A

After completion of 802.1x authentication and 802.1x key management, the client and the AP perform a Four-Way Key Handshake and exchange a nonce, a WPA information element, a pairwise transient key (PTK), and MIC key information. This ensures validity of the AP and creates a trusted session between the client and the AP. The final step is the two-way key handshake that the client and the AP exchange. The purpose of this handshake is to derive a group transient key (GTK), which provides a group...

Analog Interfaces

A gateway can have many types of analog interfaces FXS (Foreign Exchange Station), FXO (Foreign Exchange Office), and E& M (Earth and Magneto or Ear and Mouth). An FX connection has a station and an office end. The office end (FXO) provides services such as battery, dial tone, digit collection, and ringing to the other end, namely the station (FXS). The FXS interface of a gateway is meant for analog phones, fax machines, and modems. To those devices, the gateway acts like the PSTN central...

Applying Link Efficiency Mechanisms

Link efficiency mechanisms discussed in this section might not be necessary on all interfaces and links. It is important that you identify network bottlenecks and work on the problem spots. On fast links, many link efficiency mechanisms are not supported, and if they are, they might have negative results. On slow links and where bottlenecks are recognized, you must calculate the overhead-to-data ratios and consider all compression options. On some links, you can perform full link compression....

Automation with Cisco AutoQoS

Cisco AutoQoS is capable of performing the following tasks and might generate appropriate configurations to accomplish them Defining the trust boundaries (or extended trust boundaries) and re-marking incoming traffic on trusted and untrusted links Defining traffic classes based on the applications and protocols discovered in the network Creating queuing mechanisms with proper configurations such as bandwidth guarantee for each traffic type, based on the DiffServ model Enabling...

AutoQoS

AutoQoS is a value-added feature of Cisco IOS. After it is enabled on a device, AutoQoS automatically generates QoS configuration commands for the device. The initial release of AutoQoS (Auto QoS VoIP) focused on generating commands that made the device ready for VoIP and IP Telephony. Later, the AutoQoS Discovery feature was introduced. The next generation of AutoQoS that takes advantage of AutoQoS discovery is called AutoQoS for the Enterprise. AutoQoS Discovery, as its name implies, analyzes...

Available Bandwidth

Packets usually flow through the best path from source to destination. The maximum bandwidth of that path is equal to the bandwidth of the link with the smallest bandwidth. Figure 2-1 shows that R1-R2-R3-R4 is the best path between the client and the server. On this path, the maximum bandwidth is 10 Mbps because that is the bandwidth of the link with the smallest bandwidth on that path. The average available bandwidth is the maximum bandwidth divided by the number of flows. Figure 2-1 Maximum...

B

BA (behavior aggregate), 101 background access, 237 VAD, 42 backups, WCS Base, 301 backward explicit congestion notification availability, 63-64 codecs, 35-36 guarantees, 67 CBWFQ, 139-140 SLAs, 187 packet telephony networks, 10 requirements codecs, 24 compression, 24-25 reserving, 141 VAD, 41-42 voice, 34-36 VoIP, 34-42 bandwidth command, 140, 219 bandwidth percent command, 140 BECN (backward explicit congestion notification), 99 behavior aggregate (BA), 101 benefits of telephony packet...

Basic Voice Encoding Converting Analog to Digital

Converting analog voice signal to digital format and transmitting it over digital facilities (such as T1 E1) had been created and put into use before Bell (a North American telco) invented VoIP technology in 1950s. If you use digital PBX phones in your office, you must realize that one of the first actions that these phones perform is converting the analog voice signal to a digital format. When you use your regular analog phone at home, the phone sends analog voice signal to the telco CO. The...

Basic Voice Encoding Converting Digital to Analog

When a switch or router that has an analog device such as a telephone, fax, or modem connected to it receives a digital voice signal, it must convert the analog signal to digital or VoIP before transmitting it to the other device. Figure 1-5 shows that router R1 receives an analog signal and converts it to digital, encapsulates the digital voice signal in IP packets, and sends the packets to router R2. On R2, the digital voice signal must be de-encapsulated from the received packets. Next, the...

Benefits of Packet Telephony Networks

Many believe that the biggest benefit of packet telephony is toll bypass, or simply long-distance cost savings. However, because the cost of a long-distance call to most parts of the world has decreased substantially, this is not even one of the top three reasons for migrating to packet telephony networks in the North American market. The main benefits of packet telephony networks are as follows More efficient use of bandwidth and equipment, and lower transmission costs Packet telephony...

Best Effort Model

The best-effort model means that no QoS policy is implemented. It is natural to wonder why this model was not called no-effort. Within this model, packets belonging to voice calls, e-mails, file transfers, and so on are treated as equally important indeed, these packets are not even differentiated. The basic mail delivery by the post office is often used as an example for the best-effort model, because the post office treats all letters as equally important. The best-effort model has some...

C

CAC (call admission control), 15, 49, 69 calculating bandwidth for VoIP, 34-42 call control models, 16-19 processing, 45 routing, 15 call admission control, 15, 49, 69 campus maps, adding, 310-312 campus networks, QoS, 188-190 carrier sense multiple access collision avoid (CSMA CA), 236-235 carrier sense multiple access collision detect (CSMA CD), 236 CAS (channel associated signaling), 14 CBWFQ (Class-Based Weighted Fair Queuing), 138-139 benefits drawbacks, 140 classification, 139-140...

Chapter

The benefits of packet telephony networks include these More efficient use of bandwidth and equipment Consolidated network expenses Improved employee productivity Access to new communication devices 2. Following are the components of a packet telephony (VoIP) network 3. The analog interfaces through which legacy analog devices can connect to a VoIP network include these 4. The digital interface options to connect VoIP equipment to PBXs or the PSTN include the...

