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Module 6
Networking
Why Network?
Despite the costs of implementation and
maintenance, networks actually save
organizations money by allowing them to:
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Consolidate (centralize) data storage
Share peripheral devices like printers
Increase internal and external communications
Increase productivity and collaboration
Networking
A network is a group of computers that can share
information through their interconnections.
1. Computers (nodes or hosts).
2. Transmission media provides a path for electrical signals
between devices.
3. Network interfaces are devices that send and receive
electrical signals.
4. Protocols are rules or standards that describe how hosts
communicate and exchange data.
Networking
Network
Type
Description
Peer-to-peer
In peer-to-peer networking (also called workgroups), each computer
controls access to its own resources. Security controls on each
computer identify who can have access to the computer's resources.
•In client/server networking, shared resources reside on special
computers called servers. Other computers, called clients connect to
the server to access resources. Security controls on the server identify
which clients can have resource access.
Client/server
Windows computers use the concept of a domain for client/server
networking. The domain identifies a group of computers with the
same security and administrative boundaries. Active Directory is a
service that provides a centralized database of resources within a
domain.
Protocols
A protocol is a rule that identifies some aspect of how computers
communicate on a network. For two computers to communicate, they
must be using the same protocols. Protocols are grouped into
protocol suites, or sets of related protocols.
• Virtually all operating systems today provide native (built-in)
support for TCP/IP.
• Most older versions of some operating systems used a different
protocol as the default protocol suite. For example, older NetWare
servers used IPX/SPX, while Mac OS systems used AppleTalk.
– Older operating systems without native TCP/IP support enabled TCP/IP
communications by either installing the protocol stack or through a
process known as encapsulation or tunneling. With this process, nonTCP/IP packets are re-packaged as TCP/IP packets at the sending
device. The receiving device strips off the TCP/IP headers to reveal the
original packets.
Protocols
Protocol
Description
HTTP
HyperText Transfer Protocol is used by Web browsers and Web servers to
exchange files (Web pages) through the World Wide Web and
intranets. HTTP can be described as an information requesting and
responding protocol.
HTML
HyperText Markup Language is a data format that is used to create
hypertext documents that can be viewed from multiple platforms.
HTML has become a common language used for programming information
in a format that is readable by web browsers.
DNS
Domain Name System is a system that is distributed throughout the
Internet to provide Host name/IP address resolution. For example, the
name www.mydomain.com would be identified with a specific IP address.
Protocols
Protocol
Description
Telnet
Remote Terminal Emulation allows an attached computer to act as a
dumb terminal, with data processing taking place on the TCP/IP host
computer.
SSH
Secure Shell allows for secure interactive control of remote systems.
SSH is a secure and acceptable alternative to Telnet.
SSL
Secure Sockets Layer secures messages being transmitted on the Internet.
It uses RSA for authentication and encryption. Web browsers use SSL
(Secure Sockets Layer) to ensure safe Web transactions.
URLs that begin with https:// trigger your Web browser to use SSL.
HTTPS
HyperText Transfer Protocol over Secure Socket Layer or HTTP over SSL.
HTTPS is a secure form of HTTP that uses SSL as a sublayer for security.
Addressing
Network devices use addresses to identify other devices. These
addresses are used to send and receive packets of electronic data over
the network. The addresses used depend on the physical make-up of
the network as well as the protocol suite being used.
Each network device is identified using a:
• physical address or MAC (like a serial number)
• logical network address (subnet) identifies a network segment.
– All devices on the same network segment share the same logical
network address.
• logical host address (name) identifies a specific host on the
network.
– Each device must have a unique logical host address.
Physical Addressing (MAC)
Each network device is identified using a physical address.
Ethernet networks use a MAC Address (physical device address)
• The MAC address is a unique hexadecimal identifier burned into the
ROM (physically assigned address) of every network interface.
• When you change the network card, the host will have a new physical
device address.
• When you move a device to another network, the physical address
remains the same (as long as the network card has not been changed).
• The MAC address is guaranteed unique through design.
– The first half (first 6 digits) of the MAC address is assigned to each
manufacturer.
– The manufacturer determines the rest of the address, assigning a
unique value which identifies the host address.
Logical Network Address
With TCP/IP, the logical network and logical host addresses are
combined into a single address called the IP address.
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An IP address is a 32-bit binary number represented as four octets (four 8-bit
numbers). Each octet is separated by a period.
A subnet mask is used to differentiate the network and host addresses.
Each IP address has a default class that includes a default subnet mask value.
The class defines the default network address portion of the IP address.
For example, an IP address of 192.168.6.11 with a default mask of 255.255.255.0.
The network address is 192.168.6.0 and the host address is 11.
Instead of using the default subnet mask, you can use custom subnet masks to
define different network addresses. This process is called subnetting.
