Network Designs and Cabling

Organizational Communications and Technologies

Prithvi N. RaoH. John Heinz III School of Public

Policy and ManagementCarnegie Mellon University

Readings

Traditional Wide Area Networks(Stallings and van Slyke)

Chapter 7

Local Area Networks (Stallings and van Slyke) Chapter 9

Objectives Identify the differences of centralized vs

distributed computing

Describe the three basic functions of any network

List two network design principles

Discuss the strengths of client/server network systems

Objectives Discuss the strengths of peer-to-peer network

systems

Describe two different media plant specifications

Token Ring Cabling Explosion of personal computers has changed

the way organizations process information

De-centralization created a number of problems for MIS managers

Sharing of information more difficult Difficult to access corporate application files Difficult to access common peripheral devices

Token Ring Cabling Centralized mainframes

One central processing device Single file system Facility to control peripherals Single communications mechanism

PC networks Many processing units Many file systems Many peripherals Many communications mecahism

Stand-Alone ComputersPrinter

Planning

CustomerServiceData

Sales Data Billing Data

Token Ring Cabling Result was localized processing or distributed

processing

Has both advantages and disadvantages over centralized processing

Advantages of Distributed Processing Networks can be grown incrementally by adding

additional workstations as needed

Localized processing allows some users to run computationally intensive applications without affecting the performance of other users

PC technology is widely known and well accepted

Vast library of application software for PC systems

Disadvantages of Distributed Processing Lack of central file storage systems to store

commonly accessible data and application files

Lack of communication facility to support sharing of peripherals

Operating a PC may require more skill Employee skill level must increase

Local Area Networks (LAN) LANs developed to restore lost functionality of

centralized mainframes

Allowed connection of independent desktop computers together

LAN geographical range is small with reasonably high data rates of transfer

Local Area Networks (LAN) LAN provides physical connection between

independent computing devices

LAN provides logical connection including Handshaking Flow control Error detection

Local Area Networks (LAN) LANs offer benefits of sharing application data

and peripherals among users Greatly reduced cost Incrementally expand network

Three basic functions of any network File transfer Remote program execution Virtual terminal services

Local Area Networks (LAN)

All other network applications (peripheral sharing)can be accomplished using one of these three basicfunctions.

Example:

Shared printing is a file transfer operation to anothercomputer where it is printed

Token Ring

Node

Node

Node

Node

Node

File Server

PrintServer

Shared printer

LAN Design Principles Client – Server LANs define one computer as

the master station or LAN Server and other computers are LAN clients

Clients depend on server for services

Central server contains Central file system Communication facility or NOS software Centralized authority to manage network

LAN Strengths Central file system

Communication can be efficiently managed by central server

Server can act to police the network traffic of clients

Client communication software is simple

LAN Weaknesses Single point of failure: no server implies no

network

All communication must involve server Even local conversation between clients

Network operating system may be overly complex

Example of NOS is Novell Netware

Peer-to-Peer Peer-to-peer networks treat all computers on

network as equal peers All computers responsible for communication

requirements of LAN

All computers are masters and manage communication amongst workstations

No single server to manage LAN

Peer-to-Peer

Peer Host Host Host

Host

Shared diskstorage

Shared printer

Peer-to-Peer Strengths No single point of failure for communication on

the network

More flexibility for storing distributed data and sharing remote peripherals

Availability of more application programming interfaces that facilitate development of network-based distributed applications

Peer-to-Peer Weaknesses Host software must be more self-sufficient

requiring it to be more complex than client software

Absence of central monitor to manage network communication

Lack of authority mechanism to resolve contention issues that may arise during operation

TCP/IP are an example of peer-to-peer networks

Interface Requirements Each computer must contain a Network

Interface Card (NIC) that physically attaches to the internal bus of the computer

NICs come in different types, speeds and price ranges

NICs handle the actual sending and receiving of data between computers that are communicating

NIC Functions Physically attaching the computer to the network

Framing the data for transmission as digital signals

Decoding received signals and converting it back to data

Error detection (usually with CRC) and retransmission

NIC Configuration Items I/O address

IRQ address

DMA channel

ROM and RAM addressing

Configuration Issues: Problems and Solutions Problem right after installation of NIC card

