QoS Evaluation Model for a Campus-Wide Network:an alternative approach

Juan Antonio Martínez (Juan Antonio Martínez (Juanan.Martinez@uab.esJuanan.Martinez@uab.es))

Comunicacions - Servei d’InformàticaComunicacions - Servei d’Informàtica

Universitat Autònoma de BarcelonaUniversitat Autònoma de Barcelona

Index

ObjectivesObjectives Classical approach to QoSClassical approach to QoS Evaluating network availability: a generic modelEvaluating network availability: a generic model Extending the model to the servicesExtending the model to the services Practical resultsPractical results Comparison to other existing products and future Comparison to other existing products and future

workwork ConclusionsConclusions

Objectives

Determine if our network reaches the ‘5 9s’ Determine if our network reaches the ‘5 9s’ objective (99.999% of availability)objective (99.999% of availability)

Obtain a generic model to evaluate the quality Obtain a generic model to evaluate the quality of the network regardingof the network regarding InfrastructureInfrastructure ServicesServices

The model must The model must Be simpleBe simple Adapt easily to network topology changesAdapt easily to network topology changes

Obtaining the model

The classical approach

Quality is evaluated as a combination of:Quality is evaluated as a combination of: DelayDelay JitterJitter Packet lossPacket loss

This approach is useful for WAN links and environmentsThis approach is useful for WAN links and environments Easy to measure in both router endpointsEasy to measure in both router endpoints

In our opinion, it is not suitable for LAN environmentsIn our opinion, it is not suitable for LAN environments Parameters are difficult to determine (distributed Parameters are difficult to determine (distributed

environment)environment) Gathered data is not significant (burst traffic)Gathered data is not significant (burst traffic)

Problems of this model

Quality is not assigned a numeric valueQuality is not assigned a numeric value In a LAN environmentIn a LAN environment

Network probes must be distributed through the Network probes must be distributed through the networknetwork

In switched environments, each segment In switched environments, each segment provides a different valueprovides a different value

Expensive to implementExpensive to implement Fluctuant values due to the traffic natureFluctuant values due to the traffic nature

In fact, there is not a model. It is just an evaluation In fact, there is not a model. It is just an evaluation of the aforesaid parametersof the aforesaid parameters

Our model:the basis

Whichever the system is, it must: Whichever the system is, it must: Be of low cost.Be of low cost. Provide QoS as a numerical value.Provide QoS as a numerical value. Be flexible enough to adapt itself to network Be flexible enough to adapt itself to network

topology changes. topology changes. Our idea is to get data from :Our idea is to get data from :

Simple tools like ‘ping’Simple tools like ‘ping’ SNMP queriesSNMP queries

We discard complex solutions (modified TCP stacks, We discard complex solutions (modified TCP stacks, proprietary PING...)proprietary PING...)

Conceptual development of the model

Assume that all network devices are known and Assume that all network devices are known and with SNMP management facilities. with SNMP management facilities.

Assume that the number of users affected by any Assume that the number of users affected by any network device failure can be determined.network device failure can be determined.

The idea beyond the process isThe idea beyond the process is Choose the critical network devices Choose the critical network devices Weight them accordinglyWeight them accordingly Determine the instant availabilityDetermine the instant availability Compute the mean valueCompute the mean value

Choosing the devices and the weights for the model

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Mathematical analysis (I)

LetLet Kd be the relative availability coefficient Kd be the relative availability coefficient di be a binary value that tells whether a di be a binary value that tells whether a

segment is accessible or notsegment is accessible or not

For the mean value this impliesFor the mean value this implies

Mathematical analysis (and II)

If we sample at constant intervalsIf we sample at constant intervals

For efficient computing, this meansFor efficient computing, this means

In this way, we can evaluate the availability with In this way, we can evaluate the availability with the number of samples, the previous mean value the number of samples, the previous mean value and the last sample. and the last sample.

