Ip Telephony Protocols

Communication over a long distance is possible, thanks to telephony technology. There are two main types of telephony currently in use. They are the Public Switched Telephone Networks (PSTN) and IP telephony. PSTN is the traditional form of telephony that relies on circuit connections to facilitate fax and telephone calls. 

IP telephony is the modern form of telephony that relies on internet protocols to facilitate communication. IP stands for Internet protocol. There are various protocols on IP telephony that make it possible to do various actions. These protocols offer diverse functionalities, unlike PSTN protocols. PSTN protocols limit innovation and have limited functionalities. 

Companies like ProIPTech that offer IP telephony services use these protocols to exchange data packets and offer communication solutions like email, video, voice, fax, and more. 

IP Telephony Protocols

Some IP telephony protocols enable media transport, others for signalling, and secure telephony. Session Initiation Protocol (SIP) and H.323  facilitate call signalling. Real-time Transport Protocols (RTP) and Real-time Transport Control Protocol (RTCP)are for media transport. 

1. Session Initiation Protocol (SIP)

Session Initiation Protocol is a signalling protocol. SIP creates a session between two or more devices, alters, and concludes the multimedia sessions—Session Initiation Protocol will exchange port numbers and IP addresses to enable systems to receive data. Transmission Control Protocol (TCP) helps to transmit data for SIP. 

SIP is also a text-based protocol and is very similar to the HTTP protocol. Furthermore, there is a request-response mechanism that comes alongside text-based protocols to make it easier to troubleshoot. It uses various messages or methods to communicate between parties. Some terms you may come across include:

  • Invite to initiate sessions
  • ACK to confirm sessions
  • BYe to terminate sessions
  • Cancel to decline an invite
  • Register to bind your permanent address to the current location
  • Options for inquiry capability

Other message examples include update, message, info, prefer, and more. 

SIP helps to make redirection and name mapping services more transparent. Session Initiation Protocol also facilitates peer to peer applications as well as IP telephony. 

2. H.323

H.323 is a communications system for packet-based multimedia. IT-UT, the international telecommunication standardization sector, recommended this protocol. The standardization sector recognizes it as a standard that interprets various protocols to offer visual/audio communication over a computer network.

H.323 is very similar to SIP because it also helps to initiate, modify, and terminate a session. The ability of H.323 to carry visual or audio across a computer network makes it a binary protocol. However, this trait does not make it friendly for technicians to troubleshoot. 

H.323 is different from SIP because it does not have easy extensibility. is because new features will call for more time so that they can be defined, undergo standardization, and implementation. Moreover, currently, companies are not making any H.323 phones. SIP devices have dominated the market. 

3. Real-time Transport Protocols (RTP)

RTP is a standard packet format that delivers audio and videos across the internet. It is mostly used by communications and entertainment systems that have streaming media, television services, push-to-talk features on the web, video teleconference applications, and like-telephony. 

A company like ProIPTech offers RTP services like IP TV and 21st-century lecture halls such as online courses, and conference rooms. RTP works very closely with RTCP. It will transmit media streams while RTCP is in charge of transfer statistics, Quality of Service, and synchronizing various streams. Moreover, RTP makes use of even-number ports while RTCP uses ports of the next higher odd number. 

Some of the other benefits of RTP are multiple destination endpoints, jitter compensation mechanisms, data packet delivery that is out of order, and packet loss detection.

4. Real-time Transport Control Protocol (RTCP)

RTCP is a protocol that sends control packets to participants of a particular call. This protocol works together with the RTP. Its primary role is to avail feedback on the quality of services RTP provides.

Even number ports give and receive RTP while the next higher od number port facilitates RTCP communication. RTCP provides the information & statistics like octets & packet counts, round trip time, and jitter. Applications use this data to regulate the quality of service parameters and make decisions like utilizing a codec. 

However, RTCP won’t provide methods of authentication and flow encryption. However, a Secure Real-time Transport Protocol (SRTP) can help implement these methods. Some applications of RCTP include IP TV, video conferencing, Voice Over IP (VOIP), and stream media. 

5. Secure Real-time Transport Protocol (SRTP)

SRTP is a security protocol. The Internet Engineering Task Force (IETF) first published SRTP in 2004. SRTP is an extension of RTP with security elements such as replay & confidentiality protection and message authentication. These extensions mainly feature in VOIP communications. 

RTCP uses authentication and encryption to minimize attack risk.

6. Session Description ⁿProtocol (SDP)

SDP is a protocol that defines two endpoints as parameters for media exchange. It is exclusively encapsulated within the Session Initiation Protocol (SIP). SDP declares various specifications and capabilities from a media endpoint. The declaration may include:

The IP address that will receive an incoming media stream

Port Number for the incoming media stream

Media category the endpoint will receive. 

There are two endpoints in a typical session. One sends an SDP with information on its specifications and capabilities. SDP does not handle any media. 

Key Takeaways

Protocols facilitate the operation of IP telephony. They help perform the following five main functions in IP telephony:

  • To initiate signals for calls
  • Send media to facilitate communication
  • Measure Quality of service
  • Define communication endpoint parameters
  • Secure communication

The protocols and functions help companies and individuals to realize the benefits of IP telephony. 

Ip Telephony Services With ProIPTech

ProIPTech is an organization that helps businesses realize the IT revolution through emerging technologies. Businesses can use these services to scale up efficiently. ProIPTech works with businesses in various industries such as insurance, manufacturing, education, healthcare, telecommunications and pharmaceuticals.  

Some of the services they offer include IP telephony, IP TV, Wireless presentation, 21st Century lecture halls and classrooms, unified communication, unified collaboration, and more. Contact them now for IP telephony and more brilliant emerging solutions. 

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