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Chapter Six
Networking
Hardware
Network Adapters
Also called network interface cards (NICs)
Connectivity devices enabling a workstation,
server, printer, or other node to receive and
transmit data over the network media
In most modern network devices, network
adapters contain the data transceiver
Types of Network Adapters
For a desktop or tower PC, network adapter
is likely to be a type of expansion board

Expansion boards connect to the system board
through expansion slots
The circuit used by the system board to
transmit data to the computer’s components
is the computer’s bus
Types of Network Adapters
PC bus types you
may encounter:




Industry Standard
Architecture (ISA)
MicroChannel
Architecture (MCA)
Extended Industry
Standard
Architecture (EISA)
Peripheral
Component
Interconnect (PCI)
Figure 6-1: The four primary
bus architectures
Types of Network Adapters
ISA


Developed in early 1980s
8-bit and later 16-bit data transfer capabilities
MCA


IBM’s proprietary 32-bit bus
Introduced in 1987
EISA

32-bit bus compatible with older ISA devices
PCI


32 or 64-bit bus introduced in the 1990s
Shorter, but much faster
Types of Network Adapters
Figure 6-2:
A system
board with
multiple bus
types
Types of Network Adapters
PCMCIA (Personal Computer Memory Card
International Association)


Developed in early 1990s to provide standard interface for
connecting any type of device to a portable computer
More commonly known as PC Cards
Figure 6-3: Typical PC Card network adapter
Types of Network Adapters
USB (universal
serial bus) port

Standard
external bus
that can be
used to
connect
multiple types
of peripherals
Figure 6-4: A USB network adapter
Types of Network Adapters
Figure 6-5: A parallel port network adapter
Types of Network Adapters
Figure 6-6: Wireless network adapters
Types of Network Adapters
Figure 6-7:
A variety of
Ethernet
network
adapters
Types of Network Adapters
Figure 6-8:
Token Ring
network
adapters
Types of Network Adapters
Figure 6-9: Ethernet network adapters for printers
Installing Network Adapters
To install modern network adapters, first install
hardware, then install software shipped with NIC
In some cases you must perform a third step:

Configure the firmware
Electrically erasable programmable read-only
memory (EEPROM)


Type of ROM found on a circuit board
Configuration information can be erased and rewritten
through electrical pulses
Installing and Configuring Network
Adapter Hardware
Figure 6-10: A properly inserted network adapter
Installing and Configuring Network
Adapter Hardware
Figure 6-11: Installing a PC Card network adapter
Installing and Configuring Network
Adapter Hardware
Jumper

Small, removable piece of plastic that contains a
metal receptacle
Figure 6-12: A jumper and a row of pins indicating two different settings
Installing and Configuring Network
Adapter Hardware
DIP switch

Small, plastic toggle switch that represents “on” or “off” status
Figure 6-13: DIP switches on a NIC
Installing and Configuring Network
Adapter Software
Ensure that the correct device driver is
installed for the network adapter and that it
is configured properly
Device driver

Software that enables an attached device to
communicate with computer’s operating
system
Installing and Configuring Network
Adapter Software
Figure 6-14: Windows 2000 Upgrade Device Driver Wizard
IRQ (Interrupt Request)
Message to the computer that instructs it to
stop what it is doing and pay attention to
something else
An interrupt is the wire on which a device
issues voltage to signal this request
Each interrupt must have a unique IRQ
number

Range from 0 to 15
IRQ (Interrupt Request)
* Most NICs
Table 6-1: IRQ assignments
IRQ (Interrupt Request)
When two devices attempt to use the same IRQ,
any of the following problems may occur:






Computer may lock up or “hang” either upon starting or
when operating system is loading
Computer may run much slower than usual
Though computer’s network adapter may work properly,
other devices may stop working
Video or sound card problems may occur
Computer may fail to connect to the network
Computer may experience intermittent data errors during
transmission
IRQ (Interrupt Request)
p. 258
Figure 6-15: Computer resource settings in Windows 2000
IRQ (Interrupt Request)
CMOS (complementary metal oxide
semiconductor)


