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+---------------+
! d i g i t a l ! I N T E R O F F I C E M E M O R A N D U M
+---------------+
To: DECnet users
Date: February 5, 1980
From: Peter Mierswa
Dept: NCSS
Loc: MR1-2/H22
Ext: 5254
Subj: DECnet V2 Loopback Functions
I have just reviewed all the procedures available with
DECnet-20 version 2 for performing loopback tests. Some of the
procedures are required for FA&T, diagnostic packs, and category A
installation. Others are not required, but are available. I found
that very few people had a clear understanding of which tests were
available and how to use them. I have prepared this memo to clarify
these procedures.
Trouble shooting a DECnet point to point communications link
must be done in a carefully planned manner. Consider the components
which can be failing: local node software, local node
communications micro processor, local node communications line
interface, local node modem or null modem, private line or common
carrier services, remote node modem, line driver, microprocessor and
software, and another entire node if you are using a 2040/50/60
(front end DN20). The problem can usually be isolated quickly to a
single component by sending data messages from the local node
through more and more of the network components until an error
occurs.
This can be done as follows. First send a number of data
messages into the local network software and back again to your
program. These "looped" messages are compared to the transmitted
messages to check for errors. Then loop the data messages through
the local software and the local communications line controller and
check it in the same way. Continue this process adding the next
component at each step until the test fails. This will isolate the
failing component.
A subset of the features available with DECnet phase III
Network Management has been implemented in DECnet V2 in order to
perform this line testing and fault isolation. Since the commands
and operational procedures differ between the 2020 and 2040/50/60
they will be treated separately. Although the DECnet-20 V2 loopback
facilities are a subset of the phase III facilities, the commands
and implementation differ.
To: DECnet users Page 2
DECSYSTEM 2020 LOOPBACK TESTS
!-------------------------------------!
! !
! MODEM !
! !
!-------------------------------------!
!
!
!
!-------------------------------------!
! ! !
! DUP ! DUP !
! ! !
!-------------------------------------!
! !
! KMC !
! !
!-------------------------------------!
! !
! DDCMP / KMC driver !
! !
!-------------------------------------!
! !
! --------NSP-------- !
! ! ! !
!---------!-----------------!---------!
! \/ /\ !
! Application level testing program !
! !
!-------------------------------------!
LOOPBACK THROUGH LOCAL NETWORK SOFTWARE - 2020
LOOPBACK THROUGH LOCAL NETWORK SOFTWARE. This is done by using
any application level program using task to task to transfer
messages to another task on the same node. This tests the network
software on the local node. This test can be performed during
normal network operation.
Example 1. Use of the EXEC to copy a file from one job to
another. Log in two jobs and type two copy commands to copy a disk
file from one directory to another, then compare the files:
@PTYCON
PTYCON> DEFINE 0 FROM
PTYCON> DEFINE 1 TO
PTYCON> ALL-LOGIN MIERSWA XXX
PTYCON>
**** FROM(0) 14:38:32 ****
2102 Development System, TOPS-20 Monitor 4(3100)
@LOGIN MIERSWA
**** TO(1) 14:38:32 ****
2102 Development System, TOPS-20 Monitor 4(3100)
@LOGIN MIERSWA
To: DECnet users Page 3
DECSYSTEM 2020 LOOPBACK TESTS
PTYCON>
**** FROM(0) 14:38:33 ****
PTYCON>
**** FROM(0) 14:38:36 ****
Job 64 on TTY224 11-Sep-79 14:38:36
**** TO(1) 14:38:36 ****
Job 16 on TTY226 11-Sep-79 14:38:36
PTYCON>
**** FROM(0) 14:38:39 ****
@
**** TO(1) 14:38:39 ****
@
PTYCON> TO-COPY SRV:.TO NEW.DAT
PTYCON>
**** TO(1) 14:39:52 ****
COPY SRV:.TO NEW.DAT
SRV:.TO => NEW.DAT.1
PTYCON> FROM-COPY TEST.DAT DCN:-TASK-TO.FROM
PTYCON>
**** FROM(0) 14:41:17 ****
COPY TEST.DAT DCN:-TASK-TO.FROM
TEST.DAT.1 => DCN:-TASK-TO.FROM
PTYCON>
**** FROM(0) 14:41:18 ****
[OK]
PTYCON>
**** FROM(0) 14:41:19 ****
@
PTYCON>
**** TO(1) 14:41:20 ****
[OK]
@
PTYCON>KILL ALL
PTYCON>EXIT
@FILCOM
*TTY:=TEST.DAT,NEW.DAT
No differences encountered
*C
@
To: DECnet users Page 4
DECSYSTEM 2020 LOOPBACK TESTS
Example 2. Use of the DYNETS utility to transfer a file to
itself through the local network software. The DYNETS utility is
part of the UETP test package for DECnet V2.
