the first Cisco platforms to converge voice and data traffic onto an IP network by .. Finally, each design chapter has a case-study example at the end that ties. Sign up today and get $5 off your first purchase. End-to-End QoS Network Design Quality of Service for Rich-Media & Cloud Networks Second Edition New best. End-to-End QoS Network Design Quality of Service for Rich-Media & Cloud Networks Second Edition New best practices, technical strategies, and proven.
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Classification and Marking Tools. IP Precedence can readily be mapped one to one into and out of The enterprise customer wants both voice and call-signaling traffic to be admitted to the service provider's Realtime class. Cisco TelePresence Fundamentals. The overwhelming volumes of traffic that such attacks can create readily can drive network device processors to their maximum levels.
Connecting Networks Companion Guide. William Alexander Hannah. Kevin Wallace. Akhil Behl. Building Wireless Sensor Networks. Robert Faludi. David Hucaby.
Cisco Router Configuration Handbook. Eric A. Richard Deal. Bob Vachon. Hacking Exposed Mobile. Neil Bergman. Eric Conrad. Building the Mobile Internet. Mark Grayson. Mastering pfSense. David Zientara. Antonio Sanchez Monge. Rick Graziani. IPv6 Address Planning. Tom Coffeen. Data Center Fundamentals. Mauricio Arregoces. Anthony Minessale II. Neil Smyth. Zhuo Xu. Gustavo A. Architecting Mobile Solutions for the Enterprise. Dino Esposito. Routing Protocols Companion Guide.
Hacking Exposed Wireless, Third Edition. Joshua Wright. Doug Marschke. IP Specialist. Madhup Gulati. Learning AWS. Amit Shah. Toby Velte. The Illustrated Network. Walter Goralski. Cacti Beginner's Guide. Thomas Urban. Cisco Unified Customer Voice Portal.
Rue Green. Chris Olsen. Continuous Authentication Using Biometrics. Issa Traore. Networking Essentials. Jeffrey S. From Science to Society. Packet Analysis with Wireshark. Anish Nath. AutoQoS is definitely the way to go.
The former group will drive more confidently. To complement these line-by-line design recommendations. These verification examples are. These verification commands are presented in context with the design examples. These examples are indicative of what can be expected in production environments. Goals and Methods The main goal of this book is to present templates that address 80 percent or more of a customer's requirement of QoS in a particular context and architecture LAN.
A key approach that we've used throughout this configuration-rich book is to incorporate inline explanations of configurations. In this way. Often these case-study examples span several devices and. Chapter 3. The QoS toolset review section. This chapter highlights the interoperation and interdependencies of these mechanisms with other QoS mechanisms.
Chapter 1. Chapter 2. Frame Relay Discard Eligibility. Chapter 6. Chapter 7. It begins by detailing the service-level requirements of voice. To set proper context for the design chapters. Chapters 3 through Chapter 9. This review is not indented to serve as feature documentation. Chapter 8. Chapter 5. Chapter 4. Platform-unique features. QoS Tools. The next chapterswhich comprise the heart of this bookcover the QoS design recommendations for protecting voice.
Chapter The Cisco QoS Baseline. ATM-to-Frame Relay service interworking. Frame Relay. The tools reviewed in previous chapters can protect voice from data. When the QoS toolset is reviewed. Five separate access-edge models are presented. QoS Best Practices. Campus QoS Design. Scavenger-Class QoS Design. Branch QoS Design. QoS design principles are introduced to show how QoS mechanisms can be strategically deployed to address application requirements while mitigating such attacks.
The QoS requirements of voice. The chapters in this part of the book are as follows: Part I: Introduction to QoS Part I of this book provides a brief background of the evolution of QoS technologies and overviews various currently available QoS features and tools.
Introduction to QoS This chapter provides a brief history of both voice and data network evolution. The following topics are introduced and briefly discussed: It is instructive to review briefly a small amount of networking history that puts QoS technology in perspective. Although these recovery methods work well for data applications. It has been saidonly partly facetiouslythat packet switching has been a year failed experiment.
PVC or SVC is defined over the underlying connectionless packet-switched network to handle a session of communication between two devices or endpoints. Packet switching chops the information flow into small chunks of data.
