© 2006 Cisco Systems, Inc. All rights reserved. QOS Lecture 5 - QOS Policy Models.

© 2006 Cisco Systems, Inc. All rights reserved.

QOS

Lecture 5 - QOS Policy Models


Three QoS Models

Model Characteristics

Best effort No QoS is applied to packets. If it is not important when or how packets arrive, the best-effort model is appropriate.

Integrated Services

(IntServ)

Applications signal to the network that the applications require certain QoS parameters.

Differentiated Services

(DiffServ)

The network recognizes classes that require QoS.


Best-Effort Model Internet was initially based on a best-effort packet

delivery service.

Best-effort is the default mode for all traffic.

There is no differentiation among types of traffic.

Best-effort model is similar to using standard mail—“The mail will arrive when the mail arrives.”

Benefits:Highly scalable

No special mechanisms required

Drawbacks:No service guarantees

No service differentiation


Integrated Services (IntServ) Model Operation Ensures guaranteed delivery and

predictable behavior of the network for applications.

Provides multiple service levels.

RSVP is a signaling protocol to reserve resources for specified QoS parameters.

The requested QoS parameters are then linked to a packet stream.

Streams are not established if the required QoS parameters cannot be met.

Intelligent queuing mechanisms needed to provide resource reservation in terms of:

Guaranteed rate

Controlled load (low delay, high throughput)


IntServ Functions

Flow Identification Packet Scheduler

Data Plane

Routing Selection Admission Control

Reservation Setup

Control Plane

Reservation Table


Benefits and Drawbacks of the IntServ Model

Benefits:Explicit resource admission control (end to end)

Per-request policy admission control (authorization object, policy object)

Signaling of dynamic port numbers (for example, H.323)

Drawbacks:Continuous signaling because of stateful architecture

Flow-based approach not scalable to large implementations, such as the public Internet


Resource Reservation Protocol (RSVP)

Is carried in IP—protocol ID 46

Can use both TCP and UDP port 3455

Is a signaling protocol and works with existing routing protocols

Requests QoS parameters from all devices between the source and destination

Sending Host

RSVP Receivers

RSVP Tunnel

Provides divergent performance requirements for multimedia applications:

Rate-sensitive traffic

Delay-sensitive traffic


RSVP Daemon

PolicyControl

AdmissionControl

Packet Classifier

PacketScheduler

Routing

RSVPDaemon

Reservation

Data


Reservation Merging

R1, R2 and R3 all request the same reservation.

The R2 and R3 request merges at R4.

The R1 request merges with the combined R2 and R3 request at R5.

RSVP reservation merging provides scalability.

R5 R4

R3

R5 R4

R1

R2Sender


RSVP in Action

RSVP sets up a path through the network with the requested QoS.

RSVP is used for CAC in Cisco Unified CallManager 5.0.


The Differentiated Services Model

Overcomes many of the limitations best-effort and IntServ models Uses the soft QoS provisioned-QoS model rather than the hard QoS

signaled-QoS model Classifies flows into aggregates (classes) and provides appropriate QoS for

the classes Minimizes signaling and state maintenance requirements on each network

node Manages QoS characteristics on the basis of per-hop behavior (PHB) You choose the level of service for each traffic class

Edge

Edge

Interior

Edge

DiffServ Domain

End Station

End Station


Methods for Implementing QoS Policy

Method Description

Legacy CLI – Coded at the CLI

– Requires each interface to be individually configured

– Time-consuming

MQC – Coded at the CLI

– Uses configuration modules

– Best method for QoS fine tuning

Cisco AutoQoS – Applies a possible QoS configuration to the interfaces

– Fastest way to implement QoS

Cisco SDM QoS wizard – Application for simple QoS configurations


Configuring QoS at the CLI Uses the CLI via console and Telnet

Traditional method

Nonmodular

Cannot separate traffic classification from policy definitions

Time-consuming and potentially error-prone task

Used to augment and fine-tune newer Cisco AutoQoS method


Guidelines for Using the CLI Configuration Method

Build a traffic policy:Identify the traffic pattern.

Classify the traffic.

Prioritize the traffic.

Select a proper QoS mechanism:

Queuing

Compression

Apply the traffic policy to the interface.


