Impairments In Data Transmission, FTP Process, Bit Rate Calculation, IPv6 Address Types, ICMPv4 Vs ICMPv6, Decentralized P2P Networks, And Essay.

Question 1: Signals travel through imperfect transmission media, describe in detail the three main causes of impairments. Answer MUST include how they affect different characteristics of signals including amplitude, phase and frequency.

Question 2: A host is sending a file from a PC using FTP. Explain the process the PC undertakes, between the time the application begins sending the file and the electrical signals leave the 100BaseT interface card. Make sure to clearly discuss what happens at each layer of the TCP/IP Model described in the textbook.

Question 3: Calculate the approximate bit rate and signal level(s) for a 3 MHz bandwidth system with a signal to noise ratio of 110?

Question 4: Compare the link local address to unique local address in IPv6. Discussion MUST include a comparison to private addresses in IPv4.

Question 5: Compare ICMPV4 and ICMPV6 protocols. Describe the different types of errors reported by the ICMPV6 Error-Reporting messages.

Question 6: What is a Decentralized P2P Network and how is it different from a centralized P2P network? List and describe the two different types of decentralized P2P network?

Question 1: Impairments in Data Transmission

Question 1

In any form of data transmission, the path used to transfer the signal from the transmitter to the receiver device is known as the transmission medium. This medium determines the transmission outcomes of a signal including the existing limitations (UNISA, 2009). Now, a transmission impairment is an attribute or property of a transmission medium that causes the transmitted signals to be distorted. Let’s focus on three types of impairments; attenuation, distortion and noise.

Attenuation

A measure of the energy lost by a signal through absorption or radiation as its travels through a medium. It’s a function of distance and is always radiated at a constant rate, therefore is smaller in shielded and shorter mediums. In itself, attenuation will occur because the signal will always spread out on the shell of the transmission medium which expands the amount of power radiated (Bourbie & Nur, 1984). Moreover, this impairment is also facilitated by impurities within the medium, which will always decrease the amplitude of the transmitted signal. Furthermore, it directly distorts the frequency of the transmitted signal while varying the phase shift.

Distortion (harmonic)

This type of impairment causes a signal to change its shape more so when a signal is made up of different frequencies i.e. different signals. Moreover, this phenomenon will occur when the signal has a varying frequency response as compared to the bandwidth of the transmission medium (IEEE). Distortions will shift the phase of a signal where the input will have varying amplifications as compared to the output signal. Moreover, it will cause varying amplifications of signal frequencies based on the filters used. In addition to this, it will result in a non-linear amplitude output i.e. an amplitude which is non-linear to the input signal.

Noise

A random and unwanted fluctuation in communication signals. Noise is also seen as an unwanted signal that is added to the intended communication signal. Noise lowers the efficeny of the communication medium by lowering the frequency and amplitude of the transmitted signal by amplifying those of the unwanted signals (Kang & Kupinski, 2012).

Question 2

File transfer protocol is a common standard used to transfer files between computers using the TCP/IP model across the internet. As a communication standard, it will use a client-server based protocol to transmit signals across two different channels. One of these channels is used as the data channel while the other is used as the control medium (Egli, 2015).

 Before, outlining the processes that occur at each layer of the TCP/IP model, let’s examine a general operation of the FTP protocol. First, the FTP completely relies on the TCP (transmission control protocol) to establish the connections used to communicate. Therefore, the FTP sessions are made possible by TCP connections that establish a medium between the server and the client.

Operation procedure (using TCP/IP model)

1.    Application layer – At this layer, the FTP protocol is able to acquire network services through its designated port number and layer socket. In this case, the port number is defined as 20.
2.    Transport layer – The client as outlined above, requests a connection to the server using the TCP. The TCP facilitates the connection and the client sends commands to the server. The server replies to the FTP request of the client which generally initiates the communication.
3.    The internet layer – However, before the command request and the reply, is facilitated, the data containing these commands must pass through the internet layer to attain the packet construct for transmission. This construct will contain the data itself, the source and destination address (the IP address).
4.    Network access layer – The packet construct identified above is then encapsulated into a frame for transmission in the actual medium (100BaseT interface). Moreover, the IP address is mapped to an address that the physical mediums (cables) can identify using their interface cards i.e. the physical address (MAC) (SQA, 2010).

