Home > Articles > Networking > Voice/IP Communications

This chapter is from the book

Basic QoS Configuration

Cisco continues to improve the ease and efficiency with which QoS mechanisms can be configured. This section addresses two of the Cisco more recent developments: MQC and AutoQoS.

Using MQC

One of the most powerful approaches to QoS configuration is the Modular Quality of Service Command-Line Interface (MQC). After you master the three basic steps of MQC, you can use them to configure a wide range of QoS tools, including queuing, policing, shaping, header compression, WRED, and marking.

Figure 6Figure 6

The first step of MQC is to create class-maps, which categorize traffic types. The following command enters you into class-map configuration mode:

Router(config)#class-map [match-any | match-all] class-name

After you are in class-map configuration mode, you can specify multiple match statements to match traffic, and all traffic that meets the criteria that you specified with the match commands is categorized under the class-map. If multiple match statements are specified, by default, all match statements must be met before a packet is classified by the class-map. However, if you use the match-any option, if any individual match condition is met, the packet is classified by the class-map. After the class-maps are defined, the first step of MQC is complete. The second step is to create a policy-map, which assigns characteristics (for example, marking) to the classified traffic.

To enter policy-map configuration mode, issue the following command:

Router(config)#policy-map policy-name

From policy-map configuration mode, enter policy-map-class configuration mode with the following command:

Router(config-pmap)#class class-name

From policy-map-class configuration mode, you can assign QoS policies to traffic that is classified by the class-map. You can also have a situation in which a packet matches more than one class-map. In that case, the first class-map that is identified in the policy-map is used. Up to 256 class-maps can be associated with a single policy-map.

Finally, in the third step of MQC, the policy-map is applied to an interface, Frame Relay map-class, or Asynchronous Transfer Mode (ATM) virtual circuit with the following command:

Router(config-if)#service-policy {input | output} policy-map-name

Following is an MQC example in which you are classifying various types of e-mail traffic (for example, SMTP, IMAP, and POP3) into one class-map. The KaZaa protocol, which is used frequently for music downloads, is placed in another class-map. Voice over IP (VoIP) traffic is placed in yet another class-map. Then, the policy-map assigns bandwidth allocations or limitations to these traffic types. The MQC example is as follows:

Router(config)#class-map match-any EMAIL
Router(config-cmap)#match protocol pop3
Router(config-cmap)#match protocol imap
Router(config-cmap)#match protocol smtp
Router(config-cmap)#exit
Router(config)#class-map MUSIC
Router(config-cmap)#match protocol kazaa2
Router(config-cmap)#exit
Router(config)#class-map VOICE
Router(config-cmap)#match protocol rtp
Router(config-cmap)#exit
Router(config)#policy-map QOS-STUDY
Router(config-pmap)#class EMAIL
Router(config-pmap-c)#bandwidth 128
Router(config-pmap-c)#exit
Router(config-pmap)#class MUSIC
Router(config-pmap-c)#police 32000
Router(config-pmap-c)#exit
Router(config-pmap)#class-map VOICE
Router(config-pmap-c)#priority 256
Router(config-pmap-c)#exit
Router(config-pmap)#exit
Router(config)#interface serial 0/1
Router(config-if)#service-policy output QOS-STUDY

Notice that the QOS-STUDY policy-map makes 128 kbps of bandwidth available to e-mail traffic. However, KaZaa version 2 traffic bandwidth is limited to 32 kbps. Voice packets not only have access to 256 kbps of bandwidth, but they also receive “priority” treatment, meaning that they are sent first (that is, ahead of other traffic) up to the 256-kbps limit.

The next logical question is, “What happens to all of the traffic that you did not classify?” Interestingly, the IOS created the class-default class-map, which categorizes any traffic that is not matched by one of the defined class-maps. Finally, in the previous example, the policy-map is applied in the outbound direction on the Serial 0/1 interface.

