Created by: Mostafa Ehab El-Nahas
Lecture 1
1. What is network?
֎ A group of 2 or more devices connected together.
2. Why networking?
֎ Sharing data and information
֎ Sharing hardware and software
֎ Centralize administration and support
3. What are the applications of networks?
֎ Resource sharing (Hardware or software)
֎ Communication (Email)
֎ Data and information sharing
֎ Remote computing
4. How many kinds of networks?
֎ Depending on one’s perspective, we can classify networks in different
ways as follows:
֎ Transmission media:
1. Wired
2. Wireless
֎ Network size:
1. LAN
2. MAN
3. WAN
֎ Management method:
1. Peer-to-peer (workgroup)
2. Client/server (Server-based)
֎ Topology:
1. Bus
2. Ring
3. Star (Tree)
4. Mesh
5. Classify networks according to size?
LAN
֎ LAN, shorts for Local Area Network.
֎ Small (short distance) network.
֎ Limited by the number of devices and the covered distance.
֎ Uses a single technology to maintain simplicity,
compatibility, and ease of management.
֎ Ethernet technology is usually the single technology
throughout LAN.
֎ Examples:
1. Network inside a department in an organization.
2. Network inside a room, building or campus.
MAN
֎ MAN, shorts for Metropolitan Area Network.
֎ Spans (Covers) a distance of a metropolitan.
֎ Costs more than LAN.
֎ Examples:
1. Network inside a metropolitan
WAN
֎ WAN, shorts for Wide Area Network.
֎ Spans (Covers) a distance of more than a metropolitan.
֎ Costs more than MAN.
֎ Uses long-range telecommunication links to connect 2 or
more LANs housed in different places far apart.
֎ Examples:
1. Network inside a country.
2. Internet
6. Classify networks according to management method?
֎ Each device is capable of functioning as either a
client (receives data) or a server (sends data).
Peer-to-peer ֎ No hierarchy among devices which means that all
devices are considered equal.
(Workgroup)
֎ No administrator for the network.
֎ Most operating systems come with built-in
peer-to-peer networking capability.
֎ Clients (workstations or hosts) are the devices that
request network resources or services.
֎ Servers are devices that manage the network and
provide network services to clients.
֎ Servers have characteristics which are:
➢ Servers must have more processing power and
Client/Server
memory than clients.
(Server-based)
➢ Run Network Operating System like (Linux) that
can manage not only data, but also users, groups,
security, and applications on the network.
➢ Servers provides centralized control on the
network, as they control security and across them
a network can be shared with other networks.
7. What are the advantages, disadvantages of peer-to-peer and
client/server?
֎ Advantages:
1. Inexpensive and easy to install.
2. Users has full accessibility of the computer.
Peer-to-peer ֎ Disadvantages:
(Workgroup)
1. Difficult to uphold (maintain) security
2. Difficult to handle uneven loading
3. 10 or less users
4. No specialized services
֎ Advantages:
1. Facilitate resource sharing across centrally
administrate and control.
2. Facilitate system backup and improve fault
tolerance.
Client/Server
(Server-based) 3. Enhance security as only administrator can have
access to Server.
4. Support a greater number of users.
֎ Disadvantages:
1. High cost for Servers.
2. Need expert to configure the network.
8. What is network topology?
֎ The network topology defines the way in which computers, printers,
and other devices are connected.
֎ A network topology describes the layout of the wire and devices as
well as the paths used by data transmissions.
9. Classify networks according to topologies?
Bus
֎ Bus topology is also known as linear bus
֎ All the devices are connected by one single cable called
Backbone (trunk or segment) that is ended with
terminators to avoid looping of signal.
֎ There are two methods to construct a bus which are:
1. Using 10Base2 coaxial cable with BNC-T connector
➢ A (Bayonet Neill-Concelman) BNC T-connectors is
connected to the NIC (Network Interface Card) of
each PC.
➢ A thin 10Base2 RG-58 coaxial cable with 10 Mbps
data transfer rate, is passed through the installed
BNC T-connectors.
