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IEN - 197
A Host Monitoring Protocol
Benjamin M. Littauer
Andrew J. Huang
Robert M. Hinden
Bolt Beranek and Newman Inc.
September 1981
IEN-197 September 1981
Table of Contents
1 Introduction.......................................... 1
2 Protocol Operation.................................... 2
2.1 Unsolicited Messages................................ 3
2.2 Status Messages..................................... 4
2.3 Statistics Messages................................. 4
3 Header Formats........................................ 6
3.1 IP Headers.......................................... 6
3.2 Monitor Header...................................... 7
4 Monitor Message Formats............................... 9
4.1 System Type 1: General Messages..................... 9
4.1.1 Message Type 1: Polling Message................... 9
4.1.2 Message Type 2: Error in Poll.................... 11
4.2 System Type 2: IMP................................. 13
4.2.1 Message Type 1: IMP Trap......................... 13
4.2.2 Message Type 2: IMP status....................... 16
4.2.3 Message Type 3: IMP Modem Throughput............. 20
4.2.4 Message Type 4: IMP Host Throughput.............. 23
4.3 System Type 3: TAC................................. 26
4.3.1 Message Type 1: TAC Trap Message................. 26
4.3.2 Message Type 2: TAC Status....................... 29
4.3.3 Message Type 3: TAC Throughput................... 32
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IEN-197 September 1981
A Host Monitoring Protocol
1 Introduction
The Host Monitoring Protocol (HMP) is used to collect
information from hosts in various networks. At present the
protocol aims at collecting information from ARPANET IMPs and
TACs in an internet environment. It is designed to be
extensible to other monitoring functions (e.g. hosts, gateways,
local nets) while its addressing and control structures allow
it to operate as well within a single network. In
implementation it is a portion of a larger system, the Network
Operations Center (NOC).
The monitoring algorithm relies on polling for
messages; the Host Monitor (HM) periodically sends a polling
message to the host being monitored, requesting a specified
report. The host then creates the report and sends it to the HM.
Missing reports are detected as unanswered polls and duplicate
polls are sent to have the report retransmitted. Some messages
cannot be polled for and these are sent to the HM
spontaneously. Checksums calculated on the data portions of all
messages assure their integrity.
The HMP implements a password scheme in order to restrict
access to monitoring information. The monitored hosts check each
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IEN-197 September 1981
poll message for a valid password before responding; this helps
prevent unauthorized use of the monitor system. The HMP is not
intended to be a highly secure protocol.
2 Protocol Operation
The HMP is designed to operate reliably in the
internet environment. To gain this measure of
reliability it uses polling. The HM sends polling messages
requesting reports to the monitored hosts. A host, upon
receiving the poll, verifies the message and, if it is
acceptable, sends the appropriate report to the poll source. The
HM, after transmitting the poll, awaits the corresponding report.
If it is not received within a reasonable interval, another
poll is sent assuming that either the previous poll or the
answering report was lost. If after a number of repeated
polls no response has been received, it can be reasonably
concluded that the host is unreachable and the polling frequency
is reduced to a background level. This minimizes traffic
but, since polling continues, a poll will reach the host once it
becomes reachable. When a report is received the normal poll
frequency is resumed.
The most important reason for choosing polling over other
methods of detecting lost messages is that it centralizes control
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IEN-197 September 1981
of monitoring in a dedicated HM, rather distributing it
throughout the network of monitored hosts. This frees resources
in the monitored systems and also allows the HM to regulate the
flow of monitoring messages to prevent overloading of the HM's
resources.
There are three classes of data with which the monitoring
protocol is concerned. These are (1) reports of unexpected
changes of status or error conditions, (2) reports of the current
state of the host, and (3) reports of statistics and throughput
data. These three kinds of data are handled in different ways by
the HMP as described below.
2.1 Unsolicited Messages
These are reports of unexpected changes of status or error
condition reports (traps) which the monitor should be informed of
as they occur. They are not polled, but are instead sent
directly to a particular HM. If the address of the HM must be
changed for unsolicited messages, it will be done by external
means (e.g. packet core protocol).
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IEN-197 September 1981
2.2 Status Messages
These are reports of the current state of a system; they
contain any kind of information which is not cumulative. The HM
will poll for these on a periodic basis. When a monitored host
receives a poll for a status message, it assembles a message with
the current data pertaining to its status. Since this is an
instantaneous "picture" of a system, it is not critical if any
particular status report is lost.