Cisco IOS Policing and Shaping Mechanisms

Cisco IOS offers class-based traffic policing. Using modular QoS command-line interface (MQC), class-based traffic policing is applied to a class within a policy map with the police command. As stated in the previous section, Cisco IOS offers different Token Bucket schemes for policing single bucket single rate, dual bucket single rate, and dual bucket dual rate. Furthermore, multiaction policing meaning taking multiple actions when traffic conforms, exceeds, or violates is also supported by...

Cisco Unified Call Manager Functions

Cisco CallManager (CCM) is call processing software it is the main component of the Cisco Unified Communication System. CCM supports the MGCP, H.323, SIP, and SCCP IP Telephony signaling protocols. Within the MGCP context, CCM acts as the CA and controls MGCP gateways, and within the SCCP context, it controls the IP phones (Skinny Clients). CCM interacts with H.323 and SIP devices. Cisco CallManager version 5.0 supports SIP clients, such as SIP-based IP phones. CallManager servers form a...

Cisco Unified Wireless Networks

The Cisco Unified Wireless Network is a total-enterprise solution composed of five comprehensive elements. The Cisco Unified Wireless Network enables the use of advanced wireless services and addresses security concerns. It also addresses deployment, control, and the management of WLAN components and RF. Following are the five elements of Cisco Unified Wireless Network Client devices Use the Cisco Compatible Extensions program to help ensure interoperability. The Cisco Compatible Extensions...

Cisco VoIP Implementations

This chapter describes Cisco Voice over IP (VoIP) implementations. Expect to see several exam questions based on the material in this chapter. This chapter has five major topics. The first topic helps you understand the basic components of VoIP networks and the benefits of VoIP networks. The second topic is about converting an analog voice signal to a digital voice signal and the concepts of sampling, quantization, compression, and digital signal processors (DSP). The third section discusses...

Cisco Wireless Control System

Cisco WCS is an advanced centralized WLAN solution for LWAPs. It provides configuration, firmware, radio management, and IDS for LWAP and their associated controllers. The same configuration, performance monitoring, security, fault management, and accounting options found on the individual controllers also exist on the WCS. It is designed to support 50 Cisco WLCs and 1500 APs. Administrators can define operator permissions within the administration menu where accounts and maintenance tasks are...

Cisco Works Wireless LAN Solution Engine

CiscoWorks WLSE is part of the CiscoWorks network management products. CiscoWorks WLSE provides centralized management for autonomous APs. WLANs benefit from the WLSE major features such as configuration, fault and policy monitoring, reporting, firmware, and radio management. In addition, the RF and device-management features help reduce operating expenses and deployment. CiscoWorks WLSE covers fault, configuration, and performance management, which are three of the FCAPS (Fault, Configuration,...

Cisco Works WLSE and WLSE Express

Two versions of CiscoWorks WLSE are available based on the network sizes WLSE and WLSE Express. WLSE is for medium to large enterprise WLAN solutions with up to 2500 managed devices. WLSE requires an external AAA server such as a Cisco ACS server since the WLSE does not include one. CiscoWorks WLSE Express includes AAA providing security services that support 802.1x LEAP, Protected Extensible Authentication Protocol (PEAP), Extensible Authentication Protocol-Flexible Authentication via Secure...

Class Based Weighted Fair Queuing

CBWFQ addresses some of the limitations of PQ, CQ, and WFQ. CBWFQ allows creation of user-defined classes, each of which is assigned to its own queue. Each queue receives a user-defined (minimum) bandwidth guarantee, but it can use more bandwidth if it is available. In contrast to PQ, no queue in CBWFQ is starved. Unlike PQ and CQ, you do not have to define classes of traffic to different queues using complex access lists. WFQ does not allow creation of user-defined classes, but CBWFQ does...

Classification and Marking

With QoS, you intend to provide different treatments to different classes of network traffic. Therefore, it is necessary to define traffic classes by identifying and grouping network traffic. Classification does just that it is the process or mechanism that identifies traffic and categorizes it into classes. This categorization is done using traffic descriptors. Common traffic descriptors are any of the following Ingress (or incoming) interface CoS value on ISL or 802.1p frame Source or...

Clustering over WAN Model

This model uses only one Cisco CallManager cluster for all sites. However, not all servers of the cluster are put in a single site together. Instead, the CCM servers, application servers, and DSP resources are distributed to different locations to provide local service to their clients (such as IP phones and gateways). The CCM servers need to communicate over the intersite IP WAN connection to perform database synchronization and replication. For clustering over WAN to work properly, the...

Command Syntax Conventions

The conventions used to present command syntax in this book are the same ones used in the IOS Command Reference. The Command Reference describes these conventions as follows Boldface indicates commands and keywords that are entered literally as shown. In actual configuration examples and output (not general command syntax), boldface indicates commands that are manually input by the user (such as a show command). Italics indicate arguments for which you supply actual values. Vertical bars ( )...

Common AutoQoS Problems

AutoQoS was developed to automate QoS configuration for common enterprise network scenarios. Therefore, the configuration that AutoQoS yields does not necessarily suit and satisfy the requirements of every network. Following are the three most common Cisco AutoQoS issues that might arise Too many traffic classes are generated classification is overengineered. The configuration that AutoQoS generates does not adapt automatically to changing network traffic conditions. The configuration that...

