DLMS User Association
Proposal for a new version of Interface Class IEC HDLC setup
(class_id: 23)
Written by Gyozo Kmethy – GNARUS ENGINEERING Services Ltd.
23d January 2002
Version 2.0, file HDLC23V1_GK020123
Replaces Version 1.0, file HDLC23V1_011122
CONTENTS
1
Introduction ...................................................................................................................... 2
2
References ....................................................................................................................... 2
3
HDLC parameter negotiation ............................................................................................ 2
3.1
3.2
4
The problem ............................................................................................................ 2
The solution ............................................................................................................ 3
3.2.1 Change in IEC 62056-46 and in the Green Book .......................................... 3
3.3 Change in conformance testing ............................................................................... 3
Maximum value of the maximum_information_field_length parameter ............................... 3
4.1
4.2
5
The problem ............................................................................................................ 3
The solution ............................................................................................................ 3
4.2.1 Change in IEC 62056-46 and the Green Book ............................................. 4
4.2.2 Change in IEC 62056-62 and the Blue Book ................................................ 4
4.3 Change in conformance testing ............................................................................... 7
Maximum value of inter_octet_time out ............................................................................. 8
5.1
5.2
6
The problem ............................................................................................................ 8
The solution ............................................................................................................ 8
5.2.1 Amendment to IEC 62056-46 and the Green Book ....................................... 8
5.2.2 Amendment to IEC 62056-62 and the Blue Book ......................................... 8
5.2.3 Modification to conformance testing ............................................................. 8
Change in the conformance test specification and test plans ............................................ 9
6.1
6.2
6.3
6.4
6.5
Support of IC 23 version 0 and 1 ............................................................................. 9
Length of the information field in the SNRM frame ................................................... 9
Parameter negotiation - max_info_field_length ........................................................ 9
Parameter negotiation: window_size ..................................................................... 10
Length of information field in an I or UI frame ........................................................ 11
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DLMS User Association
1
Introduction
During performing conformance tests with the first versions of the COSEM CTT three
problems have been identified with the HDLC parameter negotiation and with the interface
class 23, IEC HDLC setup:

negotiation of the HDLC parameters max_info_field_ length and window_size;

maximum values of the max_info_field_length parameter;

maximum value of the inter-octet time out parameter.
The purpose of this paper to propose modifications to conformance testing and to the
interface class IEC HDLC setup. This is the second version of the document, taking into
account the comments received on the first version.
2
References
[1] draft IEC 62056-46 Electricity metering - Data exchange for meter reading, tariff and load
control – Part 46: Data link layer using HDLC protocol
[2] ISO/IEC 13230:2000 Information technology – Telecommunication and information
exchange between systems – High level data link control procedures
[3] DLMS UA 1000-2:2001 COSEM Three layer connection oriented architecture (the Green
Book), Second edition
[4] draft IEC 62056-62 Electricity metering - Data exchange for meter reading, tariff and load
control – Part 62: COSEM Interface classes
[5] DLMS UA 100-1:2001 COSEM Identification system and interface objects (the Blue Book),
fourth edition.
[6] COSEM conformance testing – Data link layer V 1.2 October 2001
3
3.1
HDLC parameter negotiation
The problem
[1] defines the negotiation of HDLC parameters:

