WAN Subsystem Configuration and Management Manual

Overview of the WAN Subsystem
WAN Subsystem Configuration and Management Manual—522463-011
2-16
Path Switching
These considerations apply to all the conditions listed in Table 2-8 on page 2-14:
•
When a TCP/IP process has been selected, and subsequently fails, the ConMgr
starts over to select an available path for the IOP.
•
For best performance, configure the IOPs in any system processors as the TCP/IP
processes because:
°
When the selected TCP/IP process is in the same system processor as the
IOP, the QIO sockets interface is used by the IOP to access the TCP/IP
process.
°
When the selected TCP/IP process is not in the same system processor as the
IOP, the message system-based sockets interface is used by the IOP to
access the TCP/IP process.
Table 2-9 describes the Parallel Library TCP/IP and NonStop TCP/IPv6 algorithm the
ConMgr process uses to decide which path an IOP will use to access the SWAN
concentrator. When the conditions described in the first column are met, the ConMgr
process determines which path to use and how the path will be accessed, as described
in the second column.
The choice of preferred path is made on these conditions:
•
If the IOP provides the preferred path, ConMgr considers this. The IOP can provide
the preferred path based on the following logic:
°
An SCF SWITCH PROC command was issued with the new path.
°
This was the last path in which the IOP successfully connected.
•
If the IOP does not provide the preferred path, ConMgr uses the preferred path
configured in the DEVICE.
•
There is no restriction of the CPU of Parallel Library TCP/IP process matching that
of the IOP process.
Note. Parallel Library TCP/IP is not supported on Integrity NonStop NS-series servers.
Parallel Library TCP/IP is supported by the WAN manager process (G06.13 and later RVUs)
on NonStop S-series systems.
Table 2-9. ConMgr Process PATH Switching Algorithm for Parallel Library TCP/IP
and NonStop TCP/IPv6
When these conditions are met... The ConMgr process will...
A. Preferred path is up. Use the ADAPTER preferred path.
B. Preferred path is down.
Alternate path is up.
Use the ADAPTER alternate path after trying
with preferred path.
C. Preferred path is down.
Alternate path is down.
Request the IOP to retry after a delay.