Compression Bandwidth Requirements and Their Comparative Qualities

Several ITU compression standards exist. Voice compression standards (algorithms) differ based on the following factors Quality degradation they cause CPU overhead due to their complexity Several techniques have been invented for measuring the quality of the voice signal that has been processed by different compression algorithms (codecs). One of the standard techniques for measuring quality of voice codecs, which is also an ITU standard, is called mean opinion score (MOS). MOS values, which...

Congestion Avoidance

Congestion avoidance is used to avoid tail drop, which has several drawbacks. RED and its variations, namely WRED and CBWRED, are commonly used congestion-avoidance techniques used on Cisco router interfaces. Congestion avoidance is one of the main pieces of a QoS solution. When the hardware queue (transmit queue, TxQ) is full, outgoing packets are queued in the interface software queue. If the software queue becomes full, new arriving packets are tail-dropped by default. The packets that are...

Congestion Avoidance Policing Shaping and Link Efficiency Mechanisms

This chapter intends to give you an overview of three main quality of service (QoS) concepts congestion avoidance, traffic shaping and policing, and link efficiency mechanisms. Each concept is presented in its own section. WRED and class-based WRED are the main mechanisms covered in the Congestion Avoidance section. Traffic shaping and policing concepts are explained in the second section you will learn the purpose of these mechanisms and where it is appropriate to use them. Different...

Consistency

AutoQoS for Enterprise uses NBAR protocol discovery. NBAR protocol discovery analyzes traffic in real-time, identifies approximately 100 Layer 4 through 7 applications and protocols using stateful and deep packet inspection, and provides bidirectional, per-interface, and per-protocol statistics. NBAR protocol discovery is able to identify and classify all of the following application types Applications that target a session to a well-known (UDP TCP) destination port number, referred to as...

Contents

Chapter 1 Cisco VoIP Implementations 5 Do I Know This Already Quiz 5 Foundation Topics 10 Introduction to VoIP Networks 10 Benefits of Packet Telephony Networks 10 Packet Telephony Components 11 Analog Interfaces 13 Digital Interfaces 14 Stages of a Phone Call 15 Distributed Versus Centralized Call Control 16 Digitizing and Packetizing Voice 19 Basic Voice Encoding Converting Analog to Digital 19 Basic Voice Encoding Converting Digital to Analog 20 The Nyquist Theorem 21 Quantization 22...

Contents at a Glance

Chapter 1 Cisco VoIP Implementations 5 Part II Quality of Service 55 Chapter 3 Classification, Marking, and NBAR 93 Chapter 4 Congestion Management and Queuing 123 Chapter 5 Congestion Avoidance, Policing, Shaping, and Link Efficiency Mechanisms 149 Chapter 6 Implementing QoS Pre-Classify and Deploying End-to-End QoS 177 Chapter 8 Wireless LAN QoS Implementation 231 Chapter 9 Introducing 802.1x and Configuring Encryption and Authentication on Lightweight Access Points 255 Appendix A Answers to...

Converged Network Issues Related to QoS

A converged network supports different types of applications, such as voice, video, and data, simultaneously over a common infrastructure. Accommodating these applications that have different sensitivities and requirements is a challenging task on the hands of network engineers. The acceptable end-to-end delay for the Voice over IP (VoIP) packets is 150 to 200 milliseconds (ms). Also, the delay variation or jitter among the VoIP packets must be limited so that the buffers at the receiving end...

D

Dashboard (Network), 303-304 data integrity, VPNs, 180 data links, overhead, 35-37 Data Link Control, 235 data plane traffic, 192 databases packet telephony networks, 11 data-link connection identifier (DLCI), 207 DCF (distributed coordinated function), 236-237 DE (discard eligible), 99 decimal bits, CoS bits, 98-99 default PHBs, 103 defining end-to-end (VoIP), 16, 62-65 link fragmentation, 171 processing, 65 propagation, 65 queuing, 65 serialization, 65 variation (jitter), 63, 65-66 delivery,...

Data Link Overhead

Transmitting an IP packet over a link requires encapsulation of the IP packet in a frame that is appropriate for the data link layer protocol provisioned on that link. For instance, if the data link layer protocol used on a link is PPP, the interface connected to that link must be configured for PPP encapsulation. In other words, any packet to be transmitted out of that interface must be encapsulated in a PPP frame. When a router routes a packet, the packet can enter the router via an interface...

Definition of QoS and the Three Steps to Implementing It

Following is the most recent definition that Cisco educational material provides for QoS QoS is the ability of the network to provide better or special service to a set of users or applications or both to the detriment of other users or applications or both. The earliest versions of QoS tools protected data against data. For instance, priority queuing made sure packets that matched an access list always had the right of way on an egress interface. Another example is WFQ, which prevents small...

Delay Variation

The variation in delays experienced by the packets of the same flow is called delay variation or jitter. Packets of the same flow might not arrive at the destination at the same rate that they were released. These packets, individually and independent from each other, are processed, queued, dequeued, and so on. Therefore, they might arrive out of sequence, and their end-to-end delays might vary. For voice and video packets, it is essential that at the destination point, the packets are released...

Deploying Endto End QoS

End-to-end QoS means that all the network components between the end points of a network communication dialogue need to implement appropriate QoS mechanisms consistently. If, for example, an enterprise (customer) uses the services and facilities of a service provider for connectivity between its headquarters and branch offices, both the enterprise and the service provider must implement the proper IP QoS mechanisms. This ensures end-to-end QoS for the packets going from one enterprise location...

Differentiated Services Model

Differentiated Services (DiffServ) is the newest of the three QoS models, and its development has aimed to overcome the limitations of its predecessors. DiffServ is not a guaranteed QoS model, but it is a highly scalable one. The Internet Engineering Task Force (IETF) description and discussion on DiffServ are included in RFCs 2474 and 2475. Whereas IntServ has been called the Hard QoS model, DiffServ has been called the Soft QoS model. IntServ, through usage of signaling and admission control,...

