P - Q

P–Q

packet

An Open Systems Interconnection (OSI) network layer transmission unit that consists of binary information representing both data and a header containing an identification number, source and destination addresses, and error-control data.

packet filtering

Prevents certain types of network packets from either being sent or received. This can be employed for security reasons (to prevent access from unauthorized users) or to improve performance by disallowing unnecessary packets from going over a slow connection.

See also packet.

PDC emulator master

A domain controller that holds the PDC emulator operations master role in Active Directory. The PDC emulator services network clients that do not have Active Directory client software installed, and it replicates directory changes to any Windows NT backup domain controllers (BDCs) in the domain.

The PDC emulator handles password authentication requests involving passwords that have recently changed and not yet been replicated throughout the domain. At any time, the PDC emulator master role can be assigned to only one domain controller in each domain.

See also Active Directory.

See also domain controller.

See also operations master.

perimeter network

An Internet Protocol (IP) network segment that contains resources, such as Web servers and virtual private network (VPN) servers, that are available to Internet users. Also known as screened subnet or demilitarized zone (DMZ).

See also Internet Authentication Service (IAS).

See also Internet Protocol (IP).

See also virtual private network (VPN).

point of presence (POP)

The local access point for a network provider. Each POP provides a telephone number that allows users to make a local call for access to online services.

Point-to-Point Protocol (PPP)

An industry standard suite of protocols for the use of point-to-point links to transport multiprotocol datagrams. PPP is documented in RFC 1661.

See also Transmission Control Protocol/Internet Protocol (TCP/IP).

Point-to-Point Tunneling Protocol (PPTP)

Networking technology that supports multiprotocol virtual private networks (VPNs), enabling remote users to access corporate networks securely across the Internet or other networks by dialing into an Internet service provider (ISP) or by connecting directly to the Internet. PPTP tunnels, or encapsulates, Internet Protocol (IP) or Internetwork Packet Exchange (IPX) traffic inside IP packets. This means that users can remotely run applications that depend on particular network protocols. PPTP is described in RFC 2637.

See also Internet Protocol (IP).

See also Internetwork Packet Exchange (IPX).

See also packet.

See also tunnel.

See also virtual private network (VPN).

poison reverse

A process that, used with split horizon, improves Routing Information Protocol (RIP) convergence over simple split horizon by advertising all network IDs. However, the network IDs learned in a given direction are advertised with a hop count of 16, indicating that the network is unavailable.

See also Routing Information Protocol (RIP).

preshared key

An Internet Protocol security (IPSec) technology in which a shared, secret key is used for authentication in IPSec policy.

See also authentication.

See also Internet Protocol security (IPSec).

print spooler

Software that accepts a document sent to a printer and then stores it on disk or in memory until the printer is ready for it.

public key infrastructure (PKI)

The laws, policies, standards, and software that regulate or manipulate certificates and public and private keys. In practice, it is a system of digital certificates, certification authorities, and other registration authorities that verify and authenticate the validity of each party involved in an electronic transaction. Standards for PKI are still evolving, even though they are being widely implemented as a necessary element of electronic commerce.

See also certificate.

See also certification authority (CA).

pull partner

A WINS component that requests replication of updated WINS database entries from its push partner.

See also push partner.

See also Windows Internet Name Service (WINS).

push partner

A WINS component that notifies its pull partner when updated WINS database entries are available for replication.

See also pull partner.

See also Windows Internet Name Service (WINS).