A Small PC Network Chapter 6 Revision 1: August 2000 Copyright 2001 Prentice Hall.

A Small PC Network

Chapter 6Revision 1: August 2000

Copyright 2001 Prentice Hall

2Previous 5 chapters

Looked at accessing the Internet

Only part of data communications and networking– Accessing the Internet dealt with WAN– Only looked at subnet using PPP and modems– What about LAN’s– Are there other subnet protocols and

technologies?

3First Five Chapters Concepts

Layered Architectures

Protocols

Connection Oriented vs connectionless

Circuit and Packet Switching

Routing

Etc.

4Why network?

Share resources– Data resources

Distributed data Data on servers

– Share programs Network versions of programs

– Site license– # of clients

– Share peripherals Printers, scanners etc.

5LAN and Layered Architecture

What layers deal with getting frames from 1 host to another on the same network (subnet)– Answer – datalink and physical

Datalink protocols– PPP– Ethernet– Token ring– FDDI

Datalink – concerns itself with a single link

Network – concerns itself with link to link(end-to-end)

6Data Link Protocols

Services– Framing– Delivery of frame

Send frame to all Pass a token around Flow control (limited amount of buffering) Error detection

7Real World Example

Travel agent – network layer– Travel from here to Florence Italy

1ST Link – Clarksville to Nashville– Use Clarksville limousine service

2nd Link – Nashville to New York– Plane (American Airlines)

3rd Link – New York to Rome– Plane (Air Italia)

4th Link – Rome to Florence– Train

8Implementation of Data Link Layer

Hardware– Adapter

NIC– Ram– DSP Chips– Interface to bus of computer– Interface to network connection

– PC handles upper layers

9Implementation of Data Link Layer

Software– Network operating system

NIC and PC are somewhat autonomous– PC sends Ip packet to NIC that puts it into

frames and sends it– Reads incoming frames and may pass them to

PC

10Small Peer-Peer PC Network

No dedicated (full-time) server

User PCs supply services to each other

So user PCs act both as clients and as servers


File Sharing

– Each PC can make certain disk drives or directories available to to other user PCs

– Can allow others read-only or full access to files there

– Can require password for access


Printer Sharing

– Each PC can make one or more printers attached to it available to others


Advantage

– No dedicated server to purchase and maintain


Disadvantages

– If someone turns off their PC or crashes it, people using its files or printer are cut out


Disadvantages

– Users often set up security poorly giving access to unauthorized people

– Special problem if home network is connected to the Internet

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Overall

– Beyond about 2-5 users, problems become too pronounced

– Beyond about 10 users, very bad idea

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17Elements of a Simple PC Network with a Dedicated Server

Hub or Switch

Server

Client PC

Client PC

Server

Wiring

18Elements of a Small PC Network

LAN Standards– We will focus on LANs that follow the

Ethernet standard (80% do)

Small Ethernet PC networks use only inexpensive UTP wiring

Speeds for NICs and Hubs or Switches– 10Base-T (10 Mbps, baseband, UTP)– 100Base-TX (100 Mbps, baseband, UTP)– 1000Base-T (Gigabit Ethernet) (1 Gbps)


Need a hub or switch to connect the PCs– Connector box with multiple plug-in jacks– Hubs and switches are described later

Each PC needs a network interface card (NIC)– Implements physical and

data link layer connectionto the LAN

Wire– Business-grade UTP telephone wiring

20Elements of a Simple PC Network

Ethernet UTP Wiring– 4-pair bundle (8 wires)– Each pair is twisted– Terminates in RJ-45

connector

Quality Level– Category 5 or Category 5e (enhanced)– Older categories (3 and 4) exist but are now

fairly rare


Ethernet UTP Wiring

– Come pre-cut in many useful lengths (1 m, 2 m, 25 m, etc.) with connectors already added to both ends

– Can also cut wire to precise lengths needed and then attach connectors

Must test the wire after cutting it and attaching connectors!