The following show commands can be used for verification and troubleshooting of an MQC configuration:

Router#show class-map [class-map-name]

(Used to view what a class-map is matching)

Router#show policy-map [policy-map-name]

(Used to view the policy that is applied to the classes within a policy-map)

Router#show policy-map interface interface-identifier [input | output]

(Used to view policy-map statistics for packets that are crossing a specific interface)

Using AutoQoS

Optimizing a QoS configuration for VoIP can be a daunting task. Fortunately, Cisco added a feature called AutoQoS to many of its router and switch platforms to automatically generate router-based or switch-based VoIP QoS configurations.

The following router platforms support AutoQoS:

  • 1700 Series

  • 2600 Series

  • 3600 Series

  • 3700 Series

  • 7200 Series

Cisco also supports the AutoQoS feature on the following Catalyst switch series:

  • 2950 (EI)

  • 3550

  • 4500

  • 6500

On a router platform, the following command enables AutoQoS from either interface-configuration mode or from DLCI-configuration mode (for a Frame Relay circuit):

Router(config-if)#auto qos voip [trust] [fr-atm]

The trust option indicates that Auto QoS should classify voice traffic based on DSCP markings, instead of using NBAR. The fr-atm option enables the AutoQoS feature for Frame Relay–to–ATM links and is issued from DLCI-configuration mode.

Before enabling AutoQoS on a router interface, consider the following prerequisites:

  • Cisco Express Forwarding (CEF) must be enabled, because AutoQoS uses NBAR, which requires the CEF feature.

  • A QoS policy must not be attached to the interface.

  • The correct bandwidth should be configured on the interface.

  • An IP address must be configured on an interface if its speed is less than 768 kbps.

  • The interface must not be administratively shut down.

Note that the interface’s bandwidth determines which AutoQoS features are enabled. If an interface’s bandwidth is less than 768 kbps, it is considered a low-speed interface. On a low-speed interface, AutoQoS configures Multilink PPP (MLP), which requires an IP address on the physical interface. AutoQoS takes that IP address from the physical interface and uses it for the virtual multilink interface that it creates.

To verify that AutoQoS is configured for a router interface, use the following command:

Router#show auto qos [interface interface-identifier]

Figure 7Figure 7

The Catalyst 6500 running in Hybrid mode (that is, using the Cat OS for switch functions) also supports AutoQoS. To enable AutoQoS on a Hybrid mode Catalyst 6500, you must first enable AutoQoS globally and then for a specific port. Following are the required commands:

Switch#set qos autoqos

(Globally enables AutoQoS)

Switch#set qos autoqos <mod/port> trust [cos | dscp]

(Enables AutoQoS for a specific port)

Note that the Catalyst 6500 can trust either CoS or DSCP values for its queuing decision. If the port is trusting DSCP markings, you can add the following command, which recognizes that the port is connected to a Cisco IP Phone or a Cisco SoftPhone (software that runs on a PC):

Switch#set port qos <mod/port> autoqos voip [ciscosoftphone | ciscoipphone]

The port must have Cisco Discovery Protocol (CDP) version 2 enabled to recognize an attached Cisco IP Phone. Although some switches do not recognize a Cisco SoftPhone, AutoQoS can be configured on Catalyst 2950 (EI) and 3550 switches, and the AutoQoS feature on these switches does recognize a Cisco IP Phone. To configure AutoQoS on these platforms, issue the following commands from interface-configuration mode:

Switch(config-if)#auto qos voip trust

(Configures the interface to trust CoS markings for classifying VoIP traffic)

Switch(config-if)#auto qos voip cisco-phone

(Detects the presence of a Cisco IP Phone, using CDP)

To troubleshoot and verify AutoQoS on a Catalyst switch, use the following commands:

Switch#show auto qos [interface interface-identifier]

(Displays the configuration that is applied by AutoQoS)

Switch#show mls qos interface [interface-identifier]

(Displays interface-level QoS statistics)

This section has broadly addressed the features that are enabled by AutoQoS. The specific features are shown in the following table.

QoS Mechanism

Router Feature

Switch Feature

Classification

NBAR and DSCP

Port trust states

Marking

CB-Marking

CoS-to-DSCP remarking

Congestion management

LLQ

WRR

Shaping

CB-Shaping or FRTS

Link efficiency

Header Compression and LFI


InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020