Glossary
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Cisco Router and Security Device Manager Version 2.2 User’s Guide
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G
global IKE policy An IKE policy that is global to a device, rather than affecting only a single
interface on that device.
GRE generic routing encapsulation. Tunneling protocol developed by Cisco that can
encapsulate a wide variety of protocol packet types inside IP tunnels, creating a
virtual point-to-point link to Cisco routers at remote points over an IP
internetwork. By connecting multiprotocol subnetworks in a single-protocol
backbone environment, IP tunneling using GRE allows network expansion
across a single-protocol backbone environment.
GRE over IPSec This technology uses IPSec to encrypt GRE packets.
G.SHDSL Also known as G.991.2, G.SHDSL is an international standard for symmetric
DSL developed by the International Telecommunications Union. G.SHDSL
provides for sending and receiving high-speed symmetrical data streams over a
single pair of copper wires at rates between 192 kbps and 2.31 Mbps.
H
H.323 A standard that enables video conferencing over local-area n etworks (LANs)
and other packet-switched networks, as well as video over the In ternet.
hash One-way process that converts input of any size into checksum output of a fixed
size, called a message digest, or just a digest. This process is not reversible, and
it is not feasible to create or modify data to result in a specific digest.
hash algorithm A hash algorithm is used to gene rate a hash value, also known as a message
digest, ensures that message contents are not changed during transmission. The
two most widely used types of hash algorithms are Secure Hash Algo rithm
(SHA) and MD5)
HDLC High-Level Data Link Control. Bit-oriented synchronous data link layer
protocol developed by the International Standards Organization (ISO). HDLC
specifies a data encapsulation method on synchronous serial links usin g frame
characters and checksums.