infovista network latency

VistaView for NetworkLatency

Seeing IT

TM

ii

Part Number: 20_300_009_22

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InfoVista SA reserves the right to revise this documentation and to make changes in content from time totime without obligation on the part of InfoVista to provide notification of such revision or change.InfoVista provides this documentation without warranty of any kind, either implied or expressed,including but not limited to, the implied warranties of merchantability and fitness for a particular purpose.InfoVista may make improvements or changes to the product(s) and/or the program(s) described in thisdocument at any time.

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VistaView for Network Latency

iii

About this book

Congratulations on your purchase of InfoVista, the Information System Quality ofService manager. With InfoVista you can interrogate resources in your InformationSystem (IS), calculate key performance indicators, and generate reports on resourcebehavior. You use these reports to monitor your Service Level Agreements (SLA) andproactively manage your IS resources.

VistaViews are turnkey applications for IS SLA reporting and analysis. They run overthe standard InfoVista “engine”.

VistaView for Network Latency provides a set of pre-configured reports specificallydesigned to monitor multiple technologies using the ping. These reports cover arange of user needs including problem tracking, daily monitoring, and trendmeasurement.

iv

InfoVista documentationThe InfoVista documentation set comprises the following volumes:

InfoVista Installation Guide

This manual describes the installation of the product.

InfoVista Quick Start

This manual gives rapid (default) procedures for installing and starting the systemand describes how to produce your first reports using templates from the standardlibraries.

InfoVista User’s Guide

This manual describes the client graphic interface, the methodology of modeling theInformation System, and the tasks which can be performed with the product.

InfoVista Reference Manual

This manual documents the syntax of all commands used by the client software intext mode.

VistaViews (of which this book describes one)

This is a set of manuals describing each of the standard libraries provided forInfoVista.

Documentation supports

The InfoVista documents listed above are provided on paper and also as PDF files onthe software distribution media. The PDF files can be viewed with the viewersoftware.

This book

This manual is divided into the following sections:

• Chapter 1 - Getting Started. This chapter provides an overview of theproduct and its main functionalities. It also explains how to model yourresources and get reports up and running as quickly as possible.

• Chapter 2 - The Reports. This chapter describes individual reports in detail.

Comments and Suggestions

At the end of this book, you’ll find a remarks form. We welcome any comments youmay have on our product or its documentation. Your remarks will be examinedthoroughly and taken into account for future versions of InfoVista.


Contents

Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Quick Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Problem area addressed by the library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Roadmap for modeling the network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Modeling an IP node. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Why group IP nodes?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Modeling a group of IP nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Modeling the resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Customizing the model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Default values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Quality of Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Reachability and response time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Drill Downs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8See Also Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Calendars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

The Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

Table of report templates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Network Manager’s Overview - for Nodes Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

What can it do? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13The Graphs & Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

IP Node Group: Availability Report. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 What can it do? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16The Graphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

IP Node Availability Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 What can it do? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20The Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

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Chapter 1Getting started

The VistaView for Network Latency contains report templates for general purposemonitoring of multiple technologies using the ping. It contains monthly, weekly,daily, hourly and real time reports which can be used to monitor IP nodes and IPnode groups.

PrerequisitesThe reports which monitor IP nodes and IP node groups use the ICMP (pingprotocol). They do not require the monitored resource to support SNMP. Theindicators in the reports have multiple formulas in order to embrace this sort ofheterogeneous environment.

2 Quick Start

Quick Start

This section is for experienced users of InfoVista. If you are new to InfoVista, werecommend you read the whole of Chapter 1 before starting.

InstallationThe VistaView for Network Latency is delivered as an InfoVista library file calledInfoVista_Network_Latency.ivl.

During installation of InfoVista V2.1, this file is copied to disk and automaticallyinstalled on the InfoVista server.

During an update or migration, the library file is simply copied to disk. You mustinstall it manually.

After installation, your InfoVista object tree will contain the library InfoVistaNetwork Latency.

See the InfoVista Installation Guide for details.