2.3 Statistics Messages
These messages, also called throughput messages, contain
data collected on a periodic basis. The information will be
collected in a monitored machine using a double buffering system.
At the end of each collection period, a message will be assembled
and the counters will be cleared. During the next collection
period, any HMs polling for a statistics message will be sent
this message.
The collection frequency for statistics messages from a
particular host must be relatively long compared to the average
round trip message time between the HM and that host to allow the
HM to re-poll if it does not receive an answer. With this
restriction it should be possible to avoid missing any statistics
messages in most cases. Each statistics message will contain a
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IEN-197 September 1981
field giving the (local) time when the data was collected, and
the time at which the message was sent (*). This will allow the
HM to schedule its polling so that the poll arrives near the
beginning of each collection period. This is done to ensure that
if a message is lost, the HM will have sufficient time to try
again to get the statistics message for that period. Sequence
numbers will be used to detect the loss of a message for a
period, and also to eliminate duplicate messages.
_______________
* The units of the local time should be large enough to guarantee
a rollover time of at least one hour.
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IEN-197 September 1981
3 Header Formats
[Note: Any field labeled "unused" is reserved for later
extensions and must be zero when sent.]
Monitor messages have the following format:
+----------------+
| Local Network |
| Header(s) |
+----------------+
| IP header |
+----------------+
| Internet |
| Monitor |
| Header |
+----------------+
| D |
| A |
| T |
| A |
+----------------+
| Padding |
+----------------+
The local header(s) depend on the local network, and do not
concern us here.
3.1 IP Headers
HMP messages are sent using the version 4 IP header as
described in IEN-128 (RFC-760). The HMP protocol number is
20 (decimal). The time to live field should be set to the
maximum value. All other fields should be set as specified
in IEN-128.
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IEN-197 September 1981
3.2 Monitor Header
The monitor header format is:
1 0 0 0
5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+---------------+---------------+
0 | System Type | Message Type |
+---------------+---------------+
1 | Port Number |
+---------------+---------------+
2 | Sequence Number |
+---------------+---------------+
3 | Password or Returned Seq. # |
+---------------+---------------+
4 | One's Complement Checksum |
+---------------+---------------+
HMP FIELDS:
System Type
Message Type
The combination of system type and message type determines
the format of the data in the monitoring message.
The system types which have been defined are:
System Type | Meaning
----------------+-----------------
1 | General Messages
2 | IMP
3 | TAC
Message types are defined for each system type according to
the needs of that system. Message types and their formats
for each system are defined below.
Port Number
The Port Number field is presently unused. It can be used
to multiplex similar messages from/to different processes in
one host.
Sequence Number
Every message contains a sequence number. The sequence
number is incremented when each new message of that type is
sent.
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IEN-197 September 1981
Password or Returned Sequence Number
The Password field of a polling message from an HM contains
a password to verify that the HM is allowed to gather
information. Responses to polling messages copy the
Sequence Number from the polling message and return it in
this field for identification and round-trip time
calculations.
Checksum
The Checksum field is the one's complement of the one's
complement sum of all the 16-bit words in the header and
data area. As with the checksum in the TCP header (see
IEN-129), the checksum also covers a 96-bit pseudo header
containing the source address, the destination address, the
protocol (20), and the length of the monitoring message in
bytes. The fields of the pseudo header are as defined for
the IP header.
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4 Monitor Message Formats
4.1 System Type 1: General Messages
4.1.1 Message Type 1: Polling Message
Description
The HM will send polls to the machines it is monitoring
according to its polling algorithm. Multiple requests can
be combined in a single message, but each request is still
considered a separate poll.
The polled machine will return a message of each type
requested; it will only answer a poll with the correct
system type and password. It will return an error message
(System Type 1; Message Type 2) if it receives a poll for
the wrong system type or an unsupported message type.
A polling message has the following form:
1 0 0 0
5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+---------------+---------------+
0 | R-Message Type| R-Subtype |
. +---------------+---------------+
. : :\ additional
. : : > message
: :/ requests
+---------------+---------------+
HMP FIELDS
System Type
General Messages = 1
Message Type
Polling Message = 1
Port Number
Unused
Sequence Number
The sequence number identifies the polling request. An HM
will have separate sequences for each host it monitors. The
sequence number is returned in the response to a poll; the
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IEN-197 September 1981
HM will use this information to associate polls with their
responses and to determine round trip times.