the max_info_field_length transmit/receive

the window_size receive transmit/receive.
These parameters, among others, are held in the server in an instance of the interface class
23 IEC HDLC setup.
The primary station proposes values of these parameters in the SNRM frame. The secondary
station sends back an UA frame with the negotiated values. These are the smal ler of the
proposed values and the values supported by the secondary station. Default values can be
used in both directions; these are not transmitted.
The parameter negotiation is described in Clause 6.4.4.3.2 of [1] and Clause 5.5.3.2.2.2,
Table 11 of [2]. The HDLC parameters are given in a PI/PL/PV (Parameter
Identifier/Parameter Value/Parameter Length) structure.
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DLMS User Association
Name
PI
PL
PV
maximum_information_field_length (transmit)
5
N
binary
maximum_information_field_length (receive)
6
N
binary
window size k (transmit)
7
4
binary
window size k (receive)
8
4
binary
The length of parameters 5 and 6 is N bytes, the value is 32 D -128 D in case of version 0 of IC
23. The length of parameters 7 and 8 is 4 bytes, the value is 1 D – to 7 D .
The problem is, that during the first conformance tests it has been found that some existing
server implementations do not accept a data link layer connection, if the proposed
max_info_field_length is smaller than the buffer used by the server. Instead of sending back
the negotiated value, they send back their own value or refuse the connection (by sending a
DM frame).
It is reasonable to expect that there is less limitation on the primary station side than on the
secondary station side. The primary station should be able to support at least the same buffer
size than the secondary station. Therefore this behaviour should be acceptable.
Another problem which has been found in some implementations, that the window size
parameters are sent back on 1 byte, instead of 4 bytes, as defined i n [2]. This may cause a
problem with client implementations. Therefore a test needs to be added to the CTT.
3.2
The solution
3.2.1
Change in IEC 62056-46 and in the Green Book
Amend [1] by adding a note a note in Clause 6.4.4.3.2 above Table 8:
Note: For reasons of communication efficiency, the value of the parameter maximum_information_field_length_
receive proposed by the primary station should be at least as big as the value of the parameter of the
maximum_information_field_length_transmit supported by the secondary station (the buffer size)
The same change will be made in clause 6.3.4.4.43.2. of [3].
3.3
Change in conformance testing
See in Clause 6 of this document.
4
4.1
Maximum value of the maximum_information_field_length parameter
The problem
Version
0
of
IC
23
defines
the
default
and
maximum
values
max_info_field_length_receive and _transmit parameters as 128 D (type unsigned).
of
the
It was felt that this was too low. To increase the efficiency of the communication, higher
values should be allowed when communication channels of high integrity are used.
4.2
The solution
Change the type of these parameters to unsigned-long and change the maximum value to
2030 (the maximum possible length of the frame is 2047 bytes, the maximum overhead is 11
bytes with four bytes addressing on the secondary used station side). The minimum value
remains 32 D and the default value 128 D .
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DLMS User Association
This requires modifying the interface class version from 0 to 1. See the new interface class
definition below.
4.2.1
Change in IEC 62056-46 and the Green Book
In Clause 6.4.3.3 of [1], change the last paragraph:
Existing paragraph:
“For data integrity reasons, in this profile, the default maximum length of the information field
is limited to 128 bytes. Other values may be negotiated at co nnection establishment time, see
6.4.4.4.3.1.”
New paragraph:
“For data integrity reasons, in this profile the default value of the maximum information length
- receive and maximum information field length - transmit HDLC parameters is 128 bytes.
Other values may be negotiated at connection establishment time, see 6.4.4.4.3.1.
Note: In order to ensure a minimal performance, the master station should offer at least a max_info_field
length_receive of 128 bytes. ”
The same changes will be made in Clause 6.3.4 .3.3 of [3].
4.2.2
Change in IEC 62056-62 and the Blue Book
Clause A.5 of [4] will be changed as follows:
A.5
IEC HDLC Setup (class_id: 23)
An instance of the IEC HDLC Setup class contains all data necessary to set up a
communication channel according to IEC 62056-46. Several communication channels can be
configured. The logical_names shall be as defined in D 1.1.12.
IEC HDLC setup
Attribute(s)
1. logical_name
2. comm_speed
3. window_size_
transmit
4. window_size_
receive
5. max_info_field_
length_transmit
6. max_info_field_
length_receive
7. inter_octet_time_
out
8. inactivity_time_
out
9. device_address
Specific method(s)
0..n
class_id = 23, version = 0
(static)
Data type
octet-string
enum
unsigned
(static)
unsigned
(static)
long-unsigned
32
2030
128
(static)
long-unsigned
32
2030
128
(static)
long-unsigned
20
6000
25
(static)
long-unsigned
0
(static)
long-unsigned
m/o
16
(static)
(static)
Min.
Max.
Def
0
1
9
7
5
1
1
7
1
120
0x3FFD
0
Notes:

The maximum value of the attributes max_info_field_length_transmit and max_info_field_length_receive has
been increased from 128 to 2030 for efficiency reasons.
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DLMS User Association

In order to ensure a minimal performance,
max_info_field_length_receive of 128 bytes.

