OSI/AS Configuration and Management Manual

Performance Considerations
OSI/AS Configuration and Management Manual—424119-001
6-7
CIRCUITS and X25PORT Attributes
CIRCUITS and X25PORT Attributes
The CIRCUITS attribute specifies the total number of circuits allowed on an X25AM
line. It is a SYSGEN attribute. When setting this value, you should consider the
frequency of connections, the amount of traffic involved on the X25AM line, and the
amount of multiplexing of transport connections that may be taking place. If this value
is set too high, the X25AM lines could get overloaded. If multiplexing is not used very
often, the demand for virtual circuits on your network connections increases. You may
need to increase the number of circuits to prevent delays when all the circuits are in use.
Use the X25PORT attribute to specify the number of X25AM ports and port numbers.
Since this attribute directs connections to specific destination ports, it is useful for
controlling traffic and establishing traffic priorities.
X25PVC Attribute
The X25PVC attribute specifies the logical channel number of the permanent virtual
circuit (PVC) to which the subdevice is to be bound. You can use PVCs to reduce the
amount of overhead associated with X25AM connection establishment. Be careful,
however, not to overuse this attribute, since PVCs used for relatively infrequent traffic
can negatively affect other users when there is contention for the use of virtual circuits.
X25NCONMULTIPLEX Attribute
The X25NCONMULTIPLEX attribute specifies the maximum number of outgoing
transport connections that can be multiplexed on an X.25 network connection. This
attribute is valid only if the MULTIPLEX attribute enables multiplexing. You should set
X25NCONMULTIPLEX to reflect the average amount of traffic expected for a given
number of connections so that the network connection is not overloaded.
Traffic and Protocol Overhead Attributes
Traffic is the amount of activity on a line and protocol overhead is the CPU processing
attributable to the OSI protocol and layer information used in peer-to-peer
communications. These performance factors can be affected by the number and
frequency of connections, the layer to which the application programs interface, the
applications being used, the line speed, the number of lines, and so on.
There are a number of attributes that can affect the amount of traffic on the lines and the
amount of CPU processing for the messages being sent. Most of the following values
can be set in OSI/AS, except where noted, which then passes the values to OSI/TS:
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Checksum Attributes on this page
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CHECKSUM (Layer 4)
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ESISCHECKSUM (Layer 3)
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IPCHECKSUM (Layer 3)
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Message-Size and PDU-Size Attributes on page 6-8
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PACKETSIZE (X25AM SYSGEN)
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TPDUSIZE (Layer 4)