Password
The monitoring password.
POLL FIELDS
R-Message Type
The message type requested.
R-Subtype
Presently unused, this field might later be used to specify
options or include additional data in a polling message.
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IEN-197 September 1981
4.1.2 Message Type 2: Error in Poll
Description
This message is sent in response to a faulty poll and
specifies the nature of the error.
An error message has the following form:
1 0 0 0
5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+---------------+---------------+
0 | Error Type |\ first
+---------------+---------------+ > error
1 | R-Message Type| R-Subtype |/ report
. +---------------+---------------+
. : :\ additional
. : : > error
: :/ reports
+---------------+---------------+
HMP FIELDS
System Type
General Messages = 1
Message Type
Error Message = 2
Port Number
Unused
Sequence Number
A 16 bit number incremented each time an error message is
sent.
Returned Sequence Number
The Sequence Number of the polling message which caused the
error.
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IEN-197 September 1981
ERROR MESSAGE FIELDS
Error Type
This field specifies the nature of the error in the poll.
The following error types have been defined.
1 = Reason unspecified.
2 = Bad R-Message Type.
3 = Bad R-Subtype.
R-Message Type
R-Subtype
These fields identify the poll request in error.
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IEN-197 September 1981
4.2 System Type 2: IMP
4.2.1 Message Type 1: IMP Trap
Description
When a trap occurs, it is buffered in the IMP and sent as
soon as possible. Trap messages are unsolicited. If traps
happen in close sequence, several traps may be sent in one
message.
Through the use of sequence numbers, it will be possible to
determine how many traps are being lost. If it is
discovered that many are lost, a polling scheme might be
implemented for traps.
A IMP trap message has the following form:
1 0 0 0
5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+---------------+---------------+
0 | # of traps lost |
+---------------+---------------+
1 : first :
. : trap :
. : data :
. +---------------+---------------+
. : additional :
. : trap :
. : data :
+---------------+---------------+
HMP Fields
System Type
IMP = 2
Message Type
IMP Trap Message = 1
Port Number
Unused
Password
Unused
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Sequence Number
A 16 bit number incremented each time a trap message is sent
so that the HM can order the received trap messages and
detect missed messages.
IMP TRAP FIELDS
# of traps lost
Under certain conditions, an IMP may overflow its internal
trap buffers and be unable to save traps to send. This
counter keeps track of such occurrences.
Trap Reports
There can be several blocks of trap data in each message.
The format for each such block is below.
+---------------+---------------+
| Size |
+---------------+---------------+
| Time |
+---------------+---------------+
| Trap ID |
+---------------+---------------+
: Trap :
: Data :
+---------------+---------------+
Size
Size is the number of 16 bit words in the trap, not counting
the size field.
Time
The time (in 640 ms. units) at which the trap occurred.
This field is used to sequence the traps in a message and
associate groups of traps.
Trap ID
This is usually the program counter at the trap. The ID
identifies the trap, and does not have to be a program
counter, provided it uniquely identifies the trap.
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Trap Data
The IMP returns data giving more information about the trap.
There are usually two entries: the values in the accumulator
and the index register at the occurrence of the trap.
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4.2.2 Message Type 2: IMP status
Description
The status message gives a quick summary of the state of the
IMP. Status of the most important features of the IMP are
reported as well as the current configuration of the
machine.
The format of the status message is as follows:
1 0 0 0
5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+---------------+---------------+
0 | Software Version Number |
+---------------+---------------+
| Last Trap Message |
+---------------+---------------+
| Hosts | Modems |
+---------------+---------------+
| Package bits |
+---------------+---------------+
| TIP version |
+---------------+---------------+
5 | restart/reload |
+---------------+---------------+
| Host |
+ +
| Test |
+ +
| Results |
+---------------+---------------+
| |
+ Crash +
10 | |
+ Data +
| |
+---------------+---------------+
| Anomalies |
+---------------+---------------+
13 | HIHD0 | HIHD1 | HIHD2 | HIHD3 |
. +---------------+---------------+
. : HIHD4 | ............... :
. +---------------+---------------+
(cont.)