This network consisted of fixed-bandwidth. ATM minimizes latency by defining fixed-length cells. The PSTN simply is not optimized for data networks: The equipment is expensive.
The resiliency of packet-switched networks caused a shift toward connectionless communication protocols that can handle packets that might arrive out of order. A Brief Historical Perspective A century ago. Several universities conducted many experiments to this effect in the s.
When processing power became available at affordable cost points. ATM was the first general data-networking technology to include a class of service concept at the lower layers of communications transport protocolsthat is. Then why not just use the PSTN?
Options for transmitting data over the voice network met with equally limited success. In theory.
Some five decades later. In these protocols. IP won out as the technology of choice for converged networks because of its ease of use. This was primarily because of nontechnical reasons. In the late s. QoS allows for the differentiated treatment of data traffic versus voice and other delay-sensitive traffic.
In an effort to find a more effective solution to support a combination of voice and data. In other words. ISDN never really took off. The key enablers for IP networks to converge successfully voice. Packet markings. QoS Evolution IP networks of the mids were invariably best-effort networks. Figure shows the broad steps in the evolution of QoS concepts since the early s.
Privately owned enterprise and service provider networks. RSVP signals bandwidth and latency requirements for each discrete session to each node along a path logical circuit that packets would take from the sending endpoint to the receiving endpoint. The nodes could use whatever features proprietary or otherwise were available.
To address this challenge. The DiffServ model describes various behaviors to be adopted by each compliant node. Figure RSVP required every node to heed its reservations. As the IntServ and DiffServ models have evolved. The signaling protocol guarantees that adequate resources are available at each hop for the flow before admitting the flow onto the network. Although this scales well which is probably why enterprises and service providers deploy it more frequently. With no clear advantage to either model.
IntServ uses a flow-based concept coupled with a signaling protocol along the packet path. Today the debates over the advantages of each continue without a clear.
QoS technologies offer a myriad of "nerd knobs" that can be turned. When viewed as individual features. In the hands of capable administrators. The most recent trend in QoS is simplification and automation. DiffServ uses packet markings to classify and treat each packet independently. QoS techniques became more sophisticated and were adapted to advanced networking technologies. In initial deployments. The realization has begun that neither method offers a complete solution and that elements of both should be combined to provide the most general method applicable to the widest range of traffic and application types.
QoS mechanisms continue to use a mix of IntServ and DiffServ technologies to offer the breadth of services required on networks. Many administrators do not have the time or the desire to delve into QoS technologies to this expert level and instead would prefer to define high-level policies and have the network simply "do the right things" to implement them.
Expectations and "quality problems" from an IT perspective tend to be more absolute and measurable. User Network Expectations The perception of how the network behaves. User complaints might result even though the network met the SLA formal or otherwise. End users. The end user has no concept of and typically very little interest in the capabilities of the networks in betweenunless. Yet they do not expect that same quality level from a cell phone or a voice call spoken into a microphone on a personal computer.
End users perceive the network quality through their end device and have certain expectations of appropriate service levels. Service providers formalize these expectations within service-level agreements SLAs. Some enterprise networks indeed might use SLAs of various levels of formality between the IT department and the customer departments that they serve. End User An end user's perception of QoS is typically subjective and relative.
Information Technologies Management IT management perceives the network quality through management statistics such as throughput. This is the general expectation. Corporate enterprise networks typically do not have such formal SLAs.
Understanding QoS Appreciating what QoS tools and methods do to packets in a network is fundamental to appreciating the effect of individual QoS tools discussed in later chapters. It's only as strong as the weakest link. QoS is a vital element in any converged network. End-to-End QoS Regardless of how it is measured.
Testing has shown that delay-sensitive applications. Figure shows the segments of the network where QoS must be deployed in the typical IP telephony enterprise network and what QoS techniques are common in each segment. QoS must be implemented across all areas of the network. To ensure the highest level of quality. To achieve this goal. This concept of unfairness applies equally to traffic for which higher levels of priority must be maintained for example.
