Owner's Manual

Appendix E. Glossary | 927
NETGEAR 8800 User Manual
DF Don’t fragment bit. This is the don’t fragment bit carried in the flags field of the IP
header that indicates that the packet should not be fragmented. The remote host
will return ICMP notifications if the packet had to be split anyway, and these are
used in MTU discovery.
DHCP Dynamic Host Configuration Protocol. DHCP allows network administrators to
centrally manage and automate the assignment of IP addresses on the
corporate network. DHCP sends a new IP address when a computer is plugged
into a different place in the network. The protocol supports static or dynamic IP
addresses and can dynamically reconfigure networks in which there are more
computers than there are available IP addresses.
DiffServ Differentiated Services. Defined in RFC 2474 and 2475, DiffServ is an
architecture for implementing scalable service differentiation in the Internet.
Each IP header has a DiffServ (DS) field, formerly known as the Type of Service
(TOS) field. The value in this field defines the QoS priority the packet will have
throughout the network by dictating the forwarding treatment given to the packet
at each node. DiffServ is a flexible architecture that allows for either end-to-end
QoS or intradomain QoS by implementing complex classification and mapping
functions at the network boundary or access points. In the NETGEAR
implementation, you can configure the desired QoS by replacing or mapping the
values in the DS field to egress queues that are assigned varying priorities and
bandwidths.
DNS Domain Name Server. This system is used to translate domain names to IP
addresses. Although the Internet is based on IP addresses, names are easier to
remember and work with. All these names must be translated back to the actual
IP address and the DNS servers do so.
domain In CFM, a maintenance domain is the network, or part of the network, that
belongs to a single administration for which connectivity faults are managed.
DoS attack Denial of service attacks occur when a critical network or computing resource is
overwhelmed so that legitimate requests for service cannot succeed. In its
simplest form, a DoS attack is indistinguishable from normal heavy traffic.
XCM8800 software has configurable parameters that allow you to defeat DoS
attacks.
DR Designated router. In OSPF, the DR generates an LSA for the multiaccess
network and has other special responsibilities in the running of the protocol. The
DR is elected by the OSPF protocol.
dropped packets These are packets that the switch received but does not transmit.
E
EBGP Exterior Border Gateway Protocol. EBGP is a protocol in the IP suite designed to
exchange network reachability information with BGP systems in other ASs.
EBGP works between different ASs.
D (Continued)