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HDLC23V1_020123

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HDLC23V1_020123

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 The problem .................................................................................................... 2

    3.2 The solution .................................................................................................... 3

    3.2.1 Change in IEC 62056-46 and in the Green Book ....................................... 3

    3.3 Change in conformance testing ......................................................................... 3 4 Maximum value of the maximum_information_field_length parameter ............................. 3

    4.1 The problem .................................................................................................... 3

    4.2 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 5 Maximum value of inter_octet_time out ....................................................................... 8

    5.1 The problem .................................................................................................... 8

    5.2 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 6 Change in the conformance test specification and test plans ......................................... 9

    6.1 Support of IC 23 version 0 and 1 ....................................................................... 9

    6.2 Length of the information field in the SNRM frame ............................................... 9

    6.3 Parameter negotiation - max_info_field_length .................................................... 9

    6.4 Parameter negotiation: window_size ................................................................ 10

    6.5 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 HDLC parameter negotiation

    3.1 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 smaller 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 32-128 in case of version 0 of IC DD

    23. The length of parameters 7 and 8 is 4 bytes, the value is 1 to 7. DD

    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 in [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 Maximum value of the maximum_information_field_length parameter

    4.1 The problem

    Version 0 of IC 23 defines the default and maximum values of the

    max_info_field_length_receive and _transmit parameters as 128 (type unsigned). D

    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 and the default value 128. DD

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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 connection 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 0..n class_id = 23, version = 0

    Attribute(s) Data type Min. Max. Def

    1. logical_name (static) octet-string

    2. comm_speed (static) 0 9 5 enum

    3. window_size_ (static) 1 7 1 unsigned

    transmit

    4. window_size_ (static) unsigned 1 7 1

    receive

    5. max_info_field_ (static) long-unsigned 32 2030 128

    length_transmit

    6. max_info_field_ (static) long-unsigned 32 2030 128

    length_receive

    7. inter_octet_time_(static) long-unsigned 20 6000 25

    out

    8. inactivity_time_ (static) long-unsigned 0 120

    out

    9. device_address (static) long-unsigned 16 0x3FFD 0

    Specific method(s) m / o

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, the primary station should offer at least a 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.

    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.

    max_info_length_transmit The maximum information field length that a device can

    transmit. During logon a higher or lower value can be

    negotiated.

    max_info_length_receive The maximum information field length that a device can

    receive. During logon a higher or lower value can be

    negotiated.

    Inter_octet_time_out 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.

    inactivity_time_out 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.

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DLMS User Association

    device_address 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

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 0..n class_id = 23, version = 0 Attribute(s) Data type Min. Max. Def 1. logical_name (static) octet-string 2. comm_speed (static) 0 9 5 enum

    3. window_size_ (static) 1 7 1 unsigned

    transmit

    4. window_size_ (static) unsigned 1 7 1

    receive

    5. max_info_field_ (static) unsigned 32 128 128

    length_transmit

    6. max_info_field_ (static) unsigned 32 128 128

    length_receive

    7. inter_octet_time_(static) long-unsigned 20 1000 30

    out

    8. inactivity_time_ (static) long-unsigned 0 120

    out

    9. device_address (static) long-unsigned 16 0x3FFD 0 Specific method(s) m / o

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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 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.

    max_info_length_transmit The maximum information field length that a device can

    transmit. During logon a smaller value can be negotiated.

    max_info_length_receive The maximum information field length that a device can

    receive. During logon a smaller value can be negotiated.

    Inter_octet_time_out 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.

    inactivity_time_out 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.

    device_address 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 sufficient, 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.

    ; On the data link layer level: Secondary stations using version 0 of 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.

    6.2 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 Incorrect frame field values Too long information field

    Reference [1] 6.4.3.10

    Classification Negative test case.

    Precondition

    Preamble

    Do Send an SNRM frame with an information field with the length 2031.

    Check If the result is not NoResponse, the verdict is FAILED H1.12.1

    Postamble 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(the minimum value specified in the interface class). The D

    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, the server shall refuse the connection. D

    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 Mode change to NRM - SNRM with information field

    ClientMaxInfoFieldLength parameter negotiation

    Reference [1] 6.4.4.4.3.2

    Classification Positive test case.

    Precondition

    Preamble Set Client HDLC parameters to default values.

    Do . Change the max_info_field_length transmit and receive parameters to 32D

    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.

    Set the max_info_field_length transmit and receive parameters to 128. Send

    an SNRM frame.

    Check 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 Mode change to NRM SNRM with information field

    ClientMaxInfoFieldLength parameter negotiation

    Reference [1] 6.4.4.4.3.2

    Classification Positive test case.

    Precondition

    Preamble Set Client HDLC parameters to default values.

    Do Change the ClientMaxInfoLengthReceive to 2031. Send an SNRM frame.

    Check If the response is not a DM, the result is FAILED.

    Postamble 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 Mode change to NRM SNRM with information field

    window size parameter negotiation

    Reference [1] 6.4.4.4.3.2

    Classification Positive test case.

    Precondition

    Preamble Set Client HDLC parameters to default values.

    Do Chamge the client window_size (receive) parameter to 2 and send an SNRM

    frame.

    Check 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

    Postamble Disconnect the data link layer.

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