@PTYCON
PTYCON> DEFINE 0 TO
PTYCON> DEFINE 1 FROM
PTYCON> ALL-LOGIN MIERSWA XXX
PTYCON>
**** TO(0) 16:46:06 ****
4097 Load-Test System, TOPS-20 Monitor 4(3056)
@LOGIN MIERSWA
**** FROM(1) 16:46:06 ****
4097 Load-Test System, TOPS-20 Monitor 4(3056)
@LOGIN MIERSWA
PTYCON>
**** TO(0) 16:46:08 ****
PTYCON>
**** TO(0) 16:46:10 ****
Job 35 on TTY227 11-Sep-79 16:46:10
PTYCON>
**** FROM(1) 16:46:11 ****
Job 29 on TTY230 11-Sep-79 16:46:11
PTYCON>
**** TO(0) 16:46:16 ****
@
**** FROM(1) 16:46:16 ****
@
PTYCON>ALL-DYNETS
PTYCON>
**** TO(0) 16:46:33 ****
DYNETS
**** FROM(1) 16:46:33 ****
DYNETS
PTYCON>
**** TO(0) 16:46:34 ****
11-Sep-79 16:46:34 * [DYNETS STARTING]
DYNETS>
**** FROM(1) 16:46:35 ****
11-Sep-79 16:46:34 * [DYNETS STARTING]
DYNETS>
PTYCON> TO-DECLARE SRV:.TO /BYTE:7 /RECL:132
PTYCON>
**** TO(0) 16:47:10 ****
DECLARE SRV:.TO /BYTE:7 /RECL:132
PTYCON>
**** TO(0) 16:47:11 ****
11-Sep-79 16:47:11 * [DYNETS OK]
DYNETS>
PTYCON> FROM-ESTABLISH DCN:-TASK-TO.FROM /BYTE:7 /RECL:132
PTYCON>
**** FROM(1) 16:47:32 ****
ESTABLISH DCN:-TASK-TO.FROM /BYTE:7 /RECL:132
PTYCON>
To: DECnet users Page 5
DECSYSTEM 2020 LOOPBACK TESTS
**** TO(0) 16:47:36 ****
% DYNETS: ACCEPTING CONNECTION FROM - 4097-TASK-FROM.TO
% DYNETS: USER-ID(SQM) PASSWORD(JPCAXS) ACCOUNT(07995)
**** FROM(1) 16:47:42 ****
% DYNETS: SEGMENT SIZE - 256
% DYNETS: OPT DATA - 101065061062060060
11-Sep-79 16:47:40 * [DYNETS OK]
DYNETS>
PTYCON> FROM-RECEIVE DCN:-TASK-TO.FROM
PTYCON>
**** FROM(1) 16:48:05 ****
RECEIVE DCN:-TASK-TO.FROM
11-Sep-79 16:48:06 * [DYNETS OK]
DYNETS>
PTYCON> FROM-SEND DCN:-TASK-TO.FROM TEST.DAT
PTYCON>
**** FROM(1) 16:50:31 ****
SEND DCN:-TASK-TO.FROM TEST.DAT
PTYCON>
**** TO(0) 16:50:39 ****
% DYNETS: SERVER LINK DISCONNECTED, REOPENING
**** FROM(1) 16:50:40 ****
11-Sep-79 16:50:39 * [DYNETS OK]
DYNETS>
PTYCON> ALL-EXIT
PTYCON>
**** TO(0) 16:50:52 ****
EXIT
11-Sep-79 16:50:52 * [DYNETS OK]
11-Sep-79 16:50:52 * [DYNETS TERMINATING] (ELAPSED TIME: 00:04:18)
@
**** FROM(1) 16:50:57 ****
EXIT
11-Sep-79 16:50:52 * [DYNETS OK]
11-Sep-79 16:50:52 * [DYNETS TERMINATING] (ELAPSED TIME: 00:04:17)
@
PTYCON>KILL ALL
PTYCON>EXIT
@RENAME (EXISTING FILE) -TASK-TO.LOG.* (TO BE) TEST.NEW
-TASK-TO.LOG.1 => TEST.NEW.1 [OK]
@FILCOM
*TTY:=TEST.DAT,TEST.NEW
No differences encountered
*C
@
To: DECnet users Page 6
DECSYSTEM 2020 LOOPBACK TESTS
Example 3. Local file transfer. Use the Network File
Transfer utility, NFT, to transfer a file through the local network
