network troubleshooting and field server

8/8/2019 Network Troubleshooting and Field Server

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Network TroubleshootingNetwork Troubleshooting

Presented by:Presented by:

Gordon MacLachlan (Mac)Gordon MacLachlan (Mac)



Presentation HighlightsPresentation Highlights

Troubleshooting tools that workTroubleshooting tools that work

Common wiring problemsCommon wiring problems

Common networking problemsCommon networking problems

Common communication problemsCommon communication problems Common configuration problemsCommon configuration problems

Common data transfer problemsCommon data transfer problems



Typical network commissioningTypical network commissioning

process:process:1.1. Install the equipmentInstall the equipment

2.2. Wire up the networksWire up the networks

3.3. Configure equipmentConfigure equipment

4.4. Establish communicationEstablish communicationlinks between equipmentlinks between equipment

5.5. Check communicationCheck communicationqualityquality

6.6.

Check data transferCheck data transfer



WhatWhat’’s in your toolbox?s in your toolbox?Troubleshooting tools that work:Troubleshooting tools that work:

Essentials:Essentials:

MultimeterMultimeter

RSRS--232 Tester (Breakout box)232 Tester (Breakout box)

Cell phoneCell phone

InternetInternet

Ethernet Crossover cableEthernet Crossover cable

Serial capture utilitySerial capture utility

Ethernet capture utilityEthernet capture utility

Also useful:Also useful:

HubHub

Oscilloscope (for noisy networks).Oscilloscope (for noisy networks).



Common Wiring ProblemsCommon Wiring Problems

RSRS--232232::

Receive/Transmit PolarityReceive/Transmit Polarity

Ground potential differences.Ground potential differences.

DTR/DSR and CTS/RTS issuesDTR/DSR and CTS/RTS issues

Cable LengthCable Length



Common Wiring ProblemsCommon Wiring ProblemsRSRS--232 Receive/Transmit Polarity:232 Receive/Transmit Polarity:

Best way to check Polarity is to use a RSBest way to check Polarity is to use a RS--232 Test box232 Test box(FieldServer supplies a mini(FieldServer supplies a mini--tester)tester)

•• With no communications, RD must be on solid.With no communications, RD must be on solid.

•• If the same light is on solid (RD or TD) when either side of If the same light is on solid (RD or TD) when either side of the test box is connected on its own, then the polarity isthe test box is connected on its own, then the polarity iswrong.wrong.

A Voltmeter can be used to check a devices pins when it isA Voltmeter can be used to check a devices pins when it isdisconnected. Receive will have a zero voltage, Transmit willdisconnected. Receive will have a zero voltage, Transmit will

have a negative voltage of have a negative voltage of --5to5to--12V (wrt ground).12V (wrt ground). Remember: Rx goes to Tx, and vice versaRemember: Rx goes to Tx, and vice versa



Common Wiring ProblemsCommon Wiring ProblemsRSRS--232 ground potential differences:232 ground potential differences:

Since signal ground is connected through theSince signal ground is connected through the

GND pin, any serious potential differencesGND pin, any serious potential differencesbetween the two devices can causebetween the two devices can cause

communications problems or even interferecommunications problems or even interfere

with the operation of the device.with the operation of the device. In the rare cases where this is genuinely aIn the rare cases where this is genuinely a

problem, use an optical isolator to separateproblem, use an optical isolator to separate

the wiring. Optical Isolatorsthe wiring. Optical Isolatorsare off are off --thethe--shelf itemsshelf items

that can be purchased online.that can be purchased online.



Common Wiring ProblemsCommon Wiring ProblemsRSRS--232 DTR/DSR and CTS/RTS issues:232 DTR/DSR and CTS/RTS issues:

NB:NB: FieldServer does notFieldServer does not

require DTR/DSR or CTS/RTSrequire DTR/DSR or CTS/RTShandshaking lines. FieldServerhandshaking lines. FieldServer

needs Tx/Rx/GND only.needs Tx/Rx/GND only.

The device connecting to theThe device connecting to theFieldServer may needFieldServer may need

handshaking. Solve this byhandshaking. Solve this by

bridging CTS to RTS (and/orbridging CTS to RTS (and/orDTR to DSR) in the connectorDTR to DSR) in the connector

connected to the device.connected to the device.



