1. End devices, also referred as
hosts: The sources and destinations
of the communication (i.e., devices
that generate and transmit
messages or receive and interpret
messages). The devices the end
users are most familiar with. These
devices act as the interface
between the end users and the
underlying network. Examples:
Computers, IP phones, mobile
phones, PDAs, etc.
2. Intermediary devices: Devices that give
network access to the attached end
devices and transport the messages
between hosts. Usually, transparent to the
end users. Also, these devices accomplish
communication functions in order to ensure
the success of the communication process.
Examples: Hubs, switches, routers, modems,
firewalls, etc.
3. Transmission media: The physical
media that connects the devices,
enabling the exchange of messages
between them. It may be wired, that is,
some copper cable (allows the
propagation of electric voltage or
current pulses) or optical fiber cable
(allows the propagation of light pulses),
or wireless, that is, some radio link
(allows the propagation of
electromagnetic waves).
4. Services: Network-aware
software applications (e.g., a web
browser) that request network
resources (e.g., data) in order to
enjoy the end user of the
application some provided service
(e.g., World Wide Web).
5. Processes:
Software that runs
on network devices in
order to support the
communication
functions - in
accordance with the
established, also in
software,
communication rules
or protocols - and
facilitate the provision
of services to the
end users. In
contrast with the
services, processes
are transparent to
the end users.
6. Messages: Well-known applications. Includes telephone calls, e-mail, web pages, etc.
Devices and media are the physical elements or hardware of the network, whereas the
services and the processes are the computer programs or software of the network.
We have to note that modern computer networks are converged data or information
networks, meaning that can carry any type of information (i.e., text, voice, graphics,
video streams, computer data and files) between a wide range of devices (e.g.,
computers, IP phones, PDAs, etc.), and provide previously separate and distinct
conventional communication methods and services, as well as new, alternative
communication forms (e.g., telephony, e-mail, instant messaging, file transfer, printer
sharing, hard disk sharing, collaboration tool, video conference, etc.) onto a common
platform.
Data transmission media
Media transmission Describes the type of physical system used to carry a
communication signal from one system to another. Examples of transmission media
include twisted-pair cable, coaxial cable, and fiber optic cable.:
Networking topologies
Coaxial cable
• Widely installed for use in
business and corporation ethernet
and other types of LANs. •
Consists of inter copper insulator
covered by cladding material, and
then covered by an outer jacket
Optical Fibers
multimodefiberisopticalfiberthatisdesignedto
carry multiple light rays or modes
concurrently, each at a slightly different
reflection angle within the optical fiber core.
used for relatively short distances because
the modes tend to disperse over longer
lengths (this is called modal dispersion) . •
Forlongerdistances,singlemodefiber
(sometimes called monomode) fiber is used.
In single mode fiber a single ray or mode of
light act as a carrier
Wirless LAN
Wireless LAN (802.11b..) : 11 to
108Mbits • HiperLAN (European
standard; allow communication at
up to 20 Mbps in 5 GHz range of
the radio frquency (RF) spectrum.
• HiperLAN/2 operate at about 54
Mbps in the same RF band.
Physical interconnection
structure of the network graph
Type of interconnection:
PAN • SAN / SAN • Local
Area Networks (LAN) •
Metropolitan Area Networks
(MAN) • Wide Area Networks
(WAN)
What is
it?
Computer networking is one of the
most exciting and important technical
fields of our time. Information and
communication are two of the most
important strategies issues for the
success of every enterprise.
A computer network is any combination of
computers and other devices that are
connected by a central Internet signal. Below
are the basic elements of a computer network,
and the setup described is what you’d most
likely use in a home environment.