormatPacket Format



Header User data Perhaps a trailer Store and forward

Packet Switched Packet Switched RoutingRouting



Header Information

Packet Format

Layer 2 Info Layer 3-5 Info Layer 2 InfoFlag Flag

Message Format

Types of Protocol Data UnitBeing Sent Through a Packet Switched Network

Protocol Data UnitsProtocol Data Units



Header TrailerUser Data

Protocol Data UnitProtocol Data Unit

Routing Fields



ROUTERNODE B

DATAC CDATAB C

NODE A NODE C

Destination NodeWon’t Change

Address of NextNode on Route

The router stores packet, reads the destination information and forwards it

to the next node

Routers Routing PacketsRouters Routing Packets

Final Path


ROUTINGCONSIDERATION

WHAT’S INCLUDED

Performance Number of hops Cost Delay Throughput

Decision Time Packet (Datagram) Session (Virtual Circuit)

Decision Place Each node (Distributed) Central node (Centralized) Originating node

Source of Information onNetwork Status

None Local Adjacent Nodes Nodes along route All nodes

Routing Strategy Fixed Flooding Random Adaptive

Adaptive Routing UpdateTime

Continuous Periodic Major load change Topology change

Packet Switched Packet Switched Network RoutingNetwork Routing


Data Switch Routing Data Switch Routing ExampleExample

Ethernet Switch Layer2 Operations Receives the Ethernet frame Looks up the 6-byte destination address in a forwarding table Sends the packet out only to the port associated with the

destination address


Ethernet SwitchEthernet Switch

10Base-T Switch

MAC #11 MAC #14MAC #13MAC #12

10Base-T Hub

MAC #21 MAC #24MAC #23MAC #22

Address Port UpdateTime

# 11 D 6:05.1441 PM # 12 C 6:04.1523 PM # 13 B 6:04.8722 PM # 14 A 6:05.1422 PM # 21 E 6:04.6623 PM # 22 E 6:04.2355 PM # 23 E 6:05.0233 PM # 24 E 6:04.9722 PM

FORWARDING TABLE

AE D C B


Data Network DevicesData Network Devices& the OSI Reference & the OSI Reference ModelModel

Gateways Routers Switches Hubs Bridges Repeaters



RepeaterRepeater

Layer 1 - Physical I physically repeat and regenerate bits for my own LAN



BridgeBridge

LAN 1 LAN 2

Layer 2 – Data Link Layer I link data frames by bridging between LANs



HubHub

USER

USER

USER

USER

Layer 2 – Data Link Layer I route packets between islands with common protocols



Data SwitchData SwitchUSER

USER

USER USER

Layer 2 – Data Link Layer I route packets between ports Packets are not sent to every port

(only to the destination port) Source: KnowledgeLink,Inc


RouterRouter

Layer 3 – Network Layer I route packets between islands with common protocols



GatewayGateway

Layer 3+ I convert protocols between islands Synchronous to asynchronous

SYNC ASYNC



Data NetworkData NetworkDevices in DataDevices in Data

Network ApplicationsNetwork Applications


Router

Router

Router

Carrier Network

Router

ChicagoRouter

LAN Hub

Client

DetroitRouter

LAN Hub

Server

CustomerNetwork

CustomerNetwork

AccessLine

AccessLine

Typical Packet Data Typical Packet Data ServicesServices


Routers replace Layer 2 frame headers & trailers so packet can travel end-to-end over many links. They provide gateways into and out of the PSTN.

IP packets / TR frames

IP packets / PPP frames

Router or Gateway modifies frame

IP packets / TR frames

Router RouterCSU CSUC.O .

T1T1TokenRing

TokenRing

Packets, Routers, and Packets, Routers, and the PSTNthe PSTN


Combined NetworkCombined Network

CMTS

MSC TELCO

NIU NIU

HostDigital

Terminal

SS7 SS7

Internet

Intranet orPublic Data Network

Average ResidencePower ResidenceCorporate A Corporate B

Trunks toTelco

Switch

Gateway



IP Telephony Using a IP Telephony Using a Computer as the TerminalComputer as the Terminal

PSTN Internet

CODEC

Gateway

Router Cable Modem

Microphone



PSTN Internet

CODEC

Gateway

RouterCable Modem

TelephoneAdapter

IP Telephony Generates IP Telephony Generates Mobile-like TrafficMobile-like Traffic



Detecting and Fixing Detecting and Fixing ErrorsErrors


Detecting and Fixing Detecting and Fixing ErrorsErrors

Committed Information Rate (CIR) Data collisions Protocol analyzers



0 1 0 0 1 1 0 1 11 1 1 0 0 1 0 0 10 0 0 1 0 0 1 1 01 1 0 1 0 1 1 0 00 1 0 1 1 0 0 1 11 1 0 1 0 1 1 1 10 0 0 1 0 1 1 0 00 0 0 0 1 0 1 1 0

Block Parity Bits

BitPosition

1234567

CharacterParity

BlockParityCharacter

Block Parity CheckBlock Parity Check



New TermsNew Terms

Longitudinal Redundancy Check (LRC) Block Parity Check Checksum XMODEM checksum



Cyclic Redundancy Cyclic Redundancy Check (CRC)Check (CRC)

Data CRC Result



Automatic Repeat Automatic Repeat Request (ARQ)Request (ARQ)

Automatic Repeat Request (ARQ) Acceptance (ACK) Reject (NAK)



Forward Error CorrectionForward Error Correction

Mathematical creation of parity bits on the transmitting end and on the receiving end.

If the parity bits on each end match, there is no error. If the parity bits do not match, the error has been

detected. Forward Error Correction can correct errors, CRC

cannot.



Types of Digital Error Types of Digital Error MeasurementMeasurement

Bit Error Rate (BER)

Block Error Rate (BLER)



Digital Error Digital Error MeasurementMeasurement

Errored Seconds

Severely Errored Seconds



Shift Register

Clock

Interface Coder

Item under test

Interface Decoder

Error Counter

Shift Register

+

Illustration Courtesy of Hewlett Packard Source: Application Note 387

+

+ data

Error

Bit Error Rate TesterBit Error Rate Tester


Industry ContributorsIndustry Contributors

Lucent Technologies, Inc. (http://www.lucent.com) Telcordia Technologies, Inc (http://www.telcordia.com) KnowledgeLink, Inc (http://www.knowledgelinkinc.com)

The following companies provided materials and resource support for this module:


Individual ContributorsIndividual ContributorsThe following individuals and their industry or educational institutions provided materials, resources, and development input for this module: Dr. Bruce Black

Rose-Hulman Institute of Technology http://www.rose-hulman.edu/

Dr. Philip DiPiazza Florida Institute of Technology http://www.fit.edu/

Mr. Jay Junkus KnowledgeLink, Inc http://www.knowledgelinkinc.com


Individual Contributors, Individual Contributors, cont.cont.

Mr. Ron Koziel KnowledgeLink, Inc http://www.knowledgelinkinc.com

Mr. Ken Robinson Ericsson http://www.ericsson.com

Basic Data Networks

Documents

network access

network topology source

network elements

frame relay network

network switch b data

protocols source

bus topology source

demand source