Firmware on a PC’s system board that enables
you to change its devices’ configurations
Requires very little energy – small battery
Information saved in CMOS is used by the
computer’s BIOS (basic input/output
system)

BIOS is a simple set of instructions enabling a
computer to initially recognize its hardware
Memory Range
and Base I/O Port
Memory range

Hexadecimal number indicating the area
memory that the network adapter and CPU
will use for exchanging, or buffering, the data
Base I/O port

Setting that specifies, in hexadecimal
notation, which area of memory will act as a
channel for moving data between the network
adapter and CPU
Firmware Settings
Once you have adjusted the network
adapter’s system resources, you may need to
modify its transmission characteristics


These settings are held in the adapter’s firmware
Ex. use full duplexing / detect a network’s speed
Loopback plug

Plugs into port and crosses over the transmit line
to the receive line so that the outgoing signal can
be redirected back into the computer for testing
Choosing the Right Network Adapter
Table 6-2:
Network adapter
characteristics
Repeaters
Connectivity devices that regenerate and amplify
an analog or digital signal
Operate in the Physical layer of the OSI Model
Only suited to bus topology networks
Extend a network inexpensively
Figure 6-16:
Repeaters
Hubs
Multiport repeater containing multiple ports
to interconnect multiple devices
Figure 6-17: Detailed diagram of a hub
Hubs
Elements shared by most hubs:

Ports – 4 to 24

Uplink port – hub to hub connection

Port for management console (optional)

Backbone port – hub to backbone

Link LED – port in use
Hubs
Elements shared by most hubs (cont.):

Traffic (transmit or receive) LED

Collision LED (Ethernet hubs only)

Power supply

Ventilation fan
Hubs
Figure 6-18: Hubs in a network design
Hubs
Passive hubs

Only repeats signal
Intelligent hubs

Possess processing capabilities
Remote management
Filter data
Diagnostic info about network
Standalone Hubs
Hubs that serve a group of computers that
are isolated from the rest of the network


Best suited to SOHO, independent departments,
or test lab environments
4 ports (hubby, hublet, minihub) to 200 ports
Disadvantage to using a single hub for many
connection ports is that it introduces a single
point of failure on the network
Stackable Hubs
Physically designed to be linked with other hubs in a single
telecommunications closet
Figure 6-20:
Stackable hubs
Figure 6-21:
Rack-mounted
stackable hubs
Modular Hubs and Intelligent Hubs
Modular hubs


Provide a number of interface options within one chassis
Most expensive type of hub
Intelligent hubs





Also called managed hubs
Network administrators can store the information
generated by intelligent hubs in a MIB (management
information base)
SNMP (Simple Network Management Protocol)
ManageWise
CastleRock
Installing a Hub
As with network
adapters, the
best way to
ensure a hub is
properly
installed is to
follow the
manufacturer’s
guidelines
Figure 6-22: Connecting a workstation to a hub
Choosing the Right Hub
Factors to consider when selecting the
right hub for your network:






Performance – switch better than hub
Cost – passive standalone hub least $
Size and growth - planning
Security – switches, routers, firewall better
Management benefits
Reliability - redundancy
Bridges
Like a repeater,
a bridge has a
single input and
single output port
Unlike a
repeater, it can
interpret the data
it retransmits
(Data Link layer)
Forward or filter
based on
destination MAC
address
Figure 6-23: A bridge
* Protocol is irrelevant / faster than routers
Bridges
Filtering database


Collection of data created and used by a bridge that
correlates the MAC addresses of connected
workstations with their locations
Also known as a forwarding table
Figure 6-24:
A bridge’s
use of a
filtering
database
Bridges
Spanning tree algorithm

Routine that can detect circular traffic patterns and
modify the way multiple bridges work together, in
order to avoid such patterns
Transparent bridging


Method used on many Ethernet networks
Polls network to create filtering database
Source-route bridging


Method used on most Token Ring networks
Bridge determines best route then adds info to data
packet
Switches
Subdivide a
network into
smaller
logical
pieces
Operate in
Data Link
layer (Layer
2)
Figure 6-25: Examples of LAN switches
Device Relationship
Repeater