Problem area addressed by the libraryThe Reachability & Response Time library uses the ping protocol to measure systemavailability. Using the traditional ping function, the InfoVista server sends a numberof ping packets to a target system. If the target responds to a ping packet then we cansay it is reachable and the time taken for the response packet to be received is theresponse time of the path between the server and the target.

With this function, the target does not need to support SNMP. This is a majoradvantage. It means that any IP device can be monitored with these reports.


Quick Start 3

However, this configuration measures the reachability of a device, as seen by theInfoVista server. Also, it measures the response time of the path from the InfoVistaserver to the device. If we want to measure response time of paths between othernetwork devices, or to measure the reachability of a target as seen by some deviceother than the InfoVista server, we must use the proxy ping protocol.

With the proxy ping protocol, the InfoVista server requests another system, such as aCisco router, to ping the target. The major advantage of this method is that we canmonitor the path between any two devices in the IP network. We are not locked in toan InfoVista-centric point of view. Of course the method is limited to systemssupporting the proxy ping function.

Roadmap for modeling the networkFor details on the vistas used for modeling IP nodes, refer to InfoVista Standard ModelLibrary.

When you are setting up InfoVista reports in a new environment, one of the mostcommon difficulties is finding system parameters quickly. We recommend thefollowing procedure.

Modeling an IP node

Step 1

Create an instance of a device vista (Router, Switch, etc) to represent the device. Ifthere is no specific vista available for the device, use the SnmpNode vista.

Step 2

Edit the property values associated with the device. You need to specify:

Router

InfoVista

PING

PROXY PING

TARGET

Getting started

4 Quick Start

• an IP address for the device.

Note:If the name of the instance is recognized by the local DNS, InfoVista will complete the ip propertyvalue automatically when you create the instance (when you click OK or Apply in the instanceproperty sheet). Therefore, when modeling devices, always try to use instance names which arerecognized by your local DNS.

In the procedure above, you did not edit the snmprd and snmpwr properties because the IP nodereports do not use the SNMP protocol. If you use the same instances in other reports which requireSNMP, you may have to edit these two properties.

In the procedure above, you modeled the device with an instance of Router, Switch, etc. The instancewill be displayed in the Instances branch of that vista in the InfoVista object tree. The instance willalso be displayed in the Instances branch of the vista IpNode, because of the rules which associatethese vistas.

Why group IP nodes?

The IpNode Group vista allows you to group IP nodes together for reportingpurposes. You may want to create several groups and run reports for each group.You can even create a group containing a single element.

The purpose of grouping instances together in the same report is to generate reportswhich give an overall visibility of a part of the network. For example, you couldcreate a group containing all the nodes on the same site.

Another use for the group is to simplify the task of network monitoring. Forexample, in a network with 500 nodes, it is much simpler, each morning, to study 10reports concerning groups of 50 nodes rather than 500 reports about one node each.

Modeling a group of IP nodes

Step 1

Create an instance of the vista IpNode Group. Drag & drop a number of IpNodeinstances to the Contents attribute.


Modeling the resources 5

Modeling the resourcesThe procedure for modeling resources is given in section “Roadmap for modelingthe network” on page 4. For details of the vistas and their properties, refer toInfoVista Standard Model Library.

Customizing the model

Default values

The following properties of IP Node affect indicators which use a threshold (theexception reports):

Note that you can specify different values for each element. For example, thethreshold response time on one path may be 500 ms, but for another, critical pathyou may decide that 200 ms is the maximum acceptable.

Admin Status 1

Large Packet Size 2048

Large Timeout 5000

Ping Delay 1000

Ping Packet Number 4

Reachability Threshold

75%

Small Packet Size 32

Small Timeout 1000

Getting started

6 Measurements

Measurements

The reachability reports measure response time and reachability for IP nodes. Whilethere is sufficient margin between these indicators and the threshold values, we cansay that the element is capable of giving good service.

