HP OpenVMS Systems Documentation

The following sections describe the types of data you should isolate when you use a LAN analysis tool to capture OpenVMS Cluster data between nodes and LAN adapters.

F.10.1 All OpenVMS Cluster Traffic

To isolate all OpenVMS Cluster traffic on a specific LAN segment, capture all the packets whose LAN header contains the protocol type 60--07.

Reference: See also Section F.8.2 for a description of the LAN headers.

F.10.2 Specific OpenVMS Cluster Traffic

To isolate OpenVMS Cluster traffic for a specific cluster on a specific LAN segment, capture packets in which:

• The LAN header contains the protocol type 60--07.
• The DX header contains the cluster group number specific to that OpenVMS Cluster.

Reference: See Sections F.8.2 and F.8.4 for descriptions of the LAN and DX headers.

F.10.3 Virtual Circuit (Node-to-Node) Traffic

To isolate virtual circuit traffic between a specific pair of nodes, capture packets in which the LAN header contains:

• The protocol type 60--07
• The destination SCS address
• The source SCS address

You can further isolate virtual circuit traffic between a specific pair of nodes to a specific LAN segment by capturing the following additional information from the DX header:

• The cluster group code specific to that OpenVMS Cluster
• The destination SCS transport address
• The source SCS transport address

Reference: See Sections F.8.2 and F.8.4 for LAN and DX header information.

F.10.4 Channel (LAN Adapter--to--LAN Adapter) Traffic

To isolate channel information, capture all packet information on every channel between LAN adapters. The DX header contains information useful for diagnosing heavy communication traffic between a pair of LAN adapters. Capture packets in which the LAN header contains:

• The destination LAN adapter address
• The source LAN adapter address

Because nodes can use multiple LAN adapters, specifying the source and destination LAN addresses may not capture all of the traffic for the node. Therefore, you must specify a channel as the source LAN address and the destination LAN address in order to isolate traffic on a specific channel.

Reference: See Section F.8.2 for information about the LAN header.

F.10.5 Channel Control Traffic

To isolate channel control traffic, capture packets in which:

• The LAN header contains the protocol type 60--07.
• The CC header datagram flags byte (the TR/CC flag, bit <7>) is set to 1.

Reference: See Sections F.8.2 and F.8.5 for a description of the LAN and CC headers.

F.10.6 Transport Data

To isolate transport data, capture packets in which:

• The LAN header contains the protocol type 60--07.
• The TR header datagram flags byte (the TR/CC flag, bit <7>) is set to 0.

Reference: See Sections F.8.2 and F.8.6 for a description of the LAN and TR headers.

F.11 Setting Up an HP 4972A LAN Protocol Analyzer

The HP 4972A LAN Protocol Analyzer, available from the Hewlett-Packard Company, is highlighted here because it meets all of the requirements listed in Section F.9. However, the HP 4972A LAN Protocol Analyzer is merely representative of the type of product useful for LAN network troubleshooting.

Note: Use of this particular product as an example here should not be construed as a specific purchase requirement or endorsement.

This section provides some examples of how to set up the HP 4972A LAN Protocol Analyzer to troubleshoot the local area OpenVMS Cluster system protocol for channel formation and retransmission problems.

F.11.1 Analyzing Channel Formation Problems

If you have a LAN protocol analyzer, you can set up filters to capture data related to the channel control header (described in Section F.8.5).

You can trigger the LAN analyzer by using the following datagram fields:

• Protocol type set to 60--07 hexadecimal
• Correct cluster group number
• TR/CC flag set to 1

Then look for the HELLO, CCSTART, VERF, and VACK datagrams in the captured data. The CCSTART, VERF, VACK, and SOLICIT_SRV datagrams should have the AUTHORIZE bit (bit <4>) set in the CC flags byte. Additionally, these messages should contain the scrambled cluster password (nonzero authorization field). You can find the scrambled cluster password and the cluster group number in the first four longwords of SYS$SYSTEM:CLUSTER_AUTHORIZE.DAT file.

Reference: See Sections F.10.3 through F.10.5 for additional data isolation techniques.

F.11.2 Analyzing Retransmission Problems

Using a LAN analyzer, you can trace datagrams as they travel across an OpenVMS Cluster system, as described in Table F-12.

Reference: See Appendix G for more information about congestion control and PEDRIVER message retransmission.

F.12 Filters

This section describes:

• How to use the HP 4972A LAN Protocol Analyzer filters to isolate packets that have been retransmitted or that are specific to a particular OpenVMS Cluster.
• How to enable the distributed enable and trigger functions.

Use the values shown in Table F-13 to set up a filter, named LAVc_TR_ReXMT, for all of the LAN retransmissions for a specific cluster. Fill in the value for the local area OpenVMS Cluster group code (nn--nn) to isolate a specific OpenVMS Cluster on the LAN.

Use the values shown in Table F-14 to filter all of the LAN packets for a specific cluster. Fill in the value for OpenVMS Cluster group code (nn--nn) to isolate a specific OpenVMS Cluster on the LAN. The filter is named LAVc_all.

Use the values shown in Table F-15 to set up a filter, named Distrib_Enable, for the distributed enable packet received event. Use this filter to troubleshoot multiple LAN segments.

Use the values shown in Table F-16 to set up a filter, named Distrib_Trigger, for the distributed trigger packet received event. Use this filter to troubleshoot multiple LAN segments.

This section describes how to set up the distributed enable and distributed trigger messages.

F.13.1 Distributed Enable Message

Table F-17 shows how to define the distributed enable message (Distrib_Enable) by creating a new message. You must replace the source address (nn nn nn nn nn nn) with the LAN address of the LAN analyzer.

Table F-18 shows how to define the distributed trigger message (Distrib_Trigger) by creating a new message. You must replace the source address (nn nn nn nn nn nn) with the LAN address of the LAN analyzer.

You can program the HP 4972 LAN Protocol Analyzer, as shown in the following source code, to capture retransmission errors. The starter program initiates the capture across all of the LAN analyzers. Only one LAN analyzer should run a copy of the starter program. Other LAN analyzers should run either the partner program or the scribe program. The partner program is used when the initial location of the error is unknown and when all analyzers should cooperate in the detection of the error. Use the scribe program to trigger on a specific LAN segment as well as to capture data from other LAN segments.

F.14.1 Starter Program

The starter program initially sends the distributed enable signal to the other LAN analyzers. Next, this program captures all of the LAN traffic, and terminates as a result of either a retransmitted packet detected by this LAN analyzer or after receiving the distributed trigger sent from another LAN analyzer running the partner program.

The starter program shown in the following example is used to initiate data capture on multiple LAN segments using multiple LAN analyzers. The goal is to capture the data during the same time interval on all of the LAN segments so that the reason for the retransmission can be located.

Store: frames matching LAVc_all 
 or Distrib_Enable 
 or Distrib_Trigger 
       ending with LAVc_TR_ReXMT 
        or Distrib_Trigger 
 
Log file: not used 
 
Block 1:   Enable_the_other_analyzers 
     Send message Distrib_Enable 
       and then 
     Go to block 2 
 
Block 2:   Wait_for_the_event 
     When frame matches LAVc_TR_ReXMT then go to block 3 
 
Block 3:   Send the distributed trigger 
     Mark frame 
       and then 
     Send message Distrib_Trigger