Single input/output
No data interpretation
Hub


Multi-port repeater
Data interpretation depends on passive/intelligence
Bridge


Single input/output
Can interpret data they retransmit
Switch

Described as a multi-port bridge
Cut-Through Mode and
Store and Forward Mode
Cut-through mode


Switching mode in which switch reads a frame’s
header and decides where to forward the data
before it receives the entire packet
Cut-through switches can detect runts, or packet
fragments
Store and forward mode

Switching mode in which switch reads the entire
data frame into its memory and checks it for
accuracy before transmitting the information
Using Switches to Create
VLANs
Virtual local area networks (VLANs)

Network within a network that is logically
defined by grouping its devices’ switch ports
in the same broadcast domain
Broadcast domain

Combination of ports that make up a Layer 2
segment and must be connected by a Layer 3
device (router or Layer 3 switch)
Using Switches to Create
VLANs
New York
Chicago
LA
Figure 6-26: A simple VLAN design
Higher-Layer Switches
Switch capable of interpreting Layer 3 data is called
a Layer 3 switch
Switch capable of interpreting Layer 4 data is called
a Layer 4 switch
These higher-layer switches may also be called
routing switches or application switches
Performance


Advanced filtering, keep statistics, and security
functions
Aren’t as feature rich as routers, but may transmit
data more quickly and easier to configure
Routers
Multiport connectivity device
Can integrate LANs and WANs running at different
transmission speeds and using a variety of protocols
Routers operate at the Network layer (Layer 3) of the
OSI Model
Performance


Slower than switches or bridges
Protocol dependent
Intelligent

Determine shortest, fastest path between 2 nodes
“Mini-computer” – processor, memory, power, I/O jacks
Router Features and Functions
Modular router

Router with
multiple slots
that can hold
different
interface cards
or other
devices
Figure 6-27: Routers
Router Features and Functions
Find shortest, fastest path between two nodes
Filter out broadcast transmission to alleviate network
congestion
Prevent certain types of traffic from getting to a
network
Support simultaneous local and remote activity
Provide high network fault tolerance through
redundant components
Monitor network traffic and report statistics to a MIB
Diagnose internal or other connectivity problems
and trigger alarms
Router Features and Functions
Static routing

Technique in which a network administrator programs
a router to use a specified paths between nodes
Dynamic routing

Automatically calculates best path between nodes
and accumulates this information in a routing table
Hop

Term used in networking to describe each trip data
take from one connectivity device to another (usually
used in the context of routing)
Router Features and Functions
Figure 6-28: The placement of routers on a LAN
Routing Protocols
To determine the best path, routers
communicate with each other through routing
protocols
In addition to its ability to find the best path, a
routing protocol can be characterized according
to its convergence time and bandwidth overhead

Convergence time
The time it takes for a router to recognize a best path in the
event of a change or outage

Bandwidth overhead
Burden placed on an underlying network to support the
routing protocol
Routing Protocols
The four most common routing protocols:

RIP (Routing Information Protocol) for IP and IPX
Oldest protocol
Stable, but slower and less secure
Creates excessive network traffic – most freq. used

OSPF (Open Shortest Path First) for IP
Improvement to RIP
Second most freq. used

EIGRP (Enhanced Interior Gateway Routing Protocol)
for IP, IPX, and AppleTalk
Only supported by Cisco routers

BGP (Border Gateway Protocol) for IP
Routing protocol of the Internet backbones
Most complex
Brouters and Routing Switches
Bridge router


Also called a brouter
Industry term used to describe routers that take on
some characteristics of bridges
Advantage is the ability to forward non-routable protocols,
such as NetBEUI
Routing switch




Router hybrid that combines a router and a switch
Another name for high-layer switch
Not as full featured as a true router
Not gained wide acceptance from networking pros
Gateways
Combination of networking hardware and
software that connects two dissimilar kinds of
networks
Popular types of gateways include:




E-mail gateways
IBM host gateways
Internet gateways
LAN gateways