Transcript Chapter 6

A Small PC Network
Chapter 6
Copyright 2001 Prentice Hall
Revision 2: July 2001
Small Peer-Peer PC Network

No dedicated (fulltime) server

User PCs supply
services to each other

So user PCs act both
as clients and as
servers
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Small Peer-Peer PC Network

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
3
Small Peer-Peer PC Network

Printer Sharing
–
Each PC can make
one or more
printers attached to
it available to
others
4
Small Peer-Peer PC Network

Advantage
–
No dedicated server
to purchase and
maintain
5
Small Peer-Peer PC Network

Disadvantages
–
If someone turns
off their PC or
crashes it, people
using its files or
printer are cut out
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Small Peer-Peer PC Network

Disadvantages
–
Users often set up
security poorly
giving access to
unauthorized
people
New
–
Special problem if
home network is
connected to the
Internet
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8
Small Peer-Peer PC Network

Overall
–
Beyond about 2-5
users, problems
become too
pronounced
–
Beyond about 10
users, very bad idea
New
Elements of a Simple PC Network
with a Dedicated Server
Hub or Switch
Client PC
Wiring
Server
Server
Client PC
9
Elements of a Small PC Network
10

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)
Elements of a Small PC Network

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 connection
to the LAN

Wire
– Business-grade UTP telephone wiring
11
Elements of a Simple PC Network
12

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
– New Category 6 is coming but will not be
New
necessary for Ethernet
Elements of a Simple PC Network

13
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!
Elements of a Simple PC Network

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
14
15
Elements of a Small PC Network

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
Bit
Bit
Elements of a Small PC Network

Ethernet Hubs
– Broadcasting is simple, so
– Hubs are inexpensive
16
Elements 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)
Must Wait
17
Elements of a Small PC Network

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
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Elements of a Small PC Network
19
Ethernet Switches
– One station transmits a frame to a switch (data
link layer operation)
– Switch only transmits frame out port of
destination PC
Switch – No broadcasting out all ports

Switch
Frame
Frame
Elements of a Small PC Network

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
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Elements of a Simple PC Network

21
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
Elements of a Simple PC Network

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
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Elements of a Simple PC Network


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
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Elements of a Simple PC Network

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
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Elements of a Small PC Network

25
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
New
in order of increasing functionality:
Windows 2000 Server, Advanced Server,
DataCenter Server
Elements of a Small PC Network

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
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Elements of a Small PC Network

UNIX
–
Powerful workstation servers run UNIX
–
Extremely reliable
–
Workstation servers running UNIX dominate
the enterprise server market
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Elements of a Small PC Network

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
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Elements of a Small PC Network

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
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Elements of a Small PC Network

30
LINUX
–
Available in Distributions New
 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
Elements of a Small PC Network

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?
New
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Servers

Options
– Put all services on one server, or
– One server per service, or
– In-Between solutions
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Servers

Option: Put All Services on One Server
– Cheapest for small organizations
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Servers

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
34
Servers

Option: Hybrid with Some Servers Offering One
Service, Others Offering Several
– Distribute services in ways that make sense for
the services, organization size, etc.
35
Servers

36
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
Server Application Software

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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
Access Rights
File
Server
No Access Rights
Server Application Software

File Service
– For sharing application program files also
– No need to install applications on each PC
 Greatly reduces installation labor
File
Server
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Server Application Software

File Server Program Access
– Program is STORED on the file server
File
Server
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Server Application Software

File Server Program Access
– But program is EXECUTED on the client PC
– Limited by power of client PCs, which do not
get very large
File
Server
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Server Application Software

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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!
Print Server
File Server
Client PC
Shared
Printer
Server Application Software

42
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
Print Server
File Server
Shared
Printer
Server Application Software

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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
Print Server
File Server
Server Application Software

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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
RJ-45 Port
Print Server
UTP
Parallel Cable
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Server Application Software

Print Server Location New
– 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
RJ-45 Port
UTP (up to 100 m)
Parallel Cable
(1-2 m only)
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Server Application Software

Typical Application Software
–
Word processing, e-mail, etc.
–
Must buy multiuser versions, not just a single
copy from a retail store
New
–
License will limit the number of users
–
Will cost more than the SOS
New
Server Application Software

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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
RAS
Client
RAS
Internal
Software
Server
Dial-Up
Telephone
Line
Dial-In
LAN
Client
Server Application 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
Access
Line
Serial Router
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Server Application Software

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
Access
Line
IP Packet with Serial
Router’s IP Address
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Server Application Software

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
Access
Line
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Server Application Software

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
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Server Application Software

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
Directory
Server
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Server Application Software

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
Directory
Server
Single
Login
File Server Systems Administration

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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
File Server Systems Administration

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
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File Server Systems Administration

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Automatic Inheritance of Access Rights
–
–
–
Assign rights to individual or group in a directory
Rights automatically inherited in lower directories
Simplifies rights assignment
Assigned Browse
And Read Rights
Application
Word Processing
Inherits Browse
And Read Rights
Inherits Browse
And Read Rights
Database
Oracle
QuickDB
File Server Systems Administration

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Blocking of Inheritance
–
–
If assign rights explicitly in subdirectory, inheritance is
blocked
Only assigned rights are effective
Assigned Browse
And Read Rights
Application
Word Processing
Assigned Browse
And Execute Rights
Inherit Browse
And Read Rights
Database
Oracle
QuickDB
(Browse and Execute Only)
File Server Systems Administration

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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 lowerlevel 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
File Server Systems Administration

Omnibus Rights
– Administrator normally has omnibus rights
– Can read, delete, etc. any file in any directory
– Serious security concern
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Setting Up a Client PC for Windows

Physically install a NIC

Set Up Microsoft Windows for Networking
– Adapter (installed with NIC)
– Protocol
– Client
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Client 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
NIC
Mother Board
Slot
Client PC Setup for Windows

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Install NIC
– Types of Slots
– ISA for up lower speeds
– PCI for higher speeds (longer slot)
– NIC must be compatible with slot
NIC
Mother Board
Slot
Client PC Setup for Windows

63
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
Client PC Setup for Windows

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
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Client PC Setup for Windows

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
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Client PC Setup for Microsoft Windows

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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
Client PC Setup for Microsoft Windows

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
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Client PC Setup for Microsoft Windows

68
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
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Setting Up a Peer-to-Peer Network
New

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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Setting Up a Peer-Peer Network
New

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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Setting Up a Peer-Peer Network
New

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
Setting Up a Peer-Peer Network

72
New
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
73
Using a Shared Resource
New

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