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Glossary - 26

ForeRunner

ATM Switch Network Configuration Manual

Glossary

Permanent Virtual Channel Connection (PVCC) -

A Virtual Channel Connection (VCC) is an

ATM connection where switching is performed on the VPI/VCI fields of each cell. A Perma-
nent VCC is one which is provisioned through some network management function and left
up indefinitely.

Permanent Virtual Circuit (or Channel) (PVC) -

a circuit or channel through an ATM network

provisioned by a carrier between two endpoints; used for dedicated long-term information
transport between locations.

Permanent Virtual Path Connection (PVPC) -

A Virtual Path Connection (VPC) is an ATM con-

nection where switching is performed on the VPI field only of each cell. A PVPC is one which
is provisioned through some network management function and left up indefinitely.

Phase Alternate Line (PAL) -

Largely a German/British development in the late 60s, used in the

UK and much of Europe. The B-Y and R-Y signals are weighted to U and V, then modulated
onto a double-sideband suppressed subcarrier at 4.43MHz. The V (R-Y) signal's phase is
turned through 180 degrees on each alternate line. This gets rid of NTSC’s hue changes with
phase errors at the expense of de-saturation. The carrier reference is sent as a burst in the back
porch. The phase of the burst is alternated every line to convey the phase switching of the V
signal. The burst's average phase is -V. (see NTSC for U.S.).

Physical Layer (PHY) -

the actual cards, wires, and/or fiber-optic cabling used to connect com-

puters, routers, and switches.

Physical Layer Connection -

an association established by the PHY between two or more ATM-

entities. A PHY connection consists of the concatenation of PHY links in order to provide an
end-to-end transfer capability to PHY SAPs.

Physical Layer Convergence Protocol (PLCP) -

a framing protocol that runs on top of the T1 or

E1 framing protocol.

Physical Medium (PM) -

Refers to the actual physical interfaces. Several interfaces are defined

including STS-1, STS-3c, STS-12c, STM-1, STM-4, DS1, E1, DS2, E3, DS3, E4, FDDI-based, Fiber
Channel-based, and STP. These range in speeds from 1.544Mbps through 622.08 Mbps.

Physical Medium Dependent (PMD) -

a sublayer concerned with the bit transfer between two

network nodes. It deals with wave shapes, timing recovery, line coding, and electro-optic con-
versions for fiber based links.

Plesiochronous -

two signals are plesiochronous if their corresponding significant instants

occur at nominally the same rate, with variations in rate constrained to specified limits.

Point of Demarcation -

the dividing line between a carrier and the customer premise that is

governed by strict standards that define the characteristics of the equipment on each side of
the demarcation. Equipment on one side of the point of demarcation is the responsibility of
the customer. Equipment on the other side of the point of demarcation is the responsibility of
the carrier.