Common Wiring ProblemsCommon Wiring ProblemsRSRS--232 Cable Length:232 Cable Length:

Maximum recommended cable Maximum recommended cable

length for RSlength for RS--232 is 50ft. This is232 is 50ft. This isconservative if you are usingconservative if you are using

18 AWG.18 AWG.

Symptoms for cable length problemsSymptoms for cable length problemsare that communications is noisy. Itare that communications is noisy. It

is unlikely that a cable that is ais unlikely that a cable that is a

bit too long will preventbit too long will preventcommunications completely.communications completely.

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RSRS--485485::

+/+/-- PolarityPolarity

Line Biasing.Line Biasing.

44--wire vs. 2wire vs. 2--wirewire

Cable LengthCable Length



Common Wiring ProblemsCommon Wiring ProblemsRSRS--485 Polarity:485 Polarity:

Unlike RSUnlike RS--232 where Tx and Rx cross232 where Tx and Rx cross

over, you connect + to +, andover, you connect + to +, and –– toto –– ininRSRS--485485

Some devices use A and B instead of +Some devices use A and B instead of +

andand –– labels. Here A is the same aslabels. Here A is the same as --, and, andB is the same as +B is the same as +



Common Wiring ProblemsCommon Wiring ProblemsRSRS--485 Line Biasing:485 Line Biasing:

Literature on RSLiterature on RS--485 guidelines485 guidelinesadvises that 120 ohm terminatingadvises that 120 ohm terminatingresistors are applied at the endresistors are applied at the end

nodes of an RSnodes of an RS--485 segment. This485 segment. Thisis ais a guidelineguideline, and not a rule., and not a rule.

Networks <100 feet usually donNetworks <100 feet usually don’ ’ t needt need

terminating resistors.terminating resistors. Line Biasing is achieved with the 120 ohmLine Biasing is achieved with the 120 ohm

resistors plus 10kOhm resistors betweenresistors plus 10kOhm resistors between

the signal and ground/5V.the signal and ground/5V.

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RSRS--485 4485 4--wire vs. 2wire vs. 2--wire:wire: FieldServer supports 2FieldServer supports 2--wire RSwire RS--485 communications, which485 communications, which

is half duplex RSis half duplex RS--485 and is the more common format found485 and is the more common format foundin industry.in industry.

44--wire RSwire RS--485 (or RS485 (or RS--422) is full duplex RS422) is full duplex RS--485. Some 4485. Some 4--wire RSwire RS--485 will allow you to connect to a 2485 will allow you to connect to a 2--wire RSwire RS--485485setup by bridging the Rx and Tx lines to make 2 wires out of setup by bridging the Rx and Tx lines to make 2 wires out of 4. These devices tolerate the visibility of Tx signals on their4. These devices tolerate the visibility of Tx signals on their

Rx lines. However, other 4Rx lines. However, other 4--wire devices do not tolerate this.wire devices do not tolerate this. It is always possible to connect 2It is always possible to connect 2--wire to 4wire to 4--wire RSwire RS--485 by485 by

using a 2using a 2--4 wire RS4 wire RS--485 converter which is commercially485 converter which is commerciallyavailable.available.



Common Wiring ProblemsCommon Wiring ProblemsRSRS--485 Cable Length:485 Cable Length:

Recommended maximum lengthRecommended maximum lengthis 4000 ft, with no more than 32is 4000 ft, with no more than 32nodes connected. This estimate isnodes connected. This estimate isfor the most part optimistic.for the most part optimistic.

Many factors can reduce theMany factors can reduce the

maximum permissible length onmaximum permissible length onan RSan RS--485 network, including485 network, includingwire gauge, installationwire gauge, installationenvironment, and vendorenvironment, and vendorequipment characteristics.equipment characteristics.

When running cable lengths closeWhen running cable lengths closeto the recommended maximumto the recommended maximum

parameters, keep an RSparameters, keep an RS--485485repeater handy just in caserepeater handy just in case……




EthernetEthernet::

Cable qualityCable quality

Direct vs. Crossover.Direct vs. Crossover.