Digital Interfaces

Gateways can also connect to telco and PBX switches using digital interfaces. A gateway can have BRI or T1 E1 digital interfaces. Using a T1 connection is common in North America, whereas E1 lines are more common in Europe. You can configure the T1 E1 interface controller as an ISDN PRI or as Channelized T1 E1 and use channel associated signaling (CAS). BRI and PRI interfaces use common channel signaling (CCS), where a D (Delta) channel is dedicated to a messaging style of signaling, such as...

Digital Signal Processors

Voice-enabled devices such as voice gateways have special processors called DSPs. DSPs are usually on packet voice DSP modules (PVDM). Certain voice-enabled devices such as voice network modules (VNM) have special slots for plugging PVDMs into them. Figure 1-8 shows a network module high density voice (NM-HDV) that has five slots for PVDMs. The NM in Figure 1-8 has four PVDMs plugged into it . Different types of PVDMs have different numbers of DSPs, and each DSP handles a certain number of...

Digitizing and Packetizing Voice

Upon completion of this section, you will be able to identify the steps involved in converting an analog voice signal to a digital voice signal, explain the Nyquist theorem, the reason for taking 8000 voice samples per second and explain the method for quantization of voice samples. Furthermore, you will be familiar with standard voice compression algorithms, their bandwidth requirements, and the quality of the results they yield. Knowing the purpose of DSP in voice gateways is the last...

Distributed Versus Centralized Call Control

Two major call control models exist distributed call control and centralized call control. The H.323 and SIP protocols are classified as distributed, whereas the MGCP protocol is considered as a centralized call control VoIP signaling protocol. In the distributed model, multiple devices are involved in setup, maintenance, teardown, and other aspects of call control. The voice-capable devices that perform these tasks have the intelligence and proper configuration to do so. Figure 1-3 shows a...

Do I Know This Already Quiz

The purpose of the Do I Know This Already quiz is to help you decide whether you really need to read this entire chapter. The 20-question quiz, derived from the major sections of this chapter, helps you determine how to spend your limited study time. Table 1-1 outlines the major topics discussed in this chapter and the Do I Know This Already quiz questions that correspond to those topics. You can keep track of your score here, too. Table 1-1 Do I Know This Already Foundation Topics...

E

E& M (Earth and Magneto or Ear and Mouth), 13 EAP (Extensible Authentication Protocol), 260-272 EAP over LAN (EAPOL), 265 EAP-FAST (Extensible Authentication Protocol-Flexible Authentication via Secure Tunneling), 264-266 EAPOL (EAP over LAN, 265 EAP-TLS (Extensible Authentication Protocol-Transport Layer Security), 266-267 early dropping, WFQ, 135 Earth and Magneto or Ear and Mouth (E& M), 13 ease, best-effort QoS model, 72 EDCF (Enhanced Distributed Coordination Function), 238 Edit QoS...

Effects of VAD on Bandwidth

VAD is a feature that is available in voice-enabled networks. VAD detects silence (speech pauses) and one-way audio and does not generate data as a result, it produces bandwidth savings. This does not happen in circuit-switched voice networks such as the PSTN, where a channel (usually a 64 Kbps DS0) is dedicated to a call regardless of the amount of activity on that circuit. It is common for about one-third of a regular voice call to be silence therefore, the concept of VAD for bandwidth saving...

Endto End Delay

There are different types of delay from source to destination. End-to-end delay is the sum of those different delay types that affect the packets of a certain flow or application. Four of the important types of delay that make up end-to-end delay are as follows Processing delay is the time it takes for a device such as a router or Layer 3 switch to perform all the tasks necessary to move a packet from the input (ingress) interface to the output (egress) interface. The CPU type, CPU utilization,...

Endto End Delivery of Voice

To review the traditional model of voice communication over the PSTN, imagine a residential phone that connects to the telco CO switch using an analog telephone line. After the phone goes off-hook and digits are dialed and sent to the CO switch, the CO switch, using a special signaling protocol, finds and sends call setup signaling messages to the CO that connects to the line of the destination number. The switches within the PSTN are connected using digital trunks such as T1 E1 or T3 E3. If...

Enterprise IP Telephony Deployment Models

Many IP Telephony deployment options, utilizing Cisco Unified CallManager, are available. The option that is suitable for an enterprise depends on the organization of that enterprise, its business strategy, budget, and objectives. You can deploy the options presented here in combination (hybrid models) or slightly differently. The four main options are as follows Multisite with centralized call processing Multisite with distributed call processing

Enterprise Voice Implementations

The main telephony elements of an enterprise Cisco VoIP implementation are gateway, gatekeeper, Cisco Unified CallManager, and Cisco IP phones. Cisco IP phones need CallManager, because it acts as an IP PBX for the Cisco IP phones. The gateways provide connectivity between analog, digital, and IP-based telephony devices and circuits. Gatekeeper is an H.323 device that provides call routing or CAC services. Enterprise voice implementations can vary based on many factors. One of those factors is...

F

Fair-queue 16 command, 141 fair-queue command, 135 FastTrack traffic, NBAR, 116-117 fault monitoring, WLSE, 295 FECN (forward explicit congestion DiffServ, 100 EXP (MPLS), 100 inner QoS, 241 Over the Air QoS, 245 FIFO (first in, first out), 128-132 filters, MAC, 259 firmware, WLSE, 295 first in, first out, 128-132 Foreign Exchange Office (FXO), 13 Foreign Exchange Station (FXS), 13 forward explicit congestion notification AutoQoS, 209 important packets first, 66 four-way handshakes, 264 fragile...

