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How VoIP Works

Voip 101:
  . The Progression of VoIP
  . The Benefits of VoIP
  . Why Transform you network?
How VoIP Works:
  . Network Elements
  . Enabling Technologies

 Network Elements
Service providers or enterprises can develop a Voice over IP architecture in one of three ways:
        —By IP-enabling an existing telephony network
        —By voice-enabling an existing IP or other packet network
        —By building a pure IP telephony network from scratch

Regardless of how you get to a Voice over IP architecture, the end result is the same. Whether your network is a pure IP network or you use other existing packet infrastructure, the architecture will have these elements in common:
  • Communication server—Also called a "call server" or "softswitch," this element is the brains of the network, providing call control, gateway control, service intelligence, and other centralized functions.
  • Signaling point—This element enables the Voice over IP network to communicate with the SS7 (Signaling System 7) network.
  • Line and trunk gateways—These elements provide connectivity to the public network (either the local line or long-haul trunking segments, respectively)
  • Core switches and routers—These elements keep traffic moving through the core of the IP network
  • Application server—This element provides voice, data, or multimedia services from a central location in the IP network.
 Enabling Technologies
A variety of technologies, including protocols, industry standards, and transmission technologies, operate behind the scenes to enable a Voice over IP network to work.

Technologies relating to Voice over IP include: ATM  | BICC | H.248 | H.323 | IP | SIP | SIP-TTDM

  • ATM (Asynchronous Transfer Mode)
    ATM is a network transmission technology that supports voice, video, and data. It uses switches to establish a logical, end-to-end circuit for each call, guaranteeing quality of service (QoS). However, unlike circuit switches, unused bandwidth in an ATM network can be readily used for other calls and services. ATM is widely used as a backbone technology in carrier and enterprise data networks. For this reason, Nortel Networks provides migration paths that extend your ATM investment as you move to a Voice over IP future at a pace that makes sense for you.

  • BICC
    The BICC (Bearer Independent Call Control) protocol is used to manage voice traffic between communication servers working with the existing SS7 network.

  • H.248
    The H.248 is an open industry standard that provides highly efficient real-time call performance and gateway control. It also enables the "many-to-one" connections required for conferencing.

  • H.323
    H.323 is one of the original Voice over IP signaling protocols.

  • IP (Internet Protocol)
    The IP (Internet Protocol) is used to route messages within an IP network. Each IP packet contains its own header, which provides the information that allows it to reach its destination. IP packet can vary in size, providing great flexibility in transporting traffic and maximizing use of available network bandwidth.

  • SIP (Session Initiation Protocol)
    SIP (Session Initiation Protocol) is a Web-based protocol that supports a wealth of IP-based devices, such as IP phones, PCs, PDAs, and wireless handsets.

  • SIP-T (Session Initiation Protocol for Telephony)
    SIP-T (Session Initiation Protocol for Telephony) provides SIP communications between communication servers.

  • TDM (Time Division Multiplexing)
    TDM (Time Division Multiplexing) is a transmission technology that enables a network to transmit multiple signals simultaneously over a single transmission path. TDM enabled telephone companies to migrate from analog to digital long distance trunking. This term is often used interchangeably with the term "circuit-switched."