How SNA Server Manages Send and Receive Window Sizes on SDLC (137437)
The information in this article applies to:
- Microsoft Host Integration Server 2000
- Microsoft SNA Server 2.0
- Microsoft SNA Server 2.1
- Microsoft SNA Server 2.11
- Microsoft SNA Server 3.0
- Microsoft SNA Server 4.0
This article was previously published under Q137437 SUMMARY
SNA Server Admin does not support configuration of the SDLC send and
receive window sizes, as the 802.2 connection does with the Unacknowledged
Send Limit and Receive Ack Threshold parameters. This article describes how
SNA Server determines the send and receive window sizes on SDLC
connections.
NOTE: Do not confuse these send and receive window sizes with the send and
receive pacing counters configured on an APPC mode entry, or with the send
and receive window sizes negotiated on a BIND exchange when establishing an
LU-LU session.
MORE INFORMATION
The SDLC send window is defined as the number of frames that SNA Server
sends before setting the P/F bit requesting an acknowledgment. By default,
the SDLC send window is set to 7. You can override the SDLC send window
value in SNA Server by modifying the value in byte 27 of Format 3 XID
frames sent from the remote system. This is the field in which the XID
sender specifies the receive window size. SNA Server then takes that value
in the Format 3 XID exchange and uses it for the SNA Server send window
size.
NOTE: The XID format is documented in the IBM SNA Formats Guide (IBM part
number GA27-3136).
The SNA Server SDLC receive window is the number of frames which the SNA
Server link service can receive before requiring an acknowledgement. For
SNA Server SDLC connections there is no configured receive windows. The
receive window is actually a function of the Credit messages that flow
between the SNA Server SDLC link service and the SNA Server service. These
Credit messages manage the internal flow control between the link service
and the server and determine the receive window size at any given instant.
Modification Type: | Major | Last Reviewed: | 2/12/2004 |
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Keywords: | kbnetwork KB137437 |
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