The information in this article applies to:
SYMPTOMSA computer running SNA Server on an Ethernet network that has an 802.2 DLC connection configured to communicate with a remote device (AS/400, 3174, or 3745, for example) on a Token Ring may exhibit the following symptoms:
CAUSEThis problem has been observed when SNA Server is connected to the remote system across a Cisco router which is configured for LLC Local Acknowledgment. The Cisco router fails to forward the SABME command sent by the remote device (for example, IBM 3745) to SNA Server, causing the connection to fail to activate. The result is that the SNA Server restarts the XID process by sending a pre-negotiation XID to the remote device. This process continues indefinitely. RESOLUTIONTo work around this problem:
MORE INFORMATION
In an LLC (802.2 DLC) session, when Device A sends a frame to Device B,
Device A expects Device B to respond before the T1 timer expires. In a WAN
environment that contains slow links, it is possible to see the T1 timer
expire before a response was received causing retransmissions. Cisco's
Local Acknowledgment feature attempts to solve this problem by splitting
the LLC session between the two devices. If Local Acknowledgment is
configured, the LLC session between two two devices is not end-to-end but
instead terminates at the local router(s). The LLC session with Device A
ends at the Router as does the LLC session with Device B. The router then
responds to the frames sent from Devices A and B instead of having the
actual device send the response. When this feature is enabled, all LLC
supervisory frames (RR, RNR, REJ) from one of the devices go no farther
than the router since the router will respond to them on behalf of the
other device.
REFERENCESFor additional information on SNA Server and 802.2 Connection Timers, please see the following article in the Microsoft Knowledge Base: Q129786 SNA Server and 802.2 Connection Timers (t1, t2, ti) Additional query words: prodsna spoofing llc2
Keywords : sna3rdparty snaadmin snadlc snasetup |
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