Protocol Testing Interview Questions and Answers

Protocol Testing Interview Questions: Part 1

Protocol testing interview questions will be normally related to specific terms used in protocol testing, generic software testing concepts, testing tools, test cases, test plans, bugs, automation questions using python or tcl or perl , networking fundamentals and indeed about routing and switching protocols.

What is a Protocol?

When computers or networking devices (like routers,switches) communicate, they use different languages like humans do.The rules and regulations followed by these devices to communicate are called as protocols.

Protocols are proposed and standardized by organizations like IETF, IEEE, W3C, ISO, ANSI, ITU etc

What is Protocol testing?

Protocol testing is a branch of software testing which deals with the testing of programs (protocols) used in networking and telecom devices.

When a protocol is accepted, a software program is developed which obeys these rules and work as mentioned in the standard. This software program is then integrated with other programs to form operating system (of routers/switches/firewall etc) . Verification of the rules mentioned in standard, packet structure, functionalities, performance , use cases etc of this software program is called as protocol testing

This is like a Manager validating if the assistant has drafted the letter in a proper format and with correct grammar and approves or rejects the communication.

Protocol testing is also known as datacom testing or L2 L3 communication protocol testing.

Protocol categories

Category Protocols
Routing or L3 Protocols OSPF, BGP, RIP, EIGRP,ISIS
Switching or L2 protocols STP, RSTP, MSTP, VTP, IEEE 802. 1q, LACP, LAGP
Security protocols IPSec, GRE, IEEE 802.1x, SSL
VoIP protocols SIP, H323, h348, MGCP, RTP, RTCP
Application layer protocols DHCP, DNS, FTP, SNMP, SMTP, SSH, NTP
Transport layer protocols TCP, UDP, SCTP, DCCP, RSVP
Wireless Protocols IEEE 802.11g, 802.11n, 802.11ac

Which are the different types of Protocol testing?

  • Conformance testing
  • Functional testing
  • Performance testing
  • Scalability testing
  • Load testing
  • Negative testing
  • User scenario testing
  • Interoperability testing
  • Competitive testing

What is the difference between Datacom testing and Telecom testing

Datacom testing
Datacom testing deals with testing of protocols and features of devices used in data communication such as routers, switches ,firewalls etc
Telecom testing
Telecom testing deals with testing of protocols used in telecommunication like 3G, 4G, LTE etc

What is the difference between Manual testing and Automation

In datacom testing, if a tester is carrying out tasks like configuring the routers/switches, capturing packets using tools like wireshark, generating traffic using tools like Ixexplorer, router tester etc we can consider that as manual testing.

Automated Testing is carried with the help of scripting languages like TCL, Python, Perl or any automation software like Ixautomate, Spirent TestCenter etc

What is the difference between Protocol testing and Software testing

Protocol testing and software testing cannot be treated as two streams, protocol testing is indeed a subdomain of software testing. Though the testing types (functional, performance, negative etc) are same, the tools used and the method of testing are different.

When a tester is testing a router or a switch, he /she is in fact testing a program which is part of the operating system of that device. So protocol testing is not the testing of physical device, but it is testing of a software in it.

Which are the testing tools used in Datacom testing?

Traffic generators
Traffic generators are used to create and send customized packets. Customization includes changing the contents of the headers, setting the size, speed, number of packets, generating different streams of packets etc. IxNetwork, Spirent SmartBits, Ostinato, Scapy, Hping,IPerf etc are some of the traffic generators used in the protocol testing industry.
Capturing tools
Capturing tools are used to capture and analyze the packets send/received in the interfaces. Tools like Wireshark , Tshark, Scapy, TcpDump can be used to check the header structure, size and the contents of the captured packets.
Simulators are used to create virtual routers/switches to setup topologies with many devices which will be difficult to setup if we are using physical devices. IxNetwork, Spirent TestCenter etc can be used to simulate virtual device

What is Regression testing?

Regression testing is normally done when a program or software is modified , this is to check the modifications are not creating new bugs. Repeated execution of test scripts is a common way of doing regression testing in most of the companies. Regression testing also done when a testing project starts and when it ends. Regression testing using test scripts from automation framework at the beginning of project helps in finding bugs in initial phase .

Protocol Testing Interview Questions: Part 2

You may get questions related to software testing concepts also, following are some of the commonly asked questions

What is the difference between Unit testing and System testing?

Unit testing is a software testing method by which individual units of source code is tested. This could also be testing of an entire module or a set of functions.

System testing is performed on the entire system after integrating all the modules or functions. Protocol testing is normally done part of system testing process.

What is Agile testing method?

Rather than doing the testing process after software is completely developed, Agile testing process does testing along with development process. This helps in finding bugs during the development phase itself and help in reducing the overall time of the project.

What is the difference between White box, Black box and Grey box testing?

White box testing involves testing of internal working of an application rather testing the functionality or performance of the application. This requires programming skills as the tester is supposed to walk through the code and the test complete program flow.

Black box testing is a software testing method where the overall functionality of the software is tested without considering the internal working. A black box tester need not know the internal structure and need not have programming skills .

In grey box testing , tester will be partially aware about internal working and overall functionalities of the application. Tester will try to find bugs related with improper internal structure or improper usage of software.

What do these acronyms stand for DUT, SUT, UUT, AUT, RUT, PUT, PR, UT

DUT – Device Under Test

SUT – System Under Test

UUT – Unit Under Test

AUT – Application Under Test

RUT – Router Under Test

PUT – Port Under Test

PR – Problem Report

UT – Unit Test

What is a test plan?

Test plan is a document detailing test coverage, target, features to be tested or not tested, approach, test methods, software/hardware requirements etc.

What is a test case?

A test case is a document detailing a set of test inputs, preconditions, topology, execution steps and expected result

What is software bug?

A software bug is coding error or a flaw in computer program. If a bug is present in the code, test case execution will fail and we will not get expected results.

What is the difference between bug severity and bug priority?

Bug severity represents how bad the bug has affected the code. It is expressing the intensity of the impact of bug in the normal working of software.

When bugs are raised, developers will fix them according to the bug priorities. Bug priority represents how important and urgent it is to fix a bug.

What is a Functional Specification Document?

Functional specification document (or just Spec in short) is document that describes the detailed working of all features, performance, capabilities and every function that the application must perform.

If you are interested to learn more about protocol testing , check out our L2 L3 Protocol Testing Course .


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