Quality of ServiceThe ultimate goal of running a network and monitoring its operation is to providesomebody with a service (usually the user!). The Global QoS indicator provides anindication of the level of this service, for a group of segments. Global QoS iscalculated by taking into account reachability and response time.

Each factor is given a different weight in the QoS calculation, as follows:

When either of these factors goes beyond preset milestones, the QoS value isreduced. The values of these milestones are set in the formulas used to calculateQoS. There are 5 milestones for each factor, of which the following table shows justthe first, middle and last:

Reachability weight = 1.0

which means it can reduce QoS by up to 100%

Response time

weight = 0.7

which means it can reduce QoS by up to 70%

MilestoneQoS drops

MilestoneQoS drops

MilestoneQoS drops

Reachability _ 95% 0% = 85% 50% < 50% 100%

Response time _ 200ms 0% = 500ms 35% > 1000ms 70%

100%

30%0%

when Response time > 1000ms (timeout)

when Reachability < 50%

QOS


Measurements 7

The resulting Global QoS indicator gives an immediate visual indication of theoperation of a group of segments.

Reachability and response timeReachability is the principal indicator of node vitality. It shows the % of time that anode responded to at least one ping packet during the display period. 4 small pingpackets are sent to the target system every 5 minutes, and then the number ofresponse packets sent back by the target are counted. If the target system responds toat least 1 packet out of 4, then the target is considered 100% reachable for the 5minute period. The reachability value is averaged over the display period to providea value of % reachability. This indicator gives a good measure of whether the nodewas “up” during this time.

Analysis of response time gives you a clear picture of the service which the network isproviding. This information is vital for proactive management of the network(planning future upgrades, for example) and also for justifying new investments orthe reorganization of part of your network.

Response time shows the average time between a ping packet being sent to the targetand a response packet being received. Response time is measured by sending 4 smallping packets every 5 minutes and 4 large packets every 30 minutes. The averageresponse time is then calculated for the case of small packets and for the case of largepackets. Timeouts are not included in the calculation.

The use of different size ping packets simulates the effect of packet size on responsetime. Interactive or conversational type applications tend to generate small packets.File Transfer type applications tend to generate large packets. The effect on responsetime of these application types can be monitored with these two indicators.

The response time indicators give a single, average value based on all ping responsepackets received. These indicators do not give any information on the range ofresponse times which were actually measured. The response time distribution indicatorsanalyze response time ranges in more detail. They show the real spread of responsetimes exhibited by the network.

Exception reports are text messages which are generated if the value of an indicator isgreater than a threshold value. Exception reports provide an excellent visual form ofalert management.

GroupsThe reports on groups calculate the same indicators as for single elements. Thedifference is that the results are averaged over the whole group. Thus the GlobalResponse Time indicator shows the average response time for all the elements in thegroup, the Global Reachability indicator shows the average reachability of all elements

Getting started

8 Measurements

in the group, etc.

The importance of the “group” reports is that they give an overall picture of theoperation of a large geographical portion of the network.

Drill DownsMost VistaView reports feature Drill Downs, which are pre-established links to otherreports. Use the Drill Down feature to quickly access and view related reports, trackproblems, or monitor trends in network behavior. Drill Downs are from group togroup, group to individual, or individual to individual reports, and includeassociations with other reports in the VistaView. A report may include Drill Downs toother display rates for the same resource, such as a Drill Down from the Monthly toWeekly, Weekly to Daily, Daily to Hourly, and Hourly to Real Time report.

To access the Drill Down feature:

1 In a report, right-click on a table cell or a data point on a graph.

2 In the contextual menu, select Reports to view the list of Drill Down reports.

The Drill Down report list includes reports that are running. Drill Down reports thatare not running are listed on the contextual menu under Reports/Instantiate. Clickon Instantiate to create the associated Drill Down report. For more information onDrill Downs, see the InfoVista User’s Guide.

See Also BoxSee also list box

This box lists drill down reports which are associated with the report globally and


Measurements 9

which have been created already. After creating a drill down report, select commandView/Refresh to update this display.

