Circuit switching is switching the hardware and dedicating the line through out, where as packet switching is no dedicated hardware.
I think I am missing the basic concept here.
I understand PVC apples for Frame relays for packet switching.
But technically speaking how do they vary? Is it like dedicating a virtual line forever??
But the PVC format goes like DSLAM/SLOT/CARD/PORT right? so how is this virtual? its same as dedicating the whole in right?
Re: Difference between circuit swicthing and PVC
8 years 10 months ago #33384
Good question. PVC (Private Virtual Circuit) looks (acts) like a dedicated circuit (line) to the router/DTE devices at both ends. But it's actually implemented using a packet switched network internally. This is where the word "virtual" comes from. So the bandwidth of the network is really shared.
Now you might ask, "If it's actually a shared packet switched, then where is the dedication part?". In-fact, frame-relay kind of simulates a dedicated line by some thing called a Committed Information Rate (CIR). When you buy a PVC, the ISP/vendor promises you a certain CIR (like 1Mbps or 4Mbps, according to the package that you payed for). Frame-relay packet switching has capabilities that can insure you (almost) always get a bandwidth not less than the CIR, possibly more. When there is a congestion in the network, some packets from subscribers that are exceeding their CIR are dropped. At normal or low load times, frame relay tends to allow more than the CIR.
I think I understood what you said.
The connection from ISP to the router is fixed (DSLAM/SL/CARD/PR). but from here on its not.
In terms of a telco, the E3/E1 links between DSLAM s and aggregators implement the packet form , where multiple O/P ports from DSLAM are connected to same Aggregator port. hence a control can be imposed here over the data flow.
Thanks for that.