P

Packet
A packet is a unit of information that can be transmitted over a network. A packet is generated at the Network Layer of the OSI model protocol stack. Information contained in the header of a packet is sufficient to transmit the packet from the sending node to the receiving node, even when the packet must traverse intermediate nodes. A packet can be an entire message, or a segment of a much larger message generated at the Application Layer.

Packet-Switched Networks
Packet switching is what occurs as a packet is traveling from the source node to the destination node when there are intermediate nodes between source and destination. When the packet travels through the intermediate node (a packet switch), it must "switch" the packet to the next node in sequence.

Peer
In networking terms, a peer is a device or process in one computer that has the same intelligence and functionality as a device or process in another computer.

Peripherals
Peripherals are parts of a computer that are not on the primary board (mother board) of a computer system. Peripherals include hard drives, floppy drives, and modems.

Peripheral Component Interconnect (PCI)
PCI is a newer 32-bit and 64-bit local bus technology for PCs. See "bus." (Servers use 64-bit PCI, and PCs use 32-bit.)

Permanent Virtual Circuit (PVC)
PVC is one of two types of virtual circuits, the other is switched virtual circuits (SVCs). A PVC behaves like a dedicated line between source and destination endpoints. When activated, a PVC will always establish a path between these two endpoints. PVC is usually used in the context of a packet switching (or cell switching) network.

Personal Computer Memory Card International Association (PCMCIA)
The PCMCIA slot in a laptop was designed for PC memory expansion. NICs and modems can attach to a laptop through the PCMCIA slot.

Personal Digital Assistant (PDA)
PDA devices are very small and provide a subset of the operations of a typical computer (PC). They are used for scheduling, electronic notepads, and small database applications.

Port
There are two primary ways the term port is used in networking. The first refers to a physical port in a device, such as an input/output (I/O) port on a switch where cables are plugged into the device. Ports also relate to processes running on nodes connected to a network. If a machine is running multiple processes, each process must be uniquely identified to communicate. "Well known" ports in TCP architecture, such as FTP and HTTP are examples of this type of port.

Private Facilities
In the context of WANs, private facilities are those owned and maintained by an organization.

Protocol
A protocol in networking is the agreed upon method of communication between computer processes attached to a network.

Public Facilities
In the context of WANs, public facilities are those leased through a carrier, such as a telephone company or long distance service provider.

Q

Q Bit
The Q bit is a bit in an X.25 packet that indicates whether or not a packet contains control information or user data.