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Network Testing and
DebuggingTCP/IP CONCEPTS, WIRING, CONFIGURATING NETWORK, PROTOCOLS
S a d e e d A m e e n P Os a d e e d a m e e n @ g m a i l . c o m
Testing and Debugging
Testing activity is carried down to find the
defect in the network and its configurations.
Identify and remove errors from computer
hardware or from network is termed as
debugging
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Possible points of failure
The cable is plugged into the wrong network
Host machine is plugged into the wrong network
Host machine has a bad network card
Machine is offline
The web server may not be running
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Testing the IP configuration
Windows systems offer a command-line tool,
called ipconfig, that lets you find out your
computer's IP configuration
The output of this command gives the IP
configuration for each interface
a computer with two network cards and one
wireless adapter has 3 interfaces each with its
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Testing the IP configuration cont
The Ethernet interface connected to the local area network (network card) is not
active since the cable is disconnected, but the PPP adapter (MTS) is configured.
Machines on a same network must use a same address range (with different
addresses) and a same subnet mask
In the case of a local network, connecting machines that do not have routable
IP addresses, so-called private address ranges must be used
The default gateway refers to, when applicable, the IP address of the machine
offering internet access. DNS servers
The DNS servers must correspond to the organization's DNS servers; most of the
time these are the service provider's DNS servers
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Testing the connection
To test the proper functioning of a network
Ping utility is a highly practical utility provided as a standard feature
with most operating systems.
Ping lets you send a data packet to a network computer and lets
you evaluate the response time
ping -t 192.168.0.3 Ping the IP addresses of the network's computers
ping -t Mickey Ping the computer names
Ping –t www.google.com ping a domain name
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Network Testing
Load Testing
Stress Testing
Negative Testing
Inopportune Testing
Conformance/Compliance Testing
Line Speed Testing
Performance Testing
Robustness/Security Testing
Interoperability [email protected]
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Load Testing
Load testing is the process of putting demand on a system or device
and measuring its response. Load testing is performed to determine a
system's behavior under both normal and anticipated
peak loadconditions
Where a system can support testing to actual volumes we have a
performance testing service to meet your requirements.
Our network testing services provides comprehensive concurrent user
simulation of user and system traffic. This can be conducted while
concurrently generating threats and attacking traffic at high loads.
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Stress Testing
Stress testing is a form of deliberately intense or thorough
testing used to determine the stability of a given nework.
It involves testing beyond normal operational capacity,
often to a breaking point, in order to observe the results
Stress testing is the process of determining the ability of a
network or device to maintain a certain level of
effectiveness under unfavorable conditions.
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Stress Testing
Actions involved may include:
Running several resource-intensive applications in a single computer at
the same time
Attempting to hack into a computer and use it as a zombie to
spreadspam
Flooding a server with useless e-mail messages
Making numerous, concurrent attempts to access a single Web site
Attempting to infect a system with viruses, Trojans, spyware or
othermalware
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Negative Testing
Process to verify that the device under test responds
correctly to error conditions or unacceptable input
conditions.
Negative testing can be challenging because the
number of incorrect conditions is unlimited.
Example of a negative test would be using a security
protocol for authentication with an incorrect parameter
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Inopportune Testing
Process to verify that the device under test is able to
react properly when an unexpected event occurs
The event is syntactically correct, but occurs when not
expected
Inopportune testing is a specific instance of negative
protocol conformance testing.
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Conformance/Compliance Testing
Testing both the capabilities and behavior of an implementation, and
checking what is observed against the conformance requirements in the
relevant International Standards.(ISO/IEC 9646-1:1994(E))
testing to see if the device under test operates according to that
requirement
This is done by creating a series of single function tests for each
requirement, resulting in thousands of tests
An example of a conformance test is to check if the “ping” command
operates correctly.
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Line Speed Testing
Process of verifying that a device can operate at its rated
line speed, when the bandwidth is 100% utilized or saturated.
process of subjecting the device under test to out of
boundary conditions
For example, if the device is rated as operating at 5 Giga
bytes per second, then the device should be able to handle
incoming traffic utilizing all the available bandwidth
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Performance Testing
Process of verifying that the performance of the
device under test meets an acceptable level
Performance testing is a superset of line speed
testing in which performance applies to many
aspects of a network device or application,
and not just line speed.