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Imp Status (cont.)
. +---------------+---------------+
. | Modem |
. + State +
. | Data |
. +---------------+---------------+
. : Modem State :
. : Data...... :
+---------------+---------------+
HMP FIELDS
System Type
IMP = 2
Message Type
IMP status message = 2
Port Number
Unused
Sequence Number
A 16 bit number incremented each time a status message is
sent.
Password
The password contains the sequence number of the polling
message to which this message responds.
IMP STATUS FIELDS
Software Version Number
The IMP version number.
Last Trap Message
Contains the sequence number of the last trap message sent
to the HM. This will allow the HM to detect how many trap
messages are being lost.
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Hosts
The number of configured hosts in this system.
Modems
The number of configured modems in this system.
Package Bits
This is a bit encoded word that reports the set of packages
currently loaded in the system. The table below defines the
bits.
Bit Package
(octal)
1 VDH
2 TIP
4 experimental
10 Cumulative Statistics
20 Trace
40 TTY
100 DDT
200 Store and Forward statistics
400 End-to-end Statistics
1000 Level measurements
TIP version
The TIP version number if a TIP is loaded or zero if not.
Restart/Reload
This word reports a restart or reload of an IMP.
Value Meaning
1 restarted
2 reloaded
Host Test Results
These three words report the result of the host test, if
any. If a test is running, the first word will contain the
host number, the second and third will contain the number of
NOPs sent and received, respectively. If no test is
running, the first word will contain a -1.
Crash Data
Crash data reports the circumstances surrounding an
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unexpected crash. The first word reports the location of
the crash and the following two are the contents of the
accumulator and index registers.
Anomalies
Anomalies is a collection of bit flags that indicate the
state of various switches or processes in the IMP. These
are very machine dependent and only a representative
sampling of bits is listed below.
Bit Meaning
(octal)
1 Sense Switch 1 ON
2 Sense Switch 2 ON
4 Sense Switch 3 ON
10 Sense Switch 4 ON
20 Override ON
200 Trace ON
2000 Message Generator ON
HIHD0 - HIHDn
Each four bit HIHD field gives the state of the
corresponding host.
Value Meaning
0 UP
1 ready line down
2 tardy
3 non-existent
4 VDH host not initialized
Modem State Data
Modem state data contains four byte fields of data. The
first field indicates the line speed in a machine dependent
fashion; the second field is the number of line protocol
ticks covered by this report; the third is the neighbor on
the line, and the fourth is a count of missed protocol
packets over the interval specified in the second field.
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4.2.3 Message Type 3: IMP Modem Throughput
Description
The modem throughput message reports traffic statistics for
each modem in the system. The IMP will collect these data at
regular intervals and save them awaiting a poll from the HM.
If a period is missed by the HM, the new results simply
overwrite the old. Two time stamps bracket the collection
interval (data-time and prev-time) and are an indicator of
missed reports. In addition, mess-time indicates the time
at which the message was sent.
The modem throughput message will accommodate up to fourteen
modems in one packet. A provision is made to split this
into multiple packets by including a modem number for the
first entry in the packet. This field is not immediately
useful, but if machine sizes grow beyond fourteen modems or
if modem statistics become more detailed and use more than
three words per modem, this can be used to keep the message
within a single ARPANET packet.
The format of the modem throughput message is as follows:
1 0 0 0
5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+---------------+---------------+
0 | Mess-Time |
+---------------+---------------+
| Software Version Number |
+---------------+---------------+
| Data-Time |
+---------------+---------------+
| Prev-Time |
+---------------+---------------+
| Total Modems | This Modem |
+---------------+---------------+
5 | |
. + modem +
. | |
. + throughput +
. | |
. +---------------+---------------+
. : modem :
. : :
. : throughput :
+---------------+---------------+
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IEN-197 September 1981
HMP FIELDS
System Type
IMP = 2
Message Type
IMP Modem Throughput message = 3
Port Number
Unused
Sequence Number
A 16 bit number incremented at each collection interval
(i.e. when a new throughput message is assembled). The HM
will be able to detect lost or duplicate messages by
checking the sequence numbers.
Password
The password contains the sequence number of the polling
message to which this message responds.
IMP MODEM THROUGHPUT FIELDS
Mess-time
The time (in 640ms. units) at which the message was sent to
the HM.