CalendarsThe graphs in the reachability reports use one of 2 calendars:

• The All Hours calendar is a modifiable calendar. By default it is active 24hours per day and 365 days per year.

• The Business Hours calendar is a modifiable calendar. It is active duringcompany working hours. By default this from 9H00AM to 8H00PM every day.

Graphs which use the All Hours calendar display data which is averaged over 24hours. The effect is to give a true picture of round-the-clock utilization. On theother hand, it tends to mask the utilization peaks. The high values of throughput(for example) experienced during company working hours will be less visible in thisreport than in a report using the Business Hours calendar.

Graphs which use the Business Hours calendar show data which is averaged onlyduring the company working hours. The effect is to show a true picture of dailyworking conditions and to mask the contribution due to off-peak utilization.

Getting started

10 Measurements


Chapter 2The Reports

This chapter is divided into sections that correspond with each report template. Areport section includes: an overview of the report features, a graphicalrepresentation of the report, a detailed description of the report, including whatvariables are measured and how they are measured, and finally a suggested way ofusing the report.

12 Table of report templates

Table of report templates

The InfoVista Network Latency library contains the following report templates:

The Network Manager’s Overview and the reports marked AH use the All Hourscalendar. By default, this calendar is active 24 hours per day. The reports markedBH use the Business Hours calendar, which is active during company working hours.For details, refer to section “Calendars”.

Report template

Type Usage What is measured Technology

Network Manager’s Overview for IP nodes

Daily Group overview

Quality of service, response time, exceptions

ICMP (ping protocol)

IP Node Group : Availability (AH)

MonthlyWeeklyDailyHourlyReal time

Node availability

Reachability, response time ICMP (ping protocol)

IP Node Group : Availability (BH)

MonthlyWeeklyDaily

Node availability


IP Node : Availability (AH)

MonthlyWeeklyDailyHourlyReal time

Node availability


IP Node : Availability (BH)

MonthlyWeeklyDaily

Node availability



Network Manager’s Overview - for Nodes Report 13

Network Manager’s Overview - for Nodes Report

What can it do?

Monitored resource a group of nodes

Usage group overview

What is measured response time, QoS, exceptions

Technology ping

Type of report Daily

Lifetime 3 months

Audience Executive officers

The Reports

14 Network Manager’s Overview - for Nodes Report

The Graphs & TableGlobal Response Time

This graph shows the average response time of all the nodes in the group. It iscalculated as the average of the response times of the individual nodes. This graphgives you an overall picture of network utilization.

An increasing response time suggests an increase in network load. Any dramaticchange should be investigated. If you note a sudden change in response time, openthe daily IP Node Group: Availability report to pin point the problematic node.

The File Transfer indicator shows the response time for large ping packets. TheInteractive indicator shows the response time for short ping packets. These twoindicators show how response time is affected by packet size. This shows you how thenetwork is responding to your specific utilization needs.

The size of packets which transit through the network is determined by the type ofapplication. Thus “Interactive” applications such as telnet or transactionalapplications with short requests and responses, tend to generate short packets. “FileTransfer” type applications which transfer large quantities of data tend to generatelarge packets.

Global QoS

Global QoS shows the overall level of Quality of Service provided by the group ofnodes. It is calculated as the average of the QoS measured on each node in thegroup. Use this graph as an immediate visual alert to possible problems in thenetwork.

Any drop in QoS should be investigated. If the group of nodes is large, then a smalldrop in the global QoS may indicate a large drop in service level of a single node.This drop will generally be associated with an exception report. Check theExceptions table to see which node is malfunctioning.

Exception Reports

An exception is a text message which records an unusual event. This table generatesan exception report each time one of the response times of a node for large packets(F.T.) or for small packets (Int.) is greater than the preset thresholds or thereachability is less than the threshold. Reports are generated every 5 minutes while anode is in error and the table shows all the exception reports generated during thelast 2 days.

Use this table to quickly recognize trouble spots. If a node is in error for more than30 minutes at a time (6 successive exceptions), then open the hourly IP Node:Availability report for that path, to investigate in more detail.