Features of This Book

Do I Know This Already Quizzes Each chapter begins with a quiz that helps you determine the amount of time you need to spend studying that chapter. If you follow the directions at the beginning of the chapter, the Do I Know This Already quiz directs you to study all or particular parts of the chapter. Foundation Topics These are the core sections of each chapter. They explain the protocols, concepts, and configuration for the topics in that chapter. If you need to learn about the topics in a...

Feedback Information

At Cisco Press, our goal is to create in-depth technical books of the highest quality and value. Each book is crafted with care and precision, undergoing rigorous development that involves the unique expertise of members from the professional technical community. Readers' feedback is a natural continuation of this process. If you have any comments regarding how we could improve the quality of this book or otherwise alter it to better suit your needs, you can contact us through e-mail at...

Foundation Summary

The Foundation Summary is a collection of information that provides a convenient review of many key concepts in this chapter. If you are already comfortable with the topics in this chapter, this summary can help you recall a few details. If you just read this chapter, this review should help solidify some key facts. If you are doing your final preparation before the exam, the information in this section is a convenient way to review the day before the exam. Benefits of packet telephony networks...

Goals and Methods

The most important and somewhat obvious goal of this book is to help you pass the Optimizing Converged Cisco Networks (ONT) exam 642-845. In fact, if the primary objective of this book were different, the book title would be misleading however, the methods used in this book to help you pass the ONT exam are also designed to make you much more knowledgeable about how to do your job. Although this book and the accompanying CD-ROM together have more than enough questions to help you prepare for...

H

See also security handshakes, four-way, 264 hardware packet telephony networks, 10 QoS, 189 queuing, 128 compression, 66, 169-170 MPLS, 100 overhead, 32-34 hierarchies, trust boundaries, 109 high availability, WLSE, 298 high-level data link control (HDLC) encapsulation, 207 hold-queue max-limit out command, 136 IBNS (Identity Based Networking Services), 292 IDSs (Intrusion Detection Systems), 260, 292 IEEE (Institute of Electrical and Electronics Engineers) 802.11 Wired Equivalent...

Header Compression

Header compression reduces serialization delay and results in less bandwidth usage, yielding more throughput and more available bandwidth. As the name implies, header compression compresses headers only for example, RTP header compression compresses Real-time Transport Protocol (RTP), User Datagram Protocol (UDP), and IP headers, but it does not compress the application data. This makes header compression especially useful for cases in which application payload size is small. Without header...

How This Book Is Organized

Although you can read this book cover to cover if you want to, it is designed to be flexible and allow you to easily move between chapters and sections of chapters to cover just the material that you need more work with. Chapter 1 of this book matches the Cisco VoIP Implementations module of the Cisco ONT official training curriculum. Chapter 2 of this book matches the Introduction to IP QoS module of the Cisco ONT official training curriculum. Chapters 3, 4, 5, and 6 of this book match the...

Identifying Voice Commands in IOS Configurations

Cisco routers that have proper interfaces can be configured to provide connectivity between analog or digital telephony devices over an IP network they are called voice gateways in those circumstances. Figure 1-16 shows two voice gateways, R1 and R2, each with an analog phone connected to its FXS interface. To provide connectivity between the two phones over the IP network, in addition to basic configurations, each of the routers (gateways) needs one plain old telephone service (POTS) and one...

Implementing and Verifying AutoQoS

Before you implement AutoQoS and enable it on router interfaces, it is useful to know the router AutoQoS deployment restrictions. Some design considerations are also worth learning with regard to deploying AutoQoS on routers. Finally, you must know the prerequisites for configuring AutoQoS on Cisco routers. You can enable Cisco AutoQoS Enterprise on certain types of interfaces and permanent virtual circuits (PVCs) only. These are the interface and PVC types on which you can enable AutoQoS...

Implementing AutoQoS

This chapter is focused on Cisco AutoQoS. AutoQoS is a QoS deployment automation tool that is suitable for midsize enterprise networks. It has evolved from its limited Voice over IP (VoIP)-focused version to an enterprise version (for Cisco routers) with protocol discovery and more general and sophisticated configuration results. This chapter provides a description for AutoQoS and its benefits followed by a lesson on implementing AutoQoS enterprise on routers and AutoQoS VoIP on Cisco LAN...

Implementing QoS

Implementing QoS involves three major steps Step 1 Identifying traffic types and their requirements Step 2 Classifying traffic based on the requirements identified Step 3 Defining policies for each traffic class Even though many common applications and protocols exist among enterprise networks, within each network, the volumes and percentages of those traffic types vary. Furthermore, each enterprise might have its own unique application types in addition to the common ones. Therefore, the first...

Implementing QoS Pre Classify

QoS pre-classify was designed so that tunneled interfaces could classify packets on the output interface before data was encrypted and tunneled. Considering the growth of VPN popularity, the ability to classify traffic within a tunnel for QoS purposes is increasingly in demand. QoS pre-classify allows Cisco IOS QoS features and services to remain effective even on tunnel interfaces and when encryption is used. Therefore, service providers and customers can continue to provide appropriate...

Info

In the first scenario displayed in Figure 3-6, the trust boundary is placed on the Cisco IP phone. The phone sets resets the CoS field to 0 (000 binary) for the frames it receives from the PC as it forwards them to the switch. The CoS value on the IP phone-generated frames that are carrying voice signaling is set to 3 (011 binary), and it is set to 5 (101 binary) for those that are carrying voice. The access switch is configured to trust the markings of the traffic received on the port that the...

