Networking Technologies
This chapter offers a brief introduction to networking
and some basic networking terms and concepts.
This material should be a review of many already
known concepts. You should be familiar with
the various networking topologies used in networks
, as well as different types of networks, such as
local area networks (LANs) and wide area networks
(WANs).
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2/29/2008
LESSON 6 ARABIC
Lesson Title :
الدروس من السادس والثلاثون حتى الدرس الأخير
وبهذا نكون قد انتهينا بفضل الله من هذه السلسله
وفى المواضيع القادمة ان شاء الله سنقوم بعرض دورة السيسكو كامله
باللغتين العربيه والانجليزيه ومعها محاكيات سيسكو لأجهزة الراوتر
لزوم التدريبات
ولا تنسوا مسانده المدونة بالضغط على اعلانات جوجل التى بلأعلى
وعلى يمين الصفحة اذا وجدتم ما يناسبكم منها وهى تحتوى ايضا على مواقع هامة فى الشبكات
السلكيه واللاسلكية
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2/25/2008
2/20/2008
LESSON 4 ENGLISH
4.0 Networking protocols
4.1 TCP/IP Suite
TCP - Transmission Control Protocol, the most
common transport layer protocol used onEthernet
and the Internet. It was developed by DARPA.
TCP is built on top of the Internet Protocol (IP)
and is nearly always seen in the combination
TCP/IP (TCP over IP).It adds reliable
communication, flow-control, multiplexing
and connection-oriented communication.
It provides full-duplex, process-to-process connections.
UDP - User Datagram Protocol. Internet standard
network layer, transport layer and session layer
protocols which provide simple but unreliable
datagram services. It adds a checksum
and additional process-to-process addressing
information. UDP is a connectionless protocol,
which, like TCP, is layered on top of IP. UDP neither
guarantees delivery nor does it require a connection.
As a result it is lightweight and efficient, but all
error processing and retransmission must be taken
care of by the application program.
POP3 - Post Office Protocol version 3. POP3
allows a client computer to retrieve electronic
mail from a POP3 server via a TCP/IP or other
connection. It does not provide for sending mail,
which is assumed to be performed via SMTP
or some other method. POP is useful for
computers without a permanent network
connection and which require a "post office"
(the POP server) to hold their mail until they can
retrieve it.
SMTP - Simple Mail Transfer Protocol, a protocol
used to transfer electronic mail between computers,
usually over Ethernet. It is a server-to-server protocol,
so other protocols are used to access the messages.
The SMTP dialog usually happens in the background
under the control of the message transport system,
but it is possible to interact with an SMTP server
using telnet to connect to the normal SMTP port, 25.
SNMP - Simple Network Management Protocol,
the Internet standard protocol developed to manage
nodes on an IP network. SNMP is not limited to TCP/IP
and can be used to manage and monitor all sorts
of equipment including computers, routers, wiring hubs, etc.
FTP - File Transfer Protocol, a client-server protocol
that allows a user on one computer to transfer files
to and from another computer over a TCP/IP network.
Also the client program the user executes to transfer files.
HTTP - HyperText Transfer Protocol, the client-server
TCP/IP protocol used on the World-Wide Web for
the exchange of HTML documents. It conventionally uses port 80.
IP - Internet Protocol, the network layer for the TCP/IP
protocol suite widely used on Ethernet networks.
IP is a connectionless, best-effort packet switching protocol. It
provides packet routing, fragmentation and re-assembly
through the data link layer.
PPP - Point-to Point Protocol, the Internet standard
for transmitting network layer datagrams
(e.g. IP packets)over serial point-to-point links.
PPP has a number of advantages over SLIP;
it is designed to operate both over asynchronous
connections and bit-oriented synchronous systems
and it can configure connections to a remote network
dynamically, and test that the link is usable. PPP can
be configured to encapsulate different network layer
protocols (such as IP, IPX, or AppleTalk) by using
the appropriate Network Control Protocol (NCP).
