Computer Network
LECTURE 1
Dr. Samar Shaker
Internet
➢What is the Internet?
Is a world wide network can connect a billion of computing devices.
• Hosts =end system.
• Running network app.
• Communication links (wired-wireless) fiber, copper, radio.
• Transmission rate.
• Bandwidth.
• Packet switches (forward packets of data).
-Switches and routers
Internet is a “network of networks”
• Home networks
• institutional networks
• ISPs (regional-global)
• What’s a protocol?
Rules of communication.
➢Human protocols:
• “what’s the time?”
• “I have a question”
• introductions
… specific messages sent
… specific actions taken when messages received, or other events
• Protocols: control sending and receiving of messages.
- e.g : TCP, IP, HTTP, 802.11
➢Network protocols:
▪ machines rather than humans.
▪ all communication activity in Internet governed by protocols.
❑Definition:
Protocols define the format, order of messages sent and received among
network entities, and actions taken on message transmission.
❑A Closer Look at Network Structure
1. Network Edge
• Hosts: clients and servers
• Servers are often located in data centers
2.Access Networks & Physical Media
• Wired communication links
• Wireless communication links
3. Network Core
• Interconnected routers
• Forms a network of networks
o General purpose computer.
o Special purpose computers.
❖Access Network(Home : Digital Subscriber Line (DSL)
• Uses the existing telephone line to connect to the central office DSLAM.
• Data over DSL line → goes to the Internet.
• Voice over DSL line → goes to the telephone network.
➢Transmission Rates
• Upstream: less than 2.5 Mbps (typically < 1 Mbps).
• Downstream: less than 24 Mbps (typically < 10 Mbps).
➢How It Works
• Voice and data are transmitted at different frequencies over the same
dedicated line to the central office.
• A splitter separates voice (telephone) and data (Internet).
• At the central office, a DSL Access Multiplexer (DSLAM) routes:
• Voice → Telephone network
• Data → Internet Service Provider (ISP)
Classification of Network
NETWORK
PAN LAN WAN MAN
PERSONAL AREA NETWORK(PAN)
✓A personal area network is a computer network
organized around an individual person.
✓It generally consists of a mobile, a computer, a cell
phone or personal digital assistant. PAN enables the
communication among these devices.
✓It can also be used for communication among
personal devices themselves for connecting to a digital
level network and internet.
✓The PANs can be constructed using wireless or
cables.
PERSONAL AREA NETWORK(PAN)
LOCAL AREA NETWORK(LAN)
✓LAN is a network which is designed to operate over a
small physical area such as an office, factory or a group
of buildings.
✓LAN’s are easy to design and troubleshoot.
✓Exchange of information and sharing of resources
becomes easy because of LAN.
✓In LAN all machines are connected to a single cable.
✓Different types of topologies such as star, tree, bus,
ring, etc Can be used.
LOCAL AREA NETWORK(LAN)
✓It is usually a privately owned network.
WIDE AREA NETWORK(WAN)
✓When network spans over a large distance or when the
computers to be connected to each other are at widely
separated locations a local area network cannot be used. A
wide area network(WAN) is installed.
✓The communication between different users of WAN is
established using leased telephone lines, satellite links and
similar channels.
WIDE AREA NETWORK(WAN)
✓Most WAN networks are used to transfer large blocks of
data between its users.
MAN (Metropolitan Area Network)
•Definition:
A MAN is larger than a LAN (Local Area Network) but smaller than a
WAN (Wide Area Network).
It usually spans a few kilometers to about 50 km.
•Purpose:
It connects multiple LANs within a city or metropolitan area so that
different organizations, offices, or buildings can share resources
efficiently.
•Examples:
• A city-wide cable TV network.
• High-speed internet provided across a city by an Internet Service
Provider (ISP).
METROPOLITAN AREA NETWORK (MAN)
DISTINGUISH BETWEEN
LAN,WAN,MAN
PARAMETERS LAN WAN MAN
Ownership of
Private Private or public Private or public
network
Geographical area
Small Very large Moderate
covered
Design and
Easy Not easy Not easy
maintenance
Coaxial cables,
Communication PSTN or satellite
Coaxial cable PSTN, optical fibre,
medium links
cables, wireless
Bandwidth Low High moderate
Data rates(speed) High Low moderate
Thank you