Common Wiring ProblemsCommon Wiring ProblemsEthernet Cable Quality:Ethernet Cable Quality:

Most common Ethernet cable inMost common Ethernet cable in

use today is CATuse today is CAT--5 UDP cable.5 UDP cable. Using CATUsing CAT--5 UDP has many5 UDP has many

advantages, but the one common problemadvantages, but the one common problem

experienced is assembly quality. Factoryexperienced is assembly quality. Factorymade cables are usually premade cables are usually pre--tested andtested and

tend to work, but cable crimped on sitetend to work, but cable crimped on site

often leads to problems that are notoften leads to problems that are notimmediately obvious.immediately obvious.

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Common Wiring ProblemsCommon Wiring ProblemsEthernet Direct Cable vs. Crossover cable:Ethernet Direct Cable vs. Crossover cable:

Use Direct Cable whenUse Direct Cable whenconnecting to a hubconnecting to a hub

Use Crossover cable whenUse Crossover cable whenconnecting directly betweenconnecting directly betweentwo devicestwo devices

Cables can be differentiated byCables can be differentiated bylooking at the connectors onlooking at the connectors oneach end of the cable. Holdeach end of the cable. Holdthem together, facing thethem together, facing the

same way (e.g.: both clipssame way (e.g.: both clipsfacing away from you). If thefacing away from you). If thewire colors follow the samewire colors follow the samepattern on both connectors,pattern on both connectors,

then it is a direct cable.then it is a direct cable.



Common Networking ProblemsCommon Networking ProblemsRSRS--232 & RS232 & RS--485:485:

Baud RateBaud Rate

Master vs. Slave.Master vs. Slave. HandshakingHandshaking

AddressingAddressing Poll timingPoll timing



Common Networking ProblemsCommon Networking ProblemsRSRS--232 & RS232 & RS--485:485: Baud RateBaud Rate

•• DonDon’ ’ t just check Baud Rate. Check Parity, Data Bits andt just check Baud Rate. Check Parity, Data Bits and

Stop bits too.Stop bits too.•• All devices on the same RSAll devices on the same RS--485 network need to485 network need tocommunicate at the same baud rate. Make sure this iscommunicate at the same baud rate. Make sure this ispossible.possible.

Master vs. Slave.Master vs. Slave.•• For Master/Slave networks (e.g.: Modbus, Metasys), oneFor Master/Slave networks (e.g.: Modbus, Metasys), one

Master usually controls all communicationsMaster usually controls all communications

•• Make sure you know who is master, and that you are notMake sure you know who is master, and that you are not

attempting Masterattempting Master--Master or SlaveMaster or Slave--Slave communications.Slave communications.




HandshakingHandshaking

••

SomeSomedevices/protocolsdevices/protocolsdemand startupdemand startuphandshaking like thehandshaking like thepassing of passwordspassing of passwordsand deviceand deviceinformation.information.

•• Check literature forCheck literature forrequirements andrequirements anddefault passwords.default passwords.




AddressingAddressing

•• Make sure the correct deviceMake sure the correct deviceaddress is being used. This is notaddress is being used. This is notalways obvious (e.g.: BACnetalways obvious (e.g.: BACnetMSTP)MSTP)

•• Server devices almost always needServer devices almost always needaddresses, but sometimes you needaddresses, but sometimes you needto configure client addresses tooto configure client addresses too(e.g.: DNP 3.0)(e.g.: DNP 3.0)

•• Some protocols may demandSome protocols may demandaddress paths or addresses ataddress paths or addresses atmultiple levels (e.g.: Modbus +,multiple levels (e.g.: Modbus +,

McQuay)McQuay)




Poll timingPoll timing•• Timing can be a very complicated issue and isTiming can be a very complicated issue and is

not uncommon as a cause for poornot uncommon as a cause for poorcommunicationscommunications

•• There are many timing factors to be aware of There are many timing factors to be aware of in a communications session (e.g.: Timeouts,in a communications session (e.g.: Timeouts,

poll delay, retry intervals, scan intervals,poll delay, retry intervals, scan intervals,probation delays, Inter character timing, etc)probation delays, Inter character timing, etc)

•• Enote067 is very helpful inEnote067 is very helpful in

helping understand howhelping understand howthese parameters interactthese parameters interact

•• Symptoms of a timingSymptoms of a timingproblem are usuallyproblem are usually

related to the presencerelated to the presenceof partial communicationsof partial communications



Common Networking ProblemsCommon Networking Problems

EthernetEthernet::

Subnets and gatewaysSubnets and gateways

Firewalls.Firewalls. PortsPorts




Common Networking ProblemsCommon Networking ProblemsEthernet:Ethernet:

Subnets and gatewaysSubnets and gateways

•• A common problem in Ethernet is that IPA common problem in Ethernet is that IPaddresses get set up correctly withoutaddresses get set up correctly withoutthe subnets and/or gateway addressesthe subnets and/or gateway addressesbeing set up correctlybeing set up correctly

•• Protocols differ in theirProtocols differ in theirIP/Subnet/gatewayIP/Subnet/gatewayrequirements, so berequirements, so beaware of theaware of therequirements for therequirements for theseparate protocols.separate protocols.




