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Glossary
GL-3
Cisco 10000 Series Router Software Configuration Guide
OL-2226-23
CoS
Class of service. The three most significant bits (the User Priority bits) of the 2-byte Tag Control
Information field in the IEEE 802.1p portion of a Layer 2 IEEE 802.1Q frame header. QoS uses the
User Priority bits for Layer 2 CoS information. IEEE 802.1p class of service-based packet matching
and marking feature enables the Cisco 10000 series router to interoperate with switches to deliver
end-to-end QoS. The IEEE 802.1p standard allows QoS to classify inbound Ethernet packets based on
the value in the CoS field and to explicitly set the value in the CoS field of outbound packets.
CPE
Customer premises equipment. Refers to equipment located in a user’s premises.
D
DBS
Dynamic Bandwidth Selection. DBS dynamically changes ATM traffic shaping parameters based on a
subscriber’s RADIUS profile. Using this feature, wholesale service providers can sell different levels
of service to retail service providers, based on the bandwidth of the ATM VC connection. The retail
service provider can then offer subscribers the ability to choose services with varying levels of
bandwidth allocation.
DF bit
Don’t Fragment indicator bit. A bit in an encapsulated header that indicates whether a router is allowed
to fragment a packet.
DHCP
Dynamic Host Configuration Protocol. Provides a mechanism for allocating IP addresses dynamically
so that addresses can be re-used when hosts no longer need them.
Dialed Number
Identification
Service
See DNIS.
DNIS
Dialed Number Identification Service. The called party number. Typically, this is a number used by call
centers or a central office where different numbers are each assigned to a specific service.
DNS
Domain Name Server. The part of the distributed database system for resolving a fully qualified domain
name into the four-part IP number used to route communications across the Internet.
downstream rate
The line rate for return messages or data transfers from the network machine to the user’s customer
premises machine.
DSCP
Differentiated Services Code Point
DSL
Digital Subscriber Line.
DSLAM
Digital Subscriber Line Access Multiplexer. Concentrates and multiplexes signals at the telephone
service provider location to the broader wide area network.
Dynamic Bandwidth
Selection
See DBS.