2. Objectives
Types of Networks
3-Layers Network Design Model
Collision Domain vs Broadcast Domain
Carrier Sense Multiple Access with Collision
Detection (CSMA/CD)
The Layered Approach
6. Classification of Computer Networks
Computer networks are classified based on
various factors. They includes:
Geographical span
Inter-connectivity
Administration
Architecture
8. Personal Area Network
personal to a user
connectivity range up to 10 meters
E.g. wireless computer keyboard
and mouse, Bluetooth enabled
headphones, wireless printers and
TV remotes
9. Local Area Network
spanned inside a building
an organization’ offices, schools,
colleges or universities
mostly operates on private IP
addresses
Ethernet is most widely employed
LAN technology and uses Star
topology
12. Metropolitan
Area Network
A Network Located within the
boundary of a metropolitan city is
called MAN usually connected
through MAN service provider.
13. Wide Area Network
Covers a wide area which may
span across provinces and
even a whole country
connectivity to MANs and
LANs
14. Wide Area
Network
When we communicate by using
the services offered by some
service provider, that
communication is called WAN.
15. Comparison
LAN
Confined to small areas i.e., it
connects several devices over a
distance of 5 to 10 km.
High speed.
Most inexpensive equipment.
Low error rates.
Data and hardware sharing
between users owned by the user.
Operates at speeds ranging from
10Mbps to 100Mbps. Now days
1000 Mbps are available.
MAN
Confined to a larger area than
a LAN and can range from
10km to a few 100km in
length.
Slower than a LAN but faster
than a WAN.
Operates at a speed of 1.5 to
150 Mbps.
Expensive equipment.
Moderate error rates.
WAN
A WAN can range from 100km to
1000km and the speed between
cities can vary form1.5 Mbps to 2.4
Gbps.
WAN supports large number of
computers and multiple host
machines.
Various segments of network are
interconnected using sophisticated
support devices like routers and
gateways.
Usually the speed is much slower
than LAN speed.
Highest possible error rate
compared to LAN & MAN.
21. The Core Layer
The core layer is responsible for transporting large amounts of traffic both reliably and
quickly.
The only purpose of the network’s core layer is to switch traffic as fast as possible.
Things we don’t want to do:
Never do anything to slow down traffic
Don’t support workgroup access here
Avoid expanding the core
Things that we want to achieve:
Design the core for high reliability
Design with speed in mind
Select routing protocols with lower convergence times
22. The Distribution Layer
The distribution layer is sometimes referred to as the workgroup layer and is
the communication point between the access layer and the core.
Functions of the distribution layer are:
Routing
Implementing tools (such as access lists), packet filtering, and queuing
Implementing security and network policies, including address translation and
firewalls
Redistributing between routing protocols, including static routing
Routing between VLANs and other workgroup support functions
Defining broadcast and multicast domains
23. The Access Layer
The access layer controls user and workgroup access to internetwork resources.
The access layer is sometimes referred to as the desktop layer.
The following are some of the functions to be included at the access layer:
Continued (from distribution layer) use of access control and policies
Creation of separate collision domains (micro segmentation/switches)
Workgroup connectivity into the distribution layer
Device connectivity
Resiliency and security services
Advanced technology capabilities (voice/video, etc.)
25. Ethernet Networks
Ethernet is a contention-based media access method that allows all hosts
on a network to share the same link’s bandwidth.
Ethernet is a family of technologies that provides data-link and physical
specifications for controlling access to a shared network medium.
Ethernet has several benefits:
Simple to install and manage
Inexpensive
Flexible and scalable
Easy to interoperate between vendors
26. Ethernet Cabling Types
Ethernet can be deployed over
three types of cabling:
Coaxial cabling
Twisted-pair cabling
Fiber optic cabling
27. Ethernet Cabling Types: Co-axial
1. Thinnet
2. Thicknet
Thicknet has a wider diameter and more shielding, which
supports greater distances. However, it is less flexible
than the smaller thinnet, and thus more difficult to work
with. A vampire tap is used to physically connect devices
to thicknet, while a BNC connector is used for thinnet.
28. Ethernet Cabling Types: Twisted-pair
1. UTP (unshielded)
2. STP (shielded)
There are several categories of twisted-pair cable:
Category 3 or Cat3: three twists per inch.
Cat5: five twists per inch.
Cat5e: five twists per inch; pairs are also twisted around each
other.
Cat6: six twists per inch, with improved insulation.
An RJ45 connector is used to connect a device to a twisted-pair
cable.
40. Remember That!
Routers separate broadcast and collision domains.
Switches separate collision domains.
Hubs belong to only one collision domain.
Switches and hubs both only belong to one
broadcast domain.
42. CSMA/CD
Ethernet networking uses a protocol called Carrier
Sense Multiple Access with Collision Detection
(CSMA/CD), which helps devices share the
bandwidth evenly while preventing two devices from
transmitting simultaneously on the same network
medium.
43.
44. CSMA/CD
When a collision occurs on an Ethernet LAN, the
following happens:
A jam signal (32-bits) informs all devices that a collision
occurred.
The collision invokes a random backoff algorithm.
Each device on the Ethernet segment stops transmitting for a
short time until its backoff timer expires.
All hosts have equal priority to transmit after the timers have
expired.
47. Why layered communication?
To reduce complexity of communication task
by splitting it into several layered small tasks
Each layer has its own task
Each layer has its own protocol