Legacy CLI QoS Example

For interactive traffic, you can use CQ and TCP header compression.

interface multilink ip address 10.1.61.1 255.255.255.0 load-interval 30 custom-queue-list 1 ppp multilink ppp multilink fragment-delay 10 ppp multilink interleave multilink-group 1 ip tcp header-compression iphc-format ! queue-list 1 protocol ip 2 tcp 23


Modular QoS CLI

A command syntax for configuring QoS policy

Reduces configuration steps and time

Configures policy, not “raw” per-interface commands

Uniform CLI across major Cisco IOS platforms

Uniform CLI structure for all QoS features

Separates classification engine from the policy


Modular QoS CLI Components


Step 1: Creating Class Maps:“What Traffic Do We Care About?”

Each class is identified using a class map.

A traffic class contains three major elements:A case-sensitive name

A series of match commands

An instruction on how to evaluate the match commands if more than one match command exists in the traffic class

Class maps can operate in two modes:Match all: All conditions have to succeed.

Match any: At least one condition must succeed.

The default mode is match all.


Configuring Class Maps

Enter class-map configuration mode. Specify the matching strategy.

class-map [match-all | match-any] class-map-name

router(config)#

description description

router(config-cmap)#

Use at least one condition to match packets.

Use descriptions in large and complex configurations. The description has no operational meaning.

match any

router(config-cmap)#

match not match-criteria


Classifying Traffic with ACLs

Standard ACL

access-list access-list-number {permit | deny | remark} source [mask]

router(config)#

access-list access-list-number {permit | deny} protocol source source-wildcard [operator port] destination destination-wildcard [operator port] [established] [log]

router(config)#

match access-group access-list-numberrouter(config-cmap)#

Extended ACL

Use an ACL as a match criterion


Step 2: Policy Maps: “What Will Be Done to This Traffic?”

A policy map defines a traffic policy, which configures the QoS features associated with a traffic class that was previously identified using a class map.

A traffic policy contains three major elements:A case-sensitive name

A traffic class

The QoS policy that is associated with that traffic class

Up to 256 traffic classes can be associated with a single traffic policy.

Multiple policy maps can be nested to influence the sequence of QoS actions.


Configuring Policy Maps Enter policy-map configuration mode. Policy maps are identified by a

case-sensitive name.

policy-map policy-map-name

router(config)#

class {class-name | class-default}

router(config-pmap)#

class class-name condition

router(config-pmap)#

Enter the per-class policy configuration mode by using the name of a previously configured class map. Use the class-default name to configure the policy for the default class.

Optionally, you can define a new class map by entering the condition after the name of the new class map. Uses the match-any strategy.


Step 3: Attaching Service Policies: “Where Will This Policy Be Implemented?”

Attach the specified service policy map to the input or output interface

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

class-map HTTP match protocol http!policy-map PM class HTTP bandwidth 2000 class class-default bandwidth 6000!interface Serial0/0 service-policy output PM

Service policies can be applied to an interface for inbound or outbound packets


Modular QoS CLI Configuration Example

router(config)# class-map match-any business-critical-trafficrouter(config-cmap)# match protocol http url “*customer*”router(config-cmap)# match protocol http url citrix

router(config)# policy-map myqos policyrouter(config-pm am)# class business-critical-trafficrouter(config-pm am-c)# bandwidth 1000

router(config)# interface serial 0/0router(config-if)# service-policy output myqos policy

1

2

3


Boolean Nesting

Salaries

HockeyPlayers

FootballPlayers

Goal: Find books that cover the salaries of either football players or hockey players.

Solution: Boolean (salaries AND [football players OR hockey players]).

Goal


MQC Example

Voice traffic needs priority, low delay, and constant bandwidth.

Interactive traffic needs bandwidth and low delay.


MQC Configuration

hostname Office!class-map VoIP match access-group 100class-map Application match access-group 101!policy-map QoS-Policy class VoIP priority 100 class Application bandwidth 25 class class-default fair-queue!interface Serial0/0 service-policy output QoS-Policy!access-list 100 permit ip any any precedence 5access-list 100 permit ip any any dscp efaccess-list 101 permit tcp any host 10.1.10.20access-list 101 permit tcp any host 10.1.10.40

Classification

QoS Policy

QoS Policy on Interface

Classification


Basic Verification Commands

Display the class maps

show class-map

router#

show policy-map

router#

show policy-map interface type number

router#

Display the policy maps

Display the applied policy map on the interface


Cisco AutoQoS


Cisco AutoQoS Features in a WAN

Feature Benefit

Autodetermination of WAN Settings

Eliminates the need to know QoS theory and design in common deployment scenarios

Autoclassification of VoIP Settings

Automatically classifies RTP payload and VoIP control packets (H.323, H.225 unicast, Skinny, SIP), and MGCP