Firewalls.Firewalls.

••

The thing about firewallsThe thing about firewallsare that they are invisibleare that they are invisibleto the installer, but canto the installer, but canstop communications in astop communications in a

heartbeatheartbeat•• Work with the SystemsWork with the Systems

Administrator to ensureAdministrator to ensurethat all necessary holes arethat all necessary holes aremade in the firewalls formade in the firewalls forthe application, and thatthe application, and thatthe network design isthe network design is

compatible with thecompatible with thecompanycompany’ ’ s security policies.s security policies.




PortsPorts•• Be aware that Ethernet protocols have ports too.Be aware that Ethernet protocols have ports too.

However, they are logical, not physical. Be aware of theHowever, they are logical, not physical. Be aware of the

port required for a given protocol, you may need toport required for a given protocol, you may need toopen a hole in a firewall for that port.open a hole in a firewall for that port.


••

Not all Ethernet protocols use IP addresses forNot all Ethernet protocols use IP addresses foraddressing. Look out for the need to use multiple oraddressing. Look out for the need to use multiple orindirect addresses (e.g.: BACnet IP,indirect addresses (e.g.: BACnet IP,Modbus/TCP),Modbus/TCP),or even MAC addressesor even MAC addresses

(e.g.: BACnet Ethernet)(e.g.: BACnet Ethernet)




System AdministrationSystem Administration•• When adding devices to anWhen adding devices to an

existing network, be awareexisting network, be awarethat this cannot be donethat this cannot be donewithout knowledge of whatwithout knowledge of whatexists on the network.exists on the network.

•• When doing a new network,When doing a new network,leave a good document trailleave a good document trailof how the network hasof how the network hasbeen configured.been configured.

•• Be aware of the issues thatBe aware of the issues thatcome with mixing DHCPcome with mixing DHCPand fixed addressingand fixed addressing

•• Ignore the above, and youIgnore the above, and youcan expect a return trip tocan expect a return trip tosite.site.



Common CommunicationCommon Communication

ProblemsProblems Transmitting polls, but getTransmitting polls, but get

no response (Timeouts)no response (Timeouts) Received Data is rejectedReceived Data is rejected

Communication stopsCommunication stops Communication exists with errors.Communication exists with errors.

http://images.google.com/imgres?imgurl=http://www.positive-way.com/business/_borders/commun2.gif&imgrefurl=http://www.positive-way.com/business/communic.htm&h=193&w=193&sz=4&tbnid=W9zPaHxUhpAJ:&tbnh=98&tbnw=98&hl=en&start=1&prev=/images%3Fq%3Dcommunication%2Bproblems%26svnum%3D10%26hl%3Den%26lr%3D%26rls%3DDVXB,DVXB:2004-52,DVXB:en



Checking communicationsChecking communications

quality using Ruinet (RUI):quality using Ruinet (RUI):1.1. Check Connection Overview forCheck Connection Overview for

communication errorscommunication errors2.2. Check System Error screen forCheck System Error screen for

System/Config errors (Messages are OK)System/Config errors (Messages are OK)

3.3. Check Node & Map Descriptor overviewsCheck Node & Map Descriptor overviewsfor missing Nodes/Map descriptorsfor missing Nodes/Map descriptors

4.4. Check Data Array overview for dataCheck Data Array overview for dataupdateupdate




ProblemsProblems Transmitting polls, but get no responseTransmitting polls, but get no response

(Timeouts)(Timeouts)•• This is the most common communication levelThis is the most common communication level

symptom.symptom.

•• Cause is usually related to Installation or NetworkCause is usually related to Installation or Networksetup errors, so review the previous slides.setup errors, so review the previous slides.

