The document discusses computer networks and networking concepts. It begins by describing networks as systems of senders and receivers and defining nodes. It then covers different types of networks (LAN, WAN, MAN), topologies (bus, ring, star, mesh), and networking devices (hubs, bridges, switches, routers). It also provides an overview of the OSI model and its seven layers. Finally, it discusses some important networking protocols like IP and routing.

2.  The network is a crucial component of
today’s computing systems.
 Resource sharing across networks has taken
the form of multitier architectures having
many different servers.
 If you think of a computing system as
collection of workstations and servers, then
surely the network is the transportation of this
configuration.

3.  A network is, fundamentally, a system of
senders and receivers – a common feature
of any communication system.
 The sender, or source, is a computer which
sends information to another.
 The receiver, or destination computer, is the
computer to which the information is sent.
 Any machine capable of communicating on
the network is a device or node.

5. There are THREE types of network available
 Local Area Networks (LAN)
 Wide Area Networks (WAN)
 Metropolitan Area Networks (MAN)

6.  Used in small geographical areas like Building or
Campus.
 Offer high-speed communications (10/100/1000Mbps)
 Provide access to many devices
 Use LAN-specific devices such as Hubs, Switches
and network interface cards

7.  Cover large areas – may span the world
 Compared to LANs – slow speed communication
 Access to WANs is limited – a LAN will access a WAN
through a single point (often a bottleneck)
 Will use devices such as routers, modems and WAN
switches

8.  Made up of LANs which are interconnected across a
metropolitan area
 Also may appeal to regional businesses
 Gives access speeds in hundreds of megabits per
second (or even gigabits speeds)
 Uses a single connection point to connect LANs
 As well as using routers will also use switches

9.  Bus Topology
 Ring Topology
 Star Topology
 Mesh Topology

10.  Network maintained by a single cable
 Cable segment must end with a terminator
 Uses thin coaxial cable (backbones will be thick
coaxial cable)
 Extra stations can be added in a daisy chain manner

11. Advantages
 Inexpensive to install
 Easy to add stations
 Use less cable than
other topologies
 Works well for small
networks
Disadvantages
 No longer recommended
 Backbone breaks, whole
network down
 Limited no of devices
can be attached
 Difficult to isolate
problems
 Sharing same cable
slows response rates

12.  No beginning or end (a ring in fact !!)
 All devices of equality of access to media
 Single ring – data travels in one direction only, guess
what a double ring allows !?
 Each device has to wait its turn to transmit

13. Advantages
 Data packets travel at
great speed
 No collisions
 Easier to fault find
 No terminators required
Disadvantages
 Requires more cable
than a bus
 A break in the ring will
bring it down
 Not as common as the
bus – less devices
available

14.  Like the spokes of a wheel (without the symmetry)
 Centre point is a Hub
 Segments meet at the Hub
 Each device needs its own cable to the Hub
 biggest type of topology
 Easy to maintain and expand

15. Advantages
 Easy to add devices as the
network expands
 One cable failure does not
bring down the entire
network (resilience)
 Hub provides centralised
management
 Easy to find device and
cable problems
 Can be upgraded to faster
speeds
Disadvantages
 A star network requires
more cable than a ring or
bus network
 Failure of the central hub
can bring down the entire
network
 Costs are higher
(installation and
equipment) than for most
bus networks

16.  Not common on LANs
 Most often used in WANs to interconnect LANS
 Each node is connected to every other node
 Allows communication to continue in the event of a
break in any one connection
 It is “Fault Tolerant”

17. Advantages
 Improves Fault
Tolerance
Disadvantages
 Expensive
 Difficult to install
 Difficult to manage
 Difficult to troubleshoot

18.  Hubs
 Bridges
 Switches
 Routers

19.  A central point of a star topology
 Allows the multiple connection of devices
 Can be more than a basic Hub – providing additional
services (Managed Hubs, Switched Hubs, Intelligent
Hubs)
 In reality a Hub is a Repeater with multiple ports
 Functions in a similar manner to a Repeater
 Works at the Physical Layer of the OSI model
 Passes data no matter which device it is addressed to

20.  Advantages – Cheap, can connect different media
types
 Disadvantages – Extends the collision domain, can
not filter information, passes packets to all connected
segments

21.  Like a Hub it connects segments
 Works at Data Layer – not Physical
 Uses Mac address to make decisions
 Acts as a ’filter’, by determining whether or not to
forward a packet on to another segment
 Builds a Bridging Table, keeps track of devices on
each segment
 It forwards packets whose destination address is on
a different segment from its own
 It divides a network in to multiple collision domains –
so reducing the number of collisions

22.  Advantages – Limits the collision domain, can extend
network distances, uses MAC address to filter traffic,
eases congestion, can connect different types of
media, some can connect differing architectures.
 Disadvantages – Broadcast packets can not be
filtered, more expensive than a repeater, slower than
a repeater – due to additional processing of packets.