4.1 TCP/IP Suite
TCP - Transmission Control Protocol, the most
common transport layer protocol used onEthernet
and the Internet. It was developed by DARPA.
TCP is built on top of the Internet Protocol (IP)
and is nearly always seen in the combination
TCP/IP (TCP over IP).It adds reliable
communication, flow-control, multiplexing
and connection-oriented communication.
It provides full-duplex, process-to-process connections.
UDP - User Datagram Protocol. Internet standard
network layer, transport layer and session layer
protocols which provide simple but unreliable
datagram services. It adds a checksum
and additional process-to-process addressing
information. UDP is a connectionless protocol,
which, like TCP, is layered on top of IP. UDP neither
guarantees delivery nor does it require a connection.
As a result it is lightweight and efficient, but all
error processing and retransmission must be taken
care of by the application program.
POP3 - Post Office Protocol version 3. POP3
allows a client computer to retrieve electronic
mail from a POP3 server via a TCP/IP or other
connection. It does not provide for sending mail,
which is assumed to be performed via SMTP
or some other method. POP is useful for
computers without a permanent network
connection and which require a "post office"
(the POP server) to hold their mail until they can
retrieve it.
SMTP - Simple Mail Transfer Protocol, a protocol
used to transfer electronic mail between computers,
usually over Ethernet. It is a server-to-server protocol,
so other protocols are used to access the messages.
The SMTP dialog usually happens in the background
under the control of the message transport system,
but it is possible to interact with an SMTP server
using telnet to connect to the normal SMTP port, 25.
SNMP - Simple Network Management Protocol,
the Internet standard protocol developed to manage
nodes on an IP network. SNMP is not limited to TCP/IP
and can be used to manage and monitor all sorts
of equipment including computers, routers, wiring hubs, etc.
FTP - File Transfer Protocol, a client-server protocol
that allows a user on one computer to transfer files
to and from another computer over a TCP/IP network.
Also the client program the user executes to transfer files.
HTTP - HyperText Transfer Protocol, the client-server
TCP/IP protocol used on the World-Wide Web for
the exchange of HTML documents. It conventionally uses port 80.
IP - Internet Protocol, the network layer for the TCP/IP
protocol suite widely used on Ethernet networks.
IP is a connectionless, best-effort packet switching protocol. It
provides packet routing, fragmentation and re-assembly
through the data link layer.
PPP - Point-to Point Protocol, the Internet standard
for transmitting network layer datagrams
(e.g. IP packets)over serial point-to-point links.
PPP has a number of advantages over SLIP;
it is designed to operate both over asynchronous
connections and bit-oriented synchronous systems
and it can configure connections to a remote network
dynamically, and test that the link is usable. PPP can
be configured to encapsulate different network layer
protocols (such as IP, IPX, or AppleTalk) by using
the appropriate Network Control Protocol (NCP).
2/18/2008
LESSON 3 ENGLISH
3.1 Networking Terms
WAN - Wide Area Network. Usually constructed
with serial lines, extending over distances greater
than one mile.
Server - A computer, which provides some service
for other computers, connected to it via a network.
The most commonexample is a file server, which
has a local disk andservices requests from remote
clients to read and write files on that disk.
Workstation - A general-purpose computer
designed to be used by one person at a time
and which offers higher performance than
normally found in a personal computer, especially
with respect to graphics, processing power and the
ability to carry out several tasks at the same time.
A device, which accesses available resources from
servers typically found in a distributed processing
environment .
Host - A computer connected to a network.
The term node includes devices such as routers
and printers, which would not normally be
called "hosts".
Peer-to-Peer Network - A network that does
not rely on the use of a central file server to share
files. Each workstation relies on another workstation
to have it's resources made available. They are very
difficult to maintain security, must be limited
number of peers to keep administration costs low,
slow response time, but they are inexpensive ,
no central point of failure and no special training required.