•• Cause can manifest itself at any levelCause can manifest itself at any level

though, so finding the cause canthough, so finding the cause cantake time. Make use of all visualtake time. Make use of all visual

symptoms (TX/Rx LEDsymptoms (TX/Rx LED’ ’ s, wiring, etc)s, wiring, etc)

to reduce the range of possibleto reduce the range of possible

causes.causes.




ProblemsProblems Communication stopsCommunication stops

•• This is a very unusualThis is a very unusualsymptom, but hard to nailsymptom, but hard to nail

down when it occursdown when it occurs

(Mainly due to the fact that(Mainly due to the fact that

the behavior is erratic)the behavior is erratic)

•• Stopped communication isStopped communication is

usually caused byusually caused by

something event driven.something event driven.Work towards identifyingWork towards identifying

the event in order tothe event in order to

expedite finding the cause.expedite finding the cause.




ProblemsProblems Communication exists withCommunication exists with

errors.errors.

•• Partial communications could bePartial communications could berelated to many devices on therelated to many devices on thenetwork, and only some notnetwork, and only some notcommunicating, or maybe evencommunicating, or maybe even

some addresses on a device thatsome addresses on a device thatare bad. Use the Hierarchical tiersare bad. Use the Hierarchical tiersin Ruinet to resolve this.in Ruinet to resolve this.

•• Another cause for partialAnother cause for partial

communications is poor qualitycommunications is poor qualityinstallation. If the same addressinstallation. If the same addresspoll succeeds only some of thepoll succeeds only some of thetime, this is most likely related totime, this is most likely related toinstallation or timing.installation or timing.



Common ConfigurationCommon Configuration

ProblemsProblems Client vs. Server mapping (wrongClient vs. Server mapping (wrong

function)function) Responsible Map DescriptorResponsible Map Descriptor

managementmanagement Missing titlesMissing titles

Client/Server node matchingClient/Server node matching

Duplicate names and/or addressesDuplicate names and/or addresses

Address range gapsAddress range gaps




ProblemsProblems Client vs. Server mapping (wrongClient vs. Server mapping (wrong

function)function)

•• Restated, this problem occurs mostRestated, this problem occurs mostcommonly when no activecommonly when no activecommunication devices are configured,communication devices are configured,or two active communication devices areor two active communication devices are

configured when only one is allowed.configured when only one is allowed. Responsible Map DescriptorResponsible Map Descriptor

managementmanagement•• Active FieldServer mappings monitor theActive FieldServer mappings monitor the

status of communication to determinestatus of communication to determinethe health of the corresponding datathe health of the corresponding dataarray value/sarray value/s

•• Consequently it is not possible to have 2Consequently it is not possible to have 2

active mappings pointing to the sameactive mappings pointing to the samedata array offset/s.data array offset/s.




ProblemsProblems Missing titlesMissing titles

•• Configuration layout can be quite flexible, but one mustConfiguration layout can be quite flexible, but one must

take care with the titles (Title, Nodes, Connections,take care with the titles (Title, Nodes, Connections,Moves, Data Arrays, etc)Moves, Data Arrays, etc)

•• The FieldServer searches for the titles to know where toThe FieldServer searches for the titles to know where tofind the corresponding keywords and parameters, so thefind the corresponding keywords and parameters, so the

titles must be there.titles must be there. Client/Server node matchingClient/Server node matching

•• Node ID specified in the Node_ID field is almost alwaysNode ID specified in the Node_ID field is almost alwaysthe device address of the server or the passivethe device address of the server or the passive

communications device. This MUST be right forcommunications device. This MUST be right forcommunications to occur.communications to occur.

•• “ “NodelessNodeless” ” protocols do exist. By nature, these are pointprotocols do exist. By nature, these are pointto point protocols where only one device is allowed to beto point protocols where only one device is allowed to be

connected to any port.connected to any port.




ProblemsProblems Duplicate names and/ or addressesDuplicate names and/ or addresses

•• Duplicates can be hard to find and are sure toDuplicates can be hard to find and are sure to

cause problems.cause problems.•• One symptom to look for is individualOne symptom to look for is individual

addresses not working when everything else isaddresses not working when everything else isworking.working.



Common Configuration ProblemsCommon Configuration Problems

Address range gapsAddress range gaps•• Be careful polling a device thatBe careful polling a device thatdocuments gaps in the addressingdocuments gaps in the addressingsystem. Donsystem. Don’ ’ t assume the addressest assume the addresses

are still there.are still there.•• Polling a range of addresses containing aPolling a range of addresses containing agap within the range will likely result ingap within the range will likely result innothing being returned.nothing being returned.