The Challenges of Converged Networks The high-level goal of QoS technologies in a converged network is to abstract the fact that there is only one network and to make voice. Application-based contention occurs when different applications from the same user or user group contend with each other for limited network resources. Best-effort or better service is provided to all desirable traffic on the network. User-based contention occurs when packets from different users.
Such networks work well if there is enough CPU. QoS technologies allow different types of traffic to contend. The latter category of traffic introduces the concept of less than best-effort service. Application-Based Contention To obtain the appropriate levels of service from often scarce network resources experiencing contention. Such Scavenger traffic. Networks without QoS enabled are described as best-effort networks.
These applications might have different service requirements from the network. Best-effort network designs treat all packets as equally important. Packet loss in the context of QoS does not relate to drops because of network outages or link flaps because these are a function of a high-availability network design. Delay or latency This is the finite amount of time that it takes a packet to reach the receiving endpoint after being transmitted from the sending endpoint.
The transmission quality of the network is determined by the following factors: Packet loss This is a comparative measure of the number of packets faithfully transmitted and received to the total number transmitted. Delay variation or jitter Also known as interpacket delay.
Before any QoS can be implemented successfully. Packetization delay The time required to sample and encode voice or video signals into packets.
In the case of voice. QoS is defined as the measure of a system's service availability and transmission quality. Service availability is a crucial foundation element of QoS.
Real-time applications. The target for high availability is This time period is termed end-to-end delay and is comprised of two components: In data networks carrying voice. Delay Variation. Serialization delay The time required to transmit the packet bits onto the physical media.
Instantaneous changes in arrival times of packets that exceed the jitter buffer's capability to compensate result in jitter buffer overruns and underruns.
A jitter buffer overrun occurs when packets containing voice or video arrive faster than the jitter buffer can accommodate. Jitter buffers can be fixed or adaptive.
A jitter buffer underrun occurs when the arrival times of packets increase to the point that the jitter buffer has been exhausted and contains no packets for the digital signal processors DSP to process when it is time to play the next piece of voice or video. Variable network delay generally is caused by congestion within the network. When this happens.
IntServ is analogous to a custom mail service. Key endpoints are the sender and receiver applications that request a desired service from the network for a set of flows. IntServ is a specification of the following: What the sender is sending rate. QoS Models As briefly introduced earlier. IntServ and DiffServ. Conceptual simplicity. By comparison. More specifically. IntServ describes three main classes of service that an application can request: Guaranteed services RFC Provides firm mathematically provable bounds on end-to-end packet-queuing delays.
The mail is delivered if and when it can be. Packets of a particular service belong to a particular "class. Call admission control CAC capabilities. All intermediate nodes must implement RSVP. DiffServ can be compared to different tiers of mail service.
Each service offers particular parameters of delivery. Periodic refresh messages are used. All network elements must maintain state and exchange signaling messages on a per-flow basis. DiffServ Overview Continuing the analogy of mail services. The premise of DiffServ is very simple: It offers different network service levels to a packet. Meaningful services can be constructed by a combination of the following: Setting a field in the IP header upon network entry or at a network boundary IPP or DSCPs Using this field to determine the nodes inside the network forward the packets Conditioning the marked packets at network boundaries in accordance with the requirements or rules of each "class" or service The essence of DiffServ is the specification of PHBs that an application can receive from the network: Expedited forwarding RFC Interoperability All vendors already are running IP.
The node can use whatever features optimize its hardware and architecture. At that time. The DiffServ model include these advantages: Scalability No state or flow information is required to be maintained. The disadvantages of the DiffServ model include the following: No end-to-end bandwidth reservations are present. Flexibility The DiffServ model does not prescribe any particular feature such as a queuing technique to be implemented by a network node.
The core of the network implements the PHBs and uses the packet markings to make queuing and dropping decisions. Performance The packet contents need be inspected only once for classification purposes. The purpose of this book is not to reiterate in depth how these tools work. To reduce the requirement for detailed recursive classification. This analysis is referred to as classification. QoS Toolset [View full size image] Packets or frames entering a network device must be analyzed to determine the treatment that they should be given.
Classification is the first QoS function to occur for any given QoS policy. QoS tools fall into the following categories: Classification and marking tools Policing and shaping tools Congestion-avoidance selective dropping tools Congestion-management queuing tools Link-specific tools Figure illustrates the relationship and overall cohesiveness of different QoS tools.
