Question 1 The OSI model has seven layers where each layer performs various functions that are integrated to ensure that the network performs efficiently. The layers are arranged as follows from the bottom to the top layer: a) The physical layer: This is the first layer of the model and it has several functions. These are: i. Bit synchronization: The physical layer is very crucial in terms of timing and synchronizing the period and the amount of bits that are transferred between the sender and the recipient of a message. It uses a clock to ensure accurate and reliable synchronization. ii. Bit rate control: The physical layer also controls the bandwidth in a network by determining the number of bits that are transferred over the network channel within the specified time which is seconds in most cases. iii. Physical topologies: The physical layer also determines the design which is used to connect all the devices that make up the network. These include routers, switches, hubs and other equipment used in a network. iv. Transmission mode: The connection of devices in the physical layer determines how data between the communicating devices flows. There are various transmission modes which are supported by the physical layer. These are simplex, half-duplex and full-duplex. In simplex, data flows in only one direction. In half-duplex data can flow in both directions but not simultaneously. In the full-duplex transmission mode, data flows in both directions at the same time. b) Data Link Layer: This is the second layer of the OSI model. Some of its functions include: i. Framing: Data that is being transmitted is segmented into pieces known as frames to make the transmission process easier. The Data link layer facilitates the framing process to ensure that the receiver acquires the accurate and relevant information within the shortest possible time. ii. Physical addressing: The frames require adequate data regarding the sender and the recipient to ensure that a message does not fail to reach the intended recipient. The Data Link Layer achieves this by adding a MAC address to the header section of each of the frames that are being transmitted. iii. Error control: The use of frames in the DLL enables the network layer to detect when frames do not reach the intended recipient. In return, the DLL is able to retransmit the lost or damaged frames using the details in the headers. iv. Flow control: The DLL ensures that the flow of data between the sender and the recipient is constant. This techniques ensures the stability of the communication channel that is established when transmitting data. v. Access control: The assigning of MAC addresses to all the computers in a network enables the Data Link Layer to determine the machines with access to certain resources. c) Network layer: The functions of the third OSI model layer are: i. Routing: The network layer assesses the different routes that a frame can use to reach its recipient and it chooses the best rou ...

1. Question 1
The OSI model has seven layers where each layer performs
various functions that are integrated to ensure that the network
performs efficiently. The layers are arranged as follows from
the bottom to the top layer:
a) The physical layer:
This is the first layer of the model and it has several functions.
These are:
i. Bit synchronization:
The physical layer is very crucial in terms of timing and
synchronizing the period and the amount of bits that are
transferred between the sender and the recipient of a message. It
uses a clock to ensure accurate and reliable synchronization.
ii. Bit rate control:
The physical layer also controls the bandwidth in a network by
determining the number of bits that are transferred over the
network channel within the specified time which is seconds in
most cases.
iii. Physical topologies:
The physical layer also determines the design which is used to
connect all the devices that make up the network. These include
routers, switches, hubs and other equipment used in a network.
iv. Transmission mode:
The connection of devices in the physical layer determines how
data between the communicating devices flows. There are
various transmission modes which are supported by the physical
layer. These are simplex, half-duplex and full-duplex. In
simplex, data flows in only one direction. In half-duplex data
can flow in both directions but not simultaneously. In the full-
duplex transmission mode, data flows in both directions at the
same time.
b) Data Link Layer:

2. This is the second layer of the OSI model. Some of its functions
include:
i. Framing:
Data that is being transmitted is segmented into pieces known
as frames to make the transmission process easier. The Data
link layer facilitates the framing process to ensure that the
receiver acquires the accurate and relevant information within
the shortest possible time.
ii. Physical addressing:
The frames require adequate data regarding the sender and the
recipient to ensure that a message does not fail to reach the
intended recipient. The Data Link Layer achieves this by adding
a MAC address to the header section of each of the frames that
are being transmitted.
iii. Error control:
The use of frames in the DLL enables the network layer to
detect when frames do not reach the intended recipient. In
return, the DLL is able to retransmit the lost or damaged frames
using the details in the headers.
iv. Flow control:
The DLL ensures that the flow of data between the sender and
the recipient is constant. This techniques ensures the stability of
the communication channel that is established when
transmitting data.
v. Access control:
The assigning of MAC addresses to all the computers in a
network enables the Data Link Layer to determine the machines
with access to certain resources.
c) Network layer:
The functions of the third OSI model layer are:
i. Routing:
The network layer assesses the different routes that a frame can
use to reach its recipient and it chooses the best routes based on
approximated time and also distance.
ii. Logical addressing:
The network layer assigns each computer on a network a unique

3. Internet Protocol address. The IP address of the sender and
receiver is inserted into the header section of the frames. This
logic addressing strategy distinguishes the computers in a
network locally and also universally.
d) Transport layer:
This layer is directly involved in the sending of data across a
channel. The functions of this layer are:
i. Segmentation and reassembly:
The transport layer divides the frames that it receives from the
session layer into smaller segments. It also ensures that each
segmented is assigned a header that contains the addresses of
the sender and the intended recipient. After the segments reach
the recipient, the transport layer at the destination arranges and
assembles the units together to form a complete message.
ii. Service point addressing:
The transport layer is effective in ensuring that the message
reaches the right process at the destination. The layer achieves
this function by using the port address which is also referred to
as service point address. This strategy ensures high accuracy
and speed.
e) Session layer:
As the name suggests, the session layer establishes and
maintains the stability of a session between two communicating
machines in a network. It also ensures authentication of the
users in a network to ensure the security of the resources
transferred in the network. Some of its functions include:
i. Session creation, stabilization, and destruction:
The session layer creates a dedicated session between the sender
and the recipient. It also ensures that the connection is stable
and terminates it after the transmission process is complete.
ii. Synchronization:
This involves the establishments of checkpoints during
transmission to check the occurrence of any errors. This
strategy is fast in identifying errors and enabling the network
manager to rectify them.
iii. Dialog controller:

