I am studying by this book: West, Jill. Network+ Guide to Networks.. [VitalSource].
What I understand from what is explained there is that there are two kind of virtual circuit technologies PVC and SVC and that Packet-switching and circuit-switching are to variants of any of those two. But later I been reading around to understand a little more and I've found some explanations that state that Packet-switching is at the top of the hierarchy since is the main used tech nowadays and there are two kind of circuit-switching used within the packet-switching networks to establish a connection that demand a more reliable services such as VoIP, and this circuit-switching can be either PVC or SVC.
Please help me to clarify if PVC and SVC can be either packet-switched or circuit-switched or if PVC and SVC are always circuit-switched and circuit-switching is a form of packet-switching?
according to West : "virtual circuit—A WAN connection logically appears to the customer to be a dedicated line, but, physically, can be any configuration through the carrier’s cloud. One advantage of virtual circuits is that a company can purchase limited bandwidth, and then use the channel only when it needs to transmit data. When that company is not using the channel, it remains available for use by other virtual circuits. Two types of virtual circuits are:
❍❍ PVC (permanent virtual circuit)—Connections that are established before data needs to be transmitted and are maintained after the transmission is complete.Note that in a PVC, the connection is established only between the two points (the sender and receiver); the connection does not specify the exact route the data will travel.
❍❍ SVC (switched virtual circuit)—Connections that are established when parties need to transmit, then terminated after the transmission is complete.
Switching determines how connections are created between nodes on a network. The two primary approaches to switching are described next:
• circuit-switched—A connection is established between two nodes before they begin transmitting data. Bandwidth is dedicated to this connection and remains available until the users terminate communication between the two nodes. While the nodes remain connected, all data follows the same path initially selected by networking devices. This is similar to telephone circuits created when you make a phone call. As you can deduce, based on your knowledge of how IP packets are assembled and routed, circuit switching is not common today for data networks.
• packet-switched—Data is broken into packets before it’s transported. Packets can travel any path to their destination because, as you already know, each packet contains the destination address and sequencing information. Consequently, packets can attempt to find the fastest circuit available at any instant. When packets reach their destination node, the node reassembles them based on control information included in the packets. The greatest advantage to packet switching lies in the fact that it does not waste bandwidth by holding a connection open until a message reaches its destination, as circuit switching does. Ethernet networks and the Internet are the most common examples of packet-switched networks. Whereas a LAN always uses packet-switched connections, a WAN can use either circuit-switched or packet-switched connections, although packet-switched connections are more common"