Server-based network - Requires a central file
server and a networking operating system that can
handle the job. They require a separate machine
and therefore expensive hardware, expensive NOS,
and without the proper training it is difficult to install
and maintain. On the other hand, data transfer speeds
are greater, security is more robust, LAN expansion
is simpler, and there are management tools available.
Cable - provides the pathway for network
communications. It's a component of a topology
determined by the NIC and standard being used.
The most common types of LAN cabling are coaxial,
unshielded twisted pair, shielded twist pair, and fiber optic.
NIC - An adapter circuit board installed in
a computer to provide a physical connection to a network.
Hub - A wiring concentrator for a LAN or WAN
that providesa central attachment point for network
cabling. Coaxial cable doesn't use hubs. There are
three types of hubs:
passive (absorbs some signal; no electronics to
process data signal),
active (cleans signal; electronics to amplify signal),
and intelligent (managed & switching hubs).
Switching hub - Intelligent hub, which contains
circuitry that very quickly, routes signals between
ports on the hub. A communications paradigm
in which a dedicated communication path is
established between the sender and receiver
along which all packets travel. The telephone
system is an example of a circuit switched network.
Also called connection-oriented.
MAU - Media Access Unit. In a Token Ring
network, a device to attach multiplenetwork
stations in a star topology, internally wired
to connect the stations into a logical ring.
The MAU contains relays to short out
non-operating workstations. Multiple MAUs
can be connected into a larger ring through
their Ring In/Ring Out connectors. Transceivers
( Transmitter-receiver) . The physical device, which
connects a host interface (e.g. an Ethernet controller)
to a local area network. Ethernet transceivers contain
electronics that apply signals to the cable and sense
other host's signals and collisions.
MAC address - Also known as the physical
addresses, operates on the data link layer.
Each address is a unique 12-digit hexadecimal
ID number, which is hard coded to the network
adapter by the factory , and is used by devices
to direct packets to other devices. Crossover cable
- A cable used to daisy-chain two network hubs
together. Can also be used to connect two PCs
together and eliminate the need for a hub.
Default Gateway - The exit and entry point
of a subnet. Subnetwork - A portion of a network,
which may be a physically independent network
segment, which shares a network address
with other portions of the network and is
distinguished by a subnet number.
A subnet is to a network what a network is
to an Internet.
Connectionless Protocol - The data
communication method in which communication
occurs between hosts with no previous setup.
Packets sent between two hosts may take
different routes. UDP is a connectionless
protocol. Also called packet switching. This is
on contrast to circuit switching, which is
connection-oriented. Connection
-oriented Protocol - A type of transport layer
data communication service that allows a host
to send data in a continuous stream to another host.
The transport service will guarantee that all data
will be delivered to the other end in the same order
as sent and without duplication. Communication
proceeds through three well-defined
phases: connection establishment, data transfer,
and connection release. The most common
example is Transmission
Control Protocol (TCP).
Attenuation - The degrading of a signal as it
travels farther from its origination. Crosstalk
- Signal overflow from one wire to another
adjacent wire. Jitter - Instability in a signal
wave; Caused by signal interference or an
unbalanced FDDI Ring or Token Ring.
NOW WE HAVE FINISHED
THE THIRD LESSON , THE NEXT
LESSON I WILL EXPLAIN THE
PROTOCOLS USED IN NETWORKING .
SEE YOU
Half-duplexing - A communication method,
which can carry data in either direction but not
both directions at once.
Full-duplexing - A term used to describe
a communications channel down which data
can travel in both directions at once.
LAN - Local Area Network. A data
communications network, which is geographically,
limited (typically to a 1 mile radius) allowing easy
interconnection of terminals, microprocessors
and computers within adjacent buildings.
Ethernet, Token-ring, and FDDI are examples
of standard LANs.
which can carry data in either direction but not
both directions at once.
Full-duplexing - A term used to describe
a communications channel down which data
can travel in both directions at once.
LAN - Local Area Network. A data
communications network, which is geographically,
limited (typically to a 1 mile radius) allowing easy
interconnection of terminals, microprocessors
and computers within adjacent buildings.
