*Packet type 2

Packet type 2, draft 990328
by Goran Eriksson, 2:201/505, get{at}get.pp.se


For discussion in the NET_DEV echomail conference.

English is a foreign language to me. Purely linguistic remarks are
welcome, but please send them to me by netmail or e-mail.


1. General

A packet file of type 2 has the following general layout

 ---------------------
 |   Packet header   |
 ---------------------
 |   Packed message  |
 ---------------------
 :                   :
 ---------------------
 |  Packed message   |
 ---------------------
 | Packet terminator |
 ---------------------

The number of packed messages may be 0 or more.


2. Packet header

2.1. General

The packet header of a packet file of type 2 has the following
general layout

 Relative byte offset                            Size in bytes
                        -----------------------
 0         00H          |    Origin Node      |  2
                        -----------------------
 2         02H          |  Destination Node   |  2
                        -----------------------
 4         04H          |        Year         |  2
                        -----------------------
 6         06H          |       Month         |  2
                        -----------------------
 8         08H          |        Day          |  2
                        -----------------------
 10        0AH          |        Hour         |  2
                        -----------------------
 12        0CH          |       Minute        |  2
                        -----------------------
 14        0EH          |       Second        |  2
                        -----------------------
 16        10H          |      Baud Rate      |  2
                        -----------------------
 18        12H          |     Packet Type     |  1
                        -----------------------
 20        14H          |     Origin Net      |  2
                        -----------------------
 22        16H          |   Destination Net   |  2
                        -----------------------
 24        18H          |    Product Code     |  1
                        -----------------------
 25        19H          |    Serial Number    |  1
                        -----------------------
 26        1AH          |      Password       |  8
                        -----------------------
 34        22H          |     Origin zone     |  2
                        -----------------------
 36        24H          |  Destination zone   |  2
                        -----------------------
 38        26H          |      Reserved       |  20
                        -----------------------

The total size of the packet header is 58 bytes.


2.2. Origin Node
This field contains information about the node number of the system
having created the packet. The field contains a 16-bit binary unsigned
integer in the range 0-65535.

See notes 1 and 2.

2.3. Destination Node
This field contains information about the node number of the system
for which the packet was created. The field contains a 16-bit binary
unsigned integer in the range 0-65535.

See notes 1 and 2.

2.4. Year
This field contains information about the year when the packet was
created. The field contains a 16-bit binary unsigned integer in the
range 0-66535.

See notes 2 and 3.

2.5. Month
This field contains information about the month when the packet was
created. The field contains an 8-bit binary unsigned integer in the
range 0-11. The following representation is used:

  Month                 represented as
  January               0
  February              1
  March                 2
  April                 3
  May                   4
  June                  5
  July                  6
  August                7
  September             8
  October               9
  November              10
  December              11

See note 3.

2.6. Day
This field contains information about the day when the packet was
created. The field contains an 8-bit binary unsigned integer in the
range 1-31.

See note 3.

2.7. Hour
This field contains information about the hour when the packet was
created. The field contains an 8-bit binary unsigned integer in the
range 0-23.

See note 3.

2.8. Minute
This field contains information about the minute when the packet was
created. The field contains an 8-bit binary unsigned integer in the
range 0-59.

See note 3.

2.9. Second
This field contains information about the second when the packet was
created. The field contains an 8-bit binary unsigned integer in the
range 0-59.

See note 3.

2.10. Baud Rate
This field is filled with the 16-bit binary unsigned integer 0 by the
system creating the packet. Any system receiving the packet may ignore
the value of this field. For historical reasons this field is called
Baud Rate.

See note 2.

2.11. Packet Type
This field is filled with the 16-bit binary unsigned integer 2 by the
system creating the packet. Any system receiving the packet should
check the contents of this field. If it does not contain the 16-bit
binary unsigned integer 2 it is recommanded that the receiving system
regards it unsafe to unpack this packet according to the format
specification for packet type 2. Any further actions by the receiving
system in this case are left to the implementation.

See note 2.

2.12. Origin Net
This field contains information about the net number of the system
having created the packet. The field contains a 16-bit binary unsigned
integer in the range 1-65535.

