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Download PDF Managing service level quality across wireless and fixed networks

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Today, our network spans over 1, route kilometres of fibre optic cable and additional coverage provided through our licensed fixed wireless system with services in Napanee and Brockville, and dedicated fibre link to Telecom Ottawa. In Kingston we have interconnections to third-party broadband providers across Ontario and every national service provider in Canada. Utilities Kingston is community owned and community minded. Our vision for the Kingston region is to become a "smart community". A smart community is a community with a vision of the future that involves the use of information and communication technologies in new and innovative ways to empower its residents, institutions and region as a whole.

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Our customers represent government, education, health care, industry, and commercial business. Our mandate is to foster the development of network connectivity and increased bandwidth to meet user needs and deliver user applications in the region. With a team of experienced broadband networking industry professionals on staff, provider partners with specialized expertise, and state-of-the-art facilities, we have the resources in place to offer a full suite of data and Internet services customers need.

Through Utilities Kingston, companies can interconnect sites to share business critical applications in real time. Our data services are Ethernet and Internet based, carried over our wholly owned, fully redundant, fibre optic backbone network. In addition, Utilities Kingston offers a range of standard services and specialized custom network design and implementation.

Recognized for superior service and reliability, our network availability for data services averages Our Broadband Networking Group can turn around custom designs in a matter of days and our implementation team's time to provision an order is less than half that of our competitors. A community owned utility corporation, we have been in business in one form or another for over years.

So, unlike many of the telecom company start-ups that have come and gone, we are in business for the long term. We have made significant investments in our next-generation network infrastructure and support facilities, such as our data centre and our reliable protected network. Utilities Kingston's growth strategy is conservative in nature and firmly grounded in sound business planning, ensuring profitable long-term growth and the staying power that long-term contracts require. At Utilities Kingston, we offer industry-leading standards for network reliability at We provide a multi-honed Internet backbone, enhancing reliability further through carrier diversity.

You'll find the terms of our Service Level Agreements SLA to be both reasonable and realistic, clearly spelling out conditions for service in plain language. The level of service quality can be tailored to each customer's service and budgetary requirements. There is no fine print. Increasingly customers need to set quality of service priorities for each of their Local Area Network LAN applications and user groups.

For example, one VLAN could be established for administrative traffic, while another set up for financial traffic, to ensure these mission critical applications aren't contending for network availability with email and Web browsing data packets. Our focused team of entrepreneurial broadband networking professionals looks beyond the obvious to come up with a range of possible solutions to meet your needs.

We won't force your requirements into an "off-the-shelf" or "bundled" solution you don't want. We're not just open to doing custom design; our dynamic organization is built for it. We specialize in customized solutions. A virtual circuit is established during a setup phase in which the path from sender to receiver is fixed and resources are allocated at each hop. Any type of service guarantee may be made by ATM since all the resources necessary for the connection are reserved for the virtual circuit.

Once a virtual circuit is established, ATM is very efficient in terms of the amount of time it takes to forward a packet at a single node. However, ATM is not very efficient in terms of utilization due to the fact the resources are reserved even when no data is flowing over the link. IntServ uses a call setup stage to reserve the path from sender to receiver and allocate resources at each hop. IntServ reserves resources on a "per-flow" basis where a flow contains all the network traffic associated with a single application.

As a result IntServ must take measures to guarantee an upper bound on the queuing delays at each hop. IntServ also provides a "controlled-load" service that makes no hard service guarantees, but is designed for real-time multimedia applications. In DiffServ, hosts on the edge of the network mark packets with the class of service they should receive.

Why Every Network Should Include Managed Connectivity

These edge hosts also shape the data they send to ensure that they don't send too much data at once. In the core of the network, routers look at the marking on each packet and forward it according to the per-hop behavior of the packet's class. For example, a packet marked for expedited forwarding will likely spend less time queued than a best-effort packet.

The primary advantage of DiffServ over IntServ is that there is much less complexity, and therefore greater efficiency, due to the fact that routers do not need to remember details for multiple flows. However, it can be difficult to implement DiffServ on a heterogeneous network, and it is possible for service guarantees to be violated across the entire network if a single edge host does not mark and shape traffic correctly. By comparison, an ATM cell is only 53 bytes long and includes 5 bytes of header.