4. The session layer uses the dialog controller to determine and
establish the appropriate transmission mode.
f) Presentation layer:
This handles how the data received at the destination is viewed
by the recipient. It has three major functions. These are:
i. Translation:
It translates the messages into human readable formats.
ii. Encryption/decryption:
On the sender’s end the presentation layer is responsible for
encrypting the message while on the recipient’s side it decrypts
the message using the appropriate key.
iii. Compression:
Helps to reduce the size of the bits that are transferred over the
network hence making the process faster.
g) Application layer:
The application layer is responsible for offering services such
as File Transfer Protocol (FTP), Mail services and also access
to directories.
In the TCP/IP model, the internet layer is similar to the network
layer of the OSI model since the functionalities performed in
the two layers are similar. All the protocls that are used to
transmit data in the network are defined in this layer. Some of
the common protocols in the network/internet layer are:
i. IP: The internet protocol ensures that data packets reach the
intended destination using unique sender and recipient
addresses.
ii. ICMP: The Internet Control Message Protocol encapsulates
the data to be transmitted and ensures that network errors are
resolved.
iii. ARP: the Address Resolution Protocol finds the addresses of
all the required hardware equipment in a network.
Question 2
Question 3

5. IP address is used as a logical address that contains the network
and the host addresses of computers in a network.
When a sender wants to send a message, the network protocols
have to acquire the physical address also referred to as MAC
address (Media Access Control) of the receiver and also the
sender. The address is usually written on the Network Interface
Card (NIC) of each machine.
On the other hand, the address resolution protocol (ARP) acts as
a link layer command which resolves the IP addresses to match
the MAC addresses of their devices.
The ARP checks whether the MAC addresses are stored in the
cache and if they are not found then it proceeds to check for
broadcasts and request the corresponding MAC addresses. Once
the receiver gets the requests it acknowledges by sending back
its MAC address and the IP address. The communication
process id then established after these details are received by
the sender. The MAC address is stored in the cache to ensure
that future reference will be faster.
Question 4
Major Network: 180.22.0.0/16
Available IP addresses in major network: 65534
Number of IP addresses needed: 44103
Available IP addresses in allocated subnets: 64506
Subnet Name
Needed Size
Allocated Size
Address
Mask
Dec Mask
Assignable Range
Broadcast
Sales
22400
32766
180.22.0.0
/17

6. 255.255.128.0
180.22.0.1 - 180.22.127.254
180.22.127.255
Marketing
11200
16382
180.22.128.0
/18
255.255.192.0
180.22.128.1 - 180.22.191.254
180.22.191.255
Online Sales
5600
8190
180.22.192.0
/19
255.255.224.0
180.22.192.1 - 180.22.223.254
180.22.223.255
Advertising
2800
4094
180.22.224.0
/20
255.255.240.0
180.22.224.1 - 180.22.239.254
180.22.239.255
Product Support
1400
2046
180.22.240.0
/21
255.255.248.0
180.22.240.1 - 180.22.247.254
180.22.247.255
Technical Support

7. 700
1022
180.22.248.0
/22
255.255.252.0
180.22.248.1 - 180.22.251.254
180.22.251.255
HQ
1
2
180.22.252.0
/30
255.255.255.252
180.22.252.1 - 180.22.252.2
180.22.252.3
BR1
1
2
180.22.252.4
/30
255.255.255.252
180.22.252.5 - 180.22.252.6
180.22.252.7
BR2
1
2
180.22.252.8
/30
255.255.255.252
180.22.252.9 - 180.22.252.10
180.22.252.11
I have arranged in ascending order so two departments are re-
aranged so just take note of two dept (Advertising & Online
Sales)
The detailed design of a simple addressing solution (with
diagram(s) and step by step workout of the calculations) that

8. accommodate for growth, is easy to administer and has the
minimum wastage of available IP address space.
Needed Size Allocated Size
(40% growth)
22400 32766 2^15 = 32768
11200 16382 2^14 = 16384
5600 8190 2^13 = 8192
2800 4094 2^12 = 4096
1400 2046 2^11 = 2048
700 1022 2^10 = 1024
1 2 2^1 = 2
1 2 2^1 = 2
1 2 2^1 = 2
we have 2^n power to do subneting as 15 14 .. 10 are number of
0s that will give us hosts out of 32 and remaining will be 1s that
give us subnet so for example HQ Sales have 32768 subnet - 2
address one for subnet starting and one for broadcast addressing
so remaining 32766 which comes by 2^15 = so remaining 32-
15=17 will be 1s that you can see by slash notation /17
Provide IP addresses and Subnet Masks for all LAN and WAN
interfaces.
Shown above table
Suppose in further future, this company experience more
growth, which leaves company with no option except upgrading
this network from IPv4 to IPv6, investigate/explore the
technical changes you may need to implement for such upgrade.
true so arround 98% of ipv4 is used now have to upgrade to
ipv6 for more address space is required
About 98% of available major network address space is used
About 68% of subnetted network address space is used
References
1. Pyles.J., Carrell, J., Tittel, E (2017). Guide to TCP/IP: IPv6
and IPv4 (5th edition). Cengage Learning ISBN 9781305946958