Extending the model to the services

Our first goal is to determine whether the Our first goal is to determine whether the service is working or not (ok/not ok)service is working or not (ok/not ok)

The explained network model is suitable for the The explained network model is suitable for the services with few changes :services with few changes : Omission of the criticity values (Kc=1)Omission of the criticity values (Kc=1) A tool to determine instant availability is A tool to determine instant availability is

needed (ping is no longer valid)needed (ping is no longer valid)

Details regarding practical implementation

Network availability

Availability is computed based on ICMP tests (Availability is computed based on ICMP tests (pingping)) Second-level granularitySecond-level granularity To compute the coefficientsTo compute the coefficients

Kc1 : from the network topology.Kc1 : from the network topology. Kc2 : from our experience. Kc2 : from our experience.

The global coefficient is computed as the arithmetic The global coefficient is computed as the arithmetic mean valuemean value

A config file stores the network devices that will be A config file stores the network devices that will be testedtested

config file example

[NETWORK]#ip_name ip_address availability coef. gw 158.109.0.3 0.203125CB 158.109.0.26 0.213541667si0swfo1+si0swfo2 158.109.2.233 0.052340183c7p1sw1 158.109.8.236 0.051626712anccswit 158.109.8.235 0.056078767m0swit 158.109.20.214 0.045519406cvcsw 158.109.4.200 0.034218037cibibfo 158.109.29.208 0.036843607hottwp1+hottwp3 158.109.31.200 0.0355879dretswit 158.109.25.201 0.050313927ecllefo 158.109.25.220 0.048658676bhum1sw1 158.109.184.203 0.042323059ftisw 158.109.21.202 0.03678653recswit 158.109.27.222 0.052368721vetswit 158.109.30.201 0.040667808

Service availability

The model is essentially the same, but now for each The model is essentially the same, but now for each machine we analyse its critical services machine we analyse its critical services

The system canThe system can Evaluate proper function of a service at a given Evaluate proper function of a service at a given

time time Compute the availability over timeCompute the availability over time

A proprietary MIB is used to determine the critical A proprietary MIB is used to determine the critical parameters of each service (SNMP queries are parameters of each service (SNMP queries are supported) supported)

Monitoring requirements

A set of ‘C’ programs (one for each service)A set of ‘C’ programs (one for each service) A global configuration file:A global configuration file:

[SERVICES]#host name services to be tested cc.uab.es smtp pop imapnews.uab.es nntpftp.uab.es ftp...

Optionally, for the services : A proprietary MIB with the data we want to

monitor (not mandatory) A modified version of the snmpd daemon

Practical Results in our Campus Network

Environment

Development :Development : PC Pentium II 300 + Linux RedHat 6.0PC Pentium II 300 + Linux RedHat 6.0 gcc 2.91.66gcc 2.91.66

Production: Production: Ultra Enterprise 450 + Solaris 2.6 (gcc 2.95.2)Ultra Enterprise 450 + Solaris 2.6 (gcc 2.95.2) PC Pentium II 400 + Linux RedHat 6.0 (gcc PC Pentium II 400 + Linux RedHat 6.0 (gcc

2.91.66)2.91.66) Our network availability has achieved monthly values Our network availability has achieved monthly values

between 0.99843 and 1.0between 0.99843 and 1.0 For the services, we use it both for availability values For the services, we use it both for availability values

and to test that they are working properly. and to test that they are working properly.

Overview of the system

A set of routines that verify that the services are A set of routines that verify that the services are working properly:working properly: bootp,dhcp,dns,ftp,http,smtp,pop,imap,radius,nntpbootp,dhcp,dns,ftp,http,smtp,pop,imap,radius,nntp

A C program that implements the mathematical modelA C program that implements the mathematical model Configuration file, which includes Configuration file, which includes

Coefficients for the modelCoefficients for the model Servers and services to be monitored. Servers and services to be monitored.