Integrated Services Model

The Integrated Services (IntServ) model, developed in the mid-1990s, was the first serious attempt to provide end-to-end QoS, which was demanded by real-time applications. IntServ is based on explicit signaling and managing reserving network resources for the applications that need it and demand it. IntServ is often referred to as Hard-QoS, because Hard-QoS guarantees characteristics such as bandwidth, delay, and packet loss, thereby providing a predictable service level. Resource Reservation...

Interpreting and Modifying AutoQoS Configurations

The show auto qos command displays all the QoS mechanisms (and the corresponding configurations) that Cisco AutoQoS has enabled on a router, with or without autodiscovery. Therefore, you can inspect all the QoS templates that were generated as a result of applying Cisco AutoQoS. You can gather several particular facts from the output of the show auto qos command, the most important of which are these The number of traffic classes. The classification options used. The traffic markings performed....

Introducing AutoQoS

With the growth of bandwidth requirements by today's applications and convergence of voice, video, and data applications over common IP infrastructures (networks), deploying QoS technologies and services is a necessity within modern networks. Although you must manage delay, jitter, available bandwidth, and packet loss, the solution must remain scalable and manageable with respect to both simplicity and cost. Following are some of the challenges that enterprises face The voice quality of IP...

L

Lack of service, 72 LANs (local-area networks) campus devices, 189 EAPOL, 265 laptops, Cisco Wireless Location Appliance, payload compression, 64, 168-169 QoS CoS on 802.1Q P Ethernet frames, 98-99 DE and CLP on ATM Frame Relay, 99 Layer 2, 100 layers, implementing trust boundaries, 109 LEAP (Lightweight Extensible Authentication Protocol), 259, 262-264 legacy CLIs, 76 levels, services, 70, 75 LFI (link fragmentation and interleaving), 208 LightWeight Access Point Protocol (LWAPP), 291...

Layer 2 12 QoS Mpls Exp Field

MPLS packets are IP packets that have one or more 4-byte MPLS headers added. The IP packet with its added MPLS header is encapsulated in a Layer 2 protocol data unit (PDU) such as Ethernet before it is transmitted. Therefore, the MPLS header is often called the SHIM or layer 2 1 2 header. Figure 3-3 displays an MPLS-IP packet encapsulated in an Ethernet frame. The EXP (experimental) field within the MPLS header is used for QoS purposes. The EXP field was designed as a 3-bit field to be...

Layer 2 Payload Compression

Layer 2 payload compression, as the name implies, compresses the entire payload of a Layer 2 frame. For example, if a Layer 2 frame encapsulates an IP packet, the entire IP packet is compressed. Layer 2 payload compression is performed on a link-by-link basis it can be performed on WAN connections such as PPP, Frame Relay, high-level data link control (HDLC), X.25, and Link Access Procedure, Balanced (LAPB). Cisco IOS supports Stacker, Predictor, and Microsoft Point-to-Point Compression (MPPC)...

Layer 2 QoS DE and CLP on Frame Relay and ATM Cells

Frame Relay and ATM QoS standards were defined and used (by ITU-T and FRF) before Internet Engineering Task Force (IETF) QoS standards were introduced and standardized. In Frame Relay, for instance, the forward explicit congestion notification (FECN), backward explicit congestion notification (BECN), and discard eligible (DE) fields in the frame header have been used to perform congestion notification and drop preference notification. Neither Frame Relay frames nor ATM cells have a field...

Legacy Command Line Interface CLI

Legacy CLI was the method used up to about six years ago to implement QoS on network devices. Legacy CLI requires configuration of few to many lines of code that for the most part would have to be applied directly at the interface level. Configuration of many interfaces required a lot of typing or cutting and pasting. Maintaining consistency, minimizing errors, and keeping the configuration neat and understandable were difficult to do using legacy CLI. Legacy CLI configuration required the user...

Link Efficiency Mechanisms

The main link efficiency mechanisms deployed today are compression- and fragmentation-based. There are several types of compression link compression, layer 2 payload compression, RTP header compression, and TCP header compression. Fragmentation is usually combined with interleaving. Compression makes link utilization more efficient, and it is a QoS technique that actually makes more bandwidth available. Fragmentation aims at reducing the expected delay of packets by reducing the maximum packet...

Link Fragmentation and Interleaving

When an interface is congested, packets first go through the software queue and then are forwarded to the hardware queue when the interface has no congestion, packets skip the software queue and go straight to the hardware queue. You can use advanced queuing methods such as LLQ to minimize the software queuing delay that delay-sensitive packets such as VoIP experience. Packets must always go through the hardware queue, which is FIFO based. If a VoIP packet ends up behind one or more large...

Low Latency Queuing

Neither WFQ nor CBWFQ can provide guaranteed bandwidth and low-delay guarantee to selected applications such as VoIP that is because those queuing models have no priority queue. Certain applications such as VoIP have a small end-to-end delay budget and little tolerance to jitter (delay variation among packets of a flow). LLQ includes a strict-priority queue that is given priority over other queues, which makes it ideal for delay and jitter-sensitive applications. Unlike the plain old PQ,...

M

Congestion, 127-130 dial plans, 45 dynamic RF, 296 EAP, 261 keys, 269 phone features, 46 radio (WLSE), 295 RF, 306 RRM, 301 SDM, 81-88 WLANs 291-292 components, 294 implementations, 292-293 need for, 291 WCS, 299-313 WLSE, 295-299 WLSE, 296 WPA, 269-272 mapping Cisco WCS Server, 309-310 inner QoS fields, 241 LLQ, 144, 161 markings, 107 modifying, 219 policies, 141 QoS markings, 240-241 mark probability denominator (MPD), 154 marking, 97-100 DSCP, 100-105 enterprise campus QoS, 189 mapping, 107...