As previously stated, many obstacles must be overcome in order to provide service guarantees in traditional wired networks. All of these obstacles exist in wireless networks, and an additional set of challenges are added that only exist in wireless or mobile networks. As a result of these additional impediments, QoS schemes used in traditional networks may not be feasible in wireless networks.

The first additional challenge of QoS in wireless networks is severe loss. Loss in wired networks is typically caused by excessive congestion that causes packets to be dropped at routers in the network. A negligible amount of data is lost due to corruption during transmission on a wire.

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A wireless link, however, typically suffers much more loss due to data being corrupted during transmission. One cause of loss in wireless transmission is fading, in which multiple versions of the same signal are received at the destination. If these signals are out of phase with each other or Doppler-shifted, they can interfere with each other. Other types of interference may also cause problems in wireless transmissions.

This interference may come from other communication occurring on the same frequency, electrical noise, or possibly even intentional communication jamming. Another obstacle in wireless QoS involves propagation delay. Some wireless networks span distances that are measured in kilometers. In these networks, propagation delay can be a tremendous burden to all communication, but especially to communication that requires a guarantee on total delay.

This problem may exist to some extent in metropolitan area networks MANs , and it is a significant issue in satellite communications. Next, there are times when it is desirable to make service guarantees in a mobile ad-hoc network MANET. Such networks may not have an infrastructure or a "coordinator" that determines which node has access to the shared channel. Instead, the nodes must enter into contention for access to the channel. This contention results in a large amount of collisions, which can result in lost data or a significant delay. In a QoS scheme for MANETs, it is generally desirable that higher-priority traffic wins the contention over lower-priority traffic, and that a minimal amount of time is wasted on contention.

Towards Smart Software Defined Wireless Network for Quality of Service Management

Finally, it can be difficult to maintain service guarantees in a network if the nodes involved are mobile. For example, in a scheme involving resource reservation, if the sender moves, a new route to the destination must be established. The possibility exists that no route to the destination exists that can provide the previous level of service guarantees, so the connection may be dropped or degraded to a lower level of service.

A similar problem can occur if a node along the route from sender to receiver moves. A final consideration when discussing QoS is user-perceived quality. It must be known what kind of service guarantee is required for a particular application. It would be wasteful to reserve resources beyond these needs. Also, by knowing which service characteristics are less important, the network can make better decisions regarding what to sacrifice, if necessary. Many applications that require QoS involve a person that is consuming the information.

These applications include audio and video, but users also expect a certain level of service when simply surfing the web or reading e-mail. Sometimes there is no quantitative way to determine the service quality for a particular application, so it is necessary to have people use the application at varying levels of QoS and ask for feedback on their experience.


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This way, it is possible to link the "intangible" user-perceived quality with the "tangible" factors that are typically studied, such as throughput and delay. It has been found that when users are surfing the web or reading e-mail, they are more tolerant of increased loss than they are of decreased throughput. Similar studies have been performed for other applications such as audio and video.

QoS schemes can work on various parts of the network architecture. Much focus has been placed on the data link layer of the protocol stack and the layers below. This section contains descriptions of some such QoS architectures. This extension enables multiple service levels and can provide service guarantees for network traffic.

This extension enables audio and video over home and office The first modification made by DCF is a contention-based media access method that is present in In DCF, the winner of the contention is the sender that transmitted first, as determined by a random function. The amount of time that the sender spends waiting is referred to as the inter-frame spacing IFS. As a result, the higher priority traffic will always win the contention.

The second modification made by These networks typically use a point coordination function PCF in which a coordinator polls the connected nodes, giving them an opportunity to transmit. If the hybrid coordinator HC determines that the channel is idle during the contention period, it can initiate a contention-free controlled access period CAP. During this period, the HC transmits frames and polls stations to allow them to transmit.

Though One example is the proposal for adaptive inter-frame spacing described in [KSE04]. When link quality degrades, the IFS for high priority traffic increases and the IFS for best effort traffic decreases. Back-off periods are similarly modified. The effect of the change is that when the link quality decreases, best effort traffic is sacrificed in order to continue to meet the guarantees of the higher priority traffic. However, the performance of best-effort traffic suffers when using AIFS.

The standard only allows for an infrastructure mode in which the base station schedules use of the channel similar to the Since Each class has its own service guarantees suited to the traffic involved. An interesting characteristic of This distinction allows for situations in which a single subscriber station has multiple flows with varying levels of QoS.