Ethernet, Token-ring, and FDDI are examples
of standard LANs.
WAN - Wide Area Network. Usually constructed
with serial lines, extending over distances greater
than one mile.
Server - A computer, which provides some service
for other computers, connected to it via a network.
The most commonexample is a file server, which
has a local disk andservices requests from remote
clients to read and write files on that disk.
Workstation - A general-purpose computer
designed to be used by one person at a time
and which offers higher performance than
normally found in a personal computer, especially
with respect to graphics, processing power and the
ability to carry out several tasks at the same time.
A device, which accesses available resources from
servers typically found in a distributed processing
environment .
Host - A computer connected to a network.
The term node includes devices such as routers
and printers, which would not normally be
called "hosts".
Peer-to-Peer Network - A network that does
not rely on the use of a central file server to share
files. Each workstation relies on another workstation
to have it's resources made available. They are very
difficult to maintain security, must be limited
number of peers to keep administration costs low,
slow response time, but they are inexpensive ,
no central point of failure and no special training required.
Server-based network - Requires a central file
server and a networking operating system that can
handle the job. They require a separate machine
and therefore expensive hardware, expensive NOS,
and without the proper training it is difficult to install
and maintain. On the other hand, data transfer speeds
are greater, security is more robust, LAN expansion
is simpler, and there are management tools available.
Cable - provides the pathway for network
communications. It's a component of a topology
determined by the NIC and standard being used.
The most common types of LAN cabling are coaxial,
unshielded twisted pair, shielded twist pair, and fiber optic.
NIC - An adapter circuit board installed in
a computer to provide a physical connection to a network.
Hub - A wiring concentrator for a LAN or WAN
that providesa central attachment point for network
cabling. Coaxial cable doesn't use hubs. There are
three types of hubs:
passive (absorbs some signal; no electronics to
process data signal),
active (cleans signal; electronics to amplify signal),
and intelligent (managed & switching hubs).
Switching hub - Intelligent hub, which contains
circuitry that very quickly, routes signals between
ports on the hub. A communications paradigm
in which a dedicated communication path is
established between the sender and receiver
along which all packets travel. The telephone
system is an example of a circuit switched network.
Also called connection-oriented.
MAU - Media Access Unit. In a Token Ring
network, a device to attach multiplenetwork
stations in a star topology, internally wired
to connect the stations into a logical ring.
The MAU contains relays to short out
non-operating workstations. Multiple MAUs
can be connected into a larger ring through
their Ring In/Ring Out connectors. Transceivers
( Transmitter-receiver) . The physical device, which
connects a host interface (e.g. an Ethernet controller)
to a local area network. Ethernet transceivers contain
electronics that apply signals to the cable and sense
other host's signals and collisions.
MAC address - Also known as the physical
addresses, operates on the data link layer.
Each address is a unique 12-digit hexadecimal
ID number, which is hard coded to the network
adapter by the factory , and is used by devices
to direct packets to other devices. Crossover cable
- A cable used to daisy-chain two network hubs
together. Can also be used to connect two PCs
together and eliminate the need for a hub.
Default Gateway - The exit and entry point
of a subnet. Subnetwork - A portion of a network,
which may be a physically independent network
segment, which shares a network address
with other portions of the network and is
distinguished by a subnet number.
A subnet is to a network what a network is
to an Internet.
Connectionless Protocol - The data
communication method in which communication
occurs between hosts with no previous setup.
Packets sent between two hosts may take
different routes. UDP is a connectionless
protocol. Also called packet switching. This is
on contrast to circuit switching, which is
connection-oriented. Connection
-oriented Protocol - A type of transport layer
data communication service that allows a host
to send data in a continuous stream to another host.
The transport service will guarantee that all data
will be delivered to the other end in the same order
as sent and without duplication. Communication
proceeds through three well-defined
phases: connection establishment, data transfer,
and connection release. The most common
example is Transmission
Control Protocol (TCP).