NIC card failure IRQ conflict

Solution is to reconfigure the IRQ to a different value

Software as well as hardware may need to be reconfigured

Problem is lobe media failure

Solution is to check cable and connectors and replace parts

Configuration Issues: Problems and Solutions Problem

Node address is not unique

Solution Another NIC card on the LAN has the same address

as your card. Replace the card for a different one from your vendor

Problem Insufficient memory for NOS or application program

to run

Configuration Issues: Problems and Solutions Solution

Adjust drivers to use alternative memory (higher)

Problem DMA failure Some NIC cards do not support DMA

Solution Reconfigure NIC to alternative DMA channel Disable DMA or disable memory cache addressing on

NIC

Configuration Issues:Problems and Solutions Problem

Hang’s up when accessing the server Bad driver or speed related problem

Solution Bad driver requires replacement from vendor

software CD Place driver on a different place on disk

Problem PC is running too fast for NIC

Configuration Issues: Problems and Solutions Solution

Upgrade NIC Slow down PC by inserting wait-states inside CMOS

setup

Problem Invalid path, No xxxx file found means that some

configuration files cannot be found

Solution Set up NOS software to point to the files

Media Two types of media used in networking systems

Bounded unbounded

Bounded Signal is contained within bounds of media in the cable

Unbounded Signal travels in the absence of a cable outside bounds

of physical media

Bounded Media Coaxial cable

Twisted pair cable

Fiber optic cable

Unbounded Media Satellite transmission

Infrared

Radio Frequency

Microwave

Laser

Twisted Pair Two kinds

Shielded (STP) Unshielded (UTP)

Twisted pair used to construct token ring LANs and 10Base-t (T for twisted pair)

Connects terminals (STP) Voice communication and wiring telephone networks Least expensive and does not require special skills to

instal Already exists mostly

Twisted Pair Various grades of cable

Level 1 used for telephone connections Level 5 used to support high speed LAN

Fiber Optic Cable Profile Transmits light rather than electrical signals

FDDI is one example (Fiber Distributed Data Interface) Token passing LAN protocol Popular for long distance carriers

Little need to regenerate signal midway Advantage over traditional cabling that have much

shorter distances of propagation before signal must be regenerated

Large bandwidth so large movements of data possible

Fiber Optic Cable Profile Advantages over traditional cabling

Immune from crosstalk Immune from noise as a result of electro-magnetic

interference (EMI) or radio frequency interference (RFI)

Fiber is typically used as a backbone media connecting LANs together sincethe cost of the media and special skills to install it may prohibit its use toeach workstation (for now)

Coaxial Cable Two kinds

Thick Thin

Generally used to construct BUS Ethernet LAN ARCNET LAN Broadband LAN

Coaxial cable can extend long distances and has a high level of immunity toelectrical interference (thicknet more so than thinnet cable)

Cable Plant Specifications Vendors provide specifications for layout of

cable plant IBM cable plant AT&T premises distribution scheme

Both use a HUB and SPOKE approach Hubs are placed in wiring closets Spokes branch out to each workstation Hubs are connected by a backbone

Design Considerations Important to lay out wiring plan, install and test

Can use a simulator to assist in prediction of behavior of network

Existing cable layouts must be carefully examined to satisfy requirements due to cost of replacement

Cost of materials is usually less than 10% of total Labor which can be 90% of total

Might as well install expensive cable?

Radio Frequency (RF) LAN Gaining popularity

No need for expensive cable plant installation and maintenance

Easier to modify, expand and dismantled

RF technology uses different spectrum to microwave

Cannot travel as far as microwave Particularly useful for LAN Wireless devices are getting more popular Unanswered issues regarding assignment of spectrum

ranges, security and reliability of transmission

Radio Frequency (RF) LAN

Workstations with RF NICs

Radio frequencyCommunicationsController

Summary LANs follow two design principles

Clients or servers Equal peers

Services include File management Print and communications services Peer-to-peer can act as servers without being

configured as such

Media can be greatest expense and source of failure

Summary Two media types available

Bounded (twisted pair, coaxial cable, fiber optic cable)

Unbounded (satellite, microwave, radio frequency)