software. This test is part of the DECnet-20 V2.0 Acceptance
Procedures.
@NFT
NFT>COPY (FROM) TEST.DAT.1 (TO) 4097::PS:<MIERSWA>NEW.DAT
Access information for node 4097::
User: MIERSWA
Account: 341
Password:
PS:<MIERSWA>TEST.DAT.1 => PS:<MIERSWA>NEW.DAT.1 [OK]
NFT>EXIT
@FILCOM
*TTY:=TEST.DAT,NEW.DAT
No differences encountered
*C
@
To: DECnet users Page 7
DECSYSTEM 2020 LOOPBACK TESTS
!-------------------------------------!
! !
! MODEM !
! !
!-------------------------------------!
!
!
!
!-------------------------------------!
! ! !
! DUP ! DUP !
! ! !
!-------------------------------------!
! !
! --------KMC-------- !
! ! ! !
!---------!-----------------!---------!
! ! ! !
! DDCMP / KMC driver !
! ! ! !
!---------!-----------------!---------!
! ! ! !
! ! NSP ! !
! ! ! !
!---------!-----------------!---------!
! \/ /\ !
! Application level testing program !
! !
!-------------------------------------!
LOOPBACK THROUGH LOCAL COMMUNICATIONS CONTROLLER - 2020
This facility is not available. Use the cable loopback
procedure which follows this description.
After verifying that the local software and applications work
successfully, perform the same tests, but force the messages out
into the communications controller and back again. This test should
not be done during normal network operations, it may interfere with
local logical link operation.
These procedures allow you to perform the local loopback tests
using the controller loopback option. The tests can be performed on
only one line at a time. First turn the line off:
$OPR
OPR>ENTER NCP
NCP>SET STATE LINE KDP_0_0 OFF
NCP>
Next, inform the local network software that loopback tests are
going to be performed, and set the line into the controller loopback
state.
To: DECnet users Page 8
DECSYSTEM 2020 LOOPBACK TESTS
NCP>SET LOCAL LOOPBACK ENABLED KDP_0_0
NCP>SET STATE LINE KDP_0_0 CONTROLLER-LOOPBACK
NCP>
Next, perform any of the tests outlined in the previous
section, or any test of your own software which makes a local link.
All messages between tasks on the local node will be routed by the
network software out into the controller and back again.
When the test is complete reset the state of the line.
NCP>SET LOCAL LOOPBACK DISABLED KDP_0_0
NCP>SET STATE LINE KDP_0_0 OFF
NCP>
To: DECnet users Page 9
DECSYSTEM 2020 LOOPBACK TESTS
!-------------------------------------!
! !
! CABLE LOOPBACK PLUG !
! ---- !
!---------!---!-----------------------!
! !
! !
! !
