Quality of Service Networking - Doc. Wiki. From Doc. Wiki. Quality of Service (Qo. S) refers to the capability of a network to provide better service to selected network traffic over various technologies, including Frame Relay, Asynchronous Transfer Mode (ATM), Ethernet and 8. Network Diagram Software - Easy network design software for network drawings with abundant examples and templates, Free Download. Hierarchical Network Design Overview (1.1) The Cisco hierarchical (three-layer) internetworking model is an industry wide adopted model for designing a reliable. SONET, and IP- routed networks that may use any or all of these underlying technologies. The primary goal of Qo. S is to provide priority including dedicated bandwidth, controlled jitter and latency (required by some real- time and interactive traffic), and improved loss characteristics. Also important is making sure that providing priority for one or more flows does not make other flows fail. Qo. S technologies provide the elemental building blocks that will be used for future business applications in campus, WAN, and service provider networks. This article outlines the features and benefits of the Qo. S provided by the Cisco IOS Qo. S. The Cisco IOS Qo. S software enables complex networks to control and predictably service a variety of networked applications and traffic types. Almost any network can take advantage of Qo. S for optimum efficiency, whether it is a small corporate network, an Internet service provider, or an enterprise network. The Cisco IOS Qo. S software provides these benefits. Control over resources - You have control over which resources (bandwidth, equipment, wide- area facilities, and so on) are being used. For example, you can limit the bandwidth consumed over a backbone link by FTP transfers or give priority to an important database access. More efficient use of network resources - Using Cisco's network analysis management and accounting tools, you will know what your network is being used for and that you are servicing the most important traffic to your business. Tailored services - The control and visibility provided by Qo. S enables Internet service providers to offer carefully tailored grades of service differentiation to their customers. Coexistence of mission- critical applications - Cisco's Qo. S technologies make certain that your WAN is used efficiently by mission- critical applications that are most important to your business, that bandwidth and minimum delays required by time- sensitive multimedia and voice applications are available, and that other applications using the link get their fair service without interfering with mission- critical traffic. Foundation for a fully integrated network in the future - Implementing Cisco Qo. S technologies in your network now is a good first step toward the fully integrated multimedia network needed in the near future. Contents. 1Qo. S Concepts. Basic Qo. S Architecture. Qo. S Identification and Marking. Qo. S Within a Single Network Element. Qo. S Management. End- to- End Qo. S Levels. Classification- Identifying Flows. IP Precedence: Differentiated Qo. S9. Congestion- Management Tools. Queue Management (Congestion- Avoidance Tools)1. Traffic- Shaping and Policing Tools. Link Efficiency Mechanisms. Qo. S Management. Qo. S on Ethernet. Multiprotocol Label Switching: Allowing Flexible Traffic Engineering. Qo. S Policy Control. SNA To. S1. 8Qo. S for Packetized Voice. Qo. S for Streaming Video. Summary. 21. Review Questions. For More Information Qo. S Concepts Fundamentally, Qo. S enables you to provide better service to certain flows. This is done by either raising the priority of a flow or limiting the priority of another flow. When using congestion- management tools, you try to raise the priority of a flow by queuing and servicing queues in different ways. The queue management tool used for congestion avoidance raises priority by dropping lower- priority flows before higher- priority flows. Policing and shaping provide priority to a flow by limiting the throughput of other flows. Link efficiency tools limit large flows to show a preference for small flows. Cisco IOS Qo. S is a tool box, and many tools can accomplish the same result. A simple analogy comes from the need to tighten a bolt: You can tighten a bolt with pliers or with a wrench. Both are equally effective, but these are different tools. This is the same with Qo. S tools. You will find that results can be accomplished using different Qo. S tools. Which one to use depends on the traffic. You wouldn't pick a tool without knowing what you were trying to do, would you? If the job is to drive a nail, you do not bring a screwdriver. Qo. S tools can help alleviate most congestion problems. However, many times there is just too much traffic for the bandwidth supplied. In such cases, Qo. S is merely a bandage. A simple analogy comes from pouring syrup into a bottle. Syrup can be poured from one container into another container