The maximum value of the inter-octet-time-out attribute has been increased from 1000 ms to 6000 ms in order
to allow using communication media, where long delays may occur. The default value has been changed to 25
ms to align with Clause 6.4.4.3.3. of IEC 62056-46.
the
primary
station
should
offer
at
least
Attribute Description
comm_speed
The communication speed supported by the corresponding
port
Enum: (0)
300 baud
(1)
600 baud
(2)
1 200 baud
(3)
2 400 baud
(4)
4 800 baud
(5)
9 600 baud
(6)
19 200 baud
(7)
38 400 baud
(8)
57 600 baud
(9)
115 200 baud
This communication speed can be overridden if the HDLC
mode of a device is entered through a special mode of
another protocol.
window_size_transmit
The maximum number of frames that a device or system can
transmit before it needs to receive an acknowledgement from
corresponding station. During logon a smaller value can be
negotiated.
window_size_receive
The maximum number of frames that a device or system can
receive before it needs to transmit an acknowledgement to
the corresponding station. During logon a smaller value can
be negotiated.
The maximum information field length that a device can
transmit. During logon a higher or lower value can be
negotiated.
The maximum information field length that a device can
receive. During logon a higher or lower value can be
negotiated.
Defines the time, expressed in ms, over which, when any
character is received from the primary station, the device will
treat the already received data as a complete frame.
Defines the time, expressed in seconds over which, when
any frame is received from the primary station, the device
will process a disconnection.
When this value is set to 0, this means that the
inactivity_time_out is not operational.
max_info_length_transmit
max_info_length_receive
Inter_octet_time_out
inactivity_time_out
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DLMS User Association
device_address
Contains the physical device address of a device:
In case of single
0x00
0x01…0x0F
0x10...0x7D
0x7E
0x7F
byte addressing:
NO_STATION Address
Reserved for future use
Usable address space
‘CALLING’ device address
Broadcast address
In case of double byte addressing:
0x0000
NO_STATION Address
0x0001..0x000F Reserved for future use
0x0010..0x3FFD Usable address space
0x3FFE
‘CALLING’ Physical Device address
0x3FFF
Broadcast address
The same change will be made to Clause 4.4.5 of [5].
Clause C1 of IEC 62056-62 – Using short names
The version of IC 23 will be amended from 0 to 1. Same change will be made in Clause 4.5.1.
of the Blue book.
Annex E of IEC 62056-62
Version 0 of the interface class (see below) will be added to Annex E. The same change will
be made in Clause 4.7 of the Blue Book.
IEC HDLC Setup (class_id: 23, version 0)
An instance of the IEC HDLC Setup class contains all data necessary to set up a
communication channel according to IEC 62056-46. Several communication channels can be
configured. The logical_names shall be as defined in D.1.1.12.
IEC HDLC setup
Attribute(s)
1. logical_name
2. comm_speed
3. window_size_
transmit
4. window_size_
receive
5. max_info_field_
length_transmit
6. max_info_field_
length_receive
7. inter_octet_time_
out
8. inactivity_time_
out
9. device_address
Specific method(s)
0..n
class_id = 23, version = 0
(static)
(static)
(static)
Data type
octet-string
enum
unsigned
Min.
Max.
Def
0
1
9
7
5
1
(static)
unsigned
1
7
1
(static)
unsigned
32
128
128
(static)
unsigned
32
128
128
(static)
long-unsigned
20
1000
30
(static)
long-unsigned
0
(static)
long-unsigned
16
m/o
6
120
0x3FFD
0
DLMS User Association
Attribute Description
comm_speed
The communication speed supported by the corresponding
port
A.5.1.1.1.1
Enum:
(0)
300 baud
(1)
600 baud
(2)
1 200 baud
(3)
2 400 baud
(4)
4 800 baud
(5)
9 600 baud
(6)
19 200 baud
(7)
38 400 baud
(8)
57 600 baud
(9)
115 200 baud
This communication speed can be overridden if the HDLC
mode of a device is entered through a special mode of
another protocol.
window_size_transmit
The maximum number of frames that a device or system can
transmit before it needs to receive an acknowledgeme nt from
corresponding station. During logon a smaller value can be
negotiated.
window_size_receive
The maximum number of frames that a device or system can
receive before it needs to transmit an acknowledgement to
the corresponding station. During logon a smaller value can
be negotiated.
The maximum information field length that a device can
transmit. During logon a smaller value can be negotiated.
max_info_length_transmit
max_info_length_receive
Inter_octet_time_out
inactivity_time_out
device_address
The maximum information field length that a device can
receive. During logon a smaller value can be negotiated.
Defines the time, expressed in ms, over which, when any
character is received from the primary station, the device will
treat the already received data as a complete frame.
Defines the time, expressed in seconds over which, when
any frame is received from the primary station, the device
will process a disconnection.
When this value is set to 0, this means that the
inactivity_time_out is not operational.
Contains the physical device address of a device:
In case of single byte addressing:
0x00
NO_STATION Address
0x01…0x0F
Reserved for future use
0x10...0x7D
Usable address space
0x7E
‘CALLING’ device address
0x7F
Broadcast address
In case of double byte addressing:
0x0000
NO_STATION Address
0x0001..0x000F Reserved for future use
0x0010..0x3FFD Usable address space
0x3FFE
‘CALLING’ Physical Device address
0x3FFF
Broadcast address
4.3
Change in conformance testing
See Clause 6 of this document.
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DLMS User Association
5
Maximum value of inter_octet_time out
5.1
The problem
Version 0 of IC 23 specifies the maximum value of the parameter inter_octet_time_out as
1000 ms. It has been found that in some cases this is not suf ficient, as there are
communication media when long delays may occur. For example, with GSM delays of 3 s
have been found in one direction.
5.2
The solution
To accommodate these requirements, it is proposed to increase the maximum value of this
parameter to 6000 ms in the new version of the interface class.
5.2.1
Amendment to IEC 62056-46 and the Green Book
No changes are necessary.
5.2.2
Amendment to IEC 62056-62 and the Blue Book
The changes are shown already in 4.2.2 of this document.
5.2.3
Modification to conformance testing
The test is defined in Clause 3.1.2 of the Data link layer test plan: test HDLC_6. No change is
necessary.
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DLMS User Association
6
Change in the conformance test specification and test plans
6.1
Support of IC 23 version 0 and 1
The CTT should support both version 0 and 1 of the interface class 23 IEC HDLC setup.

