Computer Networks Assignment: Research on Quality of Service

Question

Task: Conduct a research and prepare a computer networks assignment on Quality of Service in Computer Networks.

Answer

Introduction
The research on computer networks assignment signifies that the computer networks are essential to carry out the networking and communication activities for the end-users. The cheap and ubiquitous network access has transformed the user demands and the way users access the online services. The advancements in the mobile technologies have further resulted in excessive demand of high-speed networks. The Internet has made it possible for the users to remain connected to the network and access the offered services irrespective of the timeframe. The development of new technologies like LTE has made it further easier for the users to have access to the services, such as video streaming, video calling, etc. without any lags [1].

Such excessive demands and increased competition in the industry has made it essential for the network operators to provide, maintain, and improve specific levels of quality. Quality of Service, QoS in computer networks is the overall measurement and performance of these networks. In the field of computer networking, the quality parameters are usually determined in terms of traffic flow, traffic prioritization, packet queuing, and resource reservation controls. There are numerous parameters that are used to measure the QoS of computer networks. Some of the primary ones include bandwidth, error rate, jitters, and latency.

There are levels of QoS that are grouped in three categories as best effort, soft QoS, and hard QoS. In the case of best effort QoS, there are no guarantees or formal specifications of quality measures required. There are various network applications and services that work well with the best effort QoS. File Transfer Protocol, FTP is one of the primary examples of the same wherein no guarantees are offered. The only measure involved is the completion of the transfer of file successfully from source to the destination. The second level is soft QoS. It is also referred as differentiated service. In this level also, there are no absolute guarantees provided [2].

However, varied priorities are set as per soft QoS for varied tasks. The networking applications and services are therefore, classified in number priority classes. For instance, the network control traffic is always prioritized above data communications to make sure that the availability and access is ensured for the end-users. The third level of QoS is hard QoS. It is also referred as guaranteed service. It is valid and applicable for the critical networking applications and services that demand complete guarantee and assurance. This could be in terms of the minimum number of resources so that the network functions are adequately carried out. The hard QoS involves the prior declaration and reservation of the resources for a dedicated networking path to make sure that the network performance does not get impacted in any case. The multimedia applications, such as real-time video streaming or audio/video calling are some of the examples of hard QoS.

With the excessive networking demands, it is now becoming difficult for the networking operators and vendors to maintain the required QoS. Ad-hoc networking, for instance, has varying resource requirements but critical network traffic flow. The research is conducted to explore the QoS associated with the computer networks in detail.

Related Work
Internet network is a collection of computer connected and integrated with one another in large-scale to meet the communication and connectivity requirements as per the resources available. A particular device can be stated as a networked device if it can exchange information.

The published literature includes various definitions of QoS. It is defined as the collective impact of service performances to identify the satisfaction level of the users for computer networks and services. Another research paper defined QoS as the measurement of the required characteristics and user demands. The quality needs vary on the basis of the network type and requirements [3]. One of the significant factors identified in QoS for computer networks is the transport layer. There are various protocols involved in the transport layer with Transmission Control Protocol, TCP and User Datagram Protocol, UDP being the primary ones. There are several factors that may impact the deterioration of the quality levels for the network channels. The types of protocols involved, specific layer performance, and packet loss are some of the significant parameters. QoS parameters and the associated quality can also be impacted by the congestion levels. The traffic load on the network channel is extremely dynamic. With the change in the network traffic load, there is an impact on the jitter and packet loss. The number and probability of the collisions on the network channels can also change accordingly.