Note: The address range from 0.0.0.0 to 0.255.255.255 is reserved for broadcast
messages to the current network. The address range from 127.0.0.0 to
127.255.255.255 is reserved for loopback addresses to the local host.
Logical Host Address
• Humans remember names (or hostnames) much easier than
numbers (especially binary numbers).
• A hostname is a label (name) assigned to a device connected
to a computer network.
• Hostnames are used to identify the device in a Domain Name
System (DNS) such as the World Wide Web.
• Hostnames that include DNS domains are often stored in the
Domain Name System together with the IP addresses of the
host they represent for the purpose of mapping the hostname
to an address, or the reverse process.
Networking Devices
Component
Description
The networking medium is the pathway for signals to pass between two
devices.
Media
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Copper cables use electrical signals.
Fiber optic cables use light pulses.
Wireless networks use radio waves with the air being the transmission medium.
A network adapter creates the signals that are sent along the networking
medium.
Network
adapter
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The term network interface card (NIC) typically describes an adapter that uses a
cable medium (such as copper or fiber optic cables).
A modem (modulator/de-modulator) converts binary data to an analog signal.
A wireless network adapter sends radio waves.
Networking Devices
Component
Description
Hub
A hub provides a central connection for multiple media
segments on the same subnet.
•The hub repeats a signal received on one port out all other
ports.
•Hubs operate in half-duplex mode because the path
between devices is shared and can only send when no other
devices are sending data.
Bridge
A bridge connects two segments within the same subnet that
use different media types. For example, use a bridge to
connect wireless clients to wired clients on the same
network.
Networking Devices
Component
Description
A switch provides a central connection for multiple media
segments on the same subnet.
Switch
•The switch receives a signal on one port, and forwards that signal only
to the port where the destination device is connected.
•Switches use the MAC address to send frames to the destination
device.
•Switches can operate in full duplex mode where a device uses a
different channel for sending and receiving, and where the transmission
paths are dedicated to only the communicating devices.
•When possible, use switches instead of hubs.
Networking Devices
Component
Description
A router connects two network segments that have a different
subnet addresses.
Router
•A router has multiple network connections, with each connection
being on a different subnet.
•Routers use the IP address within a packet to move packets between
networks.
•Routers maintain a list of known networks and the next router in the
path to reach the destination network.
Networking Standards
Method
Ethernet
Wireless
Dialup
Description
Ethernet is the most common local area networking standard for wired networks.
Ethernet can use copper and fiber optic cables. Ethernet uses network interface
cards, hubs, switches, and routers to connect devices.
Wireless networking uses radio waves for sending network data within a local area
network. An access point with an integrated router allows wireless clients to
communicate with hosts on different networks (such as the Internet).
A dialup connection uses a modem connected to the phone line to communicate with
another host through a wide area connection.
•Dialup connections are available anywhere a dialup telephone line exists.
•Data transfer rate 56 Kbps.
•Dialup connections cannot be used for both voice (phone calls) and data at the same
time.
Networking Standards
Method Description
Digital Subscriber Line provides broadband digital data transmission over existing
telephone lines. A DSL router (sometimes called a DSL modem) connects the computer to
(DSL)
the telephone line. DSL is not available to every location; the end location must be within
a fixed distance of telephone switching equipment.
Cable networking uses a cable TV connection to create a wide area connection to the
Cable
Internet. A cable modem (router) connects the computer to the cable network for
sending networking signals.
Cellular networking uses a digital mobile phone for Internet access. Mobile phones with
Cellular digital data plans use cellular calls to connect to the Internet. You can install a cellular
adapter in a notebook computer to provide cellular access.
Satellite networking uses radio signals sent and received from a satellite. Requires direct
Satellite line of sight (dish placement is crucial). Is subject to mild atmospheric and weather
conditions (fog or slight wind can disrupt service). Provides nearly 100% global coverage.
Coaxial Cable
Coaxial cable is an older technology that is
usually implemented with a bus topology.
Advantages
• Highly resistant to Electromagnetic Interference (EMI)
• Highly resistant to physical damage
Disadvantages
• Expensive
• Inflexible construction (difficult to install)
• Unsupported by newer networking standards
Twisted Pair cable
Twisted pair cables support a wide variety of
fast, modern network standards
Advantages
• Inexpensive compared to other media types
• Easy to install and manage
• Very common (media and tools are easy to obtain)
Disadvantages
• Most susceptible to EMI of all the media types
• Cables are more easily damaged than other types
Fiber Optic Cable
With fiber optic cabling the plastic or glass core
carries the signal.
Advantages
• Totally immune to Electromagnetic Interference (EMI)
• Highly resistant to eavesdropping
• Supports extremely high data transmission rates
• Allows greater cable distances without a repeater
Disadvantages
• Very expensive
• Difficult to work with and requires special training