Measuring Traffic Rates

The operating systems on Cisco devices measure traffic rates using a bucket and token scheme. The token and bucket scheme has a few variations single bucket with single rate, dual bucket with single rate, and dual bucket with dual rates. The Cisco ONT course covers only the single bucket with single rate model. To transmit one byte of data, the bucket must have one token. Tokens are put into the bucket at the rate equivalent to the SLA rate for example, for a Frame Relay virtual circuit, the...

Modular QoS Command Line Interface MQC

Cisco introduced MQC to address the shortcomings of the legacy CLI and to allow utilization of the newer QoS tools and features available in the modern Cisco IOS. With the MQC, traffic classification and policy definition are done separately. Traffic policies are defined after traffic classes. Different policies might reference the same traffic classes, thereby taking advantage of the modular and reusable code. When one or more policies are defined, you can apply them to many interfaces,...

Multisite with Centralized Call Processing Model

In the multisite with centralized call processing model, the Cisco Unified CallManager (CCM) cluster and application servers are placed at one of the sites usually a main or central site. This IP Telephony solution spans multiple sites in other words, all devices such as IP phones and MGCP gateways at all sites are under the control of the CCM cluster at the central site. Notice that even though call processing is centralized, DSP resources can be distributed. If network connectivity, such as...

Multisite with Distributed Call Processing Model

In the multisite with distributed call processing model, each site has its own Cisco Unified CallManager cluster controlling all call processing aspects of that site hence the term distributed call processing. Application servers and DSP resources are also distributed at all sites. Sites, in this case, do not depend on the call processing offered at another site. In distributed call processing, each site has a CallManager cluster. Please note that the other resources (voice mail, IPCC, IVR, DSP...

N

NAC (Network Admission Control), 292 National Institute of Standards and Technology (NIST), 271 navigating WCS, 302 NBAR (Network Based Application Recognition), 97, 110-117, 205 Network Admission Control (NAC), 292 Network Based Application Recognition, 97, 110-117, 205 Network Dashboard, 303-304 network interface card, 258 Cisco Unified Wireless Networks, 291-292 converged, 62-68 enterprise, 42-49 outages, 62 packet telephony networks benefits of, 10-11 components, 11-13 services, 295...

On campus

On the service provider cloud Table 6-3 provides a short list of important QoS-related tasks that might be necessary at different locations on the customer and provider premises. Implementing these and possibly other tasks on both the customer and provider devices supports the effort to provide end-to-end QoS. Table 6-3 Necessary QoS Tasks (at Different Spots) for End-to-End QoS Table 6-3 Necessary QoS Tasks (at Different Spots) for End-to-End QoS Phone and access switch configurations WRED...

Overview of WLAN Security

Affordability, ease of use, and convenience of wireless devices, wireless local-area networks (WLAN), and related technologies have caused a substantial increase in their usage over recent years. At the same time, the number of reported attacks on wireless devices and networks has surged. Hackers have access to affordable wireless devices, wireless sniffers, and other tools. Unfortunately, the default wireless security settings are usually open and vulnerable to intrusion and attacks. For...

P

(PDLMs), 111 packet voice DSP modules (PVDMs), 25 packets access, 134 loss, 63, 66-68 periods, 36 size, 35 telephony networks benefits of, 10-11 components, 11-13 voice, 27-34 packets per second (pps), 35 pairwise master key (PMK), 264 pairwise transient key (PTK), 270 PAM (pulse amplitude modulation), 20 parameters compression (Layer 2), 168-169 voice, 34-36 payload-type keyword, 117 PBX phones, 11 PCM (pulse code modulation), 20 PDLMs (Packet Description Language Modules), 111 PDU (protocol...

Packet Telephony Components

A packet telephony network must perform several mandatory functions, and it can perform many optional ones. This requires existence and proper operation of various components. Some devices can perform multiple functions simultaneously for example, for a small deployment a gateway can also act as a gatekeeper. The following is a list of the major components of a packet telephony network, but not all of the components are always present and utilized Phones There might be analog phones, PBX...

Protocols Used in Voice Encapsulation

Even though the term VoIP implies that digitized voice is encapsulated in IP packets, other protocol headers and mechanisms are involved in this process. Although the two major TCP IP transport layer protocols, namely TCP and UDP, have their own merits, neither of these protocols alone is a suitable transport protocol for real-time voice. RTP, which runs over UDP using UDP ports 16384 through 32767, offers a good transport layer solution for real-time voice and video. Table 1-5 compares TCP,...

Qa

Some of the questions that follow challenge you more than the exam by using an open-ended question format. By reviewing now with this more difficult question format, you can exercise your memory better and prove your conceptual and factual knowledge of this chapter. The answers to these questions appear in Appendix A. 1. List at least three benefits of packet telephony networks. 2. List at least three important components of a packet telephony (VoIP) network. 3. List three types of analog...

QoS Pre Classify Applications

Two commonly used tunneling protocols that are relevant to VPNs, discussed in the ONT course, are GRE and IPsec. Because these tunneling protocols, at the tunnel end points, encapsulate the original IP packet and use a new IP header, the original IP header is no longer available to the QoS mechanisms on the outbound (egress) interface. The good news is that the original ToS byte of an IP packet is copied to a ToS byte of the new IP header. Therefore, if the QoS mechanisms on the egress...

