Voice over IP:
IP telephony describes a solution to transport voice traffic over IP. We can use IP to transport voice, video, and data communications. There are numerous benefits to this type of infrastructure, including simplified administration, cost savings on telecommunications fees, and unified messaging services.
Voice traffic and data traffic require two completely different solutions. Data traffic is relatively resilient and tolerant of slow WAN links, lost packets, and unsequenced packets. Voice traffic, on the other hand, is not. Voice requires packets to be received in the same order in which they were sent; if a packet is lost, it should remain lost, as retransmitting the packet would only confuse the person on the receiving end of the call.
To support voice traffic, several enhancements components must be added to the data network infrastructure. These components include:
1. Specialized router interface.
2. Specialized LAN switch modules and interfaces
3. IP telephone handsets
4. Cisco CallManager servers: Offers a scalable, reliable, and manageable solution for central point calling process. It has set standard of performance for IP telephony call processing. Cisco CallManger takes the place of PBX and works with PBX for any legacy telephony devices. For fault tolerant the telephony network need clustering callmanger. Clustering combines two or more CallManger servers into logical unit. Clustering provides enough server so that if one fails, the other servers within the cluster assume its load without compromising service.
5. Cisco Unity Mail allow users to listen to their e-mail over the telephone, check voice messages from the Internet, and (when integrated with a supported third-party fax server) forward faxes to any local fax machine.
6. Foreign Exchange Office Interface: Connect the IP network to off-premises equipment such as a PSTN CO or to a PBX tie-line interface. One of the main funcation...