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
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
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 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
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
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
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