Plenum Wiring

– For wiring run through airways; covering does not give off toxic fumes if it burns

Required if wires are run through air conditioning ducts

Needed in false ceilings and false floors

– More expensive but required by law and concern for employee safety


Ethernet Hub Operation– One station transmits a single bit to a hub (physical

layer operation)– Hub broadcasts bit to all attached stations– All but the destination PC should ignore the message

Hub Hub

BitBit


Ethernet Hubs– Broadcasting is simple, so– Hubs are inexpensive


Ethernet Hubs Can Create Latency– Only one station may transmit at a time

or the signals will collide and be unreadable

– Other stations must wait (latency)

Must Wait


Ethernet Hubs Can Create Latency– Becomes a problem with 100+ PCs and

10 Mbps hub– 200 PCs is upper limit for tolerable

service with a 10 Mbps hub

Must Wait


Ethernet Switches– One station transmits a frame to a switch (data

link layer operation)– Switch only transmits frame out port of

destination PC– No broadcasting out all portsSwitch

Switch

Frame Frame


Ethernet Switches– Multiple conversations can take place

simultaneously because there is no broadcasting, which ties up all ports

– No wait to transmit; no Latency

Switch


Client PCs

– End user’s desktop or notebook PC

– Add network interface card (NIC)

– With Win95, Win98, Win NT, or Win 2000 Professional, and Macintosh, no extra software is needed

– Networks have many client PCs


Servers

– Provide services to client PCs

– Usually PCs themselves

– Most PC nets have multiple servers

– Require a NIC

– Require a server operating system (SOS)

– Require application software


Server Operating System (SOS)– Servers need operating systems more reliable

than client PC operating systems– Windows NT/2000 Server, Novell NetWare,

UNIX, LINUX

Application Software– Provides the services offered by the servers– E-mail, word processing, file sharing, etc.– More expensive than the SOS


Novell NetWare SOS

– Once dominant, but market share has shrunk

– Excellent file and print service

– Excellent directory service (later)

– Until recently, was not sufficiently robust and scalable for servers other than file servers


Microsoft Windows Server Operating System

– More robust than desktop Windows (Win 95, Win 98, Win 2000 Professional, etc.)

– All 32-bit code

– Microsoft Windows NT Server before 2000

– Newer Microsoft Windows 2000 Server

Versions in order of increasing functionality: Windows 2000 Server, Advanced Server, Data Center Server

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Microsoft Windows Server Operating System

– Easy to install, learn, and use because resembles desktop Windows

– Becoming dominant for small business and small department servers

– Windows NT Server has had serious reliability and scalability problems

– Windows 2000 Server versions promise to improve reliability and scalability


UNIX

– Powerful workstation servers run UNIX

– Extremely reliable

– Workstation servers running UNIX dominate the enterprise server market


UNIX

– Expensive to buy

– Must retrain staff or hire UNIX staff

– Many versions of UNIX exist Most run the same application software However, have different management

utilities, etc., requiring training for each version used

– Not for Small PC Networks


LINUX– Version of UNIX– Runs on Intel PCs ( and compatibles); low cost– Available free

But usually pay around $50 to $150 for packaged version

– Reliable like other UNIX versions– Open Source: Many people are developing

tools to add to the LINUX core


LINUX

– Available in Distributions A distribution has the LINUX kernel plus

other programs Available on CD-ROM or by downloading Distributions from different LINUX vendors

differ in the specific programs included Differences make selection, implementation

difficult

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LINUX

– Requires Extensive Labor to Set Up, Maintain

– Device driver software often is lacking for printers, disk drives, and other devices

– Requires more training because it is UNIX

– Better distributions and support coming?

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40Servers

Options– Put all services on one server, or– One server per service, or– In-Between solutions

41Servers

Option: Put All Services on One Server– Cheapest for small organizations

42Servers

Option: One Service Application per Server– Can optimize hardware for application– More reliable, because a crashing service does

not crash others– Security: users cannot log into one service,

switch to another easily

43Servers

Option: Hybrid with Some Servers Offering One Service, Others Offering Several– Distribute services in ways that make sense for

the services, organization size, etc.

