Pilz PSSnet SHL 8T MRP - Manual (Page 333)

Glossary
PSSnet SHL - Command Line Interface
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333
be programmed after its
construction.
CPLD. See “Complex
Programmable Logic Device.” on
page 332.
D
DAPI. See “Device Application
Programming Interface” on
page 333.
Device Application Programming
Interface. DAPI is the software
interface that facilitates
communication of both data and
control information between the
Application Layer and HAPI, with
support from System Support.
DHCP. See “Dynamic Host
Configuration Protocol.” on
page 333.
Differentiated Services. Diffserv is
a protocol for specifying and
controlling network traffic by class so
that certain types of traffic get
precedence - for example, voice
traffic, which requires a relatively
uninterrupted flow of data, might get
precedence over other kinds of
traffic. Differentiated Services is the
most advanced method for
managing traffic in terms of what is
called Class of Service (CoS).
Unlike the earlier mechanisms of
802.1P tagging and Type of Service
(ToS), Differentiated Services
avoids simple priority tagging and
depends on more complex policy or
rule statements to determine how to
forward a given network packet. An
analogy is made to travel services,
in which a person can choose
among different modes of travel -
train, bus, airplane - degree of
comfort, the number of stops on the
route, standby status, the time of
day or period of year for the trip, and
so forth. For a given set of packet
travel rules, a packet is given one of
64 possible forwarding behaviors -
known as per hop behaviors (PHBs).
A six-bit field, known as the
Differentiated Services Code Point
(DSCP), in the Internet Protocol
(Internet Protocol) header specifies
the per hop behavior for a given flow
of packets. Differentiated Services
and the Class of Service approach
provide a way to control traffic that is
both more flexible and more
scalability than the Quality of
Service approach.
Diffserv. See “Differentiated
Services.” on page 333..
Dynamic Host Configuration
Protocol. DHCP is a protocol for
assigning dynamic IP addresses to
devices on a network. With dynamic
addressing, a device can have a
different IP address every time it
connects to the network. In some
systems, the device's IP address
can even change while it is still
connected. DHCP also supports a
mix of static and dynamic IP
addresses. Dynamic addressing
simplifies network administration
because the software tracks IP