Transcript Chapter 5

Local Area Networks, 3rd Edition
David A. Stamper
Part 2: Hardware
Chapter 5
LAN Hardware
© 2001 by Prentice Hall
5-1
Chapter Preview
In this chapter you will study:
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Servers
Backup devices
Workstation hardware
LAN adapters
Printers
Miscellaneous hardware
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Server Platforms
• File Services
– File Servers
• A file server allows users to share files. Only one
copy of application software like word processing,
spreadsheet, or database must reside on a file
server. Individual clients share these applications.
– Database Servers
• The database server was developed to solve
problems like passing an entire file over the medium.
The most common example of a database server is
the SQL server. Structured query language (SQL) is a
standard database definition, access, and update
language for relational databases.
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Server Platforms (cont.)
• Print Services
– When a client shares a printer on the KAN, it can submit
jobs to the printer at any time. The print job is collected
on disk, and printing is deferred until the printer is
available for printing a new job and the print job is the
next one eligible to be printed.
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Print Server Technology
Client
Print Server
Application
Server
Spooler
Client
Spooler
Print
Monitor
Router
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Server Selection Considerations
• Server Disk Drives
– When choosing a server, you should carefully
select the server’s disk subsystem. There are
five factors that are critical when choosing a
server’s disk subsystem:
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Storage Capacity
Average Access Time
Separation of Function
Fault Tolerance
Drive Interface
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Server Selection Considerations
(cont.)
• Server Memory
– In Intel-based servers, there are two classes of
memory—Level 1/2 cache and standard random access
memory (RAM)
• Processors and Processor Speed
– The processing power of the server is also a critical
factor. It seldom makes sense to select a server that has
fast disks and plenty of memory but a slow CPU. In
general, the server ought to be one of the fastest—if not
the fastest—computers on the network.
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Server Selection Considerations
(cont.)
• Processor Bus
– A variety of buses are available. The bus is the path over which data
is transferred between the CPU, memory, and peripherals.
• Expansion and Power
– A server should have sufficient expansion capability and the power
to use the expansion slots effectively. Network server capacity can
be expanded by adding hardware to the existing server or by adding
additional servers.
• Compatibility
– The server platform you choose must be compatible with the
topology, MAC protocol, applications, and system software on the
network.
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IBM-Compatible System Buses
Industry standard
architecture (ISA)
Enhanced industry
standard architecture
(EISA)
Micro channel
architecture (MCA)
Video electronics
standards association
(VESA)
Peripheral component
interconnect (PCI)
PC-Card (formerly
PCMCIA)
VESA local (VL-Bus)
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Backup Devices
• Floppy Diskette Drives
– The major disadvantages of this backup method is the low capacity
and speed of the backup media.
• Removable Disk Drives
– Manual intervention is necessary for changing disk cartridges,
whereas some tape backup system provide tapes with much higher
storage capacity and with automatic tape changing.
• Hard-Disk Drives
– The arguments for and against this alternative are much the same as
those for diskettes. The major difference is that the capacity of harddisk drives is greater than that of diskettes.
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Backup Devices (cont.)
• Optical Disk Drives
– Optical disk drives are gaining popularity as input,
output, and backup devices. The reasons for this are
their decreasing costs and large storage capacity.
• Magnetic Tape Drives
– A magnetic tape drive is the usual choice for a backup
device. Magnetic tapes are less expensive than the other
options. They hold large volumes of data, are easy to use
and store, and generally provide good performance.
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Primary Backup Technologies
Diskette backup
1.44 MB
Hard drive, fixed
Multiple capacities
Hard drive, removable cartridge
40 MB to over 1 G
Tape backup, 4mm or 1/4 inch
2.88 MB
20 MB
To 15 GB
60 MB
150 MB
160 MB
500 MB
1.2 GB
2.2 GB
15 GB
70 GB
(compressed)
Tape backup, 8mm or VCR
To 2.2 GB
Tape backup, 9-track
To 100 MB
Optical drives
To 4 GB
Digital versatile disks (when
available)
10-14 GB
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Backup Functions
Back up all files
Incremental backup
Differential backup
Maintain index on tape and disk
Back up all files modified since a
particular date
Maintain cross-reference of tape
serial numbers and backup
Back up by directory
Back up manually
Back up automatically by time or
calendar
Back up by list of files
Back up all but a list of files to be
excluded
Back up by index
Start backup from workstation or server
Compress data
Back up by interface to a database
Back up multiple volumes
Back up using wildcard characters in file
names
Generate reports
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Workstations
• Diskless Workstations
– A diskless workstation does not have any local disk
drives. Instead, a diskless workstation has its boot logic
in a read-only memory (ROM) chip located on the LAN
adapter.
– Because diskless workstations have no disk drives, they
are inherently less expensive than those with disks.
• Workstation Memory and Speed
– The speed of the workstation’s processor must be
compatible with the type of work for which it is being
used. Basically, it is the application, not the LAN, that
determines the power of the workstations.
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LAN Adapters
• If you have chosen an architecture, medium, and
media access control protocol, you have
narrowed the options for LAN adapters, also
known as a network interface card (NIC).
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LAN adapters provide the connection between
the medium and the bus of the workstation or
server. LAN adapters are designed to support a
specific protocol using a specific medium,
although a few can support two or three different
medium types.
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Printers
• One major factor that affects the success of a
LAN is printer support. Some LANs have
restrictions regarding the distribution of printers
and the number of printers that can be supported
by one server.
• A printer driver is a software module that
determines how to format data for proper printing
on a specific type of printer. The printers you
intend to use must be supported by the software
drivers provided by the LAN operating system or
printer vendor.
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Hubs and Switches
• Some LAN architectures use wiring
hubs to provide device
interconnection.
• Hubs vary in the number of ports
available. A very common
configuration is 8 ports, with 12- and
16-port hubs as common
alternatives. Hubs may be standalone or stackable.
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Making Connections
• The objective of network connection—that
is, connecting a computer to the LAN
medium—is to provide a data path
between the medium and the computer’s
memory.
• The interface or connection to the medium
is called the communications interface
unit (CIU), and the interface or connection
to the computer’s bus is called the bus
interface unit (BIU).
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Details of Node-to-Medium
Connection
LAN Node
Node’s I/O Bus
Bus interface Unit (BIU)
Transceiver
Communications Interface
Unit (CIU)
LAN Medium
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Transceiver Located on a LAN
Adapter
Ethernet
Controller
Encoder/
Decoder
Transceiver
RAM
Bus
Interface
Cable
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