OSI/TS Configuration and Management Manual

Configuring the OSI/TS Subsystem
OSI/TS Configuration and Management Manual—424831-001
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Traffic and Protocol Overhead Attributes
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. To reduce TSP
overhead, a ten-to-one multiplexing ratio is normally effective.
Traffic and Protocol Overhead Attributes
Traffic is the amount of activity (data being transmitted) 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, as follows:
•
Checksum attributes
•
CHECKSUM (Layer 4)
•
ESISCHECKSUM (Layer 3)
•
IPCHECKSUM (Layer 3)
•
Message-size and PDU-size attributes
•
PACKETSIZE (X25AM SYSGEN)
•
TPDUSIZE (Layer 4)
•
Window-size attributes
•
L4WINDOW (Layer 4)
•
L3WINDOW (Layer 3, X25AM)
•
L2WINDOW (Layer 2, X25AM)
These attributes are detailed in the following subsections.
Checksum Attributes
OSI/TS provides a checksum capability in the transport class 4 protocol (CHECKSUM),
the ES-IS routing exchange protocol (ESISCHECKSUM), and the IP (IPCHECKSUM).
You can turn the checksum capability on or off using SCF commands.
Checksums add a small amount of overhead for each PDU and incur some processing
overhead in the calculation of the checksum at both ends of the connection. In most
lightly loaded systems, this overhead probably is not noticeable. However, in heavily
loaded systems with many large PDUs, checksums are a potential factor in high CPU
utilization.