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Foundation Summary 679

Foundation Summary

The “Foundation Summary” is a collection of tables and figures that provide a convenient review of many key concepts in this chapter. For those of you already comfortable with the topics in this chapter, this summary could help you recall a few details. For those of you who just read this chapter, this review should help solidify some key facts. For any of you doing your final prep before the exam, these tables and figures are a convenient way to review the day before the exam.

QPM needs to be able to communicate with the routers and switches, as well as learn about what devices are in the network. Figure 9-6 outlines the overall location and functions between the QPM server and the rest of the network.

Figure 9-6 QPM Server and Communication with Other Devices

Network Devices

Telnet

COPS

 

SNMP

Cisco Works 2000

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

QPM

 

 

Inventory

 

LDAP Directory

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

680 Chapter 9: Management Tools and QoS Design

Table 9-10 lists some of the types of SAA probes supported in IOS 12.2.

Table 9-10 Types of SAA Probes

Type of Probe

Function

 

 

ICMP echo

Measures availability between a router and any other devices by sending ICMP

 

echos (pings)

 

 

IP Path echo

Measures hop-by-hop response time by pinging each successive device in the route

 

to the true destination of the probe.

 

 

TCP connection

Measures the time required to establish a TCP connection to a specified TCP port on

 

a specified IP host.

 

 

UDP echo

Measures the round-trip time to send a packet to a specified UDP port number on a

 

specified IP host

 

 

UDP jitter

Measures jitter, one-way delay, and packet loss in each direction

 

 

FTP

Measures time required to retrieve (FTP get) a specified file from a specified FTP

 

server

 

 

HTTP

Tests the time taken to do DNS lookup to find a web server, TCP connection

 

establishment time to the server, or the time required to download an object from

 

the server

 

 

DNS

Measures the round-trip time between sending a DNS request and receiving a

 

response

 

 

DLSw

Measures DLSw round-trip times, including DLSw stack delays, between a source

 

and destination, without requiring an SAA agent on the destination host

 

 

To meet the requirement to gather larger amounts of network performance information, SMS includes several components. Figure 9-7 shows the components, with an explanation of each component following the figure.

Foundation Summary 681

Figure 9-7 Service Management Solution Components

SAA Agents

Network Devices

 

Telnet/SNMP

 

 

 

 

 

 

 

 

 

Telnet/SNMP

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Collection

 

 

 

 

......

 

 

 

 

 

 

Collection

 

Manager

 

 

 

 

 

 

 

 

 

 

 

Manager

 

 

 

 

 

 

 

 

 

 

 

(CM)

 

 

 

 

 

HTTP/XML

 

 

 

 

 

(CM)

 

 

 

 

End User

 

 

 

 

 

 

 

 

 

 

Flows

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

HTTP/XML

 

 

 

 

 

 

Service Level Manager (SLM)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Flows

 

 

 

 

 

 

and CiscoWorks 2000

 

 

 

 

 

 

 

 

 

 

 

 

Table 9-11 lists many of the most important features of the various QoS management products and identifies which products support the features.

Table 9-11 Summary of QoS Management Tool Features

Feature

QDM

QPM

IPM

SMS

SAA

 

 

 

 

 

 

Supports a wide variety of routers

Yes

Yes

Yes

Yes

Yes

 

 

 

 

 

 

Supports a wide variety of switches

No

Yes

No

No

No

 

 

 

 

 

 

Free?