QoS Service Class

Planning and implementing QoS policies entails three main steps Step 1 Identify network traffic and its requirements. Step 2 Divide the identified traffic into classes. Step 3 Define QoS policies for each class. In Step 1, you use tools such as NBAR to identify the existing traffic in the network. You might discover many different traffic types. In Step 1, you must then recognize and document the relevance and importance of each recognized traffic type to your business. In Step 2, you group the...

QoS Service Level Agreements SLAs

An SLA is a contractual agreement between an enterprise (customer) and a service provider regarding data, voice, and other service or a group of services. Internet access, leased line, Frame Relay, and ATM are examples of such services. After the SLA is negotiated, it is important that it is monitored for compliance of the parties involved with the terms of the agreement. The service provider must deliver services as per the qualities assured in the SLA, and the customer must submit traffic at...

Quantization

Quantization is the process of assigning numeric values to the amplitude (height or voltage) of each of the samples on the PAM signal using a scaling methodology. A common scaling method is made of eight major divisions called segments on each polarity (positive and negative) side. Each segment is subdivided into 16 steps. As a result, 256 discrete steps (2 x 8 x 16) are possible. The 256 steps in the quantization scale are encoded using 8-bit binary numbers. From the 8 bits, 1 bit represents...

R

See RF radio frequency identification, 305 radio management, WLSE, 295 radio resource management (RRM), 301 RADIUS (Remote Authentication Dial In User Service) EAP features, 260 servers, 262 random early detection (RED), 154-156 random wait timers, 236 random-detect command, 158 rates CIR, 165, 186 packets, 35 traffic, 165-167 RC4 vulnerabilities, 259 Real-Time Protocol Control Protocol (RTCP), 117 Real-time Transport Protocol. See RTP REAP (Remote-Edge Access Point), 293...

Reducing Header Overhead

An effective way of reducing the overhead imposed by IP, UDP, and RTP is Compressed RTP (cRTP). cRTP is also called RTP header compression. Even though its name implies that cRTP compresses the RTP header only, the cRTP technique actually significantly reduces the overhead imposed by all IP, UDP, and RTP protocol headers. cRTP must be applied on both sides of a link, and essentially the sender and receiver agree to a hash (number) that is associated with the 40 bytes of IP, UDP, and TCP...

Single Site Model

In the single-site model, as the name implies, the enterprise has one site, and within that site it has a Cisco CallManager cluster deployed. The local IP phones and perhaps MGCP gateways are under the control of CCM, and CCM can communicate with H.323 and SIP devices. Calls that are external to and from the site are routed through a gateway to the PSTN. The gateway DSPs can provide codec, compression, transcoding, or conferencing resources. If the site has a WAN connection to another place,...

Sitetosite

The most common Layer 3 tunneling protocols are as follows Generic routing encapsulation (GRE) Internet Protocol security (IPsec) QoS pre-classify is a Cisco IOS feature that allows packets to be classified before tunneling and encryption occur. The need to classify traffic within a traffic tunnel is growing side by side with the growth in VPN popularity. The QoS pre-classify feature provides access to the original (encapsulated) IP packet header fields. If IP QoS classification needs access to...

Sitetosite VPNs

The first category of VPN, remote access VPN, is either client-initiated or network access server (NAS)-initiated. When a person uses a VPN client application to establish a secure tunnel across an Internet service provider (ISP) (shared) network directly to an enterprise network, the VPN is referred to as client-initiated. In the network access server (NAS)-initiated case, however, the user dials in to the ISP, and the ISP NAS in turn establishes a secure tunnel to the enterprise private...

Some nonIP applications

HTTP applications based on URL, MIME type, or host name You can enable Cisco AutoQoS Enterprise on certain types of interfaces and permanent virtual circuits (PVCs) only. These are the interface and PVC types that you can enable AutoQoS Enterprise for on a Cisco router Serial interfaces with PPP or HDLC encapsulation. Frame Relay point-to-point subinterfaces. (Multipoint is not supported.) ATM point-to-point subinterfaces (PVCs) on both slow (< 768 kbps) and fast serial (> 768 kbps)...

Stages of a Phone Call

The three most popular VoIP signaling and control protocols are H.323, which is an ITU standard Media Gateway Control Protocol (MGCP), which is an Internet Engineering Task Force (IETF) standard and Session Initiation Protocol (SIP), also an IETF standard. Regardless of the signaling protocol used, a phone call has three main stages call setup, call maintenance, and call teardown. During call setup, the destination telephone number must be resolved to an IP address, where the call request...

Step 1 Identifying Traffic Types and Their Requirements

Identifying traffic types and their requirements, the first step in implementing QoS, is composed of the following elements or substeps Perform a network audit It is often recommended that you perform the audit during the busy hour (BH) or congestion period, but it is also important that you run the audit at other times. Certain applications are run during slow business hours on purpose. There are scientific methods for identifying the busy network moments, for example, through statistical...

Step 2 Classifying Traffic Based on the Requirements Identified

The definition of traffic classes does not need to be general it must include the traffic (application) types that were observed during the network audit step. You can classify tens or even hundreds of traffic variations into very few classes. The defined traffic classes must be in line with business objectives. The traffic or application types within the same class must have common requirements and business requirements. The exceptions to this rule are the applications that have not been...

Step 3 Defining Policies for Each Traffic Class

After the traffic classes have been formed based on the network audit and business objectives, the final step of implementing QoS in an enterprise is to provide a network-wide definition for the QoS service level that must be assigned to each traffic class. This is called defining a QoS policy, and it might include having to complete the following tasks Setting a maximum bandwidth limit for a class Setting a minimum bandwidth guarantee for a class Assigning a relative priority level to a class...