The manufacturer has to declare the version of the IC 23 used: 0 or 1 and the values of
the HDLC parameters used by the server.
6.2

On the data link layer level: Secondary stations using version 0 o f the interface class
send back the max_information_field_length parameter values on one byte. Secondary
stations using version 1 send the parameter on two bytes. The CTT shall be able to
handle both.

On the COSEM objects test level, the CTT should accept both version 0 and version 1
of IC 23.
Length of the information field in the SNRM frame
The CTT shall test that the server refuses an SNRM frame in which the length of the
information field is more than 2030.
The test is described in Clause 3.1.5.13 of [6]: Test HDLC_1 subtest 12, and it has to be
modified. In Pack 3 (V0.17) of the test tool the test is done with an information field length of
7*256-1. This is not correct, as it is still a valid value.
Test HDLC_1 Subtest 12: Too long information field
Test Case
Reference
Classification
Precondition
Preamble
Do
Check
Postamble
Incorrect frame field values – Too long information field
[1] 6.4.3.10
Negative test case.
Send an SNRM frame with an information field with the length 2031.
If the result is not NoResponse, the verdict is FAILED H1.12.1
Make sure that the device is still there by sending a correct SNRM frame. If
there is no response, the result is FAILED H1.12.2.
Remark
6.3
Parameter negotiation - max_info_field_length

If version 0 is used, the CTT shall test the max_info_field_length parameter negotiation
with sending a value of 32 D (the minimum value specified in the interface class). The
secondary station shall accept it, or if the value is too small for the server, it may refuse it
by sending a DM frame. If the proposed value is refused, the CTT shall propose a value of
128. The server shall accept it and send back an UA with the correctly negotiated HDLC
parameters.

