Router Getting Started Guide

Glossary
GL-4
Cisco IOS XR Getting Started Guide
OL-10957-02
forwarding
Process of sending a frame toward its ultimate destination by way of an internetworking device.
FRR
fast reroute. Automatically reroutes traffic on a label switch path (LSP) if a node or link in an LSP fails.
FRR reduces the loss of packets traveling over an LSP.
FTP
File Transfer Protocol. Application protocol, part of the TCP/IP protocol stack, used for transferring
files between network nodes. FTP is defined in RFC 959.
G
GE
Gigabit Ethernet. Standard for a high-speed Ethernet, approved by the IEEE 802.3z standards committee
in 1996.
Gigabit Ethernet
Standard for a high-speed Ethernet, approved by the IEEE 802.3z standards committee in 1996.
GUI
graphical user interface. A user environment that uses pictorial and textual representations of the input
and output of applications and the hierarchical or other data structure in which information is stored.
Such conventions as buttons, icons, and windows are typical, and many actions are performed using a
pointing device (such as a mouse). Microsoft Windows and the Apple Macintosh are prominent
examples of platforms using a GUI. See also CLI.
H
HA
High availability is defined as the continuous operation of systems. For a system to be available, all
components, including application and database servers, storage devices, and the end-to-end network,
need to provide continuous service.
HDLC
high-level data link control. ISO communications protocol used in X.25 packet-switching networks.
HDLC provides error correction at the data link layer and contains the following subsets: LAPB and
SDLC.
hexadecimal
A number system having 16 as its base. This number representation uses the digits 0–9, with their usual
meaning, plus the letters A–F (or a–f) to represent hexadecimal digits with values of (decimal) 10 to
15. The far right digit counts ones, the next counts multiples of 16, then 16^2 = 256, and so on.
Hexadecimal is more succinct than binary for representing bit masks, machines addresses, and other
low-level constants but it is still reasonably easy to split a hex number into different bit positions. For
example, the top 16 bits of a 32-bit word are the first four hex digits.
hop
Passage of a data packet between two network nodes (for example, between two routers). See also hop
count.
hop count
Routing metric used to measure the distance between a source and a destination.
HTTP
Hypertext Transfer Protocol. Used by web browsers and web servers to transfer files, such as text and
graphic files. HTTP is the set of rules for exchanging files (text, graphic images, sound, video, and other
multimedia files) on the World Wide Web. Relative to the TCP/IP suite of protocols (which are the basis
for information exchange on the Internet), HTTP is an application protocol.