Initial Policy Generation

Reduces the time needed to establish an initial, feasible QoS policy solution

VoIP LLQ Provisioning

Provisions LLQ for the VoIP bearer and bandwidth guarantees for control traffic

WAN Traffic Shaping

Enables WAN traffic shaping (FRTS, CIR and burst)

Link Efficiency Enables link efficiency mechanisms (LFI and cRTP) as appropriate

Management Provides SNMP and syslog alerts for VoIP packet drops


Cisco AutoQoS Features in a LAN

Feature Benefit

Simplified Configuration

One-command voice configuration does not affect other network traffic. Can be fine tuned.

Queue Configuration

Configures queue admission criteria, Cisco Catalyst strict-priority queuing with WRR scheduling, modifies queue sizes and weights.

Automated & Secure

Detects Cisco IP Phones and enables AutoQoS settings. Protects against malicious activity during Cisco IP phone relocations and moves.

Optimal VoIP Performance

Leverages decades of networking experience and uses all advanced QoS capabilities of the Cisco Catalyst switches.

End-to-End Interoperability

Works with AutoQoS settings on all other Cisco switches and routers.

Trust Boundary Enforcement

Enforces the trust boundary on Cisco Catalyst switch access ports, uplinks, and downlinks

NBAR Support Enables NBAR for different traffic types


Cisco AutoQoS Use Guidelines Make sure that:

Any QoS configurations on the WAN interface are removed.

CEF is enabled.

NBAR is enabled.

Correct bandwidth statement is configured on the interface.

Cisco AutoQoS is enabled on the interface.


Cisco AutoQoS Example

Enable Cisco AutoQoS on relevant devices (such as LAN switches and WAN routers) that need to perform QoS.


Cisco AutoQoS Example (Cont.)

interface Serial1/3 ip cef bandwidth 1540 ip address 10.10.100.1 255.255.255.0 auto qos voip

IP CEF and Bandwidth

AutoQoS for VoIP Traffic Recognized by NBAR


Cisco Security Device Manager (SDM)


Steps 1 to 4: Creating a QoS Policy

1.

2.

3.

4.


Step 5: Launching the QoS Wizard


Step 6: Selecting the Interface


Step 7: Generating a QoS Policy


Reviewing the QoS Configuration


Completing the Configuration: Command Delivery Status


Monitoring QoS Status

1.

2.

A

B


Comparing QoS Implementation Methods

Legacy CLI MQCCisco

AutoQoSCisco SDM QoS Wizard

Ease of use PoorModerately

easySimple Simple

Ability to fine-tune

Acceptable Very good Limited Limited

Time to implement

Longest Average Shortest Short

Modularity Poor Excellent Excellent Very good


Network-Based Application Recognition(NBAR)

•NBAR is a new classification engine in Cisco IOS® Software that can recognize a wide variety of applications

•Including Web-based applications and client/server applications that dynamically assign TCP or User Datagram Protocol (UDP) port numbers

•After the application is recognized, the network can invoke specific services for that particular application.

•NBAR currently works with quality-of-service (QoS) features to help ensure that the network bandwidth is best used to fulfil your business objectives.


Why NBAR is used

•Today's applications require high performance to help ensure competitiveness in an increasingly fast-paced business environment.

•The network can provide a variety of services to help ensure that your mission-critical applications receive the bandwidth they need to provide this performance.

•The difficulty is that today's Internet-based and client-server applications make it difficult for the network to identify and provide the proper level of control you need.

•NBAR solves this problem by adding intelligent network classification to your infrastructure.


NBAR fits into the Content Networking framework

•NBAR provides intelligent network classification that can be used to determine which services the network should provide.

•NBAR currently works with QoS features so that one can provide differentiated classes of service (CoSs) to different applications.


Advantages of NBAR

•Help Ensure Performance for Mission-Critical Applications

•Reduce WAN Expenses

•Manage Web Response

•Improve VPN Performance

•Improve Multiservice Performance

© 2006 Cisco Systems, Inc. All rights reserved. QOS Lecture 5 - QOS Policy Models.

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Transcript of © 2006 Cisco Systems, Inc. All rights reserved. QOS Lecture 5 - QOS Policy Models.