Re: T1: Physical vs Logical Circuit

On Tue, 14 Mar 2006 00:46:40 GMT, John McHarry <jmcharry@xxxxxxxxxxx>
wrote:

On Mon, 13 Mar 2006 16:18:12 -0600, Bob Simon wrote:

A book on WAN technologies divides circuits into physical and logical.
Physical circuits are subdivided into exclusive-use (like a printer
cable or an RS-232 cable to a modem) and shared-use (Ethernet or Token
Ring between a PC and a server).

A logical or virtual circuit is defined as "a communications path that
appears to be a single circuit between the source and destination
nodes. A virtual circuit is not a physical circuit; it is a logical
conection between devices configured over one or more physical
circuits." These are subdivided into PVCs and SVCs.

This all seems a bit arbitrary to me. After all, an Ethernet is not a
single piece of wire. Are these commonly accepted definitions?

Is a T1 always a PVC? Would it be considered a physical circuit if
both end points are connected by the same switching office?

A T1 can be a physical circuit, as all were in the beginning. These days
it is often split out of a higher level physical circuit, like a fiber
optic path at one of the OC levels. That would make it virtual, but, since
it is always there, rather than being set up and taken down conversation
by conversation, it is a PVC in that case. It really has nothing to do
with the physical location of the end points.

I am confused by your comment that all T1s were physical in the
beginning. As I understand it, any interlata T1 consists of an IXC
plus two local loops. That's at least three circuits that appear to
be a single circuit to the nodes terminating it. So it would be
logical, not physical. No?

The terms are in general use. Your proposed definition isn't very precise.

I did not propose a definition, at least not intentionally. What is
it that you think I proposed?
.

Relevant Pages

  • Re: T1: Physical vs Logical Circuit
    ... cable or an RS-232 cable to a modem) and shared-use (Ethernet or Token ... appears to be a single circuit between the source and destination ... A virtual circuit is not a physical circuit; ...
    (comp.dcom.telecom.tech)
  • T1: Physical vs Logical Circuit
    ... appears to be a single circuit between the source and destination ... A virtual circuit is not a physical circuit; ... These are subdivided into PVCs and SVCs. ...
    (comp.dcom.telecom.tech)
  • Re: Rheem air handler wiring
    ... Boltig the new meter panel and outdoor load center up against the PVC ... protection for each circuit outside of the unit. ... The mast and hood and service wire ...
    (alt.home.repair)
  • Re: powerPC simulation
    ... interfaced with nand flash,FPGA,DDR and ethernet ASIC. ... cycle accurate Functional simulation of the above circuit. ... What is the procedure for doing functional simulation. ...
    (comp.arch.embedded)
  • Fibre Channel over Gigabit WAN Ethernet without FCIP possible?
    ... we need to extend it to a second location via a 1GB WAN-Ethernet ... circuit. ... Isnt it possible to kind of bridge the FC traffic over the ethernet ... I found also there is a FCoE (Fibre Channel over Ethernet) specs in ...
    (comp.dcom.lans.ethernet)