Yes

No

No

No

No

 

 

 

 

 

 

Allows network-wide QoS policy definition, followed by

No

Yes

No

No

No

automatic deployment of appropriate configurations

 

 

 

 

 

 

 

 

 

 

 

Creates graphs of real-time performance

Yes

Yes**

Yes

No

No

 

 

 

 

 

 

Creates graphs of historical performance

Yes*

Yes

Yes

Yes

No

 

 

 

 

 

 

continues

682 Chapter 9: Management Tools and QoS Design

Table 9-11 Summary of QoS Management Tool Features (Continued)

Feature

QDM

QPM

IPM

SMS

SAA

 

 

 

 

 

 

Creates historical graphs to compared to service levels

No

No

No

Yes

No

 

 

 

 

 

 

Requires extra software loaded into router/switch Flash

Yes

No

No

No

No

memory

 

 

 

 

 

 

 

 

 

 

 

End-user viewing of reports and configuration using a web

Yes

Yes

Yes

Yes

No

browser

 

 

 

 

 

 

 

 

 

 

 

Manages only a single device from a browser

Yes

No

No

No

No

 

 

 

 

 

 

Manages entire network from one browser window

No

Yes

Yes

Yes

No

 

 

 

 

 

 

Creates configuration for router probes that measure latency

No

No

Yes

Yes

No

and jitter

 

 

 

 

 

 

 

 

 

 

 

Implements the actual probes and responses when necessary

No

No

No

No

Yes

for measuring network performance

 

 

 

 

 

 

 

 

 

 

 

*QDM supports historical trending for up to five days of policy history.

**Through the use of the CB-QOS MIB

Figure 9-8 outlines the four-step design process as suggested in the Cisco DQOS course.

Figure 9-8 Four Steps for QoS Design

Step 1

Determine Customer

Priorities/QoS Policy

Step 4

Monitor the

 

Characterize

Step 2

Network

 

the Network

 

 

 

 

 

 

 

 

Implement

the Policy

Step 3

You must decide on a delay budget for the voice calls, and then examine all the call paths to decide whether the delay budget can be met. The delay components, along with recommended overall delay budgets, are listed in Tables 9-12 and 9-13.

 

 

 

 

Foundation Summary 683

 

 

 

 

 

Table 9-12 One-Way Delay Budget Guidelines for Voice

 

 

 

 

 

 

 

One Way Delay (ms)

 

Description

 

 

 

 

 

 

0–150

 

ITU G.114 recommended acceptable range

 

 

 

 

 

 

0–200

 

Cisco’s recommended acceptable range

 

 

 

 

 

 

150–400

 

ITU G.114’s recommended range for degraded service

 

 

 

 

 

 

400+

 

ITU G.114’s range of unacceptable delay in all cases

 

 

 

 

 

Table 9-13 Delay Components, Variable and Fixed

 

 

 

 

 

 

 

 

Delay

Fixed or

 

 

Component

Variable

Comments

 

 

 

 

 

Codec

Fixed

Varies slightly based on codec and processing

 

 

 

 

load; considered fixed in course books (and

 

 

 

 

probably on exams). Typically around 10 ms.

 

 

 

 

 

Packetization

Fixed

Some codecs require a 30-ms payload, but

 

 

 

 

packetization delay does not vary for a single

 

 

 

 

codec. Typically 20 ms, including when using

 

 

 

 

G.711 and G.729.

 

 

 

 

 

Propagation

Variable

Varies based on length of circuit. About

 

 

 

 

5ms/100 km.

 

 

 

 

 

Queuing

Variable

This is the most controllable delay component for

 

 

 

 

packet voice.

 

 

 

 

 

Serialization

Fixed

It is fixed for voice packets, because all voice

 

 

 

 

packets are of equal length. It is variable based on

 

 

 

 

packet size for all packets. The delay is based on

 

 

 

 

the clock speed of the WAN circuit.

 

 

 

 

 

Network

Variable

Least controllable variable component. Latency is

 

 

 

 

potentially higher in a packet-switched network

 

 

 

 

than in a leased line.

 

 

 

 

 

De-jitter buffer (initial playout delay)

Variable

This component is variable because it can be

 

 

 

 

configured for a different value. However, that

 

 

 

 

value, once configured, remains fixed for all calls

 

 

 

 

until another value is configured. In other words,

 

 

 

 

the initial playout delay does not dynamically

 

 

 

 

vary.