September 20, 2005
VoIP QoS
In the absence of uniform standards, most VoIP vendors have their own solutions that they try to push. Integrated Services is one such solution. Integrated services or intserv was a project that was carried out by the IETF with the objective of "defining a minimal set of global requirements which transition the Internet into a robust integrated-service communications infrastructure." This was intended to enable smooth transfer of audio and video streams in real-time using IP.
IETF concentrated on three issues, namely
• A clear understanding of the services that will be provided.
• A clear understanding of the interfaces for end-to-end routing.
• A clear understanding of any additional requisites for enabling the Internet to support real-time data transfer.
These objectives were explained in three documents, namely RFC 1633, RFC 2212, and RFC 2215. These documents explain the intricacies of the integrated services model and the manner in which the network bandwidth requirements must be met to run the applications.
Resource reservations and admission control are the two major components of this service. They carry out the functions of reserving bandwidths for an application and diverting additional bandwidth to an application, if necessary, but without affecting the other applications. The packet scheduler, the admission control routine, the classifier, and the reservation setup protocol are mechanisms for tracking the flow of data in a network. Packet streams are forwarded by the packet scheduler, which uses procedures such as timers and queues. The packets are grouped by the classifier into a particular class based upon the header details. A decision algorithm run by the admission control allows a router to decide whether the bandwidth can support a new data flow at a given point in time. The details of the flow are maintained by the reservation setup protocol.
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