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Robustness/Security Testing
Process of subjecting a device under test to particular input streams
The input streams may be one of three types:
Random input streams
Valid input streams
Invalid input streams
Security testing is more broadly defined to include monitoring /
surveillance and the detection of specific exploits like IP spoofing or
phishing etc
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Interoperability Testing
Process of testing devices from multiple manufacturers by interacting
in such a manner as to exercise the network protocol under test
Interoperability testing is very useful in the early stages of a new
product
As products mature, interoperability testing becomes less valuable as
it does not uncover enough new bugs to warrant the cost of setting
up, configuring and managing network equipment from various
manufacturers.
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Penetration testing
Evaluating the security of a network by hacking.
Basically, it is an analysis of system for any potential
vulnerabilities that may result from any of the following:
Poor or improper system configuration
Known and / or unknown hardware or software
flaws
Operational weaknesses in process
Technical countermeasures
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Penetration testing cont
Importance of Penetration Testing:
It prevents financial loss through from hackers or extortionists or
disgruntled employees
It prevents financial loss through unreliable business systems and
processes
From an operational perspective, penetration testing helps shape
information security strategy.
It protects your brand by avoiding loss of consumer confidence
and business reputation.
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Basic Network Troubleshooting Tools
Ping
The most commonly used network tool is the ping utility
This utility is used to provide a basic connectivity test between the
requesting host and a destination host.
This is done by using the Internet Control Message Protocol (ICMP)
which has the ability to send an echo packet to a destination host
and a mechanism to listen for a response from this host
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Tracert/traceroute
once the ping utility has been used to determine basic
connectivity, the tracert/traceroute utility can used to determine
more specific information about the path to the destination host
It includes the route the packet takes and the response time of
these intermediate hosts
Tracert for Windows machines and traceroute for Linux/unix
based machines
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Ipconfig/ifconfig
The utilities that can be used to find out this IP configuration
information include the ipconfig utility on Windows machines and
the ifconfig utility on Linux/unix based machines.
One of the most important things that must be completed when
troubleshooting a networking issue is to find out the specific IP
configuration of the variously affected hosts
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Nslookup
Some of the most common networking issues revolve around issues with
Dynamic Name System (DNS) address resolution issues.
The nslookup utility can be used to lookup the specific IP address(es)
associated with a domain name. If this utility is unable to resolve this
information, there is a DNS issue
Along with simple lookup, the nslookup utility is able to query specific
DNS servers to determine an issue with the default DNS servers
configured on a host
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Netstat
the current state of the active network
connections on a host
It is also possible to use the netstat utility to
determine which services on a host that is
associated with specific active ports
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PuTTY/Tera Term
When connecting to a variety of different types of
equipment, a telnet, SSH or serial client is required; when
this is required both the puTTY and Tera Term programs are
able to provide these functionalities.
The selection of one over the other is strictly a personal
preference.
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Subnet and IP Calculator
These can be used to unsure a correct IP address selection and with
this a correct IP address configuration
While this type of tool is used by senior level network engineers, much of
the information obtained from the tool becomes simpler to calculate
the longer and more experience you have in the field
Two of the more commonly used free IP calculators include
Wildpackets (Bitcricket) Network Calculator and Solarwinds Advanced
Subnet Calculator
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Speedtest.net/pingtest.net
A very easy test that can be used to both determine the Internet bandwidth
available to a specific host and to determine the quality of an Internet
connection is the use of the tools available at the speedtest.net and
pingtest.net websites
The speedtest.net site provides the ability to determine the amount of
bandwidth that is available to a specific host at a specific point in time
This is a good tool to use when measuring how long it is going to take to
upload or download information from a local to remote host
The pingtest.net website is used to determine the quality of the connection by
measuring the ping response times and jitter amounts over a short period of
time. [email protected]
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Speedtest.net/pingtest.net cont
This information can be used to determine a likelihood
of how well the measured connection will deal with
certain types of high demand traffic like Voice over IP
(VoIP) or gaming
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Pathping/mtr
In an effort to take advantage of the benefits of both
the ping and tracert/traceroute commands, the
pathping and mtr utilities were developed
Both of these tools take the functionality and
information that can be obtained from these types of
tools and provide a more detailed single picture of the
path characteristics from a specific host to a specific
destination
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Route
This utility is used to display the current status of the routing table on a host
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