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Learn More about VoIP Architecture & Call Components

By, Harry Bhatia


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A lot has been written about the features and benefits of VoIP services. So, in this blog, we would concentrate on understanding the architecture and components of Voice over Internet Protocol (VoIP) services. We would consider the major components along with their individual functional characteristics.

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The 4 major VoIP components include: 

Signaling Gateway Controller

Media Gateway

Media Server

Application Server

SIGNALING GATEWAY CONTROLLER The signaling gateway controller (SGC) is a known as ‘called agent’ due to its call control function and is popularly referred to as a ‘Media Gateway Controller’ because of media gateway control function included in the system. The SGC entity is the heart of VoIP platform and performs multiple roles out of which connecting the PSTN world with the IP world is its main function. Some of the main characteristics of SGC component are: 

Supporting signaling system 7 (SS7) protocol stack

Supporting voice call control protocols such as H.323 or SIP

Supporting media control protocols such as Megaco (H.248) or MGCP

Generating detail call records

Providing bandwidth management control using admission control mechanisms

Supporting bandwidth policing mechanisms

Allocating media connections


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MEDIA GATEWAY The transmission of voice packets is performed by the media gateway by using RTP transmission protocol. The media gateway performs extra functions such as packetization when it’s used in a converged IP/PSTN network. It requires using IP trunks on one side and TDM trunks from the other. Some functions of the media gateway can be listed as below: 

Supporting MEGACO or MGCP

Transmitting voice data using RTP

Supporting E1/T1 Trunks

Supporting various compression algorithms

Managing digital signal processing (DSP) resources


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MEDIA SERVER The role of media server comes into the picture when additional features such as video conferencing or voicemail are needed. It also assists when announcements or special tones need to be transmitted. Media server performs the following functions: 

Voice activated dialing

Voicemail function

Transmitting customized call progress tones or special service announcements

Transmitting voicemail to email

Supporting Interactive Voice Response (IVR)

APPLICATION SERVER Application Server takes the responsibility to provide value-added services to the IP network. The server provisions both – customer specific and global services. Moreover, session specifications and call characteristics are also influenced by the application server. Below are its main functions: 

Offering basic services like call forwarding, call waiting, call transfer, etc.

Supporting private dialing plans

Generating call detail records (CDR)

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Once you opt for VoIP phone services, it is important to decide on a reliable VoIP service provider who can assist you with business-specific requirements and provide cost-effective services to your business. The Net Activity team is well-versed and wellequipped to serve your organization with a functional VoIP system. Please visit to know the details or contact Harry Bhatia at 888-545-5346.


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VoIP Architecture & Call Components - Things You Must Know  

Know the major components along with their individual functional characteristics of Voice over Internet Protocol (VoIP) services.

VoIP Architecture & Call Components - Things You Must Know  

Know the major components along with their individual functional characteristics of Voice over Internet Protocol (VoIP) services.