!---------!---!-----------------------!
! ! ! ! !
! DUP ! ! DUP !
! ! ! ! !
!---------!---!-----------------------!
! ! !------------- !
! ! KMC ! !
! ! ! !
!---------!-----------------!---------!
! ! ! !
! DDCMP / KMC driver !
! ! ! !
!---------!-----------------!---------!
! ! ! !
! ! NSP ! !
! ! ! !
!---------!-----------------!---------!
! \/ /\ !
! Application level testing program !
! !
!-------------------------------------!
LOOPBACK THROUGH LOCAL COMMUNICATIONS INTERFACE CABLE - 2020
This facility has been thoroughly tested. There are problems
however in resetting the state of the line following the test. It
may be necessary to restart NETCON following each test.
After verifying that the local software and applications work
successfully, perform the same tests, but force the messages out
into the communications interface cable, loopback plug, and back
again. This test should not be performed during normal network
operations. It may interfere with local logical links.
These procedures allow you to perform the local loopback tests
using the cable loopback option. The tests can be performed on only
one line at a time. First turn the line off:
$OPR
OPR>ENTER NCP
NCP>SET STATE LINE KDP_0_0 OFF
NCP>
To: DECnet users Page 10
DECSYSTEM 2020 LOOPBACK TESTS
Then place a loopback plug on the cable of the line to be
tested. Your local field service office can help you locate a
loopback plug if you do not already have one.
Next, inform the local network software that loopback tests are
going to be performed, and set the line into the cable loopback
state.
NCP>SET LOCAL LOOPBACK ENABLED KDP_0_0
NCP>SET STATE LINE KDP_0_0 CABLE-LOOPBACK
NCP>
The cable loopback test in the 2020 can appear to succeed even
if the KDP or cable is not working. The reason for this is that
until a successful node init is performed through the loopback
cable, local links go through core. The UETP controlled acceptance
test solves this problem by running a macro program before the test
begins which executes the NODE JSYS and waits for the node init to
be successful before it begins the test. You should also do this if
you use the cable loopback test without the UETP control file. See
the UETP control file DNV2LL.CMP for an example of the macro
program.
Next, perform any of the tests outlined in the previous
section, or any test of your own software which makes a local link.
All messages between tasks on the local node will be routed by the
network software out into the cable and back again.
When the test is complete remove the loopback plug and reset
the state of the line.
NCP>SET LOCAL LOOPBACK DISABLED KDP_0_0
NCP>SET STATE LINE KDP_0_0 OFF
NCP>
This test, using the DYNETS example from the previous section
is part of the DECnet-20 V2.0 Acceptance Procedures. If this test
is successful at both nodes of a point to point connection, but the
network hookup fails, then the problem has been isolated to the
modems and private line or common carrier.
To: DECnet users Page 11
DECSYSTEM 2020 LOOPBACK TESTS
!-------------------------------------!
! !
! MODEM !
! ---- !
!---------!---!-----------------------!
! !
! !
! !
!---------!---!-----------------------!
! ! ! ! !
! DUP ! ! DUP !
! ! ! ! !
!---------!---!-----------------------!
! ! !------------- !
! ! KMC ! !
! ! ! !
!---------!-----------------!---------!
! ! ! !
! DDCMP / KMC driver !
! ! ! !
!---------!-----------------!---------!
! ! ! !
! ! NSP ! !
! ! ! !
!---------!-----------------!---------!
! \/ /\ !
! NCP !
! !
!-------------------------------------!
LOOPBACK THROUGH THE LOCAL MODEM - 2020
This test is not available in DECnet-20 version 2. It is
included here for completeness. This test would be performed by
placing the line in maintenance state, putting the modem in loopback
mode, and using the NCP command LOOP LINE. However, the code to
place a line into maintenance state has not been written. This test
would be usable during normal network operations.
To: DECnet users Page 12
DECSYSTEM 2040/50/60 LOOPBACK TESTS
!-------------------------------------!
! !
! MODEM !
! !
!-------------------------------------!
!
!
!
