IBM 8285 Nways, Installation And User Manual

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Other Problems
Cannot create a PVC between two switches located in different clusters.
Explanation:
Ÿ This is normal. The ATM Workgroup Switch does not allow the creation of PVCs over network-to-network (NNI)
links.
Ÿ You have created two different PVCs, each one ending at the NNI port.
Note: Make sure that the VPI used by the PVC on the NNI port corresponds to the VPI of the logical link defined
on that port.
ATM server/token-ring client's applications fail: frames are lost. Token-ring clients located behind a
Token-ring/ATM bridge can connect to an ATM server, but the applications/sessions keep failing, while clients
connected directly to ATM have no problems.
Explanation: The frame size on the ATM server is larger than the maximum frame size allowed by the bridge.
Steps to Take:
1. Change the MAX_FRAME_SIZE on the ATM server to the maximum value allowed by the bridge (8281 max frame
size should be 8939 bytes).
Note: You may have to change the MAXDATARCV parameter of the OS/2 token-ring NETBIOS clients to 4168
in the PROTOCOL.INI file.
Workgroup Switch Terminal/TELNET very slow or PING to workgroup switch very slow.
Explanation: The workgroup switch is congested by Signalling Calls.
Steps to Take:
1. If you cannot be in front of the workgroup switch, perform a remote login to it using TELNET. First make sure that
the trace is not active, then disable the ports one at a time until the TELNET session gives a normal response
time. The last port that you disabled should be the one through which the congesting calls were coming.
2. If you can be in front of the workgroup switch, log on to the configuration console. First make sure that the trace is
not active, then look at the Output Activity LEDs and disable the port for which the Output Activity LED is
constantly lit. If the workgroup switch has a 155Mbps ATM I/O Card, disable it.
When there is congestion, it is often due to the failure of a major ATM component (ARP server, LAN emulation server,
switch down, public network down, file server down). You have to determine which of these ATM components failed.
Problems of ATM connections/performance through a WAN (VP tunnel).
Steps to Take:
1. Check the switch configurations at both sides.
2. Check that the VPI corresponds to the VPI provided by your network provider.
3. Check that the bandwidth is lower or equal to the Maximum Peak Rate negotiated with your network provider.
The actual bandwidth used by the media modules is the maximum one (155Mbps for an A2-155 module, 100Mbps
for an A4-FB100 module etc.), even if a lower value is specified with the SET_LOGICAL_LINK command.
4. Check that one NNI port on one side is defined as 'network-side' and that the NNI port on the other side is defined
as 'user-side'.
Chapter 21. Troubleshooting
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