- Packet
- The unit of data sent
across a network. "Packet" a generic term
used to describe unit of data at all levels of the
protocol stack, but it is most correctly used to
describe application data units. See also: datagram,
frame. [Source: RFC1392]
- Packet InterNet
Groper (PING)
- A program used to test
reachability of destinations by sending them an ICMP
echo request and waiting for a reply. The term is used
as a verb: "Ping host X to see if it is up!"
See also: Internet Control Message Protocol. [Source:
RFC1208]
- Packet Switch Node (PSN)
- A dedicated computer
whose purpose is to accept, route and forward packets
in a packet switched network. See also: packet
switching, router. [Source: NNSC]
- packet switching
- A communications
paradigm in which packets (messages) are individually
routed between hosts, with no previously established
communication path. See also: circuit switching,
connection- oriented, connectionless. [Source:
RFC1392]
- PAD
- Packet Assembler
Disassembler; the hardware or software interface
between a user's terminal and a packet-switching
network. A PAD assembles the user's input characters
into packets for network transmission, and
disassembles packets of output characters into their
component characters for output on the terminal. The
PAD facility may run on a host computer or on a
dedicated processor (such as the JNT-PAD).
- Particle Physics
Network Co-ordinating Group (PPNCG)
- The Particle Physics
Network Co-ordinating Group (PPNCG) is responsible for
the networking interests of the UK particle physics
community. Formally it is a sub-committee of the
Particle Physics Committee (PPC) of the Particle
Physics and Astronomy Research Council (PPARC). PPNCG
is also a Affiliated Group of the JANET National User
Group, through which the views of the users on JANET
and UKERNA services are presented to the JISC
Committee on Networking. See also: JANET National User
Group.
- PCI
- Protocol Control
Information. The protocol information added by an OSI
entity to the service data unit passed down from the
layer above, all together forming a Protocol Data Unit
(PDU). [Source: RFC1208]
- PD
- Public Domain
- PDU
- See: Protocol Data Unit
- PEM
- See: Privacy Enhanced
Mail
- PGP
- See: Pretty Good Privacy
- PHP
- PHP: Hypertext
Processor. An HTML-embedded scripting language used to
create dynamic web pages by running scripts on the web
server and embedding the results in web pages.
Available from http://www.php.net/.
- Physical Layer
- The OSI layer that
provides the means to activate and use physical
connections for bit transmission. In plain terms, the
Physical Layer provides the procedures for
transferring a single bit across a Physical Media.
[Source: RFC1208]
- Physical Media
- Any means in the
physical world for transferring signals between OSI
systems. Considered to be outside the OSI Model, and
therefore sometimes referred to as "Layer
0." The physical connector to the media can be
considered as defining the bottom interface of the
Physical Layer, i.e., the bottom of the OSI Reference
Model. [Source: RFC1208]
- PING
- See: Packet INternet
Groper
- Pink Book
- the document describing
the implementation of X25 protocol level 3 over a
Connection Orientated Network Service based on lower
layers of Ethernet protocol. This enables
interconnectivity between e.g. Ethernet based PCs and
X25 based hosts, and supports Coloured Book protocols
for file transfer and terminal access, e.g. with the
Rainbow package. Since it is based on ISO standards,
Pink Book is not strictly a "Coloured Book"
in the JANET usage.
- Point Of Presence
(POP)
- A site where there
exists a collection of telecommunications equipment,
usually digital leased lines and multi-protocol
routers. [Source: RFC1392]
- Point-to-Point
Protocol (PPP)
- The Point-to-Point
Protocol, defined in RFC
1661, provides a method for transmitting packets
over serial point-to-point links. There are many other
RFCs which define extensions to the basic protocol.
See also: Serial Line IP. [Source: FYI4]
- polling
- Connecting to another
system to check for things like mail or news.
- POP
- See: Post Office
Protocol and Point Of Presence
- port
- A port is a transport
layer demultiplexing value. Each application has a
unique port number associated with it. See also:
Transmission Control Protocol, User Datagram Protocol.
[Source: RFC1392]
- Portal
- A web site integrating
many facilities within one user interface. Only of
value if the infrastructure for personal information
databases, authentication and authorisation methods,
group communication, business processes and timely
content have already been engineered for harmonious
web access. Driver software to address a multiplicity
of browser devices, from PCs and personal digital
assistants to mobile phones and interactive TV, should
make content available in many environments.