If version 1 is used, the CTT shall test the parameter negotiation with sending different
values between 32 and 2030 and checking the negotiated parameters against the values
declared in the PICS.

If the proposed value is larger than 2030 D , the server shall refuse the connection.
This test is defined in Clause 3.2.2.3 of the Data link layer test plan as HDLC_2 Subtest 3.
and shall be modified as follows:
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DLMS User Association
Test Case
Reference
Classification
Precondition
Preamble
Do
Mode change to NRM - SNRM with information field
ClientMaxInfoFieldLength parameter negotiation
[1] 6.4.4.4.3.2
Positive test case.
Set Client HDLC parameters to default values.
Change the max_info_field_length transmit and receive parameters to 32 D .
Expect a UA frame with a max_info_field_length receive and transmit
parameters with a value of 32 D .
If a DM frame is received go to the second pass:
Send a DISC and expect a DM.
Check
Set the max_info_field_length transmit and receive parameters to 12 8. Send
an SNRM frame.
If there is no response, or if after the second pass the response is not an UA
frame, or the negotiated HDLC parameters are not correct (values between
32 and 128) then the Verdict is FAILED.
Postamble
Remark
HDLC_2 SubTest 4
The purpose of this test is to check that the server refuses a proposed value of the
max_info_field_length parameter above 2030.
Test Case
Reference
Classification
Precondition
Preamble
Do
Check
Postamble
Mode change to NRM – SNRM with information field
ClientMaxInfoFieldLength parameter negotiation
[1] 6.4.4.4.3.2
Positive test case.
Set Client HDLC parameters to default values.
Change the ClientMaxInfoLengthReceive to 2031. Send an SNRM frame.
If the response is not a DM, the result is FAILED.
Check that the server is still there by sending a correct SNRM frame and
expect an UA frame. Send a DISC and expect a DM.
Remark
6.4
Parameter negotiation: window_size
The test is already described in Clause 3.2.2.4 of [6] as Test HDLC_2 Subtest 4 and it has to
be modified to test also that the server sends back the window size parameters on four bytes.
Test Case
Reference
Classification
Precondition
Preamble
Do
Check
Postamble
Mode change to NRM – SNRM with information field
window size parameter negotiation
[1] 6.4.4.4.3.2
Positive test case.
Set Client HDLC parameters to default values.
Chamge the client window_size (receive) parameter to 2 and sen d an SNRM
frame.
If there is no response, or the response is not an UA frame, or the negotiated
parameter is not sent back as a four byte value, or the negotiated parameter
is not correct, then the Verdict is FAILED H2.XXX
Disconnect the data link layer.
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DLMS User Association
Remark
6.5
Length of information field in an I or UI frame
This is a new test. The CTT shall test that if an I or UI frame has an information field which is
longer than 2030 D , the server answers with an FRMR frame.
According to Clause 6.4.3.10 of IEC 62056-46, if the length of the information field in an I
frame exceeds the max_info_field_length which can be accommodated by the secondary
station, the secondary station shall respond with an FRMR frame.
Test Case
Reference
Classification
Precondition
Preamble
Do
Check
Postamble
I frame exchange – too long information field
[1] 6.4.3.10
Negative test case.
The data link layers are connected, the HDLC parameters have been correctly
negotiated, the secondary station is NRM mode.
Send an I frame with an information field which is longer than the negotiated
server_max_info_field_length_receive parameter.
The server shall send back an FRMR frame.
Check that the data link layer is still connected by sending a good I frame and
check the response.
Remark
11