Chapter 9 Qos

8/4/2019 Chapter 9 Qos

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© Copyright 2004 Maples ESM Technologies

QoS




Enterprise NetworkRequirements for QoS




Network Availability Problem Areas

Network administrators need a way to manageproblem areas on an application basis.




Solution: QoS-Enabled Infrastructure

Allows you to do the following:

• Predict response times for end-to-end network services

• Manage jitter-sensitive applications, such as audio andvideo playbacks

• Manage delay-sensitive traffic, such as real-time voice

• Manage loss in times of inevitable bursty congestion

• Set traffic priorities across the network

• Support dedicated bandwidth

• Avoid and manage network congestion




Comparing QoS Architectures

• Best-effort services

– Basic connectivity with no guarantees

– FIFO queues

• Integrated Services

– Manages traffic on a per-flow basis

– Provides customized services per traffic stream

– End-to-end application registration

• Differentiated Services

– Manages traffic on a type-of-traffic basis

– Does not provide individual stream visibility

– Implemented per hop




Integrated Services (IntServ)Architecture

• Provides multiple servicelevels

• Requests specific kind ofservice from the networkbefore sending data

• Uses RSVP

• Uses intelligent queuing

mechanisms• End-to-end




Differentiated Services (DiffServ)Architecture

• Multiple-service model to satisfy differing requirements

• Implemented through six-bit DSCP field definitions

• DSCP field is in IP header in the ToS field




Queuing Components

Each queuing mechanism has three maincomponents:

• Classification

• Insertion policy

• Service policy




FIFO Queuing




Priority Queuing




Custom Queuing




Low Latency Queuing




IP RTP Priority




Weighted Fair Queuing




Class-Based Weighted Fair Queuing




Weighted Round Robin




Configuring Traffic Classes andTraffic Policies

• Creates a traffic policy

• Defines a traffic class

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

• Attaches the traffic policy to an interface

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

class-name

Switch(config)#policy-map policy-name




Configuring Traffic Classes andTraffic Policies (Cont.)

• Configures the policy-map class trust state, which selects thevalue that QoS uses as the source of the internal DSCP value

• Enables QoS on the interface

Switch(config)#mls qos

Switch(config-if)#mls qos trust {cos | dscp |

ip_precedence}




Verifying the Modular QoS CLIConfiguration

Switch#show class-map Class Map match-any class-default (id 0) Match anyClass Map match-any class-simple (id 2) Match any

Class Map match-all ipp5 (id 1) Match ip precedence 5Class Map match-all agg-2 (id 3)

Switch#show policy-map max-pol-ipp5Policy Map max-pol-ipp5class ipp5class ipp5 police flow 10000000 10000 conform-action set-prec-transmit 6 exceed-action

policed-dscp-transmit trust precedence police 2000000000 2000000 2000000 conform-action set-prec-transmit 6exceed-action policed-dscp-transmit

Switch#show class-map class-map-name

Switch#show policy-map interface interface-spec




Verifying the Modular QoS CLIConfiguration (Cont.)

Switch#show policy-map interface fastethernet 5/36 input

FastEthernet5/36service-policy input: max-pol-ipp5class-map: ipp5 (match-all)0 packets, 0 bytes5 minute rate 0 bps match: ip precedence 5

class ipp5 police 2000000000 2000000 conform-action set-prec-transmit 6 exceed-action policed-dscp-transmit

Switch#show policy-map interface interface-spec

[ input | output ] class class-name




Class-Based Marking

• Mark packets by setting the IP Precedence bits or the IPdifferentiated services code point (DSCP) in the IP type ofservice (ToS) byte.

• Mark frames by setting the Layer 2 class of service (CoS)value.

• Associate a local quality of service (QoS) group valuewith a packet.

• Set the cell loss priority (CLP) bit setting in the ATM

header of a packet from 0 to 1.• Set the Frame Relay discard eligible (DE) bit in the

address field of the Frame Relay frame from 0 to 1.