At this point. Such protection can be achieved only through call admission control CAC mechanisms. Packets that are not discarded are subject to congestion management queuing to prioritize and protect various traffic types when congestion happens to the transmission link.
Link-specific tools usually are required only at WAN edges and include mechanisms for compression or fragmentation to reduce delay and jitter. Packets are marked and the markings are trusted. Marking establishes a distinct trust boundary that demarcates the point where the packet markings are set properly and.
IntServ mechanisms. Packets are marked. Some QoS tools such as marking and policing can be applied in both the ingress and egress directions of the traffic flow on an interface. When packets enter a network device.
Such tools are very effective in protecting real-time voice from nonreal-time data traffic. In the first two scenarios. Packets are unmarked. The QoS mechanisms primarily DiffServ described previously are applicable to packets already admitted to the network. Other tools such as queuing can be applied only in the egress direction with some platform-specific exceptions. After marking.
Layer 2 parameters CoS. The result included the following: The portfolio of QoS mechanisms and options became very rich and. This is just an example of a possible configuration. During the early s. Cisco spent significant development effort to implement an extensive QoS tool and feature set.
FR DE. Three main components make up the MQC: Example Example demonstrates a sample MQC policy. In response to this feedback. Simplifying QoS In the late s. The QoS Baseline defines up to 11 classes of traffic that are used in all Cisco design guides.
The set of 11 classes is designed to accommodate the QoS needs of an enterprise not only for today. The QoS Baseline was developed with two primary goals: To document which QoS features are required on platforms that are considered QoSenabled products To provide a gap analysis of which features. To address the needs of the both expert and casual QoS users. MQC supports up to different traffic classes within a policy map.
The QoS Baseline does not dictate that every enterprise deploy all these traffic classes immediately. Although adept QoS administrators might see this as desirable. For existing platforms. To that end. Beyond its engineering influence. It gives a starting point for network design and implementation.
In Another factor in the complexity of QoS deployment is the inconsistency of QoS features across specific hardware platform releases or software releases. Even if an enterprise needs only a handful of these 11 classes today. Table gives a summary of the QoS Baseline recommendations. Table This initiative is called Consistent QoS Behavior code and should remove most if not all of the traditional QoS idiosyncrasies between the distributed and nondistributed platforms.
These changes are discussed in more detail in Chapter 3. Automatic QoS. Such projects are ongoing. Cisco is consolidating and improving the QoS code bases of the distributed router architectures such as the Cisco series of routers and the nondistributed router families such as the Cisco to series routers. As part of this effort. These adjustments in the default behavior eliminate the need for access lists and explicit marking configurations that were required in earlier software releases.
The only class that is not assigned automatically. For campus Catalyst switches. AutoQoS is supported on Frame Relay. Automatic QoS AutoQoS is essentially an intelligent macro that enables an administrator to enter one or two simple AutoQoS commands to enable all the appropriate features for the recommended QoS settings for an application on a specific interface. Low-latency queuing LLQ for voice. AutoQoS performs the following automatically: By entering one global or one interface command depending on the platform.
In its initial version. It performs the following automatically: Table shows the classes of traffic automatically detected and provisioned for by AutoQoS Enterprise. AutoQoS Enterprise creates class maps and policy maps on the basis of Cisco experience and best-practices methodology. AutoQoS template generation and installation This phase generates templates from the data collected during the autodiscovery phase and installs the templates on the interface.
Autodiscovery data collection The autodiscovery phase uses protocol discovery based on Network-Based Application Recognition NBAR to detect the applications on the network and perform statistical analysis on the network traffic. These templates then are used as the basis for creating the class maps and policy maps for the network. After the class maps and policy maps are created. It reduces human error and lowers training costs. The AutoQoS Enterprise feature consists of two configuration phases.
Unlike conventional regression testing of QoS features. Catalyst queuing. The objective was to make the tests as representative of real-life enterprise environments as possible. Many "nerd-knobs" within the QoS toolset could be turned and tuned. There were far too many platform-specific idiosyncrasies to keep in mind. QoS tools were enabled simultaneously with availability tools. The results from these extensive tests were summarized and published in late as the QoS Design Guide.
