| |
|
P |
| P |
 |
Parity bit |
| PABX |
|
Private Automatic Branch Exhange |
| Packet-switched |
|
A network in which data is transmitted in units called
packets. The packets can be routed individually over
the best available network connection and reassembled
to form a complete message at the destination. |
| Packet |
|
A
series of bits containing data and control information,
including source and destination node addresses, formatted
for transmission from one node to another. |
| Packet
switching |
|
Type
of data transfer that occupies a communication link
only during the time of actual data transmission.
Messages are split into packets an reassembled at the
receiving end of the communication link. |
| PAD |
|
Packet
Assembler-Dissembler, the mechanism for disassembling
packets at the sending end and assembling them to form
the complete message at the receiving end; traditionally
used in X.25 networks. |
| PAL |
|
Programmable Array Logic |
| PAP |
|
Password
Authentication Protocol, authentication scheme for
PPP links. A password can be specified for both devices
on a remote link. Failure to authenticate will result
in a dropped connection prior to start of data transmission. |
| Parallel
Tasking |
|
3Com
technology which allows adapters to transmit data to
the network before an entire frame has been
loaded from the coomputer into the adapter's buffer,
and to transmit data to the computer's main memory
before an entire fram has been received from the network.
In effect, a fram can reside on the network, the adapter,
and in computer memory simultaneously, boosting throughput. |
| Path-Control
Layer |
|
Layer
3 in the SNA architecture model. This is the SNA layer
that routes packets through an
internetwork. |
| PBA |
|
Printed
Board Assembly |
| PBX |
|
Private
Branch Exchange |
| PCM |
|
Pulse
Code Modulation |
| PCMCIA |
|
Portable Computer Memory Card Industry Association,
an industry group that has developed a standard for
credit-card-size peripherals for portable computers. |
| |
|
|
| PCR |
|
Peak Cell Rate |
| PDH |
|
Plesiochronous
Digital Hierarchy |
| PDNs |
|
Public Data Networks |
| PDU |
|
Protocol Data Unit, OSI terminology for "packet." A
PDU is a data object exchanged by protocol machines
within a given layer of the OSI Reference Model containing
both Protocol Control Information and user data. |
| PEP |
|
Packet Exchange Protocol |
| PHY |
|
The physical layer of FDDI; also, a term for FDDI fiber
optic cable. In the layer structure, PHY is positioned
between the MAC and the PMD. |
| Physical
Address |
|
An
address identifying a single node. |
| Physical
Layer |
|
First
layer of the OSI Reference Model; governs hardware
connections and byte-stream encoding for transmission.
It is the only layer that involves a physical transfer
of information between network nodes. The Physical
layer insulates Layer 2, the Data Link layer, from
medium-dependent physical characteristeics such as
baseband, broadband, or fiber-optic transmission. Layer
1 defines the protocols that govern transmission media
and signals. |
| Physical
media |
|
Any
physical means for transferring signals between OSI
systems. Considered
outside the OSI
Model, and sometimes referred to as "Layer 0," or
the bottom of the OSI Reference Model. |
| PID |
|
Protocol
IDentifier |
| Ping
Packet |
|
Internet
groper, A program used to test reachability of destinations
by sending them an ICMP echo request
and waiting for a reply. Ping is used as a verb: "Ping
the host to see if it is available." |
| PLID |
|
Physical
Location Identification |
| PLIM |
|
Physical
Layer Interface Module |
| PLL |
|
Phase Locked Loop, function that ensures accurate signal
timing in a token ring network automatically, as opposed
to Tank circuits which must be adjusted manually. |
| PMD |
|
Physical
Layer Medium-Dependent single mode, the sublayer of
the ATM Physical Layer that defines connectors, fiber
optic parameters, etc.
Point-to-point a circuit connecting two nodes only, or a configuration requiring
a separate physical connection between each pair of nodes. |
| |
|
|
| Point-to-point |
|
A
circuit connecting two nodes only, or a configuration
requiring
a separate physical connection between each
pair of nodes. |
| Polling |
|
A method of controlling the sequence of transmission
by devices on a multipoint line by requiring each device
to wait until the controlling processor requests it
to transmit. |
| POP |
|
Point of Presence |
| Port |
|
The
physical connector on a device enabling the connection
to be made.
|
| Port
multiplier |
|
A
concentrator providing connection to a network for
multiple
devices. |
| PostScript |
|
A printer/display protocol developed by Adobe Corp.
PostScript is an actual printing and programming language
to display text and graphics. Unlike line/ASCII printers,
which print character input verbatim, PostScript printers
accept and interpret an entire PostScript page before
printing it. |
| POTS |
|
Plain Old Telephone Service |
| PPP |
|
Point-to-Point Protocol, successor to SLIP; provides
router-to-router and host-to-network connections over
both synchronous and asynchronous circuits. |
| PPPoE |
|
PPP over Ethernet |
| PPSDN |
|
Public Packet-Switched Data Network |
| PPTP |
|
Point to Point Tunnelling Protocol |
| PRA |
|
Primary Rate Access |
| Presentation
Layer |
|
OSI
layer that determines how application information is
represented (encoded) while in transit
between two end systems. |
| PRI |
|
Primary
Rate-Interface, ISDN interface to primary access, consisting
of a single 64 Kbps D channel plus 23 or
30 B channels for voice and/or data. |
| Print
Server |
|
A
dedicated computer that manages printers and print
requests from other nodes on the network. |
| PROM |
|
Programmable read-only memory whose data cannot be
altered. |
| |
|
|
| PROM |
|
Programmable
read-only memory whose data cannot be altered. |
| Protocol |
|
Any
standard method of communicating over a network. |
| Protocol
converter |
|
Device
for translating the data transmission code and/or protocol
of one network or device to the corresponding code
or protocol of another network or device, enabling
equipment with different conventions to communicate
with one another. |
| Protocol
stack |
|
Related
layers of protocol software that function together
to implement a particular communications architecture. |
| Protocol
translator |
|
Network
device or software that converts one protocol into
another, similar, protocol. |
| PS |
|
Pots Splitter |
| PSDN |
|
Packet
Switching Data Network |
| PSK |
|
Phase-Shift
Keying |
| PSPC |
|
Passive Low Pass Filter Central office |
| PSTN |
|
Public Switched Telephone Network |
| PTI |
|
Payload
Type Identifier |
| PTT |
|
Post
Telephone and Telecommunicaitons (Authority) |
| PVC |
|
Permanent Virtual Circuit, generally, a virtual circuit
that is permanently established. PVCs save bandwidth
associated with circuit establishment and tear down
in situations where certain virtual circuits exist
all the time. |
| |
|
|