44Servers

Cost (Which is Cheapest?)– Difficult to know– For small organization, most or all services on one

usually is cheapest– For larger organizations, optimization through multiple

servers often minimizes costs

45Server Application Software

File Service Allows File Sharing– File server stores program and data files– Shared file be accessed by any user with access

rights– Built into most SOSs

FileServer

Access Rights

No Access Rights


File Service– For sharing application program files also– No need to install applications on each PC

Greatly reduces installation labor

FileServer


File Server Program Access– Program is STORED on the file server

FileServer


File Server Program Access– But program is EXECUTED on the client PC– Limited by power of client PCs, which do not

get very large

FileServer


Print Service– Also built into SOSs– Print jobs go to shared printers– But they first go to the file server– Not directly to the print server!

File Server

Print Server

SharedPrinterClient PC


Print Service– File server stores print job in a print queue until

print server is ready to print it– File server sends the print job to the print server

File Server

Print Server

SharedPrinter


Print Server– Print server feeds the print job to the printer– Print servers are simple and inexpensive because the

file server does most of the work– Low print server cost allows shared printers can be

scattered throughout the office

File Server

Print Server


Print Server– Connects to printer via parallel port on the print

server; no special printer needed– Has NIC to connect to the hub or switch– Requires an RJ-45 port on the hub or switch

Print Server

Parallel Cable

UTPRJ-45 Port


Print Server Location– Parallel cable distance limitation requires print

server to be within 1-2 meters of the printer– UTP allows print server to be up to 100 meters

from the hub or switch

Print Server

Parallel Cable(1-2 m only)

UTP (up to 100 m)RJ-45 Port

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Typical Application Software

– Word processing, e-mail, etc.

– Must buy multiuser versions, not just a single copy from a retail store

– License will limit the number of users

– Will cost more than the SOS

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New


Remote Access Service (RAS)– User dials into a remote access server– Server authenticates the user (user must prove identity)– If authenticated, user may use internal servers– Client PC needs RAS software

LAN

InternalServer

RAS

Dial-InClient

Dial-UpTelephone

Line

RASClient

Software


Internet Access for a Simple PC LAN– Serial Router– Simple, inexpensive router– One RJ-45 port for LAN, one suitable port for

ISP Connection

Serial Router

AccessLine


Serial Routers– May provide security to stop outside hackers

Network address translation (NAT) hides addresses of internal machines

Only serial router’s IP address appears in outgoing packets

Serial Router AccessLine

IP Packet with SerialRouter’s IP Address


Serial Routers– Provide security to stop outside hackers

May provide a firewall (discussed in Chapter 10) to prevent unauthorized access from Internet hackers

Serial Router

AccessLine


Directory Servers– Problem: Most networks have many servers– To use a resource, must know the server

To send e-mail, address is user@server Files must be accessed on particular servers


Directory Servers– Directory server knows all resources on all

servers– Can send mail to user (without @server)– Can search for a specific file across servers

DirectoryServer


Directory Servers– Know user access rights on all servers– Single login to directory server– After that, get access to all other servers where

user has access rights

DirectoryServer

SingleLogin

62File Server Systems Administration

Set Access Rights for Each Directory, File– The ability to even see a directory or file

(otherwise, it will be invisible)

– The ability to get a read-only copy of a file in a directory (a copy that cannot be edited and then saved under the same name)

– The ability to create, edit, and delete files and subdirectories

– The ability to assign access rights in a directory to other users


Set Up Access Rights for Each Directory, File

– Must be done for each individual in each directory!

– Usually, however, assign individual to groups

– Give access rights to groups

– Members of groups then get those rights

– Using groups greatly simplifies the assignment of access rights


Automatic Inheritance of Access Rights– Assign rights to individual or group in a directory– Rights automatically inherited in lower directories– Simplifies rights assignment

Application

Word Processing Database

Oracle QuickDB

Assigned BrowseAnd Read Rights

Inherits BrowseAnd Read Rights

Inherits BrowseAnd Read Rights


Blocking of Inheritance– If assign rights explicitly in subdirectory, inheritance is

blocked– Only assigned rights are effective

Application

Word Processing Database

Oracle(Browse and Execute Only)