The preset threshold values for each node are configured with property values on theinstance of Node which is used to model the node. The default values have been


Network Manager’s Overview - for Nodes Report 15

chosen to suit most networks. Each exception report includes the threshold value inthe message. If you feel that the report is overstating a problem (too manymessages), or understating a problem (too few messages), you can customize thethresholds to suit your specific environment.

The Reports

16 IP Node Group: Availability Report

IP Node Group: Availability Report

What can it do?Monitored resource a group of IP nodes

Usage node availability

What is measured reachability, response time

Technology ICMP (ping protocol)

Type of report Real Time Hourly Daily Weekly Monthly

Lifetime 1 week 1 month 3 months 1 year 3 years

Audience Trouble shooters Network Analysts Executive Officers


IP Node Group: Availability Report 17

The GraphsGlobal Reachability

This graph shows the % reachability of the group as a whole. It is calculated as theaverage of the reachability rates for each of the IP nodes in the group. This graphgives you an overall picture of the vitality of the group.

A decrease in Global Reachability suggests that at least one of the nodes is notresponding. If the global availability value decreases permanently, look at the VitalityAnalysis table to pin point the faulty node.

Global Response Time

Global Response time shows the average response time of all the IP nodes in thegroup. It is calculated as the average of the response times of the individual nodes.This graph gives you an overall picture of network utilization.

An increasing response time value suggests an increase in network load. Anydramatic change should be investigated. If you note a sudden change in Globalresponse time, look at the Vitality Analysis table to pin point the problematic node.


For a more precise analysis of group response time, refer to the two Response timedistribution graphs.

Response Time Distribution

Response time distribution shows the distribution of the ping response packets,according to response time. Response time distribution (interactive) takes intoaccount all the responses to small packets for all the IP nodes in the group.Response time distribution (file transfer) shows the same information for large pingpackets. Use these graphs to get a more precise indication of group response timesand their evolution over time.

The size of packets which transit through the network is determined by the type ofapplication. Thus “interactive” applications such as telnet or transactionalapplications with short requests and responses, tend to generate short packets. “FileTransfer” type applications which transfer large quantities of data tend to generatelarge packets.

These two graphs show how response time is affected by packet size. This shows youhow the network is responding to your specific utilization needs.

Large packet response time is generally greater than for small packets. One factor issimply the fact that large packets take longer to transmit. The different packet sizesused in the report show up the different problems experienced by different

The Reports

18 IP Node Group: Availability Report

applications. A graph showing only small packet response times would possibly hidethe problems experienced by larger packets, such as buffer pool management orfragmentation in the routers.

Note:The real time report does not have Response time distribution graphs.

The two packet sizes used for the ping function may be different for each IP node inthe group. They are listed in the Vitality Analysis table. They are defined withproperties on the instances of the vista IpNode used to model the devices in thegroup. The default values have been chosen to suit most configurations but you canadjust them to suit your environment. For details, refer to section “Customizing themodel” in chapter 1.

Vitality Analysis Table

The Vitality Analysis table groups together a number of indicators for the individualIP nodes in the group. Click on the title of a column to sort the table by increasingvalue. Click on the title again to sort by decreasing value. In this way you can displaythe top IP nodes or the bottom IP nodes with vitality problems. Normally, the samenodes will always be at the top or bottom of the table. Any sudden change in positionin the table or any sudden change in value should be investigated.

There is no fixed rule for the expected values of these indicators, what is moreimportant is any sudden change in value. However it is clear that an IP node whichhas a low reachability figure or a high response time is not giving good service. If youspot a potential trouble spot, open the IP Node: Availability report for that node inorder to analyze the problem in more detail.

Reachability is the principal indicator of node vitality. Reachability is measured bysending 4 small ping packets to the target at regular intervals and then calculatingthe % of time that the node responded to at least one ping packet during the displayperiod. This indicator gives a good measure of whether the node was “up” duringthis time.