at or below the size of the spout. If the amount poured is greater than the size of the spout, syrup is wasted. However, you can use a funnel to catch syrup pouring at a rate greater than the size of the spout. This allows you to pour more than what the spout can take, while still not wasting the syrup. However, consistent overpouring will eventually fill and overflow the funnel. Basic Qo. S Architecture The basic architecture introduces the three fundamental pieces for Qo. S implementation (see Figure: A Basic Qo. S Implementation Has Three Main Components). Qo. S identification and marking techniques for coordinating Qo. S from end to end between network elements. Qo. S within a single network element (for example, queuing, scheduling, and traffic- shaping tools). Qo. S policy, management, and accounting functions to control and administer end- to- end traffic across a network. Figure: A Basic Qo. S Implementation Has Three Main Components Qo. S Identification and Marking Identification and marking is accomplished through classification and reservation. Classification To provide preferential service to a type of traffic, it must first be identified. Second, the packet may or may not be marked. These two tasks make up classification. When the packet is identified but not marked, classification is said to be on a per- hop basis. This is when the classification pertains only to the device that it is on, not passed to the next router. This happens with priority queuing (PQ) and custom queuing (CQ). When packets are marked for network- wide use, IP precedence bits can be set (see the section "IP Precedence: Signaling Differentiated Qo. S"). Common methods of identifying flows include access control lists (ACLs), policy- based routing, committed access rate (CAR), and network- based application recognition (NBAR). Qo. S Within a Single Network Element Congestion management, queue management, link efficiency, and shaping/policing tools provide Qo. S within a single network element. Congestion Management Because of the bursty nature of voice/video/data traffic, sometimes the amount of traffic exceeds the speed of a link. At this point, what will the router do? Will it buffer traffic in a single queue and let the first packet in be the first packet out? Or, will it put packets into different queues and service certain queues more often? Congestion- management tools address these questions. Tools include priority queuing (PQ), custom queuing (CQ), weighted fair queuing (WFQ), and class- based weighted fair queuing (CBWFQ). Queue Management Because queues are not of infinite size, they can fill and overflow. When a queue is full, any additional packets cannot get into the queue and will be dropped. This is a tail drop. The issue with tail drops is that the router cannot prevent this packet from being dropped (even if it is a high- priority packet). So, a mechanism is necessary to do two things. Try to make sure that the queue does not fill up, so that there is room for high- priority packets. Allow some sort of criteria for dropping packets that are of lower priority before dropping higher- priority packets. Weighted random early detect (WRED) provides both of these mechanisms. Link Efficiency Many times low- speed links present an issue for smaller packets. For example, the serialization delay of a 1. If a voice packet were to get behind this big packet, the delay budget for voice would be exceeded even before the packet left the router! Link fragmentation and interleave allow this large packet to be segmented into smaller packets interleaving the voice packet. Interleaving is as important as the fragmentation. There is no reason to fragment the packet and have the voice packet go behind all the fragmented packets. Note: Serialization delay is the time that it takes to put a packet on the link. Cisco Networking, Best VPN Security, Routing, Catalyst- Nexus Switching, Virtualization Hyper- V, Windows Server, IP PBXAccurately monitoring your organization’s business application performance, service provider SLA breaches, network infrastructure traffic, bandwidth availability, Wi- Fi capacity, packet loss, delay, jitter and other important metrics throughout the network is a big challenge for IT Departments and IT Managers. Generating meaningful reports for management with the ability to focus on specific metrics or details can make it an impossible task without the right Network Management System. The continuous demand for businesses network infrastructure to support, uninterrupted, more applications, protocols and services has placed IT departments, IT Managers and, subsequently, the infrastructure they manage, under tremendous pressure. Knowing when the infrastructure is reaching its capacity and planning ahead for necessary upgrades is a safe strategy most IT Departments try to follow. The statistics provided by the Cisco Visual Networking (CVN) Index Forecast predict an exponential growth in bandwidth requirements the coming 5 years: These types of reports, along with the exponential growth of bandwidth & speed requirements for companies of all sizes, raises a few important questions for IT Managers, Network Administrators and Engineers: Is your network ready to accommodate near- future demanding bandwidth requirements? Is your current LAN infrastructure, WAN and Internet bandwidth sufficient to efficiently deliver business- critical applications, services and new technologies such as Io. T, Wi- Fi - 8. 