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Chapter 11. Introduction to Exchange Ser... > The Unified Messaging Infrastructure

The Unified Messaging Infrastructure

Because the Unified Messaging component of Exchange Server 2007 connects with telephony and fax systems, you should be familiar with basic telephony concepts and terminology.

  • Private Branch eXchange (PBX) A PBX is a device that acts as a switch for switching telephony calls. This device is used to provide internal telephone connections and offer access to telephone numbers through shared outside lines to make calls external to the company. Additional communication devices can be connected to a PBX besides telephones—such as fax machines, voice mail systems, and others. Calls from outside the company are transferred to the appropriate extension or forwarded by a human operator.

  • IP-PBX An IP-PBX is a PBX that operates with Internet Protocol (IP). This simplifies the infrastructure because telephones can be connected to the same local area network (LAN) as the computers and servers. The IP-PBX switches calls to the appropriate phone by using the IP address of the telephone. For using IP-based telephony, all telephones must support the IP protocol. A hybrid IP-PBX supports IP phones, but is also able to connect traditional analog and digital telephones.

  • Voice over Internet Protocol (VoIP) This technology enables the use of IP-based networks as the infrastructure for telephone calls.

  • IP or VoIP gateway IP/VoIP gateways are hardware devices that can be used to connect legacy PBX systems to local area networks to provide IP-based telephony services. These gateways convert the legacy protocols from the PBX to VoIP-based protocols like SIP and RTP. For an up-to-date list of supported gateways, see the link in the shortcut area of this section.

  • Dial plan The dial plan is a set of rules that is used by the PBX to determine which action to take when it receives a call. For example, a 0 is often used to get to the public telephone network. When the first number is not a 0, the PBX knows it will be an internal call, but then needs to know how many more numbers to wait for before taking action. Within the Unified Messaging server, the dial plan creates a link between an Exchange Server 2007 recipient’s phone extension in the Active Directory and the recipient’s Unified Messaging—enabled mailbox. After a dial plan is configured, a Unified Messaging server must be added to the plan. This links the dial plan and the server and enables the server to accept and handle incoming calls.

  • Hunt group A hunt group is a set of extensions shared by users. When a PBX receives a call for a number that is assigned to a hunt group, it searches through the connected extensions to find an available phone. Hunt groups are often used to distribute calls among members of support or sales departments. Customers call one number for the support team, and the call could be routed to any member of the team who is not currently on the phone. Within the Unified Messaging configuration, a hunt group is a logical representation of an existing PBX or IP-PBX hunt group. This provides Unified Messaging possibilities for the pilot number (shared telephone number of the hunt group).


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