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12Chapter
Softswitch
Switching has evolved from circuit switching (CS), to packet switching (PS),
Internet Protocol (IP) switching, and multiprotocol label switching (MPLS).
e traditional public switched telephone network (PSTN) and the Internet (or
other Internet protocol-based networks) require specific paths for the traditional or
VoIP call to take from the source to the destination. Duplex channels are required
for transmit and receive operations. e traditional fixed-network Internet requires
three basic functions: routing, transmission, and billing. ese three requirements
must be translated for IP communications.
For the PSTN, most ...