Interview questions for VoIP

1. What is VoIP?

Voice over Internet Protocol (VoIP) is the technology to send your voice (analog data) over the internet (digital data) to an end user. It enables users to use the Internet as the transmission medium for voice calls at a very low cost.

2. What major challenges and problems did you face at your last position?

• Interfacing different call origins, Hardware related issues.

• Structure and Organization. Nothing was documented and whenever I completed a job, there were hidden things I was expected to do.

3. How does VoIP (voice over Internet protocol) work? What makes it different from traditional phone service?

In VoIP, phone conversations are converted to packets that flit all over the Internet or private networks, just like e-mails or Web pages, though voice packets get priority status. The packets get reassembled and converted to sound on the other end of the call but in traditional phone service, a phone conversation is converted into electronic signals that traverse an elaborate network of switches, in a dedicated circuit that lasts the duration of a call.

4. How do you decide what gets top priority when scheduling your time?

• As per the urgency of the requirement and the tasks having certain dependencies.

• Depending on the dependence on other module, time span, resource availability.

• I decide on the basis of time log, against its severity of the issue.

• Meeting the deadline putting more work and some extra hours in the relevant protion of work.

5. What are some disadvantages of using VoIP?

VoIP is far better than traditional telephony but it has some drawbacks as listed below:
• Some VoIP services don’t work during power outages and the service provider may not offer backup power.
• Not all VoIP services connect directly to emergency services through 9-1-1.
• VoIP providers may or may not offer directory assistance/white page listings.

6. What Is The Actual Cost Of Voip Telephony?

If you only want to use VoIP to communicate with other users in your VoIP network, you can do that free of charge. If however you want to be able to use VoIP to make and receive calls to/from people who are out of your VoIP network or do not have VoIP, you will need to subscribe to a VoIP service provider plan, and a gateway service may be also needed that provides a bridge between VoIP and the conventional phone networks

7. What basic set-up equipment is needed for VoIP?

For general VoIP set up we require the following things:
• Broadband connection
• VoIP phone
• Nexton soft-switches
• Router
• Audiocodec
•  Astric server

8. Is It Possible To Replace The Current Traditional Corporate Pbx With A Voip One?

Definitely yes. VoIP is a very cost-effective option for those companies who want to upgrade their old PBX systems and VoIP ensures new features that traditional PBX systems simply do not. To change to a VoIP system, companies can buy an IP PBX, but it is also possible to add some VoIP functionalities into an existing phone system

9.  What is PVDM and what is the use of it?

 PVDM stands for Packet Voice DSP (digital signal processor) Module and it enables Cisco Integrated Services Routers to provide high-density voice connectivity, conferencing, and transcoding capabilities in Cisco IP Communications solutions.

10. Which Protocols Describe Voip Connections?

VoIP has been implemented in various ways using both proprietary protocols and protocols based on open standards. You can see the VoIP protocols below:
o H.323
o Media Gateway Control Protocol (MGCP)
o Session Initiation Protocol (SIP)
o H.248 (also known as Media Gateway Control (Mega co))
o Real-time Transport Protocol (RTP)
o Real-time Transport Control Protocol (RTCP)
o Secure Real-time Transport Protocol (SRTP)
o Session Description Protocol (SDP)
o Inter-Asterisk exchange (IAX)
o Jingle XMPP VoIP extensions
o Skype protocol
o Team speak

11.  What is VoIP gateway and explain the basic features of it?

A VoIP gateway works as a bridge between an IP network and the PSTN. It converts analog telephony signals to digital.
VoIP gateways include the following features:
• * Call routing, packet processing and control signalling managementVoice and fax compression/decompressionExternal controller interfaces, for example to a soft switch, billing system or network management system

12. How To Get Started On Voip Programming?

The best way for creating any VoIP application is using a VoIP development kit. These SDKs are intended to provide a background support for your VoIP project by offering prewritten VoIP components. It is quite effective and comfortable to use these prewritten components, as you can save time and money as well. (During the soft phone development that will be described below, Osaka VoIP SIP SDK has been used for this purpose, that supports all the .NET programming languages, so C# as well.)
For using these toolkits, you have to add your preferred SDK as reference in you IDE. After you have added it, you can reach all VoIP components that are needed to be able to define the behaviour of such VoIP applications as soft phones, call recorders, IVR menu systems, software-based IP phone systems (PBX), etc.

13. What is SLRG & why do we use it?

SLRG (Standard Local Route Groups) eliminates the pairing between the gateway and the Route Pattern, thus creating a more flexible method of selecting a PSTN gateway.
Because it reduces the number of route patterns that need to be created per country, a huge amount of administrative overhead can be saved, especially for organizations with a large number of sites.

14. What is the basic difference between VoIP and POTS (Plain old telephone systems) dial-peers?

VoIP dial peers route calls to other VoIP systems via IP protocol where POTS dial peers route calls to legacy PBX systems via local ports which can be analog (like FXS, FXO) or digital (like E1/T).

15. What is the signalling and what is the difference between CAS and CSS?

Signalling is a way of information exchange to establishment and control of a telecommunication circuit and the management of the network.
Common channel signalling (CAS) uses a dedicated channel for the signalling where Channel Associated Signalling (CAS) conveys signalling information relating to multiple bearer channels. These bearer channels therefore have their signalling channel in common.
CCS with E1 =30 B channels and 1 D channel
CCS with T1 = 23 B channels and 1 D channel
CAS with E1 = 31 B Channels
CAS with T1 = 24 B Channels
B=Bearer channels responsible for carrying voice signal
D=Data channel responsible for signalling control.