2. Using 10Base5 coaxial cable with vampire tap
➢ An (Attachment Unit Interface) AUI cable is
connected to the AUI serial port of the NIC
(Network Interface Card) of each PC.
➢ An (Attachment Unit Interface) AUI cable is
connected to the AUI serial port of the NIC
(Network Interface Card) of each PC.
➢ The second end of the AUI cable is connected to
the vampire tap.
➢ A thick 10Base5 RG-8 or RG-11 coaxial cable with
10 Mbps data transfer rate, is punctured by the
vampire tap.
֎ Advantages:
1. Easy to implement and extend.
2. Well suited for temporary networks that must be set
up in a hurry.
3. The cheapest topology to implement
4. Failure of one station does not affect others
֎ Disadvantages:
1. Difficult to administer/troubleshoot
2. Limited cable length and number of stations
3. A cable break can disable the entire network
4. Maintenance costs may be higher in the long run
5. Performance degrades as additional devices are added.
Dual Ring
Ring
֎ In ring, each networked workstation had two connections
one to each of its nearest neighbors.
֎ Data is transmitted unidirectionally around the ring and
in both directions in case of (Dual ring).
֎ Sending and receiving of data takes place by the help of
the TOKEN.
֎ TOKEN is a frame travels around the ring, stopping at
each node. If a node wants to transmit data, it adds
the data as well as the destination address to the frame.
֎ The frame then continues around the ring until it finds
the destination node, which takes the data out of the
frame.
֎ To construct a ring, we connect each NIC for each PC with
Multi-Station Access unit device (MSAU) (MAU) using
MSAU cable.
֎ There are two protocols to transmit digital data in ring:
1. FDDI (Fiber Distributed Data Interface):
➢ A set of ANSI protocols for sending digital data over
fiber optic cable using (dual token ring).
2. SONET (Synchronous Optical Networking)
➢ A set of protocols to transmit multiple large volume
digital data over fiber optic cable for long distances.
֎ Advantages:
1. Very organized.
2. Performance is better than that of Bus topology.
3. No need for network server to control the connectivity
between workstations.
4. Additional components do not affect the performance
of network.
5. Each computer has equal access to resources.
֎ Disadvantages:
1. Each packet of data must pass through all the devices
between source and destination, slower than star
topology.
2. If one workstation or port goes down, the entire
network gets affected.
3. Network is highly dependent on the wire which
connects different components.
Tree
Star
֎ In star, each device is connected to a single point
(Central device) which may be a hub, switch or a router.
֎ All signals transmission through the central device; if
down, entire network down.
֎ Depending on the intelligence of the central device, two
or more devices may send message at the same time.
֎ Each networked device in star topology can access the
media independently.
֎ Star topology becomes the dominant topology type in
contemporary Ethernet LANs.
֎ When installed, the star topology resembles spokes in a
bicycle wheel.
֎ The extended star topology (tree topology), provides an
efficient network structure for larger networks.
֎ In tree, by using network devices like bridges, switches,
and routers, it significantly reduces traffic on the
network by ensuring packets are only sent to their
intended destinations.
֎ Advantages:
1. Compared to Bus topology it gives far much better
performance.
2. Easy to connect new nodes or devices.
3. Centralized management which helps in monitoring
the network.
4. Failure of one node or link doesn’t affect the rest of
network.
֎ Disadvantages:
1. If central device fails whole network goes down.
2. The use of hub, a router or a switch as central device
increases the overall cost of the network.
3. Performance and as well number of nodes which can
be added in such topology is depended on capacity of
central device.
Mesh
֎ The mesh topology connects all devices (nodes) to each
other for redundancy and fault tolerance.
֎ It is used in WANs to interconnect LANs and for mission
critical networks like those used by banks and financial
institutions.
֎ More used in Ad Hoc networks.
֎ Disadvantages:
1. High cost and difficult to install.
2. The chance of redundant connections is high