From here, the client’s initial command reaches the destination (server) and a reply is sent through the same process in reverse. This reply establishes the connection and the actual transfer of files is initiated (Egli, 2015). On completion, the original sender (client) sends out a termination command to the TCP connection which ends the transmission.

Question 2: The FTP Process

Question 3

In this question we are given the following values: Bandwidth 3 MHz

SNR 110

We could use Nyquist formula to get the bit rate, where

Bit rate = 2 x Bandwidth x Log₂ Signal level (L)

However, we lack the signal level and in its place we have SNR. Therefore, the Shannon capacity formal applies:

Capacity = bit rate = B x Log₂ (1 + SNR)

       = B x Log₂ SNR = 3,000,000 x Log₂ 110

                   = 20344079.14 = 20.3441 MHz

Signal level: 20344079.14 = 6,000,000 x Log₂ L

          3.390679857 = Log₂ L, therefore, L = 2^3.390679857

  = 10.48808848 Levels

Question 4

Link-local addresses are IP version 6 unicast addresses that are automatically acquired by all connected interfaces configured using the IPv6 addressing. These addresses (link local) are configured using the prefix (link-local) of FE80:: /10 which basically represent 1111 1110 10 in binary notation. Furthermore, unlike other addresses, they are not bound to the physical addresses (MAC) as they are configured using the EUI-64 format. Nevertheless, they also can be configured manually using the same prefix format seen above (FE80::/10) but with the link-local command (Cisco, 2011). In comparison with other addresses (more so, ULA), these addresses are unique to a given network link. Therefore, they cannot be routed which prevents routers from forwarding them to other networks.

On the other hand, unique local addresses (ULA) are a consequence of the industrial disapproval of site local addresses which failed to meet the needs of the industry. In comparison to link local addresses, they are routable which means they can be used in different networks and segments, unlike link-local addresses that are designated as single network schemes. However, this routeing is only performed within a given network domain and not the internet. Moreover, ULA holds similar functions to IPv4 addresses that fall within the RFC1918 addressing standard. In addition to this, ULA enables organisations or users to map and number their resources based on unique addresses that fall only within their mandated domain that they administrate. However, these addressing scheme is never tied to routeing policies which simplifies the interaction with a service provider (ISP) (Study CCNA, 2017).

Question 5

Despite its tremendous functionalities, the IP protocol cannot outline the fate of data packets nor can it provide diagnostic data on transferred information. In place for these deficiencies is the Internet Control Message Protocol (ICMP), a diagnostic and control tool used to configure and deposit IP packets (Shichao, 2017). Now, ICMPv4 and ICMPv6 are the different versions of ICMP that are used in the industry based on the addressing scheme/version used i.e. ICMPv4 for IPv4 and ICMPv6 for IPv6. A general overview of the two will outline the integral role played by ICMPv6 on IPv6 operations as compared to ICMPv4.

For one, ICMPv6 is used for other purposes beyond the overall duty of reporting and signalling error messages. ICMPv6 is used to discover neighbours a role that is similar to IPv4 ARP (address resolution protocol). Moreover, it is also used to discover routes using the router discovery functionalities. Finally, it also used to manage and monitor hand-offs in mobile communication (in IPv6). On its end, ICMPv4 is only concerned with error detection and control, a role also accomplished by ICMPv6 (Shukla, 2009).

ICMP will always report errors to the original sender or source of information, this operation principle is facilitated by the source addresses usually stored in the IP structure. Moreover, ICMP will only report errors for other (higher protocols) to manage and correct.

