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P

P2MP LSP — See point-to-multipoint LSP.

package — Collection of files that make up a JUNOS software component.

packet — Fundamental unit of information (message or fragment of a message) carried in a packet-switched network, for example, the Internet. See also PSN.

packet aging — Occurs when packets in the output buffer are overwritten by newly arriving packets. This happens because the available buffer size is greater than the available transmission bandwidth.

packet capture — Packet capture can be either of the following:

Packet sampling method, in which entire IPv4 packets flowing through a router are captured for analysis. Packets are captured in the Routing Engine and stored as libpcap-formatted files on the router. Packet capture files can be opened and analyzed offline with packet analyzers such as tcpdump or Ethereal. See also traffic sampling.
J-Web packet sampling method for quickly analyzing router control traffic destined for or originating from the Routing Engine. You can either decode and view the captured packets in the J-Web interface as they are captured, or save the packets to a file and analyze them offline with packet analyzers such as Ethereal. J-Web packet capture does not capture transient traffic.

packet classification — See classification.

packet data protocol — See PDP.

Packet Forwarding Engine — Portion of the router that processes packets by forwarding them between input and output interfaces.

packet loss priority — See PLP.

packet or cell switching — Transmission of packets from many sources over a switched network.

packet–switched network — See PSN.

PADI — PPPoE Active Discovery Initiation packet. A Point-to-Point Protocol over Ethernet (PPPoE) initiation packet that is broadcast by the client to start the discovery process.

PADO — PPPoE Active Discovery Offer packet. A Point-to-Point Protocol over Ethernet (PPPoE) offer packet that is sent to the client by one or more access concentrators in reply to a PPPoE Active Discovery Initiation (PADI) packet.

PADR — PPPoE Active Discovery Request packet. A Point-to-Point Protocol over Ethernet (PPPoE) packet sent by the client to one selected access concentrator to request a session.

PADS — PPPoE Active Discovery Session Confirmation packet. A Point-to-Point Protocol over Ethernet (PPPoE) packet sent by the selected access concentrator to confirm the session.

PADT — PPPoE Active Discovery Termination packet. A Point-to-Point Protocol over Ethernet (PPPoE) packet sent by either the client or the access concentrator to terminate a session.

partial sequence number PDU — See PSNP.

passive flow monitoring — Technique to intercept and observe specified data network traffic by using a routing platform such as a monitoring station that is not participating in the network.

path attribute — Information about a BGP route, such as the route origin, AS path, and next-hop router.

PathErr message — RSVP message indicating that an error has occurred along an established path LSP. The message is advertised upstream toward the ingress router and does not remove any RSVP soft state from the network.

PathTear message — RSVP message indicating that the established LSP and its associated soft state should be removed by the network. The message is advertised downstream hop by hop toward the egress router.

PBB — Provider backbone bridge. Defined in IEEE 802.1ah, PBBs offer a scalable solution for building large bridged networks by improving MAC address scalability and service instance scalability.

PBBN — Provider backbone bridge network. See PBB.

pcap — Software library for packet capturing. See also libpcap.

PC Card — (Previously known as a PCMCIA Card.) The removable storage media that ships with each router that contains a copy of the JUNOS software. The PC Card is based on standards published by the Personal Computer Memory Card International Association (PCMCIA).

PCI — Peripheral Component Interconnect. Standard, high-speed bus for connecting computer peripherals. Used on the Routing Engine.

PCI Express — Peripheral Component Interconnect Express. Next-generation, higher-bandwidth bus for connecting computer peripherals. A PCI Express bus uses point-to-point bus topology with a shared switch rather than the shared bus topology of a standard PCI bus. The shared switch on a PCI Express bus provides centralized traffic routing and management and can prioritize traffic. On some J-series Services Routers, PCI Express slots are backward compatible with PCI and can accept Physical Interface Modules (PIMs) intended for either PCI Express or PCI slots.

PCMCIA — Personal Computer Memory Card International Association. Industry group that promotes standards for credit card-size memory and I/O devices.

PDH — Plesiochronous Digital Hierarchy. Developed to carry digitized voice more efficiently. Evolved into the North America, European, and Japanese Digital Hierarchies, in which only a discrete set of fixed rates is available, namely, NxDS0 (DS0 is a 64-kbps rate).

PDP — Packet data protocol. Network protocol, such as IP, used by packet data networks connected to a GPRS network.

PDU — Protocol data unit. A packet of data passed across a network. The term refers to a specific layer of the OSI seven-layer model and a specific protocol.

peak information rate — See PIR.

PEC — Policing equivalence classes. In traffic policing, a set of packets that are treated the same way by the packet classifier.

peer — Immediately adjacent router with which a protocol relationship has been established. Also called a neighbor.

peering — Practice of exchanging Internet traffic with directly connected peers according to commercial and contractual agreements.

PEM — Privacy Enhanced Mail. A technique for securely exchanging electronic mail over a public medium. Power Entry Module. Distributes DC power within the router chassis. Supported on M40e, M160, M320, and T-series routing platforms.

penultimate hop popping — See PHP.

penultimate router — Last transit router before the egress router in an MPLS label-switched path.

