SIT202 Computer Networks

Answer:

Transport Communication protocol/ Internet protocol (TCP/IP) is a suite or a set of communications protocols that allow two or more devices to communicate on the internet; by providing end-to-end communication that comprises how it should be broken into packets, addressing, its transmission and the how it will be received at the destination (Wang et al.,2016). 

The TCP/IP has four layers namely application, transport, network and internet layer, that aid in its functionalities.

The packets transmitted comprise headers with the host’s addresses for sending and receiving. During encapsulation, as the packets travel across the TCP/IP protocol stack, the protocols at every layer are added from the basic headers. The figure below shows the life cycle of a packet from origin to destination.

In order for the data to travel from source to destination, every OSI layer must communicate with its peer layer at the destination. In this process, all the protocol interchanges, between the layers, the information is known as the Protocol Data Units (PDU).

 Every layer relays on the functional services of the layers beneath it, by use of encapsulation to convey the PDU into its data field from its upper layer. The relevant headers that will be required for the layer to perform are added. The headers contain all the information such as the source and destination addresses. The network layer will offer services to the transport layer which will eventually present its data to the internetwork subsystem. This involves encapsulation of the PDU to relay data up to the internetwork subsystem layer while attaching the required headers to create a datagram

Decapsulation involves the process of reversing encapsulation by opening wrapped packets that were sent over the network. Using our diagram above, the reverse will occur when the packets reach the destination computer. Data is transmitted back to the lower layers of the TCP/IP protocol stack and the corresponding headers are unpacked/unwrapped and the information in the headers are used to convey the packets to the exact network that they were intended to reach(Lin et al., 2016).

A network loop involves a configuration where there are several paths between devices which ensure packets are constantly repeated. Network flooding will occur in the diagram since the hub will transmit everything that it receives blindly to all the connections

The loop will eventually create broadcast storms as a result of broadcasts and multicasts being forwarded by switch 1 and switch 2 out of every port. In the next loop, the switches will again broadcast the frames thus flooding the network. Since the network does not use any loop avoidance, the frames will loop forever in the network as shown below since it is being broadcasted in a loop topology.

When the host F in LAN 1 sends unicast frames to host A on LAN 2, the hub will broadcast the frames to both switch 1 and switch 2. Both the switch will again provide the same services and forward the frames. This is inappropriate since hub 1 in LAN 1 will receive the same frame twice which will cause additional overhead to the network. This will continue and eventually, the network will be flooded endlessly. The MAC address filter tables on the two switches will not be able to decide the device location since the switches are receiving the frames from the two sources linking to the switch.

In the end, data encapsulation will occur at the TCP/IP layers in the transport layer protocol. The data is transformed to TCP/UDP messages with their headers. It is then encapsulated inside the body containing the IP address of the data, usually referred to as IP datagram. After the encapsulation, the data is passed to the data-link layer for transmission across the network to Bob.

Routers are used to find the shortest or the fastest of the route path between two devices that are connected to it. Each interface of the router R1 connects to the IP network which links to router R2 since they have the same subnetwork. When the router receives the datagram from Alice PC, the network layer adds the network adds the source and destination IP address in the packet. The data-link layer adds the header to form the frame which is forwarded to the physical layer.

The frames will be converted into binary and forwarded to the destination MAC address of the other router in Bob’s end, Router R2. The router will receive the frame and remove the headers in the decapsulation process. Then, find the destination IP address in the packet. It will then match the destination IP address to Bob’s Computer IP address in its routing table and forward the packet through the router’s interface to that network. This procedure will be repeated until all the packets are received by Bob.

Point to point comprises of methods for encapsulating multi-protocol datagrams, the link control protocol for establishing configuration and verify data-link connections which aid in transporting secured multi-protocol data across the point-to-point links in a Wide Area Network (Li et al., 2015).