Attenuation - The degrading of a signal as it
travels farther from its origination. Crosstalk
- Signal overflow from one wire to another
adjacent wire. Jitter - Instability in a signal
wave; Caused by signal interference or an
unbalanced FDDI Ring or Token Ring.
NOW WE HAVE FINISHED
THE THIRD LESSON , THE NEXT
LESSON I WILL EXPLAIN THE
PROTOCOLS USED IN NETWORKING .
SEE YOU
2/15/2008
INTRODUCTION
WELCOME
Welcome to the NETWORKS blog .
Here you will find all you need to
start a new way towards networks
configuration and administration .
You will find a free lessons , free books
and all what you need to be a successful
network administrator .
Thank you for joining me .
Here you will find all you need to
start a new way towards networks
configuration and administration .
You will find a free lessons , free books
and all what you need to be a successful
network administrator .
Thank you for joining me .
LESSON 1 ENGLISH
1.1 What is networking ?
• Users can save their important files and documents
on a file server, which is more secure than storing
them on their workstations because a file server can
be backed up in a single operation.
• Users can share a network printer, which costs
much less than having a locally attached printer for
each user’s computer.
• Users can share groupware applications running on
application servers, which enables users to share
documents, send messages, and collaborate directly.
• The job of administering and securing a company’s
computer resources is simplified since they are
concentrated on a few centralized servers.
• This definition of networking focuses on the basic
goals of networking computers: increased
manageability, security, efficiency, and cost-
effectiveness over non-networked systems.
We could also focus on the different types of networks:
• Local area networks (LANs), which can range
from a few desktop workstations in a small
office/home office (SOHO) to several thousand
workstations and dozens of servers deployed
throughout dozens of buildings on a university
campus or in an industrial park
• Wide area networks (WANs), which might be a
company’s head office linked to a few branch
offices or an enterprise spanning several
continents with hundreds of offices and
subsidiaries
• The Internet, the world’s largest network and the
“network of networks”
We could also focus on the networking architectures
in which these types of networks can be implemented:
• Peer-to-peer networking, which might be
implemented in a workgroup consisting of
computers running Microsoft Windows 98 or
Windows 2000 Professional .
• Server-based networking, which might be based on
the domain model of Microsoft Windows NT, the
domain trees and forests of Active Directory in
Windows 2000, or another architecture such as
Novell Directory Services (NDS) for Novell
NetWare .
• Terminal-based networking, which might be the
traditional host-based mainframe environment;
the UNIX X Windows environment; the terminal
services of Windows NT 4, Server Enterprise
Edition; Windows 2000 Advanced Server .
1.2 Network Operating Systems
-Windows NT
A networking operating system designed using a Directory
to manage certain resources.
NT's primary file system is NTFS. Provides an inherently
GUI console at the server.
Clients - Windows NT Workstation best serves Windows NT
Server because of the common NTFS file system and they
are optimized to work best with each other.
However, Windows95/98, Windows for Workgroups, DOS, UNIX,
Macintosh, and even NetWare clients can be connected to
a Windows NT environment.
-UNIX
UNIX is a command line operating system written in
the C programming language. GUI interface can be
achieved by installing special software such as X-Windows. Used
mainly in a multi-user environment on minicomputers.
Several different version available and allows a great deal
of flexibility when performing network operations.
Many UNIX protocols are the standard for today’s Internet.
Clients - Unix specific clients such as Sun Sparc stations work
best with their manufacturer's Network Operating System (NOS).
-Novell NetWare
A networking operating system designed using a bindery
or Directory Service to manage most resources.
NetWare’s primary file system is a combination of FAT (File Allocation
Table) and DET (Directory Entry Table). Provides an inherently text
based and command prompt console at the server.
Clients - Novell NetWare works well with most popular clients
such as DOS, Windows 3.11, Windows 9x, Windows NT Workstation.
