A Small PC Network

Chapter 6

Copyright 2001 Prentice HallRevision 2: July 2001

2Small Peer-Peer PC Network

No dedicated (full-time) server– User PCs supply services – User PCs act as clients & servers

File Sharing

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

– Can allow read-only or full access

– Can require password for access

Printer Sharing

– PC can make printers attached to it available to others

3Small Peer-Peer PC Network

Advantage

– No dedicated server to purchase and maintain

Disadvantages

– PC crashes or turned off, people using its files or printer are disconnected

– Security often gives access to unauthorized people

Special problem if home network is connected to the Internet

4Elements of a Simple PC Network with a Dedicated Server

Hub or Switch

Server

Client PC

Client PC

Server

Wiring

5Elements 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 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)

6Elements of a Small PC Network

Need a hub or switch to connect the PCs– Connector box with multiple plug-in jacks

Each PC needs a network interface card (NIC)– Implements physical & data link layer

connection to the LAN

Wire– Business-grade UTP telephone wiring

7Elements of a Simple PC Network

Ethernet UTP Wiring– 4-pair bundle (8 wires) & RJ-45 connector

– Pre-cut lengths (1 m, 2 m, 25 m, etc.) & connectors on both ends

– Cut wire to lengths needed and attach connectors

Quality Level– Category 5 or Category 5e (enhanced)– Older categories (3 and 4) exist but are now fairly rare– New Category 6 is coming (not necessary for Ethernet)

Plenum Wiring– For Air conditioning ducts (no toxic fumes if burns)

8Elements of a Small PC Network

Ethernet Hub Operation (Broadcasting)– 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– Operation is simple, hubs inexpensive

Hub Hub

BitBit

9Elements of a Small PC Network

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)– Becomes a problem with 100+ PCs and 10 Mbps hub– Problem is intolerable with 200+ PCs with a 10 Mbps hub

Must Wait

10Elements of a Small PC Network

Ethernet Switches– Station transmits frame to switch (data link layer operation)– Switch only transmits frame out port of destination PC– Multiple conversations can take place simultaneously

because there is no broadcasting, which ties up all ports– No wait to transmit; no Latency; No shared speeds– More costly than hubs

Switch

Switch

Frame Frame

11Elements of a Simple PC Network

Client PCs

– End user’s desktop or notebook PC

– Add network interface card (NIC)

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

– Networks have many client PCs

12Elements of a Simple PC Network

Servers– Provide services to client PCs– In peer-to-peer, PCs are clients & servers

dedicated servers needed for more than 5 PCs

– Most PC nets have multiple servers (1:10-50)– Require a NIC– Require a server operating

system (SOS)– Require application software

13Elements of a Simple PC Network

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

than client PC operating systems– Often bundled with some application software– Windows NT/2000 Server, Novell NetWare,

UNIX, LINUX

Application Software– Provides the services offered by the servers– E-mail, word processing, file sharing, etc.– Largest expense for PC Networks

14Elements of a Simple PC Network

Novell NetWare SOS – Once dominant, but market share has shrunk– Excellent file, print & directory service

UNIX (Not for Small PC Networks)

– Powerful workstation servers run UNIX– Extremely reliable & highly functional– Expensive & difficult to learn

Many versions of UNIX exist

– Must retrain staff or hire UNIX staff

15Elements of a Small PC Network

LINUX (Version of UNIX)– Runs on Intel PCs ( and compatibles)– Cost free or 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– Requires Extensive Labor to Set Up, Maintain– Device driver software often is lacking– Requires more training because it is UNIX

16Elements of a Small PC Network

Microsoft Windows 2000 Server Operating System– Formerly Microsoft Windows NT Server

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

– All 32-bit code

– Easy to install, learn, and use (resembles desktop Windows)

– Becoming dominant for small business and small department servers

– Windows 2000 Server promise improvedreliability & scalability

17Servers

Option: Put All Services on One Server– Cheapest for small organizations– SOS is multitasking; multiple applications is no problem

Option: One Application per Server– Can optimize hardware for application– More reliable, crashing service does not crash others– Security: users must log into appropriate server

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

organization size, disk storage, processing speed.

18Servers

Cost (Difficult assessment)– Small organization: all services on single server– Larger organizations: optimization through multiple

servers often minimizes costs

Typical Application Software– Word processing, e-mail, etc.

– Must buy multi-user versions, not just a single copy from a retail store

– License will limit the number of users

– Will cost more than the SOS

19Server 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

20Server Application Software

Sharing application program files – Program is STORED on the file server not each PC

– Greatly reduces installation labor– But program is EXECUTED on the client PC– Limited by power of client PCs, which do not get very

large

FileServer

21Server Application Software

Print Service– Also built into SOSs– Print jobs go to shared printers– But they first go to the file server & print queue

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

File Server

Print Server

SharedPrinterClient PC

22Server Application Software

Print Server– Print server feeds the print job to the printer– Simple and inexpensive (file server does work)– Low print server cost allows shared printers can be

scattered throughout the office

File Server

Print Server

23Server Application Software

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– Parallel cable 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

UTPRJ-45 Port

24Server Application Software

Remote Access Service (RAS)– User dials into PC Network via modem– Server authenticates the user

User has equivalent access as local users Lower response times due to telephone line speeds

– Client PC needs RAS software

LAN

InternalServer

RAS

Dial-InClient

Dial-UpTelephone

Line

RASClient

Software

25Internet Access for a Simple PC LAN

Serial Router– Simple, inexpensive router ($1,000 - 3,000)– One RJ-45 LAN port, one ISP Connection port– 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 May provide firewall preventing unauthorized access

Serial Router

Access Line

IP Packet with SerialRouter’s IP Address

26Server Application Software

Directory Servers: Server of resources spread among network– To use a resource, must know the server

Files must be accessed on particular servers– Directory server knows all resources on all servers

Can search for a specific file across servers– Directory server knows user access rights on all servers– Single login to directory server grants access to all other

servers where user has access rights

27File Server Systems Administration

Set Access Rights for Each Directory, File– Ability to see directory or file

– Ability to get read-only copy of a file in a directory

– Ability to create, edit, & delete files & subdirectories

– Ability to assign access rights to other users

– Rights can be assigned to individuals or group

Using groups simplifies assignment of access rights

– Assign individual to groups

– Give access rights to groups

– Members of groups then get those rights

28File Server Systems Administration

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

29File Server Systems Administration

Blocking of Inheritance– Assigning rights explicitly blocks inheritance– Only assigned rights are effective

Application

Word Processing Database

Oracle(Browse and Execute Only)

QuickDB

Assigned BrowseAnd Read Rights

Assigned BrowseAnd Execute Rights

30File Server Systems Administration

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

31Setting Up a Client PC for Windows

Physically install a NIC

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

32Client 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, screw in place– Types of Slots

ISA for lower speeds PCI for higher speeds (longer slot) NIC must be compatible with slot

SlotMother Board

NIC

33Client PC Setup for Windows

Install the NIC– Boot system after installation

Windows should recognize the new NIC Setup: fairly automatic, may be asked for NIC disk Some NICs have their own setup disks and should

bypass automatic Windows setup. Check the NIC documentation