Software Version Number
The IMP version number.
Data-Time
Data-time is the time (in 640ms. units) when this set of
data was collected. (See Description.)
Prev-Time
Prev-time is the time (in 640 ms. units) of the previous
collection of data (and therefore, is the time when the data
in this message began accumulating.)
Total Modems
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This is the number of modems in the system.
This Modem
This Modem is the number of the first modem reported in this
message. Large systems that are unable to fit all their
modem reports into a single packet may use this field to
separate their message into smaller chunks to take advantage
of single packet message efficiencies.
Modem Throughput
Modem throughput consists of three words of data
reporting packets and words output on each modem. The
first word counts packets output and the following two
count word throughput. The double precision words are
arranged high order first. (Note also that messages from
Honeywell type machines (316s, 516s and C30s) use a fifteen
bit low order word.) The first block reports output on the
modem specified by "This Modem". The following blocks
report on consecutive modems.
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4.2.4 Message Type 4: IMP Host Throughput
Description
The host throughput message reports traffic statistics for
each host in the system. The IMP will collect these data at
regular intervals and save them awaiting a poll from the HM.
If a period is missed by the HM, the new results simply
overwrite the old. Two time stamps bracket the collection
interval (data-time and prev-time) and are an indicator of
missed reports. In addition, mess-time indicates the time
at which the message was sent.
The host throughput format will hold only three hosts if
packet boundaries are to be respected. A provision is made
to split this into multiple packets by including a host
number for the first entry in the packet.
The format of the host throughput message is as follows:
1 0 0 0
5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+---------------+---------------+
0 | Mess-Time |
+---------------+---------------+
| Software Version Number |
+---------------+---------------+
| Data-Time |
+---------------+---------------+
| Prev-Time |
+---------------+---------------+
| Total Hosts | This Host |
+---------------+---------------+
5 : host :
. : throughput :
+---------------+---------------+
HMP FIELDS
System Type
IMP = 2
Message Type
IMP host Throughput message = 4
Port Number
Unused
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Sequence Number
A 16 bit number incremented at each collection interval
(i.e. when a new throughput message is assembled). The HM
will be able to detect lost or duplicate messages by
checking the sequence numbers.
Password
The password contains the sequence number of the polling
message to which this message responds.
IMP HOST THROUGHPUT FIELDS
Mess-time
The time (in 640ms. units) at which the message was sent to
the HM.
Software Version Number
The IMP version number.
Data-Time
Data-time is the time (in 640ms. units) when this set of
data was collected. (See Description.)
Prev-Time
Prev-time is the time (in 640 ms. units) of the previous
collection of data (and therefore, is the time when the data
in this message began accumulating.)
Total Hosts
The total number of hosts in this system.
This Host
This host is the number of the first host reported in this
message. Large systems that are unable to fit all their
host reports into a single packet may use this field to
separate their message into smaller chunks to take advantage
of single packet message efficiencies.
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Host Throughput
Each host throughput block consists of twelve words in the
following format:
+---------------+---------------+
| messages to network |
+---------------+---------------+
| messages from network |
+---------------+---------------+
| packets to net |
+---------------+---------------+
| packets from net |
+---------------+---------------+
| messages to local |
+---------------+---------------+
| messages from local |
+---------------+---------------+
| packets to local |
+---------------+---------------+
| packets from local |
+---------------+---------------+
| words to imp |
| (double precision) |
+---------------+---------------+
| words from imp |
| (double precision) |
+---------------+---------------+
Each host throughput message will contain several blocks of
data. The first block will contain data for the host
specified in First Host Number. Following blocks will
contain data for consecutive hosts. All counters are single
precision with the exception of the two word counters which
are double precision. The double precision words are
arranged high order first. Note also that messages from
Honeywell type machines (316s, 516s and C30s) use a fifteen
bit low order word.
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4.3 System Type 3: TAC
4.3.1 Message Type 1: TAC Trap Message
Description
When a trap occurs, it is buffered in the TAC and sent as
soon as possible. Trap messages are unsolicited. If traps
happen in close sequence, several traps may be sent in one
message.
Through the use of sequence numbers, it will be possible to
determine how many traps are being lost. If it is
discovered that many are lost, a polling scheme might be
implemented for traps.
