Network managers have long awaited practic

问题：

Network managers have long awaited practical voice-over-IP (VOIP) solutions. VOIP promises ease network management and decreases (1) by converging a company’s telephony and data infrastructures into one network. And a VOIP solution implemented at a company’s head-quarters with far-reaching branch offices can (2) tremendous amounts of money in long distance phone bills, provided that solution delivers POTS-like voice (3) over the Internet.

VOIP gateways are designed to convert voice from the (4) domain to the circuit switched domain. VOIP solutions use a digital signal processor (DSP) to process the voice data, preparing the voice sample for transmission by compressing voice and removing jitter. The VOIP equipment must comply with the (5) H.323 standard defined by the International Telecommunication Union, or ITU.

4（）

A．framing

B．message

C．circuit

D．packet