23.  A multiport Bridge, functioning at the Data Link Layer
 Each port of the bridge decides whether to forward
data packets to the attached network
 Keeps track of the Mac addresses of all attached
devices (just like a bridge)
 Acts like a Hub, but filters like a Bridge
 Each port on a Switch is a collision domain

24.  Advantages - Limits the collision domain, can
provide bridging, can be configured to limit broadcast
domain
 Disadvantages – More expensive than a hub or
bridge, configuration of additional functions can be
very complex

25.  Works at Network Layer in an intelligent manner
 Can connect different network segments, if they are
in the same building or even on the opposite side of
the globe
 Work in LAN, MAN and WAN environments
 Allows access to resources by selecting the best
path
 Can interconnect different networks – Ethernet with
Token Ring
 Changes packet size and format to match the
requirements of the destination network

26.  Advantages – Limits the Broadcast domain, can
function in LAN or WAN, connects differing media
and architectures, can determine best path/route,
can filter broadcasts
 Disadvantages – Expensive, must use routable
protocols, can be difficult to configure (static routing),
slower than a bridge

28.  The OSI model was developed to enable different
manufacturers networking products to work together.
 For a variety of reasons, the model was never widely
implemented.
 However it is used widely in colleges to teach
network layers and by companies to describe their
products.
 The OSI reference model defines 7 layers for network
communication - each layer defines a particular
network function.

29.  It breaks network communication into smaller simpler
parts.
 It standardizes network components to allow multiple-
vendor development and support.
 It allows different types of network hardware and
software to communicate with each other.
 It prevents changes in one layer from affecting the
other layers, so that they can develop more quickly.
 It breaks network communication into smaller parts to
make learning it easier to understand.

31.  The lowest, bottom, layer – responsible for the
physical connection between devices
 The NIC converts the data (bits) in to transmission
signals.
 Transmissions may be analogue or digital
 Responsible for the rate of transmission
 Includes all components such as the type of
connector (RJ-45, Token Ring, BNC, SC connector)
 Devices at this level include NICs, repeaters, hubs
and concentrators

32.  The data link is responsible for node to node validity
and integrity of the transmission
 The data link layer uses MAC, or hardware addresses
for communication.
 LAN communications, each machine on the same
connected media type needs a unique MAC address.
 A MAC address is 48 bits as 12 characters length in
hexadecimal number.

33.  Each host on segments needs a unique host number
from within the assigned network number. (IP
Address)
 The combination of the network and host number
assigned to a device provides a unique layer-3
address throughout the entire network.
 IP is 32 Bit Dotted decimal Number.
 The network layer supports both connection-orientated
and connectionless service from higher-layer
protocols.
 Network-layer protocols typically are routing protocols.

34.  It sets up and maintains a session connection between
two devices.
 It can provide for the reliable or unreliable delivery of
data across this connection. (TCP, UDP)
 Transport-layer functions typically include flow control,
virtual circuit management (Ports or Threads), and
error checking and recovery using checksum.
 Ensure Delivery of entire file or message
 The lowest layer that have any awareness of Network

35.  The Session layer arbitrates the dialogue between two
communicating nodes, opening and closing that
dialogue as necessary.
 It controls the direction and mode (half -duplex or full-
duplex).
 It also supplies recovery checkpoints during file
transfers.
 Responsible for
 Handshaking, Keep alive message, Session
termination
 Dialog Control (Simplex, Half duplex, Full Duplex)
 Example : NFS, SQL, RPC

36.  When data are transmitted between different types of
computer systems, the presentation layer negotiates
and manages the way data are represented and
encoded.
 For example, it provides a common denominator
between ASCII and EBCDIC machines formats.
 Tasks like Data Compression, Decompression,
Encryption, Decryption are associated with this layer.
 Also associated with Multimedia operations.
 Examples of presentation layer protocols and
standards include ASCII, BMP, GIF, JPEG, WAV, AVI,
and MPEG.

37.  ‘Closest’ layer to the user
 Works with the applications you use to communicate
over the network
 This interface can be command-line-based or
graphics-based.
 The most common are telnet, FTP, web browsers, and
e-mail.

38.  One of the most important protocols.
 Main purpose is to provide logical addressing through
the use of an IP address.
 Uses IP address to route information between
networks, therefore every device requires a unique
address.
 Developed to function within a UNIX environment in
the days of ARPAnet.

39.  require connect different network segments.
 Routing can be done over the LAN, WAN or MAN
 Routing table is use to route the packet across the
networks.
 Route added can be added 2 ways.
 Static Routes : routes are manually configured by a
network administrator.
 Dynamic Routes : adjust automatically to changes in
network topology, and information it receives from
other routers.