!-------------------------------------!
! ! ! ! !
! DUP ! DUP ! ! !
! ! ! ! !
!------------------! ! !
! ! ! !
! KMC ! DMC ! DUP !
! ! ! !
!-------------------------------------!
! !
! DDCMP / drivers !
! !
!-------------------------------------!
! !
! NSP !
! !
!-------------------------------------!
! !
! MCB EXEC + TASKS !
! !
!-------------------------------------!
! !
! DTE driver !
! !
!-------------------------------------!
!
DTE
!
!-------------------------------------!
! !
! DTE driver !
! !
!-------------------------------------!
! !
! --------NSP-------- !
! ! ! !
!---------!-----------------!---------!
! \/ /\ !
! Application level testing program !
! !
!-------------------------------------!
LOOPBACK THROUGH LOCAL NETWORK SOFTWARE - 2040/50/60. This
test is the same as the local network software test for the 2020.
It can be performed during normal network operations.
To: DECnet users Page 13
DECSYSTEM 2040/50/60 LOOPBACK TESTS
LOOPBACK THROUGH THE FRONT END SOFTWARE - 2040/50/60. This
test is not available in DECnet-20 version 2. It would involve
sending messages to a task in the front end which would mirror the
messages back to the sender in the KL.
To: DECnet users Page 14
DECSYSTEM 2040/50/60 LOOPBACK TESTS
LOOPBACK THROUGH THE FRONT END COMMUNICATIONS CONTROLLER -
2040/50/60. This test is not available in DECnet-20 version 2.
This test would require the capability of setting a line in the
front end in controller loopback state, and then use a loopback task
in the front end. Neither of these facilities is available.
To: DECnet users Page 15
DECSYSTEM 2040/50/60 LOOPBACK TESTS
!-------------------------------------!
! !
! --- CABLE LOOPBACK PLUG !
! ! ! !
!--!-!--------------------------------!
! ! !
! ! !
! ! !
!--!-!--------------------------------!
! ! ! ! ! ! !
! DUP ! DUP ! ! !
! ! ! ! ! ! !
!--!-!-------------! ! !
! ! --------! ! ! !
! ! KMC ! ! DMC ! DUP !
! ! ! ! ! !
!--!---------!------------------------!
! ! ! !
! ! DDCMP / drivers !
! ! ! !
!--!---------!------------------------!
! ! ! !
! ! ! NSP !
! ! ! !
!--!---------!------------------------!
! ! ! !
! ! MCB EXEC + TASKS !
! ! ! !
!--!---------!------------------------!
! ! ! !
! ! !DTE driver !
! ! ! !
!--!---------!------------------------!
! ! !
! ! DTE
! ! !
!--!---------!------------------------!
! ! ! !
! ! !DTE driver !
! ! ! !
!--!---------!------------------------!
! ! ! !
! ! ! NSP !
! ! ! !
!--!---------!------------------------!
! \/ /\ !
! Application level testing program !
! !
!-------------------------------------!
LOOPBACK THROUGH COMMUNICATIONS INTERFACE CABLE ON FRONT END -
2040/50/60.
To: DECnet users Page 16
DECSYSTEM 2040/50/60 LOOPBACK TESTS
Once you have established that your local network software is
working successfully the next step is to loop data messages through
the communications lines in the MCB. This test is made possible by
a resident task in the front end, TEST72. This task waits for a
network connection from a user program in the KL. After accepting
the connection, this task reads the line id of the line to be tested
from the first line of the data file sent to the task. That line is
enabled by TEST72 for cable loopback. The remainder of the data
file is sent by TEST72 into the line, through the loopback plug, and
then back to the task on the KL. This test is part of the DECnet-20
V2.0 Acceptance procedures. This test is not to be performed during
normal network operations. Failures from this test may require a
front end reload.
N.B. A bug prevents this test from running on a DMC. To test
a DMC use the loop line command to the NCP command subset of OPR.
The loopback plug for a DMC makes the DMC's internal clock available
for the loop line command.