THUS WE HAVE FINISHED THIS LESSON , I AM WAITNG YOUR
QUESTIONS AND SUGGESTIONS , SEE YOU
Networking means connecting computers so that they can
share files, printers, applications, and other computer-
related resources. The advantages of networking
computers together are pretty obvious:
share files, printers, applications, and other computer-
related resources. The advantages of networking
computers together are pretty obvious:
• Users can save their important files and documents
on a file server, which is more secure than storing
them on their workstations because a file server can
be backed up in a single operation.
• Users can share a network printer, which costs
much less than having a locally attached printer for
each user’s computer.
• Users can share groupware applications running on
application servers, which enables users to share
documents, send messages, and collaborate directly.
• The job of administering and securing a company’s
computer resources is simplified since they are
concentrated on a few centralized servers.
• This definition of networking focuses on the basic
goals of networking computers: increased
manageability, security, efficiency, and cost-
effectiveness over non-networked systems.
We could also focus on the different types of networks:
• Local area networks (LANs), which can range
from a few desktop workstations in a small
office/home office (SOHO) to several thousand
workstations and dozens of servers deployed
throughout dozens of buildings on a university
campus or in an industrial park
• Wide area networks (WANs), which might be a
company’s head office linked to a few branch
offices or an enterprise spanning several
continents with hundreds of offices and
subsidiaries
• The Internet, the world’s largest network and the
“network of networks”
We could also focus on the networking architectures
in which these types of networks can be implemented:
• Peer-to-peer networking, which might be
implemented in a workgroup consisting of
computers running Microsoft Windows 98 or
Windows 2000 Professional .
• Server-based networking, which might be based on
the domain model of Microsoft Windows NT, the
domain trees and forests of Active Directory in
Windows 2000, or another architecture such as
Novell Directory Services (NDS) for Novell
NetWare .
• Terminal-based networking, which might be the
traditional host-based mainframe environment;
the UNIX X Windows environment; the terminal
services of Windows NT 4, Server Enterprise
Edition; Windows 2000 Advanced Server .
1.2 Network Operating Systems
-Windows NT
A networking operating system designed using a Directory
to manage certain resources.
NT's primary file system is NTFS. Provides an inherently
GUI console at the server.
Clients - Windows NT Workstation best serves Windows NT
Server because of the common NTFS file system and they
are optimized to work best with each other.
However, Windows95/98, Windows for Workgroups, DOS, UNIX,
Macintosh, and even NetWare clients can be connected to
a Windows NT environment.
-UNIX
UNIX is a command line operating system written in
the C programming language. GUI interface can be
achieved by installing special software such as X-Windows. Used
mainly in a multi-user environment on minicomputers.
Several different version available and allows a great deal
of flexibility when performing network operations.
Many UNIX protocols are the standard for today’s Internet.
Clients - Unix specific clients such as Sun Sparc stations work
best with their manufacturer's Network Operating System (NOS).
-Novell NetWare
A networking operating system designed using a bindery
or Directory Service to manage most resources.
NetWare’s primary file system is a combination of FAT (File Allocation
Table) and DET (Directory Entry Table). Provides an inherently text
based and command prompt console at the server.
Clients - Novell NetWare works well with most popular clients
such as DOS, Windows 3.11, Windows 9x, Windows NT Workstation.
THUS WE HAVE FINISHED THIS LESSON , I AM WAITNG YOUR
QUESTIONS AND SUGGESTIONS , SEE YOU
LESSON 2 ENGLISH
2.1 The OSI Model
*NOTE*
The OSI model graphical explanation is available at this link
http://www.4shared.com/file/37894066/
cbcacee0/The_OSI_Model__1_.html
2.2 Networking Devices
Internetworking devices offer communication between
local area network (LAN) segments. There are five
primary types of internetworking devices:
repeaters, bridges, routers, brouters, and gateways.
The OSI layer at which they establish the LAN-to-LAN
connection can differentiate these devices very generally.
Each device offers the functionality found at its layer(s)
of connection and uses the functionality of all lower layers.