Type:

1.    Destination unreachable – occurs when a router cannot direct a data packet to the appropriate destination, instead it discards the data. Moreover, it can occur when a host is unable to deliver a message or data.
2.    Source quench – an error that will occur when the source sends too much data to a destination or router while they are congested. ICMPv6 will send this message to notify the source of the problem so that it slows its transmission.
3.    Time exceeded – a consequence of the time-to-live parameter where routers discard data exceeding their TTL i.e. zero value.

Question 6

First, peer to peer (P2P) network is a communication network that enables devices to connect directly to each other without the need of a central server (regulatory device). Therefore, the devices involved in the network have equal rights and privileges acting both as the server and client based on the communication instance (Munirathinam, 2009). Furthermore, these networks (P2P) have advanced due to technological advancement which has resulted into the different types seen today. The decentralised P2P network is the absolute representation of non-centralised networks where devices (peers) are connected extensively to form infinitely long networks without using a central management system. Moreover, each peer has a partial outlook which limits their view to a few devices which they are allowed to exchange services. In addition to this, the size of the network (which is infinitely long) is usually determined by the size and number of layers of the participating computers.

On the other hand, centralised P2P networks will use a central server to manage the connections established by the participating computers. However, the devices involved will still have equal rights establishing direct connections with other devices but a central device is used as a directory to store the information contained in each computer (Lupu, 2010). Therefore, the central item is used as a record to store all the information contained in each of the participating computers. Furthermore, it will facilitate communication by directing peers to their intended recipients and sources.

Types of decentralised P2P networks

1.    Structured networks – networks that use an accepted algorithm or structure to optimise the operations of the network. Therefore, a global standard or protocol is used to ensure each node is able to search and acquire a connection with the intended device or peer.
2.    Unstructured networks – networks whose operation principles are opposite of those of the structured network where no algorithms or protocols are used to facilitate communication. Moreover, these networks hold a close resemblance to centralised P2P networks as they will use a central administrator to govern operations and not a set standard (Rodrigues & Druschel, 2010)

References

Bourbie. T & Nur. A. (1984). Effects of attenuation on reflections: Experimental test. Journal of geophysical research. Retrieved 03 May, 2017, from: https://onlinelibrary.wiley.com/doi/10.1029/JB089iB07p06197/abstract

Cisco. (2011). Understanding IPv6 Link Local Address. Retrieved 03 May, 2017, from: https://www.cisco.com/c/en/us/support/docs/ip/ip-version-6-ipv6/113328-ipv6-lla.pdf

IEEE. RF, RFIC & Microwave theory, design. Retrieved 03 May, 2017, from: https://www.ieee.li/pdf/essay/phase_noise_basics.pdf

Kang. D & Kupinski. M. (2012). Effect of noise on modulation amplitude and phase in frequency-domain diffusive imaging. Journal of biomedical optics. Retrieved 03 May, 2017, from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4098065/

Rodrigues. R & Druschel. P. (2010). Peer-to-Peer Systems. Communication of the ACM. Retrieved 03 May, 2017, from: https://cacm.acm.org/magazines/2010/10/99498-peer-to-peer-systems/fulltext

Scottish Qualifications Authority. (2010). TCP/IP Model Layers. LO4: Implement Basic Networks and Security. Retrieved 03 May, 2017, from: https://www.sqa.org.uk/e-learning/HardOSEss04CD/page_06.htm

Shichao. (2017). Chapter 8. ICMPv4 and ICMPv6: Internet Control Message Protocol. Retrieved 03 May, 2017, from: https://notes.shichao.io/tcpv1/ch8/

Shukla. R. (2009). Icmp V4 And Icmp V6. Retrieved 03 May, 2017, from: https://www.slideshare.net/engineerrd/icmp-v4-and-icmp-v6

Study CCNA. (2017). IPv6 unique local addresses. Retrieved 03 May, 2017, from: https://study-ccna.com/ipv6-unique-local-addresses/

UNISA. (2009). Transmission media. Chapter 4. Retrieved 03 May, 2017, from: https://www.di-srv.unisa.it/~vitsca/RC-0809I/ch04.pdf