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Appendix C: Glossary
Boot Protocol (BOOTP)
BOOTP is used to provide bootup information for network devices, including IP address
information, the address of the TFTP server that contains the devices system files, and the name
of the boot file.
Class of Service (CoS)
CoS is supported by prioritizing packets based on the required level of service, and then placing
them in the appropriate output queue. Data is transmitted from the queues using weighted
round-robin service to enforce priority service and prevent blockage of lower-level queues. Priority
may be set according to the port default, the
packet’s priority bit (in the VLAN tag), TCP/UDP port
number, or DSCP priority bit.
Differentiated Services Code Point (DSCP)
DSCP uses a six-bit tag to provide for up to 64 different forwarding behaviors. Based on network
policies, different kinds of traffic can be marked for different kinds of forwarding. The DSCP bits
are mapped to the Class of Service categories, and then into the output queues.
Domain Name Service (DNS)
A system used for translating host names for network nodes into IP addresses.
Dynamic Host Control Protocol (DHCP)
Provides a framework for passing configuration information to hosts on a TCP/IP network. DHCP
is based on the Bootstrap Protocol (BOOTP), adding the capability of automatic allocation of
reusable network addresses and additional configuration options.
IEEE 802.1D
Specifies a general method for the operation of MAC bridges, including the Spanning Tree
Protocol.
IEEE 802.1Q
VLAN Tagging
—Defines Ethernet frame tags which carry VLAN information. It allows switches to
assign end stations to different virtual LANs, and defines a standard way for VLANs to
communicate across switched networks.
IEEE 802.1p
An IEEE standard for providing quality of service (QoS) in Ethernet networks. The standard uses
packet tags that define up to eight traffic classes and allows switches to transmit packets based on
the tagged priority value.
IEEE 802.3ac
Defines frame extensions for VLAN tagging.
IEEE 802.3x
Defines Ethernet frame start/stop requests and timers used for flow control on full-duplex links.
(Now incorporated in IEEE 802.3-2002)
