Glossary
Access Control List (ACL)
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 ) inform ation .
Address Resolution Protocol (ARP)
ARP converts between IP addresses and MAC (i.e., hardware) addresses. ARP is
used to locate the MAC address corresponding to a given IP a ddress. Th is allows
the switch to use IP addresses for routing decisions and the correspondin g MAC
addresses to forward packets from one hop to the next.
Boot Protocol (BOOTP)
BOOTP is
used to provide bootup information for network devices, includin g 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 l evel of ser vice, 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 preve nt
blockage of lower-level queues. Priority may be set a ccording to the po rt de fau lt, th e
packet’s priority bit (in the VLAN tag), TCP/UDP port number, IP Precedence bit, or
DSCP priority bit.
Differentiated Services (DiffServ)
DiffServ
provides quality of service on large networks by employing a well-defined
set of building blocks from which a variety of aggreg ate forw arding beha viors may
be built. Each packet carries information (DS b yte) us ed by eac h hop to gi ve 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 mecha nisms suc h
as traffic meters, shapers/droppers, packet markers at the boundaries of the
network.
Differentiated Services Code Point Service (DSCP)
DSCP uses a six-bit tag to provide for up to 64 different forwarding behavio rs. Ba se d
on network policies, different kinds of traffic can be marked for different kind s of
forwarding. The DSCP bits are mapped to the Class of Service categor ies, and then
into the output queues.
Domain Name Service (DNS)
A system used for translating host names for network nodes into IP addres ses.
Glossary-1