Delay is one of the effective measurements to determine QoS. There are impacts that can be caused on the delay on the basis of the physical media involved, network congestion, or the distance. The congestion on the computer networks take place due to the reduced output capacity as compared with the inflow on the router. This can lead to excessive queues in the network channels. There are ways defined in the literature to manage and prevent the congestion which automatically leads to the improvements in the QoS levels. The implementation of flow control over the computer networks is one of the mechanisms to assure the same. Flow control refers to the intelligent management of the data flow within the network in order to manage and provide the guaranteed speed. It is implemented to ensure that the queues do not exceed the capacity and there is effective regulation of the allocation of buffers on the network routers. The same shall involve determination of the buffers and links involved. The combination of all of these can ensure effective flow of the data packets with increased speed and reduced queuing [4].

Traffic shaping utilizing token bucket method is identified as a significant and reliable flow control mechanisms. Token bucket refers to the process of controlling the rate of network traffic provided to a network. The method utilises Token Bucket Filter, TBF as a measure to identify if the class is within limit, at limit, or beyond the assigned limit. TBF works along with the base of the token bucket to manage and control the flow. All the packets to be transmitted over the network shall have a token on the respective bucket. In the scenarios wherein the token is not available then the packet shall wait till the required number of tokens is available for packet transmission. It provides the mechanism to enhance unused bandwidth resulting in the marked improvements in QoS.

There is a lot of research conducted to determine the ways in which QoS for computer networks can be improved. Scheduling algorithm is proposed in the research work designed with the aim to increase minimal resources to minimize and maintain the resources. Hierarchical Token Bucket, HTB is also mentioned in several research papers as the mechanism to carry out bandwidth management and promote the QoS levels. To validate the use of HTB for increased QoS, the network quality is compared before and after the use of HTB. The results showed that the use and implementation of HTB led to effective control of the internet access. The clients were able to get the required bandwidth in each case. Token bucket, as a result, is one of the significant mechanisms to improve QoS for computer networks [5].

In the current times, the wired networks are seldom used and the major reliance for computing and networking is on the wireless networks and technologies. This is because of the availability, mobility, and ease of service that comes with the wireless networks. However, in terms of QoS, the concerns and challenges to maintain quality is more in mobile wireless networks as compared with fixed wireless or wired networks. There are numerous factors identified in the research papers behind the same. The mobile wireless networks can be managed through one or multiple mobile routers (MR). The scenarios wherein mobile networks involve numerous connections to transmit the packets to maintain the network load or redundant fall-back connection when the primary connection is lost, these are referred as multi-home mobile networks.

There are several ways to ship the MRs with a variety of network interfaces, such as WiMAX, GPRS, and others. It is crucial that the flow is allocated and controlled effectively to meet the demand and performance associated with the computer networks. Numerous WLAN technologies along with the 3GPP technologies allow the mobile equipment to be connected at any place and at any time. The wireless technologies, such as IEEE 802.11 a/b/g or Bluetooth enable the mobile terminals to get connected to the internet irrespective of the location. The mobile devices manufactured in the current times, such as Smartphones, tablets, or others are equipped with multiple network interfaces. These multi-homed devices can be simultaneously managed with the respective network interfaces [6]. There are certain benefits attached with multi-homing that promotes the QoS too. It allows route recovery on failure. Also, it makes sure route recovery is unaffected in the case of redundancy or load sharing. Multi-homing comes with the need to enable continuous access to the network to ensure that the connectivity of the hosts does not get adversely impacted. It may not be possible for the network flow to get the expected QoS requirements in every circumstance.

There are reliability problems and issues that can be determined for the mobile networks. The in-depth reliability analysis can be conducted to determine the root cause of the problem that may have emerged due to the packet loss or the issues around duplication. The analysis can also assist in the determination of the parameters that may have led to the issue in the first place. The published literature suggests that the network service providers shall use the reliability analysis to determine the performance of different applications.

QoS prediction is another technique that can be used to get rid of the QoS issues in mobile and ad-hoc networks. As per the mobile network topology and the point of attachment of the mobile network nodes within the network, these nodes may have varied prefixes. The scenarios in which the mobile network node is multi-homed, the nodes have the option to stick to the default router [7].