RTT (File Transfer) and RTT (Interactive) show the average response time of eachnode measured with large ping packets and small ping packets respectively. Thisgives you an indication of how each node is behaving. An increasing response timemay be due to the IP node being overloaded or the network path becomingcongested between the InfoVista server and the IP node.

Response time is measured by sending 4 small ping packets every 5 minutes and 4large ping packets every 30 minutes, to the target system. The response time is thencalculated as the average of all responses to the large packets or to the small packets.These two indicators show you how response time is affected by packet size.

Large packet response time is generally greater than for small packets. One factor issimply the fact that large packets take longer to transmit. The different packet sizesused in the report show up the different problems experienced by different


IP Node Group: Availability Report 19

applications. A graph showing only small packet response times would possibly hidethe problems experienced by larger packets, such as buffer pool management orfragmentation in the routers.

Size (FT) shows the size, in octets, of the large ping packets used to ping each IPnode. Size (Int.) shows the size of the small ping packets. This data is shown forinformation only. The ping packet sizes are initially defined with properties on theinstances of vista IP Node which are used to model the nodes in the group. Thedefault values have been chosen to suit most configurations but you can adjust themto suit your environment. For details, refer to section “Customizing the model” inchapter 1.

The Reports

20 IP Node Availability Report

IP Node Availability Report

What can it do?Monitored resource an IP node

Usage node availability

What is measured reachability and response time

Technology ICMP (ping protocol)

Type of report Real Time Hourly Daily Weekly Monthly

Lifetime 1 week 1 month 3 months 1 year 3 years

Audience Trouble shooters Network Analysts Executive Officers


IP Node Availability Report 21

The GraphReachability

Reachability is the principal indicator of node vitality. The InfoVista server sends 4small ping packets every 5 minutes to the target system, and then counts the numberof response packets sent back by the target. Reachability is then calculated as the %of time that a node responded to at least one ping packet during the display period.This indicator gives a good measure of whether the node was “up” during this time.

A drop in Reachability means that a node did not respond to one batch of pingpackets. A temporary problem may be due to an overloaded node or a congestednetwork. A permanent problem suggests a node that went off line.

Response Time

Response time shows the average response time of an IP node. It is measured as theaverage time between a ping packet being sent to the target and a response packetbeing received by the InfoVista server. Response time is measured by sending 4 smallping packets every 5 minutes and 4 large packets every 30 minutes.


Response Time Distribution

Response time distribution shows the distribution of the ping response packets,according to response time. The two graphs analyze in detail the response timeswhich the IP node is exhibiting. Response time distribution (interactive) takes intoaccount all the responses to small packets. Response time distribution (FileTransfer) takes into account all the responses to large packets.

The distribution graphs give a detailed analysis of response times and their evolutionover time. The size of packets which transit through the network is determined bythe type of application. Thus “Interactive” applications such as telnet ortransactional applications with short requests and responses, tend to generate shortpackets. “File Transfer” type applications which transfer large quantities of data tendto generate large packets.

These two graphs show you how response time is affected by packet size. This showsyou how the network is responding to your specific utilization needs. Large packetresponse time is generally greater than for small packets. One factor is simply thefact that large packets take longer to transmit. The different packet sizes used in thereport show up the different problems experienced by different applications. Agraph showing only small packet response times would possibly hide the problemsexperienced by larger packets, such as buffer pool management or fragmentation inthe routers.

The Reports

22 IP Node Availability Report

Note:The real time report does not have Response time distribution graphs.

The ping packet sizes used are displayed at the top of the respective graphs as well asthe timeout value. These parameters are set with properties of the instance ofIpNode which you used to model the monitored device. The default values havebeen chosen to suit most configurations but you can adjust them to suit yourenvironment.


Remarks form

We welcome any comments you may have on our product and its documentation. Your remarkswill be examined thoroughly and taken into account for future versions of InfoVista.

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InfoVista SA6 rue de la Terre de Feu91 952 Courtaboeuf cedexFrance

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Thank you for your cooperation.

VistaView for Network Latency December 2000

infovista network latency

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