See notes 1 and 2.

2.13. Destination Net
This field contains information about the net number of the system for
which the packet was created. The field contains a 16-bit binary
unsigned integer in the range 1-65535.

See notes 1 and 2.

2.14. Product Code
This field contains information about the product code assigned to the
programme creating the packet. The field contains an 8-bit binary
unsigned integer in the range 0-255.

Product codes are assigned to programmes by the FTSC. See FTA-1005.
That document also contains information about what product codes to
use by programmes which have not yet been assigned a product code by
the FTSC.

2.15. Serial Number
This field may contain information about the serial number of the
programme creating the packet. The field contains a 8-bit binary
unsigned integer in the range 0-255. If a programme does not want to
assign any serial number to this field it should fill this field with
the 8-bit binary unsigned integer 0.

2.16. Password
This field contains information about a packet level password. The
field contains an array of 0-8 ASCII characters, each in the range
'0'..'9', 'A'..'Z'. The programme creating the packet should fill all
unused bytes in this field with the 8-bit binary unsigned value 0. Any
programme receiving a packet should ignore any bytes in this field
after the first occurence of an byte with the value 0. The comparison
of passwords in a received packet file is done case insensitively.

Any programme receiving a packet with a password differing from the
password set up between the system having created the packet and the
system receiving it (including the absence of a password when one has
been agreed upon) should consider the information contained in the
packet about the system that has created as unreliable. Any further
actions by the receiving system in this case are left to each
implementation.

See note 5.

2.17. Origin Zone
This field may contain information about the zone number of the system
having created the packet. The field contains a 16-bit binary unsigned
integer in the range 1-65535. If a programme does not wish to enter a
zone number into this field it should fill it with the 16-bit binary
unsigned value 0.

See notes 1, 2 and 4.

2.18. Destination Zone
This field may contain information about the zone number of the system
for which the packet was created. The field contains a 16-bit binary
unsigned integer in the range 1-65535. If a programme does not wish to
enter a zone number into this field it should fill it with the 16-bit
binary unsigned value 0.

See notes 1, 2 and 4.

2.19. Reserved
This field is filled by the programme creating the packet with an
array of bytes with the 8-bit binary unsigned value 0. Any programme
receiving a packet should ignore the contents of this field.


3. Packed message format

3.1. General
The packed message in a packet file of type 2 has the following
general layout

 Relative byte offset
                        -----------------------
 0         00H          |     Packet Type     |
                        -----------------------
 2         02H          |    Origin Node      |
                        -----------------------
 4         04H          |  Destination Node   |
                        -----------------------
 6         06H          |     Origin Net      |
                        -----------------------
 8         08H          |   Destination Net   |
                        -----------------------
 10        0AH          |      Attribute      |
                        -----------------------
 12        0CH          |        Cost         |
                        -----------------------
 14        0EH          |    Date and Time    |
                        -----------------------
 34        22H          |       To-name       |
                        -----------------------
                        |      From-name      |
                        -----------------------
                        |       Subject       |
                        -----------------------
                        |    Message body     |
                        -----------------------

The total size of the packed message is variable.

3.2. Packet Type
This field is filled with the 16-bit binary unsigned integer 2 by the
system creating the packet. Any system receiving the packet should
check the contents of this field. If it does not contain the 16-bit
binary unsigned integer 2 it is recommanded that the receiving system
regards it unsafe to unpack this packet according to the format
specification for packet type 2. Any further actions by the receiving
system in this case are left to the implementation.

See note 2.

3.3. Origin Node
This field contains information about the node number of the system
having created the message. The field contains a 16-bit binary
unsigned integer in the range 0-65535.

See notes 1 and 2.

3.4. Destination Node
This field contains information about the node number of the system
for which the message was created. The field contains a 16-bit binary
unsigned integer in the range 0-65535.

See notes 1 and 2.

3.5. Origin Net
This field contains information about the net number of the system
having created the message. The field contains a 16-bit binary
unsigned integer in the range 1-65535.

See notes 1 and 2.

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