Optionally, a modified version of the Optionally, a modified version of the snmpd snmpd daemon if daemon if access to the proprietary MIB is desired. access to the proprietary MIB is desired.

Measured availability data

Network Availability Data

98,000%

98,500%

99,000%

99,500%

100,000%

Avail.Data 99,916 99,916 99,916 99,932 99,929 99,940 99,844 99,912 98,636 99,993 99,970 99,985

Abr00 Mai00 Jun00 Jul00 Ago00 Set00 Oct00 Nov00 Dec00 Gen01 Feb01 Mar01

‘on line’ service monitoring

Based on the programs that are used to check Based on the programs that are used to check service availabilityservice availability

Useful to network operators to detect Useful to network operators to detect network problemsnetwork problems

Operating modes :Operating modes : Interactive: provides a report with Interactive: provides a report with

configurable debugconfigurable debug Cron-based : generates mail/sms messages Cron-based : generates mail/sms messages

if any problems are detectedif any problems are detected

Interactive execution example*** 14:35:06.308612 blues.uab.es:smtp ...220 blues Sendmail 5.65v4.0 (1.1.19.2/17Dec99-1023AM) Tue, 7 Nov 2000 13:44:20 +QUIT221 blues closing connection*** 14:35:06.351857 blues.uab.es:smtp 116b,0.0432s,2.6Kb/s OK!*** 14:35:06.360239 blues.uab.es:pop3 ...+OK POP3 blues v7.63 server readyQUIT+OK Sayonara*** 14:35:06.512647 blues.uab.es:pop3 49b,0.152s,0.31Kb/s OK!*** 14:35:06.521040 blues.uab.es:imap ...* OK blues IMAP4rev1 v12.261 server readyA01 LOGOUT* BYE blues IMAP4rev1 server terminating connectionA01 OK LOGOUT completed*** 14:35:06.622567 blues.uab.es:imap 121b,0.102s,1.2Kb/s OK!*** 14:35:06.631185 news.uab.es:nntp ...200 news.cesca.es InterNetNews NNRP server INN 2.3.0 ready (posting ok).QUIT205 .*** 14:35:06.884128 news.uab.es:nntp 81b,0.253s,0.31Kb/s OK!*** 14:35:06.892686 ftp.uab.es:ftp ...220 koala FTP server (Version wu-2.5.0(1) Wed Oct 20 12:02:15 DST 1999) ready.

Comparison to other existing products and future work

Comparison

As a monitoring tool, there are other existing As a monitoring tool, there are other existing products, which are really powerfulproducts, which are really powerful Big BrotherBig Brother NoCoLNoCoL

Regarding the graphic tools, they generate Regarding the graphic tools, they generate no data, but simply display it.no data, but simply display it.

None of these gives a detailed model for the None of these gives a detailed model for the network availability or monthly reportsnetwork availability or monthly reports

Future work

Analysis and integration of multiple metersAnalysis and integration of multiple meters Improvement of the Web interfaceImprovement of the Web interface WAP interface to the monitoring systemWAP interface to the monitoring system

Conclusions

Benefits of the system

Proper working of all servers and services is easy and Proper working of all servers and services is easy and centrally verifiedcentrally verified

Easy adaptation to network changes Easy adaptation to network changes Network devicesNetwork devices New servers or servicesNew servers or services

Monthly reports of both internal and external Monthly reports of both internal and external connectivityconnectivity

Availability reports of the relevant servicesAvailability reports of the relevant services Easy to integrate with graphic tools such as MRTGEasy to integrate with graphic tools such as MRTG

For more information...

This presentation:This presentation: ftp://ftp.uab.es/pub/terena/QoS.pptftp://ftp.uab.es/pub/terena/QoS.ppt

The paper can be found at:The paper can be found at: ftp://ftp.uab.es/pub/terena/QoS.pdfftp://ftp.uab.es/pub/terena/QoS.pdf

Doubts, comments, suggestions...