Network Design(500-700 words)

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 routes based on approximated time and also distance.

ii. Logical addressing:

The network layer assigns each computer on a network a unique 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:

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

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	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	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 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