Discussion
Assumptions and Limitations
The fluctuations in the wireless networking channels can be frequent which can have an impact on the multi-hop network flows. Such is not the case with the wired networks. The wireless networks have these limitations due to frequent fluctuations occurring due to numerous physical layer phenomena comprising of fading and multi-path interference.

Also, the background noise and interference associated with the nearby nodes can cause adverse implications on the overall quality. The majority of the networks in use in the present times are the mobile ad-hoc networks. The end-to-end quality associated with these network channels can experience quick changes. The data packets contend for the shared media present on the adjacent links of a flow. The contention between the network packets associated with the same stream at different nodes has an impact on the QoS metrics associated with the network connection. The primary reason behind the contention is determined as the sharing of the wireless channel by the nodes present in the vicinity [8].

Interference can have an impact on the transmissions at the nodes beyond the neighbours. These effects are determined in the ad-hoc networks that involve the single frequency for the purpose of communication in a shared channel. The wireless networks designed as single-hop infrastructure networks the frequency planning is involved in the scenarios when nearby base stations can be configured to work at the other frequencies to bring down the interference level. The transmissions in the case of wireless networks and media are not effectively received once the transmission range is crossed. Beyond the range, the leftover power may be sufficient to interfere with the other transmissions. As a result, the interference associated with the non-neighbouring nodes can lead to the drop of the data packets. Therefore, it becomes necessary in the multi-hop paths to have QoS designed and implemented for each hop as well as the end-to-end path. In the single-hop, the two layers responsible for QoS parameters are physical and MAC layers. In the case of end-to-end route, the routing layer is the one primarily responsible for QoS properties and metrics.

Trends and Measures
There are numerous network-based applications used by the end-users for carrying out the personal and professional activities. The QoS requirements and needs for these applications vary and are summed up in table 1.

The applications included in the table are some of the very commonly used applications. Emails, for instance, is the primary mode of business communication in the current times. Video conference is another significant application being used by the individual users and the business groups [9]. The applications as per the QoS requirements can be classified in three main categories as high delay-sensitive, medium delay-sensitive and low delay-sensitive. Telephony and video conference are the ones that can be put in the first categories followed by web access and remote login for category two and the rest of the applications in the low delay-sensitivity category of applications.

Table 1: QoS requirements of different applications

It is essential that the techniques and mechanisms are identified to forward the packets and carry out the traffic control as per the needs of the application and the network performance.

An intelligent technique is proposed to map the application demands with the network performance. There are multiple steps involved in the proposed technique to make sure that the mapping is effective and the positive impacts are witnessed on the QoS levels. The first step shall include the determination of the network interfaces available for use. The next step shall include the determination of the data rates along with the actual throughout associated with the identified network interfaces. These shall then be assigned the performance in the range of low, medium, or high. The application demand shall be determined thereafter and it shall also be assigned in the range as low, medium, or high. The next step shall involve receiving the packets from the mobile network node or the mobile router. The packet type shall be determined as low, medium, or high.

On the basis of the packet type, the forwarding of the packet and its mapping with the network interface shall be determined accordingly. For example, if the packet type is high then it shall be mapped with high performance interface, such as WiMAX [10]. Similarly, medium packets shall be mapped with interfaces as IEEE 802.11x. The low packets shall be mapped with the interfaces like GPRS. These steps of mapping the packets with the network interfaces shall be repeated until the complete data transfer is conducted.

Mobile router associated with a mobile network shall be able to identify the number of network interfaces available. These interfaces can be of varying types, such as WiMAX, IEEE 802.11x, or others. The mobile network can also be present within another network which can lead to the creation of nested network. In this way, the root mobile router can have child routers and the hierarchy can go on with the nesting of the networks. However, in this process, overhead also goes up. The root mobile router identifies the data rates and throughput associated with all the network interfaces. The evaluation then leads to the mapping of the performance type with the network interface.