Configuring Class-Based Marking



• Specifies a predefined class

Switch(config-pmap)#class class-name

• Specifies the IP Precedence of packets within a traffic class

Switch(config-pmap-c)#set ip precedence ip_prec_value




Configuring an IP DSCP Value





• Specifies the IP DSCP value of packets within a traffic class

Switch(config-pmap-c)#set ipdscp ip_dscp_value




Network-Based ApplicationRecognition Features

• Works with QoS features to provide:

– Guaranteed bandwidth

– Bandwidth limits

– Traffic shaping

– Packet coloring• Introduces new classification features:

– Classification of applications which dynamically assignTCP/UDP port numbers

– Classification of HTTP traffic by URL, HOST, or MIME type

– Classification of Citrix ICA traffic by application name

– Classification of application traffic using subportinformation




Configuring NBAR

• Specifies a protocol supported by NBAR as a matching criterion

Switch(config-cmap)#match protocol protocol-name

•

Defines a traffic class

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

class-name




Configuring NBAR (Cont.)





• Attaches the traffic policy to the interface

Switch(config-if)#service-policy [input | output]

policy-name




Policy-Based Routing Tasks

• Classify traffic based on extended access listcriteria.

• Set IP Precedence bits, giving the network theability to enable differentiated classes of service.

• Route packets to specific traffic-engineered

paths.




IP RTP Priority Commands

• Reserves a strict priority queue for a set of RTP packet flowsbelonging to a range of UDP destination ports

Switch(config-if)#ip rtp priority start-port port-range bw

• Changes the percent of bandwidth allocated for LLQ and IPRTP Priority

Switch(config-if)#max-reserved-bandwidth percent

• Lists fair queuing configuration and statistics for a particularinterface

Switch#show queue interface-type interface-number




Configuring Low Latency Queuing





• Specifies that traffic in this class be queued in the priorityqueue within the allocated bandwidth

Switch(config-pmap-c)#priority bandwidth




Monitoring Low Latency Queuing

• Lists fair queuing configuration and statistics for a particularinterface

Switch#show queue interface-type interface-number

• Displays the configuration of all classes configured for allservice policies on the specified interface

Switch#show policy interface interface-number

• Displays the configuration of all classes for a specifiedservice policy map for all classes for all existing policy maps

Switch#show policy-map policy-map-name




Weighted Round-Robin Queuing

• Used on Catalyst Layer 3 switches on egress ports tomanage the queuing and sending of packets

• Places a packet in one of four queues based on IPPrecedence, from which it derives a delay priority

Default Queue Weight

0, 1

Queue AssignmentDelay PriorityIP Precedence

0 0 1

2, 3 1 1 2

4, 5 2 2 4

6, 7 3 3 8




Configuring Weighted Round-RobinQueuing

• Specifies the weight of the two WRR queues

Switch(config-if)#wrr-queue bandwith weight1 weight2

• Assigns the CoS to queue threshold

Switch(config-if)#wrr-queue cos-map [1 | 2] [1 | 2] cos1

cos2 priority-queue cos-map Q cos1 cos2

• Configures the threshold values

Switch(config-if)#wrr-queue random-detect max-threshold

queueID threshold1 threshold2




Configuring WRED at theInterface Level

• Configures the minimum and maximum thresholds

Switch(config-if)#random-detect dscp dscpvalue min-

threshold max-threshold [ mark-probability-denominator ]

• Configures WRED to use the DSCP value when calculatingdrop probability

Switch(config-if)#random-detect dscp-based




Configuring WRED at the Class Level

• Configures the minimum and maximum thresholds

Switch(config-pmap-c)#random-detect dscp dscpvalue min-

threshold max-threshold [ mark-probability-denominator ]

• Configures WRED to use the DSCP value when calculatingdrop probability for traffic in this class

Switch(config-pmap-c)#random-detect dscp-based




Verifying the Configuration

Switch#show queueing interface gig 1/1Interface GigabitEthernet1/1 queueing strategy: Weighted Round-Robin

QoS is disabled globallyTrust state: trust DSCPDefault COS is 0Transmit group-buffers feature is enabled Transmit queues [type = 1p2q2t]:Queue Id Scheduling Num of thresholds-----------------------------------------

1 WRR low 22 WRR high 23 Priority 1

.....(output truncated)

Switch#show queueing interface interface-spec



© C h 200 l S h l

QoS debug Commands

Description

debug ip rsvp Provides information about messagesreceived, minimal detail about thecontent of these messages, andinformation about state transitions

debug priority Displays priority queueing output

Chapter 9 Qos

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