QuickDB

Assigned BrowseAnd Read Rights

Inherit BrowseAnd Read Rights

Assigned BrowseAnd Execute Rights


The Assignment of Rights: Recap– Rights can be assigned to individuals or group

Group members receive all rights assigned to the group

– Rights are automatically inherited in lower-level directories, unless

– Rights are explicitly assigned in a directory, in which case automatic inheritance is blocked and only explicitly assigned rights are in effect in that directory


Omnibus Rights– Administrator normally has omnibus rights– Can read, delete, etc. any file in any directory– Serious security concern

68Setting Up a Client PC for Windows

Physically install a NIC

Set Up Microsoft Windows for Networking– Adapter (installed with NIC)– Protocol– Client

69Client PC Setup for Windows

Install NIC– Physically open systems unit– Main printed circuit board is the mother board– Has slots for expansion boards– Press NIC expansion board into slot, use screw

to hold in place

SlotMother Board

NIC


Install NIC– Types of Slots– ISA for up lower speeds– PCI for higher speeds– NIC must be compatible with slot

SlotMother Board

NIC


Install the NIC

– Boot system after installation

– Windows should recognize the new NIC

– Setup will be fairly automatic, although you may be asked to provide a disk that came with the NIC

– Some NICs have their own setup disks and should bypass automatic Windows setup. Check the NIC documentation


Set Up Microsoft Networking

In Windows 95 and Windows 98,

– Go to the Start Button

– Choose Settings

– Choose Control Panel

– Double click the Network icon

– This opens the Network Dialog Box


Be sure the Configuration tab is selected in the Network Dialog Box – You will see adapters, protocols, clients, and

services that have already been added

Operations– Add: To add an adapter, protocol, client, or

service– Remove: To remove one– Properties: To see or change the properties of

the selected adapter, protocol, client, or service

74Client PC Setup for Microsoft Windows

Adding a Protocol

– In the Network Dialog Box, clicking the “Add” button takes you to the Select Network Component Type dialog box

– Choose Protocol, then hit Add

– You then go to the Select Network Protocol dialog box

– Choose the Manufacturer and Protocol your server requires


Configuring a Protocol

– In the Network Dialog Box, click on the protocol you installed

– Click the Properties button takes you to the properties dialog box for that protocol

– Set up the properties

– Bind the protocol to your client and adapter


Client

– In the Network Dialog Box, clicking the “Add” button takes you to the Select Network Component Type dialog box

– Choose Client, then hit Add

– You then go to the Select Network Client dialog box

– Choose the manufacturer and client your server requires

77Setting Up a Peer-to-Peer Network

For Each PC– Install the Client for Microsoft Networks– This supports peer-peer networking

Implement Sharing– In the Network Dialog Box,– Click the File and Print Sharing button– Enable file and print sharing by clicking on the

appropriate boxes

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78Setting Up a Peer-Peer Network

To Share a Specific Printer– Choose Start, Settings, Printers– Right click on icon for printer to be shared– Choose Sharing in the pop-up menu– Select Shared As in the Properties Dialog Box

and give the printer any name– Give a password if desired– Anyone can now use it if they have the

password or if you set no password

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To share a disk or directory’s files

– In Explorer or My Computer, right click on disk or directory to be shared

– Select Sharing in the pop-up menu

In (name of item selected) Sharing Dialog Box

– Click Shared As radio button

Give shared name (how others will refer to it)

Add a comment if desired

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In (name of items selected) Sharing Dialog Box

– Select an Access Type Radio Button Read-Only

– Anyone can read but cannot change– Can give password

Full (can do anything)– Can do anything– Can give password

Depends on Password– Can give different passwords for read-only, full

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81Using a Shared Resource

Using a Shared printer– In application, choose Print– Select printer as usual– May need to give password

Using a Shared File or Directory– Choose Network Neighborhood– Select the desired file or directory– May need to give password

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A Small PC Network Chapter 6 Revision 1: August 2000 Copyright 2001 Prentice Hall.

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Transcript of A Small PC Network Chapter 6 Revision 1: August 2000 Copyright 2001 Prentice Hall.