A root mobile router can receive the packets from all the nodes, such as mobile network node along with the visiting node, fixed node, child router, and so on. The mode of operation associated with these nodes can vary from one another. The packet type is then determined on the basis of the application demand. This is the methodology that will provide the mechanism to effectively map the packet type with the correct network interface. For example, the video conferencing applications are the high-sensitivity applications and these shall be mapped with the WiMAX network interface [11]. It will ensure that the required QoS is offered and maintained. In case of the low-sensitivity applications, such as emails, the network interface can also be low, such as GPRS. It is the task of the root mobile router to determine and check for the type of the packets involved. With correct mapping, it will be possible to allocate the resources effectively and manage the traffic flow and control.

The technique will also be extremely useful to manage and maintain the QoS levels in the case of multi-homed networks.

Figure 1: Applications and their demands

Figure 2: Network Interfaces and Performance

The intelligent technique proposed and applied on the different computer networking applications is further illustrated in the graphical manner. The figure 1 shows the applications mapped with their respective demands on X and Y Axis respectively. The demands are represented in the range of low, medium, and high. This is in accordance of the classification of the applications on the basis of the delay-sensitivity. For example, the delay-sensitivity of the video conferencing apps is way higher than the one associated with email or file transfer. The correct determination of the demand of the applications can lead to the adequate mapping with the network interface type [12].

The network interfaces and their performance is also analysed and represented using the graph as illustrated in figure 2. The network interfaces are placed on X axis and the performance levels are placed on the Y axis. The performance levels as 1, 2, or 3 indicate low, medium, and high respectively. The three network interfaces as GPRS, IEEE 802.11x, and WiMAX have the performance levels as low, medium, and high in the same order.

Delay is one of the compelling estimations to decide QoS. There are impacts that can be caused on the delay based on the physical media included, network congestion, or the distance. The congestion on the PC networks happen because of the diminished yield capacity as contrasted and the inflow on the router. This can prompt over the top queues in the network channels.

The execution of flow control over the PC networks is one of the systems to guarantee the same. Flow control alludes to the intelligent management of the information flow inside the network to manage and give the ensured speed. It is executed to guarantee that the queues don't surpass the capacity and there is viable regulation of the allocation of buffers on the network routers. The same will include assurance of the buffers and links included. The mix of these can guarantee successful flow of the information packets with sped up and diminished queuing.

The mobile gadgets made in the current occasions, like Smartphones, tablets, or others are outfitted with multiple network interfaces. These multi-homed gadgets can be all the while managed with the separate network interfaces. There are sure advantages appended with multi-homing that advances the QoS too. It permits route recovery on failure. Also, it ensures route recovery is unaffected on account of redundancy or load sharing. Most of the networks being used in the current occasions are the mobile specially appointed networks. The conflict between the packets related with the same stream at various hubs affects the QoS metrics related with the network association.

It would be a good idea to invest in the company that produces the QoS technologies and measures. This is because of the increasing need to make sure that quality aspect is always maintained in the computer networks. Also, the adherence with the laws and regulations is important as it will automatically result in the promotion of QoS levels. The compliance with the defined laws will make sure that the unauthorized deviations do not occur.

Conclusion
The variation in the application demand and the network interfaces cannot be avoided. The customers shall be offered with the required services, quality, and performance without wasting the resources. QoS is concerned with the customers as well as the service providers. The increased level of customer satisfaction with poor usage of the resources or vice versa cannot be termed as QoS for the computer networks. The intelligent technique proposed in the research can be applied to ensure that the customer satisfaction and needs are met with optimal resource utilization.

There are a few limitations also associated with the research work conducted. The networking and communication technologies are witnessing massive changes with the emergence of Internet of Things (IoT) networks and similar technologies. The QoS for IoT and similar technologies is not covered as part of the research work. Also, network security and its impact on QoS and vice versa has also not been explored. These are the major activities that will be covered in the future research activities.

References
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