A TAC trap message has the following form:
1 0 0 0
5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+---------------+---------------+
0 | # of traps lost |
+---------------+---------------+
1 : first :
. : trap :
. : data :
. +---------------+---------------+
. : additional :
. : trap :
. : data :
+---------------+---------------+
HMP FIELDS
System Type
TAC = 3
Message Type
TAC Trap Message = 1
Port Number
Unused
Password or Returned Sequence Number
Unused
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Sequence Number
A 16 bit number incremented each time a trap message is sent
so that the HM can order the received trap messages and
detect missed messages.
TAC TRAP FIELDS
# of traps lost
Under certain conditions, a TAC may overflow its internal
trap buffers and be unable to save traps to send. This
counter keeps track of such occurrences.
Trap Reports
There can be several blocks of trap data in each message.
The format of the trap data is as follows:
+---------------+---------------+
| Size |
+---------------+---------------+
| Time |
+---------------+---------------+
| Trap ID |
+---------------+---------------+
: Trap :
: Data :
+---------------+---------------+
Size
Size is the number of 16 bit words in the trap, not counting
the size field.
Time
The time (in 640ms. units) at which the trap occurred. This
field is used to sequence the traps in a message and
associate groups of traps.
Trap ID
This is (usually) the program counter at the trap. The ID
identifies the trap, and does not have to be a program
counter, provided that it uniquely identifies the trap.
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Trap Data
The TAC returns data giving more information about the trap.
There are usually two entries: the values in the accumulator
and the index register at the occurrence of the trap.
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4.3.2 Message Type 2: TAC Status
Description
The status message gives a quick summary of the state of the
TAC. Status of the most important features of the TAC are
reported as well as the current configuration of the
machine.
A TAC status message has the following form:
1 0 0 0
5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+---------------+---------------+
0 | Version Number |
+---------------+---------------+
| Last Trap Message |
+---------------+---------------+
| Bit Flags |
+---------------+---------------+
| Free PDB count |
+---------------+---------------+
| Free MBLK count |
+---------------+---------------+
5 | # of TCP connections |
+---------------+---------------+
| # of NCP connections |
+---------------+---------------+
| restart/reload |
+---------------+---------------+
| |
+ Crash +
| |
+ Data +
10 | |
+---------------+---------------+
HMP FIELDS
System Type
TAC = 3
Message Type
TAC Status Message = 2
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IEN-197 September 1981
Port Number
Unused
Sequence Number
A 16 bit number incremented each time a status message is
sent.
Returned Sequence Number
Contains the sequence number from the polling message
requesting this report.
TAC STATUS FIELDS
Version Number
The TAC's software version number.
Last Trap Message
Contains the sequence number of the last trap message sent
to the HM. This will allow the HM to detect how many trap
messages are being lost.
Bit Flags
There are sixteen bit flags available for reporting the
state of various switches (hardware and software) in the
TAC. The bits are numbered as follows for purposes of the
discussion below.
1 1 0 0 0
5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | | | | | | | | | | | | | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The bit flags report the status of the following:
Bit Meaning
0 0 => DDT override off; 1 => override on.
1-4 0 => Sense Switch n is off; 1 => SSn on.
5 0 => Extended DDT not enabled;
1 => Extended DDT enabled.
6 0 => Traps going to console;
1 => Traps going to remote monitor.
7-15 unused
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Free PDB count
The number of PDBs on the free queue.
Free MBLK count
The number of MBLKs on the free queue.
# of TCP connections
# of NCP connections
The number of open connections for each protocol.
Restart/Reload
This word reports a restart or reload of the TAC
Value Meaning
1 restarted
2 reloaded
Crash Data
Crash data reports the circumstances surrounding an
unexpected crash. The first word reports the location of
the crash and the following two are the contents of the
accumulator and index registers.
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4.3.3 Message Type 3: TAC Throughput
Description
The TAC throughput message reports statistics for the
various modules of the TAC. The TAC will collect these data
at regular intervals and save them awaiting a poll from the
HM. If a period is missed by the HM, the new results simply
overwrite the old. Two time stamps bracket the collection
interval (data-time and prev-time) and are an indicator of
missed reports. In addition, mess-time indicates the time
at which the message was sent.