The Link Control Protocol (LCP) is used in creation, configuration and establishment of logical connections/link between the source IP address and the destination IP address. It also eliminates any error that might be detected in the link. The Password Authentication Protocol (PAP) is primarily used in granting access rights or authentications between the two ends without encrypting the passwords. The Challenge Handshake Control Program (CHAP) is used in an encrypted authentication in point to point network and provide protection against playback attacks that might arises It is often considered very secure as compared to PAP. The Network Control Program is used in the provision of configuration and management of facilities that are applied in the point to point network configuration. It makes it possible for devices to communicate and access resources from one another remotely through point to point network. The Internet Protocol Control Protocol (IPCP) is used in the provision of configuration IP addresses and management of end to end devices connected in a point to point network. It enables and disables the relevant modules of the IP on both ends

Modulation involves the process of impressing of the data so that it can be transmitted on the radio carries. The main reason why digital signals are modulated is to squeeze the most data possible into the least possible amount of spectrum. It ensures data is transmitted as fast as possible in an assigned bandwidth. Through the process of digital modulation, the noises are eliminated and robustness to the signals is improved.

The broadband transmission involves the transmission of digital signals through a band-pass channel after modulating the signals; converting the signals from digital to analog signals. The bandpass channel is a type of a channel whose bandwidth does not start from zero as shown below (Chung et al., 2015).

The broadband transmission comprises three techniques which are the Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK) and Phase Shift Keying (PSK). In ASK, the amplitude of the carrier is modulated according to the message signals, in PSK it conveys data by modulating the carrier wave and in the FSK, deals with the conversion of signals into binary states; 0 and 1.

The network set up will have a total of Eight (8) collisions.

Five collisions are experienced in the connection where the switches are. This is because the switch causes the collision in every device that is connected to its port. Therefore, there will be a collision between Switch 1 and PC-5, between Switch 2 and PC-6, between Switch 1 and Switch 2, between Switch 2 and Switch 3, between Router and Switch 3 summing up to a total of 5 collisions as shown in the red spots marked

A hub forwards the collisions, thus all the devices connected on a hub will experience a resultant of one collision. The network will experience three collisions as a result of hubs; there will be one resultant collision as a result of PC-4 and Hub 1, the second collision will be as a result of PC-2 and Hub 2, and the third collision will be as a result of PC-1, PC-2, Hub 5, Hub 4 and Hub 3 as shown in the yellow spots of the diagram above.

Bridge operates at the data-link layer. It connects and forwards packets between network segments that use the same communication protocols in a network. It has the capability of filtering and forwarding frames based on the MAC address of the frames.

A hub forwards the collisions, thus all the devices connected on a hub will experience a resultant of one collision. The network will experience three collisions as a result of hubs; there will be one resultant collision as a result of PC-4 and Hub 1, the second collision will be as a result of PC-2 and Hub 2, and the third collision will be as a result of PC-1, PC-2, Hub 5, Hub 4 and Hub 3 as shown in the yellow spots of the diagram above.

Bridge operates at the data-link layer. It connects and forwards packets between network segments that use the same communication protocols in a network. It has the capability of filtering and forwarding frames based on the MAC address of the frames. 

Reference

Chung, S., Ma, R., Teo, K.H. and Parsons, K., 2015, January. Outphasing multi-level RF-PWM signals for inter-band carrier aggregation in digital transmitters. In Radio and Wireless Symposium (RWS), 2015 IEEE (pp. 212-214). IEEE.

Li, D., Ouyang, J., Li, H. and Wan, J., 2015. State of charge estimation for LiMn2O4 power battery based on strong tracking sigma point Kalman filter. Journal of Power Sources, 279, pp.439-449.

Lin, A.D., Franke, H., Li, C.S. and Liao, W., 2016. Toward performance optimization with CPU offloading for virtualized multi-tenant data center networks. IEEE Network, 30(3), pp.59-63.

Wang, Y., Gamage, T.T. and Hauser, C.H., 2016. Security implications of transport layer protocols in power grid synchrophasor data communication. IEEE Transactions on Smart Grid, 7(2), pp.807-816.