-Repeater (Physical) A network device used to regenerate or
replicate a signal. Repeaters are used in transmission systems
to regenerate analog or digital signals distorted by
transmission loss. Analog repeaters frequently can
only amplify the signal while digital repeaters can
reconstruct a signal to near its original quality.
In a data network, a repeater can relay messages
between subnetworks that use different protocols or
cable types. Hubs can operate as repeaters by
relaying messages to all connected computers. A
repeater cannot do the intelligent routing performed
by bridges and routers.
-Bridge (Data Link) A device that connects two
local-area networks (LANs), or two segments of
the same LAN .
The two LANs being connected can be alike or
dissimilar. For example, a bridge can connect an
Ethernet with a Token-Ring network.
Unlike routers, bridges are protocol independent.
They simply forward packets without analyzing and
re-routing messages. Consequently, they're faster
than routers, but also less versatile.
-Router (Network) A device that connects two LANs.
Routers are similar to bridges, but provide additional
functionality, such as the ability to filter messages
and forward them to different places based on
various criteria.
The Internet uses routers extensively to forward
packets from one host to another.
Brouter Data Link/Network Short for bridge router,
a device that functions as both a router and a bridge.
A brouter understands how to route specific types of packets,
such as TCP/IP packets. Any other packets it receives are
simply forwarded to other network(s) connected to
the device (this is the bridge function).
-Gateway (Top 4 layers) In networking, a combination of
hardware and software that links two different types of networks.
Gateways between e-mail systems, for example,
allow users on different e-mail systems to exchange
messages.
The Open System Interconnection (OSI) Model is a seven
layer model that helps designers of network operating
systems and software to create relatively standardized software.
This is useful when trying to get different operating systems to talk
to each other. Although the model is only a blueprint, it is
almost universally followed.
layer model that helps designers of network operating
systems and software to create relatively standardized software.
This is useful when trying to get different operating systems to talk
to each other. Although the model is only a blueprint, it is
almost universally followed.
*NOTE*
The OSI model graphical explanation is available at this link
http://www.4shared.com/file/37894066/
cbcacee0/The_OSI_Model__1_.html
2.2 Networking Devices
Internetworking devices offer communication between
local area network (LAN) segments. There are five
primary types of internetworking devices:
repeaters, bridges, routers, brouters, and gateways.
The OSI layer at which they establish the LAN-to-LAN
connection can differentiate these devices very generally.
Each device offers the functionality found at its layer(s)
of connection and uses the functionality of all lower layers.
-Repeater (Physical) A network device used to regenerate or
replicate a signal. Repeaters are used in transmission systems
to regenerate analog or digital signals distorted by
transmission loss. Analog repeaters frequently can
only amplify the signal while digital repeaters can
reconstruct a signal to near its original quality.
In a data network, a repeater can relay messages
between subnetworks that use different protocols or
cable types. Hubs can operate as repeaters by
relaying messages to all connected computers. A
repeater cannot do the intelligent routing performed
by bridges and routers.
-Bridge (Data Link) A device that connects two
local-area networks (LANs), or two segments of
the same LAN .
The two LANs being connected can be alike or
dissimilar. For example, a bridge can connect an
Ethernet with a Token-Ring network.
Unlike routers, bridges are protocol independent.
They simply forward packets without analyzing and
re-routing messages. Consequently, they're faster
than routers, but also less versatile.
-Router (Network) A device that connects two LANs.
Routers are similar to bridges, but provide additional
functionality, such as the ability to filter messages
and forward them to different places based on
various criteria.
The Internet uses routers extensively to forward
packets from one host to another.
Brouter Data Link/Network Short for bridge router,
a device that functions as both a router and a bridge.
A brouter understands how to route specific types of packets,
such as TCP/IP packets. Any other packets it receives are
simply forwarded to other network(s) connected to
the device (this is the bridge function).
-Gateway (Top 4 layers) In networking, a combination of
hardware and software that links two different types of networks.
Gateways between e-mail systems, for example,
allow users on different e-mail systems to exchange
messages.
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