Voice Over Internet Protocol
VOIP-Voice Over Internet Protocol
What is special about VOIP is that it’s just another thing you can do on the Internet, whereas it is the only thing — or nearly the only thing except for the dial-up modem and fax — that you can do on the public switched telephone network. Vinton Cerf
Introduction:
Voice over Internet Protocol (VoIP), is a technology that allows you to make voice calls using a broadband Internet connection instead of a regular (or Analog) phone line. Some VoIP services may only allow you to call other people using the same service, but others may allow you to call anyone who has a telephone number — including local, long-distance, mobile, and international numbers. Also, while some VoIP services only work over your computer or a special VoIP phone, other services allow you to use a traditional phone connected to a VoIP adapter.
If you have an internet connection, you call anyone without the need for local phone service. VoIP solutions work on any computer because it’s built upon many years of open standards.
VoIP service :
The providers do more than establishing calls. They perform routing of outgoing and incoming calls through existing telephone networks. Landlines and cell phones depend on the Public Switched Telephone Network (PSTN).
Traditional telephones use analog lines to carry voice signals. If you want to make calls, you have to have extra wiring installed.
Working:
- VoIP services convert your voice into a digital signal that travels over the Internet. If you are calling a regular phone number, the signal is converted to a regular telephone signal before it reaches the destination.
- VoIP can allow you to make a call directly from a computer, a special VoIP phone, or a traditional phone connected to a special adapter. In addition, wireless “hot spots” in locations such as airports, parks, and cafes allow you to connect to the Internet and may enable you to use VoIP service wirelessly. According to fig.1.
- Voice over IP converts data, such as voice or video, into a digital signal and transfers it over the internet as digital data packets. To use VoIP technology, you need a VoIP service or application to facilitate the calls, internet access, and a SIP trunk or VoIP provider.
- Some broadband or telephony providers offer IP telephony as standard or alongside traditional PSTN services. However, most telco providers are gradually making the switch to all IPs. In the case that your regular phone service provider offers VoIP solutions, you won’t need to employ a separate SIP trunk or VoIP provider.
- Using packet-switched technology to transmit voice, VoIP uses a series of protocols to facilitate calls. These include the RTP (Real-Time Transport) protocol which defines a standard packet format to deliver media over the internet.
- Additionally, SIP (Session Initiation Protocol) is a signaling protocol used to establish, maintain and terminate a session between 2 or more participants. Voice and video data are broken down into packets that are sent over the internet and then reconstructed to be delivered in real-time as the original voice or video message.
VoIP equipment:
The two main types of VoIP telephones are hardware-based and software-based.
A hardware-based VoIP phone looks like a traditional hard-wired or cordless telephone and includes similar features, such as a speaker or microphone, a touchpad, and a caller ID display. VoIP phones can also provide voicemail, call conferencing and call transfer.
Software-based IP phones, also known as softphones, are software clients installed on a computer or mobile device. The softphone user interface often looks like a telephone handset with a touchpad and caller ID display. A headset equipped with a microphone connects to the computer or mobile device to make calls. Users can also make calls via their computer or mobile device if they have a built-in microphone and speaker.
VOIP Protocols:
Voice over IP has been implemented with proprietary protocols and protocols based on open standards in applications such as VoIP phones, mobile applications, and web-based communications.
VoIP protocols include:
There are Certain Protocols in VOIP in fig.2. some detailed information about Protocols.
· Session Initiation Protocol (SIP): connection management protocol developed by the IETF. SIP is used to signal and control interactive communication sessions
· H.323: one of the first VoIP call signaling and control protocols that found widespread implementation.
H.323 Features:
H.323 is less complex protocols such as MGCP and SIP.
H.323 deployments are increasingly limited to carrying existing long-haul network traffic.
Media Gateway Control Protocol (MGCP): The connection management for media gateways. It implements the media gateway control protocol architecture for controlling media gateways connected to the public switched telephone network (PSTN).
MGCP Features:
· It is an ailment with RFC 3035.
· It can work with IPv4 and IPv6.
· It can be extended with MGCP software for additional abilities.
· It supports working with SIP and H.323 protocols.
· H.248:2. H.248 is an ITU standard also known as MEGACO-Media Control Gateway.
H.248 Features:
· H.248 is a master/slave communications protocol with two basic constructs called Terminations — media connections called physical (time slots) and ephemeral (IP flow) and Contexts — associations between terminations which can be added or deleted.
· H.248 is a control protocol for media gateways across a converged internetwork consisting of the traditional PSTN and modern packet networks
· Real-time Transport Protocol (RTP):is a network protocol used to deliver streaming audio and video media over the internet, thereby enabling the Voice Over Internet Protocol (VoIP).
RTP Features:
- Packets are sequence-numbered and time-stamped for reassembly if they arrive out of order. This lets data sent using RTP be delivered on transports that don’t guarantee ordering or even guarantee delivery at all.
- This means RTP can be — but is not required to be — used atop UDP for its performance as well as its multiplexing and checksum features.RTP supports multicast
· Real-time Transport Control Protocol (RTCP): The sister protocol for RTP providing stream statistics and status information.
RTCP Features:
· RTP does the delivery of the actual data, whereas RTCP is used to send control packets to participants in a call and quality of service being provided by RTP.
·TCP does not provide any flow encryption or authentication methods, but such mechanisms can be implemented with the use of the Secure Real-time Transport Protocol (SRTP).