First, insure that the line you wish to test is in the OFF
state, and place the loopback plug on the cable for that line. Your
local field service representative can help you obtain the loopback
connectors if you don't already have them. Then, set the state of
the line to ON.
Next, create or edit any ascii text file with text lines of 80
or fewer characters such that the first line of text is the ascii
line specification for the line you wish to test in the form
DDD_C_U. Where DDD is the device type (KDP, DMC, or DUP), C is
controller number, and U is the unit number. This text file must
not contain line numbers. Edit this file and follow the
instructions carefully. The front end will crash if the line number
is invalid or the logical link to the Test72 task is aborted.
Then, use DYNETS to create a logical link from the KL node to
the Test72 task on the front end node and loop the data file text to
the front end and back:
@DYNETS
12-Sep-70 08:51:23 * [DYNETS STARTING]
DYNETS>ESTABLISH DN20A-TASK-TEST72 /BYTE:7 /RECL:80
% DYNETS:SEGMENTS SIZE - 256
% DYNETS: OPT DATA -
12-SEP-79 08:51:46 * [DYNETS OK]
DYNETS>RECEIVE DN20A-TASK-TEST72
12-Sep-79 08:52:30 * [DYNETS OK]
DYNETS>SEND DN20A-TASK-TEST72 TEST.DAT
12-Sep-79 08:54:23 * [DYNETS OK]
The same line can be tested over and over again with no
problems. However, DYNETS must be restarted for each test. When
testing more than one line remember that the loopback plug should
only be put on the line when the line is in the off state. Also,
To: DECnet users Page 17
DECSYSTEM 2040/50/60 LOOPBACK TESTS
following the test on a particular line, that line must be turned
off then on again. If any problems occur in performing this test,
reload the front end and perform the test again before you assume
hardware or software problems.
To: DECnet users Page 18
DECSYSTEM 2040/50/60 LOOPBACK TESTS
!-------------------------------------!
! !
! --- MODEM !
! ! ! !
!--!-!--------------------------------!
! ! !
! ! !
! ! !
!--!-!--------------------------------!
! ! ! ! ! ! !
! DUP ! DUP ! ! !
! ! ! ! ! ! !
!--!-!-------------! ! !
! ! --------! ! ! !
! ! KMC ! ! DMC ! DUP !
! ! ! ! ! !
!--!---------!------------------------!
! ! ! !
! ! DDCMP / drivers !
! ! ! !
!--!---------!------------------------!
! ! ! !
! ! ! NSP !
! ! ! !
!--!---------!------------------------!
! ! ! !
! ! MCB EXEC + TASKS !
! ! ! !
!--!---------!------------------------!
! ! ! !
! ! !DTE driver !
! ! ! !
!--!---------!------------------------!
! ! !
! ! DTE
! ! !
!--!---------!------------------------!
! ! ! !
! ! !DTE driver !
! ! ! !
!--!---------!------------------------!
! ! ! !
! ! ! NSP !
! ! ! !
!--!---------!------------------------!
! \/ /\ !
! NCP LOOP LINE command !
! !
!-------------------------------------!
LOOPBACK THROUGH A MODEM ON A FRONT END COMMUNICATIONS
INTERFACE - 2040/50/60. This test is an integral part of the
Network Control software. It can be run during production to test a
single line while other lines are up and running.
To: DECnet users Page 19
DECSYSTEM 2040/50/60 LOOPBACK TESTS
To perform this test set the state of the line to be tested to
MAINTENANCE. Place the local modem or remote modem in loopback mode
or for the DMC insert the loopback plug (no modem is necessary) and
enter the LOOP command to NCP. The LOOP command is documented in
the DECnet manual. The command will transmit a sequence of test
data and compare it with the data returned from the modem in
loopback mode. This command allows you to vary the number, length
and content of the test messages and will report how many messages
were sent successfully. Note that this test currently works on ICC
commlink II modems but does not work on Bell 208A's. Note also that
the use of a COUNT larger than 255 will generate the NETCON error
"Unknown NETCON error".