Operation Manual

Glossary
SIP Software Release 6-0-0
J613-M0524-00
105
C
challenge/response An authentication technique whereby a server sends
an unpredictable challenge to the user, who computes a response using
some form of authentication token.
checksum A small, integer value computed from a sequence of octets by
treating them as integers and computing the sum. A checksum is used to
detect transmission errors. The sender computes a checksum and appends it
to a packet when transmitting. The receiver verifies the packet’s contents by
re-computing the checksum and comparing it to the value sent. Many
TCP/IP protocols use a 16-bit checksum computed with one’s compliment
arithmetic.
CIR Committed Information Rate. The rate, measured in bits per second and
averaged over a set time interval, at which a Frame Relay network provider
contracts to transfer information across the network under normal
conditions.
codec Compression/decompression. Pertaining to adapters that compress
and decompress video files. The letters "CODEC" represent "compression /
decompression"; in the past, they represented "coder/decoder."
compression A technique for reducing the apparent amount of traffic on a
data link. The router, for instance, supports Van Jacobson’s header
compression for IP over Point-to-Point Protocol links. This is an option
which reduces the normal 40 byte header to 4---5 bytes.
congestion A condition that occurs when the offered load exceeds the
capacity of a data communication path.
CPE Customer Promise Equipment.
CPU Central Processing Unit. In the router, this is a microprocessor that
controls all operations necessary to the functioning of the router.
D
data link layer The network layer that is responsible for data transfer across
a single physical connection, or series of bridged connections, between two
network entities.
datagram A self-contained, independent entity of data carrying sufficient
information to be routed from the source to the destination computer
without reliance on earlier exchanges between this source and destination
computer and the transporting network. See frame, packet.
dialup A temporary, as opposed to dedicated, connection between machines
established over a standard phone line.
directed broadcast A packet deliver system that delivers a copy of a given
packet to “all hosts” on a specific network. A single copy of a directed