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D. GLOSSARY
ACL Access Control List. ACLs can limit network traffic and restrict access
to certain users or devices by checking each packet for certain IP or
MAC (i.e., Layer 2) information.
ARP Address Resolution Protocol converts between IP addresses and
MAC (hardware) addresses. ARP is used to locate the MAC address
corresponding to a given IP address. This allows the switch to use IP
addresses for routing decisions and the corresponding MAC
addresses to forward packets from one hop to the next.
COS Class of Service 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, IP Precedence bit, or DSCP priority bit.
DHCP Dynamic Host Control Protocol. 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.
DHCP OPTION 82 A relay option for sending information about the requesting client (or
an intermediate relay agent) in the DHCP request packets forwarded
by the switch and in reply packets sent back from the DHCP server.
This information can be used by DHCP servers to assign fixed IP
addresses, or set other services or policies for clients.
DHCP SNOOPING A technique used to enhance network security by snooping on DHCP
server messages to track the physical location of hosts, ensure that
hosts only use the IP addresses assigned to them, and ensure that
only authorized DHCP servers are accessible.
DIFFSERV Differentiated Services provides quality of service on large networks
by employing a well-defined set of building blocks from which a
variety of aggregate forwarding behaviors may be built. Each packet
carries information (DS byte) used by each hop to give it a particular
forwarding treatment, or per-hop behavior, at each network node.
DiffServ allocates different levels of service to users on the network
with mechanisms such as traffic meters, shapers/droppers, packet
markers at the boundaries of the network.
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