Question

1.) In your own words, explain the how IP addressing is implemented in a network infrastructure. Why is it important to know Subnetting and VLSM?

2.) Explain Functions at the OSI and TCP/IP Model Layers.

Answer 1

Question 1.

IP Address:

An IP address is an identifier or label used to identify a machine on the internet or a particular network. Each of the devices on the internet must have an IP address for identification.

IPv4 is the first version of Internet Protocol that uses a 32-bit address and this protocol is most widely used.

Total number of IP address supported by IPv4 = 2³²

The netmask and subnet mask is used to divide the IP address as given below:

The netmask is a sequence of '1' followed by a sequence of '0' and it is used to divide an IP address into multiple subnets.

The subnet mask is a sequence of '1' followed by a sequence of '0' and it is used to separate a big network into smaller multiple networks.

The subnet mask is used to separate the IP address into a network address and host address.

It is made by setting '1' to all network bits and '0' to all host bits. In a network, the first and last IP addresses are used for the special purpose and the remaining addresses are used as a host address.

In VLSM(Variable Length Subnet Mask), subnetting is done multiple times as given below:

193.62.83.0/23

193.62.83.0/24

193.62.83.0/25

For example:

Let us suppose the given IP address is:

193.62.83.0/23

The netmask in binary representation will be:

11111111 11111111 11111110 00000000

The netmask in decimal representation will be:

255 255 254 0

Here, 23 bits are used for network id, and the last 9 bits are used for host id.

Total number of IP addresses will be = 2⁹ = 512

In a network, the first and last IP addresses are used for the special purpose and the remaining addresses are used as a host address.

The total number of the host in this network will be = 512 - 2 = 510

Question 2.

OSI Model:

This model contains seven layers.

The seven layers are:

1. Application layer
2. Presentation layer
3. Session layer
4. Transport layer
5. Network layer
6. Datalink layer
7. Physical layer

The application layer is the topmost layer and it provides end-user access. This layer controls the communication to the devices and data is presented in visual form to the end-user.

The presentation layer is responsible for the translation, encryption, and compression of the data. The presentation layer is the sixth layer or the uppermost second layer of the OSI model. This layer is also known as the syntax layer as well. At the sender, end data is encrypted for security reasons and then decrypted at the receiver end.

The main responsibilities of the presentation layer are given below:

• Conversion and translation
• Encryption and Decryption
• Compression

The session layer is responsible for the session establishment, maintain and synchronize the interaction between the devices.

The transport layer is responsible for the end to end communication between the sender and receiver over the internet. It provides logical communication between the sender and receiver and ensures the end to end delivery of the packet. The header of this layer contains the port address of the sender and receiver and divides the stream of bytes received from the upper layer into segments.

The transport layer main protocols are:

• TCP(Transmission Control Protocol)
• UDP(User Datagram Protocol)
• SCTP(Stream Control Transmission Protocol)

The network layer is responsible for the internetworking, addressing, routing, and packetizing of the data.

The data link layer is responsible for framing the data and identify each device uniquely on a network.

This layer has two sublayers:

1. Logical Link Control layer
2. Media Access Control Layer

The functions of the MAC sublayer are given below:

1. This layer is a sublayer of the data link layer and it encapsulates the data frame so that it can be moved over a physical medium and provide the abstraction of the physical layer.
2. It is responsible for moving the packet across a shared network and perform collision resolution by retransmission if a collision occurs.

At the physical layer, the data is transmitted and received over the physical network and this layer is the lowest layer. This layer is responsible for the data transfer on a directly attached network.

This layer knows the details of the underlying network and formats the data.

This layer converts the data into an electrical pulse and checks for errors on incoming frames.

TCP/IP Network Model:

TCP/IP stands for Transmission Control Protocol / Internet Protocol is a network model that is used as an architectural model for the current internet architecture. This contains four layers.

The four layers are:

1. Application layer
2. Transport layer
3. Internet layer
4. Network access layer

The application layer is the topmost layer and it provides end-user access. This layer controls the communication to the devices and data is presented in visual form to the end-user.

This layer is an abstraction layer and ensures error recovery, data integrity, and privacy.

The protocol used by this layer are:

• HTTP
• FTP
• TFTP
• SMTP
• TELNET
• DNS

The standard port number of HTTP is = 80

The standard port number of SMTP is = 25, 587, 465

The standard port number of DNS is = 53

The transport layer is responsible for the end to end communication between the sender and receiver over the internet. It provides logical communication between the sender and receiver and ensures the end to end delivery of the packet. The header of this layer contains the port address of the sender and receiver and divides the stream of bytes received from the upper layer into segments.

The transport layer main protocols are:

• TCP(Transmission Control Protocol)
• UDP(User Datagram Protocol)
• SCTP(Stream Control Transmission Protocol)

The internet layer protocols are responsible for the host to host the delivery of the data packet.

The network layer main protocols are:

• IP(Internet Protocol)
• ICMP(Internet Control Message Protocol)
• DHCP(Dynamic Host Configuration Protocol)
• ARP(Address Resolution Protocol)
• RARP(Reverse Address Resolution Protocol)

The network access layer is the lowest layer of the TCP/IP network model.

This is the combination of two layers:

1. Physical layer
2. Datalink layer

The network access layer is a layer at which data is transmitted and received over the physical network and this layer is the lowest layer. This layer is responsible for the data transfer on a directly attached network.

This layer knows the details of the underlying network and formats the data.

This layer format the data into the frame and then converted into an electrical pulse and checks for errors on incoming frames.