Protocol: ISO 8073 / TP TP PCI / Überblick
PDU Part: Variable Part
Field: (various fields / parameters)
Length: n bytes
Contents: the contents depend on the current TPDU type.
The parameters listed in the variable part may occur in any order. Each parameter is defined by code, length, and value:
Parameter Code 1 Byte
Parameter Length 1 Byte
Parameter Value n Byte(s)
The checksum parameter can be used by all TP classes (any PTDU type):
Checksum Parameter
Parameter Code: 1100 0011
Parameter Length: 2
Parameter Value: result of algorithm
Each TPDU's variable part may have one or more of these parameters (explanation below):
1000 0101 Acknowledge Time
1000 0110 Residual Error Rate
1000 0111 Priority
1000 1000 Transit Delay
1000 1001 Throughput
1000 1010 Subsequence Number
1000 1011 Reassignment Time
1000 1100 Flow Control Confirmation
1100 0000 TPDU Size
1100 0001 Invalid TPDU
1100 0001 TSAP-ID / calling TSAP
1100 0010 TSAP-ID / called TSAP
1100 0011 Checksum
1100 0100 Version Number
1100 0101 Protection Parameters (user defined)
1100 0110 Additional Option Selection
1100 0111 Alternative Protocol Classes
1110 0000 Additional Information on Connection Clearing
Acknowledge Time
Used only if class 4 is the preferred class. This parameter conveys the max. acknowledge time A(L) to the remote transport entity. It is an indication only, and is not subject to negotiation. The parameter value is a binary number expressing the max. ACK time in milliseconds.
CODE: 1000 0101
LENGTH: 2
VALUE: n
Residual Error Rate
CODE: 1000 0110
LENGTH: 3
VALUE: 1st octet: target value, power of 10
2nd octet: minimum acceptable, power of 10
3rd octet: TSDU size of interest, expressed as a power of 2
Priority
CODE: 1000 0111
LENGTH: 2
VALUE: integer (0 is the highest priority)
Transit Delay
CODE: 1000 1000
LENGTH: 8
VALUE: Octets:
01-02 : target value, calling-called user direction
03-04 : maximum acceptable, calling-called user direction
05-06 : target value, called-calling user direction
07-08 : maximum acceptable, called-calling user direction
Throughput
Not used if class 0 is the preferred class. When the average throughput is emitted, it is considered to have the same value as the maximum throughput. Values are expressed in octets per second.
CODE: 1000 1001
LENGTH: 12 or 24
VALUE: 1st. 12 octets / Maximum Throughput:
Octets:
01-03 : target value, calling-called user direction
04-06 : minimum acceptable, calling-called user direction
07-09 : target value, called-calling user direction
10-12 : minimum acceptable, called-calling user direction
2nd. 12 octets (optional) / Average Throughput:
Octets:
13-15 : target value, calling-called user direction
16-18 : minimum acceptable, calling-called user direction
19-21 : target value, called-calling user direction
22-24 : minimum acceptable, called-calling user direction
Subsequence Number
Optionally used (class 4). This parameter is used to ensure that AK TPDUs are processed in the correct sequence. If it is absent, this is equivalent to transmitting the parameter with a value of zero.
CODE: 1000 1010
LENGTH: 2
VALUE: 16-bit subsequence number
Reassignment Time
Not used if class 0, 2 or 4 is the preferred class. This parameter conveys the Time to Try Reassignment (TTR) which shall be used when following the procedure for reassignment after failure.
CODE: 1000 1011
LENGTH: 2
VALUE: n, a binary number where n is the TTR value expressed in
seconds.
Flow Control Confirmation
Optionally used (class 4). This parameter contains a copy of the information received in an AK TPDU, to allow the transmitter of the AK TPDU to be certain of the state of the receiving transport entity.
CODE: 1000 1100
LENGTH: 8
VALUE: 1. Lower window edge (32 bits). Bit 8 of octet 1 of the
parameter value field is set to zero, the remainder
contains the YR-TU-NR value of the received AK TPDU.
When the format has been selected, only the least
significant seven bits (bits 1 to 7 of octet 4 of the
parameter value field) of this field are significant.
2. Your subsequence (16 bits). Contains the value of the
subsequence parameter of the received AK TPDU, or zero
if this parameter was not present.
3. Your credit (16 bits). Contains the value of the CDT
field of the received AK TPDU. When normal format has
been selected, only the least significant four bits
(bits 1 to 4 of octet 2 of the Your Credit field) of
this field are significant.
TPDU size
CODE: 1100 0000
LENGTH: 1 octet
VALUE: VALUE OCTETS
----------- ------
0000 1101 = 8192
0000 1100 = 4096
0000 1011 = 2048
0000 1010 = 1024
0000 1001 = 512
0000 1001 = 512
0000 1000 = 256
0000 0111 = 128 (default)
Invalid TPDU
CODE: 1100 0001
LENGTH: n (number of octets in the value field)
VALUE: Contains a bit pattern of rejected TPDU header up to
and including the octet which caused the rejection.
This parameter is mandatory in class 0.
TSAP-ID
Transport Service Access Point ID. When either network address unambiguously defines the transport address this information may be omitted.
CODE: 1100 0001 calling TSAP
1100 0010 called TSAP
LENGTH: (not defined)
VALUE: TSAP-ID
Checksum
CODE: 1100 0011
LENGTH: 2 octets
VALUE: result of algorithm
Version Number
This defines the version of the transport protocol standard used for this connection.
CODE: 1100 0100
LENGTH: 1 octet
VALUE: 0000 0001 = default
Protection Parameters (user defined)
CODE: 1100 0101
LENGTH: user defined
VALUE: user defined
Additional Option Selection
CODE: 1100 0110
LENGTH: 1 octet
VALUE: BIT OPTION
--- ---------------------------------------------------------
4 =1 : use of network expedited in class 1
=2 : non-use of network expedited in class 1
3 =0 : use of receipt confirmation in class 1
=1 : use of explicit ACK variant in class 1
2 =0 : 16-bit checksum shall be used in class 4
=1 : 16-bit checksum shall not be used in class 4
1 =0 : use of transport expedited data transfer service
=1 : non-use of transport expedited data transfer service
Default value = 1.
Alternative Protocol Classes
Not used if class 0 is the preferred class.
CODE: 1100 0111
LENGTH: n
VALUE: Encoded as a sequence of single octets; each encoded
as the Class Option octet but with bits 4 to 1 set to
zero.
Additional Information related to the clearing of the connection
CODE: 1110 0000
LENGTH: n
VALUE: user defined