The response was very favorable.
It is important to keep in mind not only the evolution of QoS. As with all technical papers. During this time. To accomplish this mandate. To address this barrier to adoption. This document quickly became one of the most downloaded technical documents ever published by Cisco. They tested QoS features not in isolation. Customers finally had not only the tools to achieve convergence of their voice and data networks. Despite the recognition that these features could enable network convergence.
This caused changes in the document because the marking recommendations put forward in the Enterprise QoS SRND reflected the best practices for an enterprise. AutoQoS Evolution Specifically. Shortly thereafter. Cisco IOS development combined the best practices put forward in the QoS design guides with the classification and marking recommendations defined in the QoS Baseline.
QoS for videoconferencing and different types of data applications. As the lines between enterprise and service provider are not only blurring but also requiring a level of cooperation previously unprecedented as discussed in additional detail in Chapter Following this. At the time.
AutoQoS Enterprise. So why is this relevant? This brief history was given to describe the cycles required in AutoQoS evolution. AutoQoS evolution depends on two prerequisites: QoS feature development Verified network design guides. As QoS continues to evolve. QoS is still evolving. These include the use of QoS as a technology not only to enable convergence. This chapter also introduced the QoS Baseline 11 classes of traffic. You are now ready to get into the principles of QoS design and then review salient details of the QoS toolset.
Chapters 10 through 16 provide design examples of how these tools are deployed in specific types of networks. Another objective of this book is to show how to deploy QoS not only for purposes such as maintaining voice quality for VoIP calls.
The goal instead is to show how these techniques are used in a holistic network design to achieve end-to-end QoS for the entire network. Chapters 3 through 9 provide a more in-depth discussion of the various QoS tool categories. These network types are included in these discussions: Summary This chapter briefly reviewed the fundamental concepts of QoS.
Cisco Press. Michael Cavanaugh.
Communications Convergence. RFC CommWeb Tech Library: Wendell Odom. An Overview": Michael Flannagan and Kevin Turek. Srinivas Vegesna.
Cisco Catalyst QoS: Quality of Service in Campus Networks. Catalyst IOS version Catalyst Cisco IOS Release Catalyst CatOS version 8. This process requires business-level objectives of the QoS implementation to be defined clearly and for the service-level requirements of applications to be assigned preferential or deferential treatment so that they can be analyzed. These enterprise applications with unique QoS requirements are discussed in this chapter: Classification and marking principles Policing and markdown principles Queuing and dropping principles DoS and worm mitigation principles Deployment principles More than just a working knowledge of QoS tools and syntax is needed to deploy end-to-end QoS in a holistic manner.
Video both Interactive-Video and Streaming-Video. QoS design principles relating to classification. Within this discussion.
These serve as guiding best practices in the design chapters to follow. The Scavenger class is examined in more detail. This technique can be effective at concealing the loss of up to 20 ms of samples. New best practices, technical strategies, and proven designs for maximizing QoS in complex networks.
This authoritative guide to deploying, managing, and optimizing QoS with Cisco technologies has been thoroughly revamped to reflect the newest applications, best practices, hardware, software, and tools for modern networks. This new edition focuses on complex traffic mixes with increased usage of mobile devices, wireless network access, advanced communications, and video. It reflects the growing heterogeneity of video traffic, including passive streaming video, interactive video, and immersive videoconferences.
It also addresses shifting bandwidth constraints and congestion points; improved hardware, software, and tools; and emerging QoS applications in network security. The authors first introduce QoS technologies in high-to-mid-level technical detail, including protocols, tools, and relevant standards. They examine new QoS demands and requirements, identify reasons to reevaluate current QoS designs, and present new strategic design recommendations.
A registered Professional Engineer P. Eng , he has 15 years of IT experience and is primarily focused on wireless and security architectures. There, she spoke at Cisco conferences, trained sales staff and partners, authored books, and advised customers. Kenneth Briley, Jr. Appendix 1 and Appendix 2. Download the sample pages includes Chapter 15 and Index. Policy 2: