OpenVMS Cluster Systems - OpenVMS Systems - HP

Troubleshooting the NISCA Protocol
F.12 Messages
F.12.2 Distributed Trigger Message
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.
Table F–18 Setting Up the Distributed Trigger Message (Distrib_Trigger)
Field
Byte
Number Value ASCII
Destination 1 01 4C 41 56 63 54 .LAVcT
Source 7 nn nn nn nn nn nn
Protocol 13 60 07 ‘.
Text 15 44 69 73 74 72 69 62 75 74 65 Distribute
25 64 20 74 72 69 67 67 65 72 20 d trigger
35 66 6F 72 20 74 72 6F 75 62 6C for troubl
45 65 73 68 6F 6F 74 69 6E 67 20 eshooting
55 74 68 65 20 4C 6F 63 61 6C 20 the Local
65 41 72 65 61 20 56 4D 53 63 6C Area VMScl
75 75 73 74 65 72 20 50 72 6F 74 uster Prot
85 6F 63 6F 6C 3A 20 4E 49 53 43 ocol: NISC
95 41 A
F.13 Programs That Capture Retransmission Errors
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.13.1 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
Troubleshooting the NISCA Protocol F–33