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Configuring APPC Communication
Defining Modes and Classes of Service
Defining Modes and Classes of Service
A mode specifies a set of characteristics that a local LU (LU type 6.2)
uses to communicate with its partner LU. These characteristics include
information about the way data is transmitted between the two LUs
(such as maximum RU lengths and pacing window sizes), and about
whether the LUs can establish parallel sessions.
In addition, you may need to specify requirements for the communication
path between the LUs, such as enforcing a certain level of network
security, minimizing transmission time, or avoiding the use of expensive
communication links. You can define these requirements using a class of
service (COS), which specifies minimum and maximum acceptable
values for characteristics such as transmission time, transmission cost,
and network security. The COS also specifies weightings associated with
different ranges of these values. This enables the node to calculate the
best route across the network when two or more routes to the same
remote LU are available.
You do not need to associate a COS with the mode; the COS name is
determined dynamically.
SNA defines a number of standard modes and associated COSs that
cover the requirements of most systems; you generally do not need to
define additional modes and COSs. You need to define a mode only if the
required mode is not one of the predefined standard modes, which can be
viewed in the Modes window.
The default mode is used if the mode name in an incoming conversation
is unrecognized. If you do not specify a default mode, the default mode is
the blank mode name.
The standard mode names and their associated COS names are shown in
Table 7-1, "Standard Mode and COS Names." For more information
about the parameters associated with these standard names, refer to the
IBM SNA manuals LU 6.2 Reference—Peer Protocols (for modes) and
APPN Architecture Reference (for COSs).
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Chapter 7
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