A TAC throughput message has the following form:
1 0 0 0
5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+---------------+---------------+
0 | Mess-Time |
+---------------+---------------+
| Data-Time |
+---------------+---------------+
| Prev-Time |
+---------------+---------------+
| Version Number |
+---------------+---------------+
| Last Trap Message |
+---------------+---------------+
5 | Bit Flags |
+---------------+---------------+
| Free PDB count |
+---------------+---------------+
| Free MBLK count |
+---------------+---------------+
| # of TCP connections |
+---------------+---------------+
| # of NCP connections |
+---------------+---------------+ ----
10 | Host Input Throughput | ^
+---------------+---------------+ |
| Host Input Abort Count | |
+---------------+---------------+ |
| Host Input Garbled Count | |
+---------------+---------------+ |
| Host Output Throughput | 1822 info.
+---------------+---------------+ |
(continued)
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IEN-197 September 1981
TAC throughput (cont.)
+---------------+---------------+ |
| Host Output Abort Count | 1822 info.
+---------------+---------------+ |
15 | Host Down Count | v
+---------------+---------------+ ----
| # of datagrams sent | ^
+---------------+---------------+ |
| # of datagrams received | |
+---------------+---------------+ IP info.
| # of datagrams discarded | |
+---------------+---------------+ |
| # of fragments received | v
+---------------+---------------+ ----
20 | # of segments sent | ^
+---------------+---------------+ |
| # of segments received | |
+---------------+---------------+ |
| # of segments discarded | |
+---------------+---------------+ TCP info.
| # of octets sent | |
+---------------+---------------+ |
| # of octets received | |
+---------------+---------------+ |
25 | # of retransmissions | v
+---------------+---------------+ ----
| # of messages sent | ^
+---------------+---------------+ |
| # of messages received | |
+---------------+---------------+ |
| # of messages flushed | |
+---------------+---------------+ |
| # of bytes sent | |
+---------------+---------------+ |
30 | # of bytes received | |
+---------------+---------------+ NCP info.
| # of ERRs received | |
+---------------+---------------+ |
| # of RASs received | |
+---------------+---------------+ |
| # of RAPs received | |
+---------------+---------------+ |
| # of NXSs received | |
+---------------+---------------+ |
35 | # of NXRs received | |
+---------------+---------------+ |
| # of RSTs received | v
+---------------+---------------+ ----
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HMP FIELDS
System Type
TAC = 3
Message Type
TAC Throughput Message = 3
Port Number
Unused
Sequence Number
A 16 bit number incremented at each collection interval
(i.e. when a new throughput message is assembled). The HM
will be able to detect lost or duplicate messages by
checking the sequence numbers.
Returned Sequence Number
Contains the sequence number from the polling message
requesting this report.
TAC THROUGHPUT FIELDS
Mess-time
The time (in 640ms. units) at which the message was sent to
the HM.
Data-Time
Data-time is the time (in 640ms. units) when this set of
data was collected. (See Description.)
Prev-Time
Prev-time is the time (in 640 ms. units) of the previous
collection of data (and therefore, is the time when the data
in this message began accumulating.)
Version Number
The TAC's software version number.
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Last Trap Message
Contains the sequence number of the last trap message sent
to the HM. This will allow the HM to detect how many trap
messages are being lost.
Bit Flags
There are sixteen bit flags available for reporting the
state of various switches (hardware and software) in the
TAC. The bits are numbered as follows for purposes of the
discussion below.
1 1 0 0 0
5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | | | | | | | | | | | | | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The bit flags report the status of the following:
Bit Meaning
0 0 => DDT override off; 1 => override on.
1-4 0 => Sense Switch n is off; 1 => SSn on.
5 0 => Extended DDT not enabled;
1 => Extended DDT enabled.
6 0 => Traps going to console;
1 => Traps going to remote monitor.
7-15 unused
Free PDB count
The number of PDBs on the free queue.
Free MBLK count
The number of MBLKs on the free queue.
# of TCP connections
# of NCP connections
The number of open connections for each protocol.
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1822 info.
These six fields report statistics which concern the
operation of the 1822 protocol module, i.e. the interface
between the TAC and its IMP.
IP info.
These four fields report statistics which concern Internet
Protocol in the TAC.
TCP info.
These six fields report statistics which concern TCP
protocol in the TAC.
NCP info.
These eleven fields report statistics which concern NCP
protocol in the TAC.
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