Secure Real-time Transport Protocol (SRTP): is an encrypted and extended version of RTP which adds further security features, such as message authentication, confidentiality and replay protection mostly intended for VoIP communications.
SRTP Features:
· SRTP uses encryption and authentication to minimize the risk of denial of service( DoS ) attacks.
· Secure RTP uses Advanced Encryption Standard (AES) as its default encryption cipher. One of the defined Segmented Integer Counter Mode and f8-mode cipher modes can be further selected to allow the AES block cipher to be used as a stream cipher for the RTP datastream.
Session Description Protocol (SDP): A syntax for session initiation and announcement for multi-media communications and WebSocket transports.
SDP Features:
· SDP is a short structured textual description.
· It conveys the name and purpose of the session, the media, protocols, codec formats, timing and transport information.
· Inter-Asterisk eXchange (IAX):This protocol used between Asterisk PBX instances is well suited for control and transmission of streaming media and VoIP (Voice over Internet Protocol).
IAX Feaures:
· Because IAX works well with all codecs, it is adaptable to almost any type of data transmission. In IAX, handshaking is not required when a call is initiated, which renders the communication vulnerable to denial-of-service (DoS) attacks.
·The risk can be reduced by the use of firewalls, passwords and other standard security countermeasures
Extensible Messaging and Presence Protocol (XMPP):This protocol for streaming XML elements over a network in order to exchange messages and presence information in close to real time.
XMPP Features:
· This protocol is mostly used by instant messaging applications like WhatsApp, instant messaging, presence information, and contact list maintenance.
· XMPP is based on client-server architecture, i.e. clients don’t communicate directly, they do it with the help of server as intermediary.
Jingle:for peer-to-peer session control in XMPP.
Jingle Features:
· which adds peer-to-peer (P2P) session control (signaling) for multimedia interactions such as in Voice over IP (VoIP) or videoconferencing communications.
· It was designed by Google and the XMPP Standards Foundation. The multimedia streams are delivered using the Real-time Transport Protocol (RTP).
Skype protocol: It peer-to-peer Internet telephony protocol used to move encrypted voice over IP (VoIP) traffic between Skype members’ computers (peers).
Skype Features:
· Skype uses RC4 encryption for signalling and AES for voice data. Skype requires that Ports 80 and 443 be open for outgoing Transmission Control Protocol (TCP) transmissions and recommends that all destination ports above 1024 also remain open.
· In addition, Ports 5060 and 8000 should remain open for incoming and outgoing UDP transmissions. Skype prefers UDP for voice transmissions.
Advantages:
1. Some VoIP services offer features and services that are not available with a traditional phone, or are available but only for an additional fee. You may also be able to avoid paying for both a broadband connection and a traditional telephone line.
2. More than one phone call can be transmitted on the same broadband phone line. This way, voice-over IP can facilitate the addition of telephone lines to businesses without the need for additional physical lines. This makes VoIP systems much more scalable.
3. Features that are usually charged extra by telecommunication companies, such as call forwarding, caller ID, or automatic redialing, are often included as standard with voice-over IP technology. What’s more, they are much easier to configure and manage.
4. Whole systems are easy and cheap to implement. Without the need for extensive amounts of infrastructure, VoIP communications systems can be deployed quickly and without much cost. What’s more, with mobile apps and web clients, there’s no need for desk phones or expensive devices, making it ideal for small businesses as well as larger enterprises.
5 . With a broadband internet connection, a good VoIP service can provide excellent call quality with very little downtime.
Disadvantages:
1. Some VoIP services don’t work during power outages and the service provider may not offer backup power.
2. Not all VoIP services connect directly to emergency services through 9–1–1.
3. VoIP providers may or may not offer directory assistance/white page listings.
4. As an internet service, it’s vulnerable to cyber attacks. There are several security risks including DOS attacks and eavesdropping. However, most reliable service providers and software systems implement tools and measures to protect against such vulnerabilities.
Real-Time Applications:
- IP Telephony Model: Telephone systems use the Voice Over Internet Protocol (IP) or other digital protocols to transfer voice communications over the internet. In fig.3 You will understand very well about how the telephony system Model uses VOIP?
- There are many more applications:
- VoIP apps for Android and iPhone: Popular personal VoIP apps in android include Skype, Viber, and WhatsApp.
- VoIP apps for Windows and macOS: Popular apps are Nextiva App, Zoiper, etc.
In Each system there are different applications here it is some common applications:
- Easy installation and setup
- Contact list management
- Visual voicemail management
- Team messaging and group chat
- Text messaging (SMS) support
Key Takeaways:
1. One could define VoIP as voice services over networks that use the Internet Protocol (IP), the public Internet itself, or public or private communications networks.
2. The fact that VoIP technology is using IP does not mean that it cannot be secured. To defeat VoIP security threats, a well-structured plan needs to be devised.
3. As VoIP gains terrain in the world of telecommunications, it seems that soon it will become one of the dominant technologies in telephony.
4. While Asia leads the worldwide roll-out of VoIP, North America is catching up fast, followed rapidly by European countries like Sweden and Austria.
I hope you like this Article. We have discussed this article in detail. If any query or information miss then please mention it in the comment box.
Authors :
· Somnath More
· Mohammed Patel
· Vidhi Mehta
· Pranjal Adhav
· Fadhl Muath