•• Make a habit of providingMake a habit of providing “ “zero datazero data” ” forforunused addresses so when polled by aunused addresses so when polled by ablock that includes unused addresses,block that includes unused addresses,FieldServer still responds.FieldServer still responds.

•• When serving data on FieldServer, it willWhen serving data on FieldServer, it willnot combine two map descriptors tonot combine two map descriptors tosatisfy an incoming poll for data, so onesatisfy an incoming poll for data, so onemap descriptor must exist that covers themap descriptor must exist that covers the

full range of the polled data for thefull range of the polled data for theFieldServer to successfully respond.FieldServer to successfully respond.

C f



Common Data TransferCommon Data Transfer

ProblemsProblems Data Types (Typecasting)Data Types (Typecasting)

Complex vs. Simple DataComplex vs. Simple DataStructuresStructures

Bit PackingBit Packing Supported functionalitySupported functionality

in protocolsin protocols

Imperial vs. MetricImperial vs. Metric



Common Data Transfer ProblemsCommon Data Transfer Problems

Data Types (Typecasting)Data Types (Typecasting)•• The FieldServer automatically typecasts dataThe FieldServer automatically typecasts dataunless special functions (like Packed Bit andunless special functions (like Packed Bit andspecial moves) are used.special moves) are used.

•• Be careful therefore, not to put float values in anBe careful therefore, not to put float values in aninteger data arrays for example, unless of courseinteger data arrays for example, unless of courseyou want to truncate at the decimal point.you want to truncate at the decimal point.

Complex vs. Simple Data StructuresComplex vs. Simple Data Structures•• Protocols like LonWorks use complex dataProtocols like LonWorks use complex data

structures to transfer multiple values in one datastructures to transfer multiple values in one dataaddress.address.

•• Plan carefully when mapping complex dataPlan carefully when mapping complex datastructures to simple data structures. You willstructures to simple data structures. You willneed to make sure complex types are keptneed to make sure complex types are kepttogether in the right arrays, and that the correcttogether in the right arrays, and that the correct

number of data arraynumber of data arraypositions are allowed for, etc.positions are allowed for, etc.



Common Data Transfer ProblemsCommon Data Transfer Problems Bit PackingBit Packing

•• Be aware that some devices send 16 status bits in anBe aware that some devices send 16 status bits in aninteger to save address space and promote efficiency.integer to save address space and promote efficiency.

•• Use Packed_Bit Data Arrays to provide binary status outUse Packed_Bit Data Arrays to provide binary status out

of a Packed_Bit integer.of a Packed_Bit integer. Supported functionality in protocolsSupported functionality in protocols

•• ExpectExpect “ “present valuepresent value” ” data to be transferred betweendata to be transferred betweendifferent protocols at all times. However, auxiliarydifferent protocols at all times. However, auxiliary

properties (Like units, data quality, etc) is not alwaysproperties (Like units, data quality, etc) is not alwayssupported by thesupported by the “ “otherother” ” protocol.protocol.

•• E.g.: Transferring BACnet data to Modbus will get youE.g.: Transferring BACnet data to Modbus will get youthe values you need, but the Units property will be lostthe values you need, but the Units property will be lostsince Modbus does not support this.since Modbus does not support this.

Imperial vs. MetricImperial vs. Metric•• Foreign made devices often provide Metric values.Foreign made devices often provide Metric values.

•• Use Scaling in the FieldServer to do MetricUse Scaling in the FieldServer to do Metric-->Imperial>Imperialconversionsconversions



ResourcesResources FieldServer WebsiteFieldServer Website

((www.FieldServer.comwww.FieldServer.com))

•• FieldServer Configuration ManualFieldServer Configuration Manual

•• FieldServer Troubleshooting ManualFieldServer Troubleshooting Manual

•• Troubleshooting Application notes (ENotes)Troubleshooting Application notes (ENotes)

http://www.fieldserver.com/





Questions?Questions?

Email Mac at:Email Mac at:

[email protected]@comcast.net



THANK YOU!THANK YOU!

……..for taking the time to attend..for taking the time to attend

this presentation.this presentation.

network troubleshooting and field server

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