Perfect Forward Secrecy — See PFS.

Peripheral Component Interconnect — See PCI.

permanent interface — Interface that is always present in the routing platform. See also management Ethernet interface and transient interface.

permanent virtual circuit — See PVC.

persistent change — Commit script-generated configuration change that is copied to the candidate configuration. Persistent changes remain in the candidate configuration unless you explicitly delete them. See also transient change.

Personal Computer Memory Card International Association — See PCMCIA.

PE router — Provider edge router. A router in the service provider’s network that is connected to a customer edge (CE) device and participates in a virtual private network (VPN).

PFC — Protocol Field Compression. Normally, PPP-encapsulated packets are transmitted with a two-byte protocol field. For example, IPv4 packets are transmitted with the protocol field set to 0x0021, and MPLS packets are transmitted with the protocol field set to 0x0281. For all protocols with identifiers from 0x0000 through 0x00ff, PFC enables routers to compress the protocol field to one byte, as defined in RFC 1661, The Point-to-Point Protocol (PPP). PFC allows you to conserve bandwidth by transmitting less data. See also ACFC.

PFS — Perfect Forward Secrecy protocol. A protocol derived from an encryption system that changes encryption keys often and ensures that no two sets of keys have any relation to each other. If one set of keys is compromised, only communications using those keys are at risk. An example of a system that uses PFS is Diffie-Hellman.

PGM — Pragmatic General Multicast. A protocol layer that can be used between the IP layer and the multicast application on sources, receivers, and routers to add reliability, scalability, and efficiency to multicast networks.

PGP — Pretty Good Privacy. A strong cryptographic technique invented by Philip Zimmerman in 1991.

PHP — Penultimate hop popping. A mechanism used in an MPLS network that allows the transit router before the egress router to perform a label pop operation and forward the remaining data (often an IPv4 packet) to the egress router.

PHY — PHY can be either of the following:

Special electronic integrated circuit or functional block of a circuit that performs encoding and decoding between a pure digital domain (on-off) and a modulation in the analog domain. see also LAN PHY and WAN PHY.
Open Systems Interconnection (OSI) physical layer. Layer 1 of the OSI model that defines the physical link between devices.

physical interface — Port on a Physical Interface Card (PIC) or Physical Interface Module (PIM).

Physical Interface Module — See multicast.

Physical Interface Card — See PIC.

PIC — Physical Interface Card. A network interface-specific card that can be installed on an FPC in the router.

PIC I/O Manager ASIC — Juniper Networks ASIC responsible for receiving and transmitting information on the physical media. It performs media-specific tasks within the Packet Forwarding Engine.

PIM — PIM can be either of the following:

Protocol Independent Multicast. A protocol-independent multicast routing protocol. PIM dense mode is a flood-and-prune protocol. PIM sparse mode routes to multicast groups that use join messages to receive traffic. PIM sparse-dense mode allows some multicast groups to be dense groups (flood-and-prune) and some groups to be sparse groups (join and leave).
Physical Interface Module. A network interface card installed in a J-series Services Router to provide physical connections to a LAN or WAN. PIMs can be fixed or removable and interchangeable. The PIM receives incoming packets from the network and transmits outgoing packets to the network. Each PIM is equipped with a dedicated network processor that forwards incoming data packets to and receives outgoing data packets from the Routing Engine. During this process, the PIM performs framing and line-speed signaling for its medium type—for example, E1, serial, Fast Ethernet, or ISDN.

PIR — Peak information rate. The PIR must be equal to or greater than the CIR, and both must be configured to be greater than 0. Packets that exceed the PIR are marked red, which corresponds to high loss priority. See also CIR, trTCM.

PKI — Public key infrastructure. A hierarchy of trust that enables users of a public network to securely and privately exchange data through the use of public and private cryptographic key pairs that are obtained and shared with peers through a trusted authority.

Plesiochronous Digital Hierarchy — See PDH.

PLMN — Public Land Mobile Network. A telecommunications network for mobile stations.

PLP — Packet loss priority. Used to determine the random early detection (RED) drop profile when a packet is queued. You can set it by configuring a classifier or policer. The system supports two PLP designations: low and high.

PLP bit — Packet loss priority bit. Used to identify packets that have experienced congestion or are from a transmission that exceeded a service provider’s customer service license agreement. This bit can be used as part of a router’s congestion control mechanism and can be set by the interface or by a filter.

PLR — Point of local repair. The ingress router of a backup tunnel or a detour LSP.

point of local repair — See PLR.

point-to-multipoint connection — Unidirectional connection in which a single source system transmits data to multiple destination end systems. Point–to–multipoint is one of two fundamental connection types. See also point-to-point connection.

point-to-multipoint LSP — RSVP-signaled LSP with a single source and multiple destinations.

point-to-point connection — Unidirectional or bidirectional connection between two end systems. Point–to–point is one of two fundamental connection types. See also point-to-multipoint connection.

Point-to-Point Protocol — See PPP.