The architecture also makes use of soft-state resource management. The combination of these elements results in an architecture that can quickly respond to changes in network topology. In typical reservation-based schemes, the reservation mechanism is typically transmitted in a separate control channel. By reducing the need for a separate channel, complexity is reduced and efficiency can increase. It also takes less time to transmit these control messages in-band than out-of-band. In this scheme, a reservation is only maintained for a certain amount of time and if no packet is received for some time, then the resources are released.

Also, there is no need for an initial reservation before data is sent - a node will attempt to reserve resources the first time it receives a new packets for which it has no reservation. This mechanism allows for a great deal of adaptability when used in a mobile ad-hoc network. Some actions can be taken in the physical layer to improve quality of service.

In AMC, the method for transmission changes when the link quality changes. As a result, more time will be required to send the same amount of data, so the MAC layer must adjust its scheduling accordingly. Using this scheme, throughput performance closely matches the performance of the channel.

When the link quality is good, it will take less time to transmit the QoS-guaranteed traffic than it will take when the link quality is bad. At these times, there will be more resources available to transmit best-effort traffic. As a result, the total bandwidth is well-utilized. When discussing QoS in wireless data networks, one must not overlook the needs of personal area networks PANs.

The most common example of a PAN is Bluetooth. Though QoS for audio is built in to the Bluetooth protocol, other applications requiring service guarantees, such as video, must rely on a QoS architecture built on top of Bluetooth. It is possible to inform the piconet master how much channel time is required by periodically responding to queries with channel time requests. The amount of channel time required can be derived from fields that are present in MPEG streams.

It is important to note that the amount of channel time required can vary within a single stream. By sending these requests periodically, the allocated channel time can vary as needed. One advantage of the architecture is that it responds well to the addition of hosts on the piconet due to the fact the bandwidth requests are sent infrequently and only the amount of bandwidth that is required at any given time is reserved.

Several people have researched efficient ways to provide service guarantees in contention-based MAC environments since such circumstances are common in MANETs. The paper also explores the abstractions used when evaluating a wireless network. It may not be appropriate to view a wireless network in terms of the "link" abstraction since spectrum, rather than the "link" is the scarce resource with which QoS schemes are concerned. If the wireless network is viewed as a continuous vector space in which physical space and spectrum may be allocated for transmission, then all available resources can be used more efficiently.

CRS is an architecture suited for a MANET with several nodes spread out over physical space such that all nodes cannot communicate directly with each other. A node that wants to transmit will send a signal in one of several "slots" in a CRS frame. Several rounds of contention will continue until each node that wants to transmit is not in range with another node that wants to transmit. In each round, a random backoff function determines which nodes are still in contention. An example contention scenario is depicted in figure 1. In this scenario, all hosts except for host B assert that they would like to transmit.

Samenvatting

Multiple rounds of contention follow until only hosts F and C are trying to transmit. While this system is very effective in terms of total bandwidth utilization, several improvements can be made. This mechanism ensures that two senders that cannot hear each other won't transmit to the same receiver at the same time.

It also allows the transmission parameters at the physical layer to be modified due to the state of the channel as perceived by both the sender and the receiver. A priority phase can be added to the beginning of the contention period. Shouldn't operators be preparing for such an eventuality as Sprint and Cingular have in the USA, where enterprises are much more used to rigorous customer service and penal clauses for failure of delivery?

To operators, who place great store on enterprise customers who tend to be more loyal and, of course, much more profitable than consumer customers, you'd think such thinking may change. But one independent consultancy says that operators tend to offer service to the level of their competition, rather than the actual demands of their enterprise users. If this continues, most operators will strive to offer a service level on a par with the standards set by the competition.

This is rather limiting since it should be their customers, not their competition, that dictates to operators. This, inCode says, is the most accurate way to gauge the end user's QoS experience. Part of this is understanding the cost and quality trade offs that an enterprise must consider when deploying applications across a wireless network. It is therefore essential that operators base their SLAs on realistic customer expectations and that meaningful measurement techniques are in place that create realistic solutions to potential problems. Ultimately therefore, the approach and tone of the SLA and the benefits they generate should be based on a mutual understanding of what the service can realistically deliver.

At the moment the operators say it is too expensive. The suppliers respond that that is exactly the issue they are there to solve. Keiran Moynihan: Yes - the critical driver underpinning the enterprise sector's push for genuine contractual SLAs is the growing dependency of the enterprise business on these wireless services which they have now incorporated into their day to day business.