avatarJairam R Prabhu

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How VoIP Enables You to Make Calls Through the Internet for Free

Voice Over Internet Protocol, Skype, Whatsapp call, Overlay networks, P2P. Part of Simplify The Tech Series.

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Today if I have to call my cousin in Australia, I can just make a call through WhatsApp or even if I have to see him, I can use the video call option. Earlier we had to use Skype, which had to be accessed only through the Computer. Both of these options are so easy now. A few years ago, we could only contact people in a foreign country using International Subscriber Dialing (ISD) which used to be very costly and had to be done from a specialised telephone booth. So what happened and how?

We talked about Whatsapp calls and Skype, both of which are examples of Internet calling services that enables you to have a voice or video call with the help of the internet. This is enabled by a technology called VoIP which is the core of Internet-based calling services.

Photo by Adem AY on Unsplash

Skype, VoIP and Overlay Network is very important concept that reaches at a trijunction between Computer Networks, Distributing and Cloud Computing.

What is VoIP?

Voice over Internet Protocol refers to a technology that enables you to call over the internet, both broadband as well as cellular connection. Voice refers to the audio and Internet Protocol (IP) refers to a set of rules which govern the movement of data across the internet.

How is VoIP different from traditional phones?

Traditional phones use telephone networks which involve a large physical infrastructure of switching networks for getting a connection. This action is performed by a telephone exchange which performs switching and connection. It is impossible to connect all the telephone sets in a city or even a state. So, what telephone connection providers use is switching circuits that get you connected to the right destination with minimal hardware.

VoIP uses Internet-based Overlay Networks for establishing a connection and transmitting the information. VoIP service providers not only establish connections but also various other services associated with computer networks. VoIP uses a digital connection, unlike analog. There are also options to convert your existing telephone system to VoIP by adding an adapter to it.

An overlay network is a network that is built over another network. Here that network is the internet. Overlay networks overcome the disadvantages and limitations of the internet.

VoIP Devices

  • IP phone is a device that is using an internet connection to make calls.
  • A softphone is a Software-based VoIP calling service. Your existing phone or laptop or personal by installing special software in your device.
  • An analog phone with an internet adapter can also be used as an IP phone.

How does VoIP work?

When you want to make a call, the device at your end will establish a connection with the router. If it is a broadband connection, then it may also be a cable modem, which is then connected to the router. The router then connects your device to the internet or to the rest of the interconnected devices. Usually, it's the Internet Service Provider (ISP) that provides you with both modem and router. (both are not the same)

The connection request is transmitted to the switch, which will provide the address of the destination. The source and destination will establish a connection. This will now enable both to communicate with each other. Now, you can share video and audio with others. Voice or video is converted to a digital signal and then transferred as data packets. At the destination, the digital signals are then converted back then to audio and video so that we people can understand.

VoIP Architecture

The data packets are sent and received through the scheduling system mainly queue which is a First In First Out (FIFO). The Internet Engineering Task Force (IETF) was in charge of designing basic standards of VoIP and also for providing Quality of Service (QoS). Gateway is the hardware-software gate that enables connection. It acts as a virtual border gate.

A codec is a software process that is for compressing/decompressing data over the internet. Codec is an acronym for compression and decompression. A VoIP codec is used for audio, text, visual compression for VoIP calls. The main success of a VoIP call is dependent on Codec.

VoIP applications

As we have discussed softphones, they use VoIP applications for the same. Both source and destination are devices and are operated by human beings. So it's not enough, there are VoIP applications that are designed to enable user-friendly usage and handling. That is where user-end applications hold importance. You have various software applications which do this job. The two big examples are Skype and Whatsapp face to face calling. Both are distinct in multiple ways but they have a common feature which is VoIP.

Advantages of VoIP

  • Internet is very common nowadays- There is no one who doesn't use the internet. Even for reading this article, you are using it. It is an integral part of our life.
  • Easy to use- It is very easy for people to understand and use. No need to know many technical details.
  • Free
  • Can call from any device- You can call from Laptop, Desktop, Tab, Smartwatch, iPad etc. Not necessarily there should be a phone with SIM.
  • Common standard across the globe- You don't have to worry about telecom operator, connection plan, activation, frequency etc. Just connect to any WiFi network around the globe and you can talk.
  • No extra charge- Applications are free, no call charge, no roaming, no STD/ISD.
  • Secure with Encryption- Use of Encryption algorithms for secure data transmission and prevent intruders from attacking and stealing.
  • Use of interactive interface for ease of usage- Applications are easy to use. They are beginner-friendly and highly interactive.

