Router Getting Started Guide

Glossary
GL-8
Cisco IOS XR Getting Started Guide
OL-10957-02
OSI
Open Systems Interconnection. International standardization program created by ISO and ITU-T to
develop standards for data networking that facilitate multivendor equipment interoperability.
OSPF
Open Shortest Path First. Link-state, hierarchical Interior Gateway Protocol (IGP) routing algorithm
proposed as a successor to Routing Information Protocol (RIP) in the Internet community. OSPF
features include least-cost routing, multipath routing, and load balancing. OSPF was derived from an
early version of the Intermediate System-to-Intermediate System (IS-IS) protocol. See also IGP and
RIP.
P
package
A group of software components installed on the router.
packet
Logical grouping of information that includes a header containing control information and (usually)
user data. Packets most often are used to refer to network layer units of data.
Packet over
SONET/SDH
POS. Packet over SONET/SDH enables core routers to send native IP packets directly over SONET or
SDH frames.
PAP
Password Authentication Protocol. Authentication protocol that allows PPP peers to authenticate one
another. The remote router attempting to connect to the local router is required to send an authentication
request. Unlike Challenge Handshake Authentication Protocol (CHAP), PAP passes the password and
the hostname or username in the clear (unencrypted). PAP does not itself prevent unauthorized access
but merely identifies the remote end. The router or access server then determines whether that user is
allowed access. PAP is supported only on PPP lines. See also PPP.
PCMCIA
Personal Computer Memory Card International Association. Standard for credit card-size memory or
I/O device.
PIE
package installation envelope. An installable software file with the suffix pie. A PIE may be a package
or a Software Maintenance Upgrade (SMU). A PIE is used to deliver Cisco IOS XR software. A PIE
may contain a single component, group of components (called a package), or set of packages. When a
PIE contains more than one component, it is called a “Composite PIE.”
PLIM
Physical layer interface module. Provides the physical interface for a line card. Also handles
media-specific functions, such as framing, clock recovery, channelization, and optical signaling for line
interfaces connecting to a Cisco CRS-1 router.
PM
performance monitoring. Provides a variety of automatic functions to aid in the maintenance and
operation of the network. PM is continuous, in-service monitoring of transmission quality that uses
software-provisionable performance parameters. Performance parameters are measured for all four
layers of the SONET signal: physical, section, line, and STS path.
POS
Packet over SONET/SDH. POS enables core routers to send native IP packets directly over
Synchronous Optical Network (SONET) or Synchronous Digital Hierarchy (SDH) frames.