Host-to-communication

1. UNIMTECH
LECTURE 2: COMPUTER NETWORKS & SECURITY
HOST-TO-HOST COMMUNICATION

2. Outline
Network Communication:
-Physical Addressing (MAC)
-Logical Addressing (IP)
OSI Internetworking Model - Importance
TCP/IP Model
IP communication Types
-Unicast
-Multicast
-Broadcast:
-Anycast

3. Network Communication
Entails two addressing concepts:
Physical Addressing (MAC Addresses)
Logical Addressing: We shall focus on IPv4 at this level of the course.
ANATOMY OF A MAC ADDRESS
A MAC address is a 48-bit length address, normally expressed in hexadecimal. It is
physically burned into all network communication devices. Computers use MAC
addresses to communicate with each other on a network. It is divided into two parts:
The first 24-bits are referred to as Organisation Unique Identifier (OUI); whereas
the remainder 24 are the serialization of the MAC address by a specific vendor. Note
that in dissimilar networks involving end to end communication, the MAC address
always change between two points during the course of the communication process.
NB: Command to view MAC address on windows : ipconfig /all from the cmd
interface.

4. Logical Addressing – IP Addressing
Format:
It constitutes 4 dotted numbers/octets; ranging from 0 – 255:
Example: 10.0.1.3
An IP address is always combined with a subnet mask and typically with a
default gateway
Example
IP: 10.0.1.3
Mask: 255.255.255.0
Default Gateway: 10.0.1.1
The Subnet Mask informs which portions of the IP address represent the
‘network’ and ‘host’.
Command to view IP address configuration on windows : ipconfig from the cmd
interface.

5. Demonstration of The Two Address Concepts in
Networks
Whilst IP addresses uniquely identify nodes on a network, they
exclusively communicate/speak to each other through their MAC
addresses!
Hypothetical Networks: 10.0.1.0, 10.0.2.0, 10.0.3.0, 10.0.4.0, 10.0.5.0-
255.255.255.0
Practically explained using the scenarios of:
i) copying a zipped file on a local network between a PC and a
server
ii) copying a zipped file from a PC to a server in a different
network

6. OSI Internetworking Model - Importance
The OSI model is a conceptual framework that depicts end-to-end
communication between end points. As a standardized architecture,
it defines network communication.
It provides a system to breakdown network communication
A standard for manufacturing equipment
Allows vendors to focus on specific areas of network
Mnemonic: ‘All People Seem To Need Data Processing’
‘Please Do Not Throw Sausage Pizza Away’

7. Understanding The Layers of The OSI Model
Application Layer
Provides an interface for applications to communicate across the network
Provides network access to network aware applications like web browsers.
Presentation Layer
It ‘generifies’ the data: That is formatting the data in such a way it is
understandable by the other end of the communication e.g. http, jpeg, etc.
It executes encryption functions as well.
Session Layer
Starts and ends sessions
Logically keeps sessions separate
N.B: It is worth noting that the top three layers, as discussed above, occurs
within the operating system of the node and of course least important to a
network engineer. The bottom four layers, discussed next, are the most
important as the job of a network engineer are defined in these four layers

8. Understanding the OSI Layers Cont’d.
Transport Layer
 It dictate how the data is sent by using the two protocols of TCP and UDP. These two respectively send data reliably or unreliably.
Programs, like VoIP, that run real-time typically choose unreliable communication.
 It defines ‘well known’ services (port numbers) by designating specific functions that run on a server or workstation.
In summary, it entails a choice between protocols (TCP/UDP) and Port Numbers
Network
 It provides ‘logical addressing’, popularly known as IP addressing
 It determines the best path to a destination by means of routing tables.
Data Link Layer
 It provides ‘physical addressing’ or ‘MAC addressing’. It’s physical because it’s burned into the NIC of the computing device
 It ensures that the data is ‘error-free’. As data traverses the network, this layer puts a check on it known as FCS to ensure that it
remains the same at the other end.
Physical Layer
Provides physical access to the cable
It combines all the ‘glossy’ applications and features into electrical signals of 0s and 1s.

9. TCP/IP (DoD) MODEL
The OSI Model describes how network communication occurs whilst the TCP/IP is how it is done!

10. IP Communication Types
Unicast : One-to-one communication between two hosts. It’s the most
predominant type of IP communication on a network. E.g. Preconfigured IP
Phone communication to a call manager on a network
Multicast: One to many communication where a single message is sent out
to a group. E.g. Music on hold in IP Teletphony, Using imaging software for
faster installation, etc
Broadcast: One to all. e.g DHCP, ARP
Anycast: One to closest. An IPv6 technology that has been adapted in IPv4
to allow having two or more servers having the same address in distant
locations over the Internet order to facilitate for clients to access the closest
resource. The routing of which is done to achieve better network latency
and minimise delays in network communication when a client requests the
resource.