Drawbacks of VoIP

  • Dependency on the Internet- The biggest advantage itself is the biggest disadvantage. It is solely dependent on the internet. If you travel to a place without internet, you cannot make a call or message. The performance of the call is directly connected to various internet parameters. Also, the speed of the internet, the strength of connection, bandwidth etc. does affect the call. Your device also needs a full-time connection throughout the call.
  • Packet loss- As data moves through Internet, data packets may get lost leading to improper connection or noise.
  • Loss for telecom operators- Earlier, a lot of telecom companies made a lot of money from international calls. Now, that scope has been heavily reduced. Everyone is making a WhatsApp or Skype call from free wifi. This has created massive losses for telecom operators. Due to this countries like UAE have banned various VoIP applications.
  • Cost- Although applications may be free, Internet will be costly in certain regions of the world. Also, video calling apps consume a lot of data, so it is wise to use them judiciously.

Skype- A Case Study

Skype is a peer to peer (P2P) video and audio calling service that started in 2003. It was later acquired by Microsoft in 2011 and directly integrated with MS Office. Skype works on a P2P basis, therefore there are only nodes of the same level. There is no server-client model present here. Instead of a centralised server, there are multiple supernodes that enable the connection. In addition to this, there is a login server, which authenticates and verifies users of the service.

Photo by Mati Flo on Unsplash

In 2014, Microsoft announced a new sub product called Skype for Business. Between 2017–20, Skype worked closely with PayPal to enable a payment service. In the 2010–19 decade, Skype was the sixth most downloaded mobile app in the world. As of today, Skype provides video conferencing for up to 50 people.

How does Skype work?

Skype uses a special concept called an Overlay network which doesn't require an IP address or Port address for the same. Ordinary nodes are connected to Supernode. So, when your node wants to make a call, it alerts the supernode and lets you connect with the supernode of the destination node. After the peer to peer connection is established, communication starts.

Data Security in Skype

Skype is popular, it is robust and provides quality service. The question is how secure is Skype? Does it leak the details of the call? Can an intruder hear or see you?

Skype is a fully secure video calling and videoconferencing VoIP application. It provides full end to end encryption just like WhatsApp. Only the callers can see and hear the other side. In the network, it is passed as secure ciphertext which is very hard to decode and possibly futile to actually do it.

For exchanging the public key in the Skype system, RSA (Rivest, Shamir, Adelman) 2048 algorithm is used which is one of the most accepted Public Key Encryption algorithms in the world. All messages between Skype client and server is protected by Transport Layer Security (TLS) and direct messages with American Encryption Standard (AES) 256 bit. Earlier RC4 was used and now Microsoft has stopped using it.

Skype also provides the option of recording. Although the recording of the meeting doesn't affect the encryption, the recording file obtained is not encrypted and can be reused. Encryption won't apply here.

Advantages

1. Scalability- The application has a lot of scope for improvement and expansion. Even the calls and conferences held are scalable. 2. Low-cost- Skype calls are free unless you use any premium plan. Even then, the premium is also very cheap compared to what you will have to give for the phone bill. 3. Reliability- Skype uses P2P, an overlay network that can be highly relied upon. 4. Security- Skype is fully end to end encrypted and highly secure. 5. Robustness- System won’t fail and is based on a strong infrastructure. 6. Performance- Compared to its counterparts, Skype provides high-quality calls and performance is superior.

Features of Skype

1. Free calling service 2. High quality over traditional services 3. File sharing is possible 4. Video conferencing 5. Messaging 6. Recording and subtitles 7. End to end Encryption 8. Available on multiple devices and platforms- Phone, Tab, PC, Xbox, Web, etc.

Conclusion

VoIP or Voice over Internet Protocol is a very interesting technology that allows users to make free calls over the internet. The calls can be audio, video or conference. Just like any technology it has both benefits and drawbacks.

Skype is an example of a free P2P video calling application. It uses the overlay network concept to provide services. It is secure, easy to use and robust. Dependency on the internet is both a plus and a minus of VoIP.

References

Ganguly, S., & Bhatnagar, S. (2008). Voip: Wireless, p2p and new enterprise voice over ip. John Wiley & Sons, Incorporated.

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Technology
Internet
Voip
Skype
Telecommunication
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