02. HD Video? Do you really receive the bandwidth and SLA that you have signed for with your internet service provider or are the links underutilized and you are paying for expensive bandwidth that you don’t need? Do you have the tools to monitor network conditions prior to potential issues becoming serious problems that impact your business? All these questions and many more are discussed in this article aiming to help businesses and IT staff understand the requirements and impact of these technologies on the organization’s network and security infrastructure. We show solutions that can be used to help obtain important metrics, monitor and uncover bottlenecks, SLA breaches, security events and other critical information. Let’s take a quick look at the topics covered in our article: Finally, we must point out that basic knowledge of the Networking and Design concepts is recommended for this article. Click to Discover how a Network Management System can help Monitor your Network, SLAs, Delay Jitter and more. Network performance metrics vary from business to business and provide the mechanism by which an organization measures critical success factors. The most important performance metrics for business networks are as follows: Connectivity (one- way)Delay (both round- trip and one- way)Packet loss (one- way)Jitter (one- way) or delay variation. Service response time. Measurable SLA metrics. Bandwidth is one of the most critical variables of an IT infrastructure that can have a major impact to all the aforementioned performance metrics. Bandwidth over saturated links can cause poor network performance with high packet loss, excessive delay, and jitter which can result in lost productivity and revenue, and increased operational costs. This rapid growth for bandwidth affects the Enterprises and Service Providers which are continually challenged to efficiently deliver business- critical applications and services while running a network at optimum performance. The necessity for more expensive bandwidth solutions is one of the crucial factors that may have a major impact on a network and applications performance. Let’s have a quick look at the new technologies with high bandwidth needs which require careful bandwidth and infrastructure planning: This surpassed standard definition by the end of 2. User demand for HD video has a major impact on a network due to the demanding bandwidth requirements as clearly displayed below: DVD,7. HD and 1. 08. 0p HD bandwidth requirements: (H. HD video requires around 2,5 Mbps or twice as much bandwidth as (H. DVD(H. 2. 64) 1. 08. HD video requires around 5. Mbps or twice as much bandwidth as (H. Ultra HD 4. 32. 0p video requires around 2. Mbps or four times as much bandwidth as (H. Wi- Fi. It is designed to give enterprises the tools to meet the demands of BYOD access, high bandwidth applications, and the always- on connected user. The 8. 02. 1. 1ac IEEE standard allows for theoretical speeds up to 6. Gbps in the 5- GHz band, or 1. Taking into consideration the growing trend and adoption of Bring- Your- Own- Device (BYOD) access, it won’t be long until multi- gigabit Wi- Fi speeds will become necessary. Each desktop delivered over WAN can consume up to 1 Mbps bandwidth and considerably more when employees access streaming video. In companies with many virtual desktops, traffic can quickly exceed existing WAN capacity, noticeably degrading the user experience. The Annual global cloud IP traffic will reach 1. ZB (1. 2 Zetta. Bytes per month) by the end of 2. ZB per year (3. 21 Exa. Bytes per month) in 2. Annual global data center IP traffic will reach 1. ZB (1. 3 ZB per month) by the end of 2. ZB per year (3. 90 EB per month) in 2. These forecasts are provided by the Cisco Global Cloud Index (GCI) which is an ongoing effort to forecast the growth of global data center and cloud- based IP traffic. Bandwidth requirements and traffic pattern are not common among various applications and need careful planning as displayed below: Data, Video, Voice and VDI bandwidth requirements & traffic patterns. An effective strategy is essential in order to monitor network conditions prior to potential issues becoming serious problems. Poor network performance can result in lost productivity, revenue, and increased operational costs. Hence, detailed monitoring and tracking of a network, applications, and users are essential in optimizing network performance.
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