Point-To-Point Protocol process — See pppd.

poison reverse — Method used in distance-vector networks to avoid routing loops. Each router advertises routes back to the neighbor it received them from with an infinity metric assigned.

policer — Filter that limits traffic of a certain class to a specified bandwidth or burst size. Packets exceeding the policer limits are discarded, or assigned to a different forwarding class, a different loss priority, or both.

policing — Method of applying rate limits on bandwidth and burst size for traffic on a particular interface.

policing equivalence classes — See PEC.

policy chain — Application of multiple routing policies in a single location. The policies are evaluated in a predefined manner and are always followed by the default policy for the specific application location.

Point of Presence — See POP.

pop — Removal of the last label, by a router, from a packet as it exits an MPLS domain.

POP — Point of presence. A physical access point to the Internet. The location of the servers, routers, and ATM switches used to provide access to the Internet.

port mirroring — Method in which a copy of an IPv4 packet is sent from the routing platform to an external host address or a packet analyzer for analysis.

PPP — Point-to-Point Protocol. A link-layer protocol that provides multiprotocol encapsulation. PPP is used for link-layer and network-layer configuration. Provides a standard method for transporting multiprotocol datagrams over point-to-point links. Defined in RFC 1661.

pppd — Point-to-Point Protocol daemon that processes packets that use PPP.

PPPoE — Point-to-Point Protocol over Ethernet. Network protocol that encapsulates PPP frames in Ethernet frames and connects multiple hosts over a simple bridging access device to a remote access concentrator.

PPPoE Active Discovery Initiation packet — See PADI.

PPPoE Active Discovery Offer packet — See PADO.

PPPoE Active Discovery Request packet — See PADR.

PPPoE Active Discovery Session Confirmation packet — See PADS.

PPPoE Active Discovery Termination packet — See PADT.

PPPoE over ATM — Point-to-Point Protocol over Ethernet frames in Asynchronous Transfer Mode. Network protocol that encapsulates Point-to-Point Protocol over Ethernet (PPPoE) frames in Asynchronous Transfer Mode (ATM) frames for digital subscriber line (DSL) transmission, and connects multiple hosts over a simple bridging access device to a remote access concentrator.

Pragmatic General Multicast — See PGM.

precedence bits — First three bits in the type-of-service (ToS) byte. On a Juniper Networks router, these bits are used to sort or classify individual packets as they arrive at an interface. The classification determines the queue to which the packet is directed upon transmission.

preference — Desirability of a route to become the active route. A route with a lower preference value is more likely to become the active route. The preference is an arbitrary value from 0 through 255 that the routing protocol process uses to rank routes received from different protocols, interfaces, or remote systems.

preferred address — On an interface, the default local address used for packets sourced by the local router to destinations on the subnet.

prefix-length-range — JUNOS software routing policy match type representing all routes that share the same most–significant bits. The prefix length of the route must also lie between the two supplied lengths in the route filter.

Pretty Good Privacy — See PGP.

primary address — On an interface, the address used by default as the local address for broadcast and multicast packets sourced locally and sent out the interface.

primary contributing route — Contributing route with the numerically smallest prefix and smallest JUNOS software preference value. This route is the default next hop used for a generated route.

primary interface — Router interface that packets go out on when no interface name is specified and when the destination address does not specify a particular outgoing interface.

Privacy Enhanced Mail — See PEM.

promiscuous mode — Used with ATM CCC Cell Relay encapsulation, enables mapping of all incoming cells from an interface port or from a virtual path (VP) to a single label-switched path (LSP) without restricting the VCI number.

Protected System Domain (PSD) — A set of Flexible PIC Controllers (FPCs) on a Juniper Networks router matched with a redundant Routing Engine pair (or single Routing Engine) on the JCS 1200 platform to form a secure, virtual hardware router.

protocol address — Logical Layer 3 address assigned to an interface within the JUNOS software.

protocol data unit — See PDU.

protocol families — Grouping of logical properties within an interface configuration, for example, the inet, inet4, and mpls protocol families.

Protocol Field Compression — See PFC.

Protocol Independent Multicast — See multicast.

protocol preference — 32-bit value assigned to all routes placed into the routing table. The protocol preference is used as a tiebreaker when multiple exact routes are placed into the table by different protocols.

provider backbone bridge — See PBB.

provider backbone bridge network — See PBBN.

provider edge router — See PE router.

provider router — Router in the service provider’s network that is not connected to a customer edge (CE) device.

Prune message — PIM message sent upstream to a multicast source or the rendezvous point (RP) of the domain. The message requests that multicast traffic stop being transmitted to the router originating the message.

PSN — See Protected System Domain.

PSN — Packet–switched network. Network in which messages or fragments of messages (packets) are sent to their destination through the most expedient route, as determined by a routing algorithm. Packet switching optimizes bandwidth in a network and minimizes latency.

PSNP — Partial sequence number PDU. A packet that contains only a partial list of the LSPs in the IS-IS link-state database.

public key infrastructure — See PKI.

Public Land Mobile Network — See PLMN.

push — Addition of a label or stack of labels, by a router, to a packet as it enters an MPLS domain.

PVC — Permanent virtual circuit. A software-defined logical connection in a network. See also SVC.

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