- POSI
- Promoting Conference for
OSI. The OSI "800-pound gorilla" in Japan.
Consists of executives from the six major Japanese
computer manufacturers and Nippon Telephone and
Telegraph. They set policies and commit resources to
promote OSI. [Source: RFC1208]
- Post Office Protocol
(POP)
- A protocol designed to
allow single user hosts to read mail from a server.
Version 3, the most recent and most widely used, is
defined in RFC
1725. See also: Electronic Mail. [Source: RFC1983]
- Postal Telegraph and
Telephone (PTT)
- Outside the USA, PTT
refers to a telephone service provider, which is
usually a monopoly, in a particular country. [Source:
RFC1392]
- postmaster
- The person responsible
for taking care of electronic mail problems, answering
queries about users, and other related work at a site.
See also: Electronic Mail. [Source: ZEN]
- PPNCG
- See: Particle Physics
Network Co-ordinating Group
- PPP
- See: Point-to-Point
Protocol
- Presentation Address
- See OSI Presentation
Address.
- Presentation Layer
- The OSI layer that
determines how Application information is represented
(i.e., encoded) while in transit between two end
systems. [Source: RFC1208]
- Pretty Good Privacy (PGP)
- A program, developed by
Phil Zimmerman, which cryptographically protects files
and electronic mail from being read by others. It may
also be used to digitally sign a document or message,
thus authenticating the creator. See also: encryption,
Data Encryption Standard, RSA. [Source: RFC1983]
- Privacy Enhanced Mail
(PEM)
- Internet email which
provides confidentiality, authentication and message
integrity using various encryption methods. See also:
Electronic Mail, encryption. [Source: RFC1392]
- PRMD
- Private Management
Domain. An X.400 Message Handling System private
organization mail system. Example:- NASAmail. See ADMD.
[Source: RFC1208]
- Prospero
- A distributed filesystem
which provides the user with the ability to create
multiple views of a single collection of files
distributed across the Internet. Prospero provides a
file naming system, and file access is provided by
existing access methods (e.g., anonymous FTP and NFS).
The Prospero protocol is also used for communication
between clients and servers in the archie system. See
also: anonymous FTP, archie, archive site, Gopher,
Network File System, Wide Area Information Servers.
[Source: RFC1392]
- protocol
- A formal description of
message formats and the rules two computers must
follow to exchange those messages. Protocols can
describe low-level details of machine-to-machine
interfaces (e.g., the order in which bits and bytes
are sent across a wire) or high-level exchanges
between allocation programs (e.g., the way in which
two programs transfer a file across the Internet).
[Source: MALAMUD]
- protocol converter
- A device/program which
translates between different protocols which serve
similar functions (e.g., TCP and TP4). [Source:
RFC1392]
- Protocol Data Unit (PDU)
- "PDU" is
internationalstandardscomitteespeak for packet. See
also: packet. [Source: RFC1392]
- protocol stack
- A layered set of
protocols which work together to provide a set of
network functions. See also: layer, protocol. [Source:
RFC1392]
- proxy
- The mechanism whereby
one system "fronts for" another system in
responding to protocol requests. Proxy systems are
used in network management to avoid having to
implement full protocol stacks in simple devices, such
as modems. [Source: RFC1208]
- proxy ARP
- The technique in which
one machine, usually a router, answers ARP requests
intended for another machine. By "faking"
its identity, the router accepts responsibility for
routing packets to the "real" destination.
Proxy ARP allows a site to use a single IP address
with two physical networks. Subnetting would normally
be a better solution. See also: Address Resolution
Protocol [Source: RFC1208]
- PSN
- See: Packet Switch Node.
- PSS
- the Packet SwitchStream
of British Telecom. PSS includes a UK packet-switching
network service as well as a set of PADs in various
cities. Now part of Global Network Services.
- PTT
- See: Postal, Telegraph
and Telephone
- PTO
- Public
Telecommunications Operator. See also: Postal,
Telegraph and Telephone.
- PTR
- Name record for a host
of given address, for reverse lookup, in Domain Name
Service.
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