Vodafone Digital Subscriber Signalling System No. 1 DSS1 Layer 2: LAPD

Transcription

1 nterface Specification Vodafone Digital Subscriber Signalling System No. 1 DSS1 Layer 2: LAPD nterface Specification Version: Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 1 of 31

2 nterface Specification Contents Contents...2 Conventions...3 Contact Scope References Normative References Reference Acquisition Definitions and Abbreviations Definitions Abbreviations Tables...7 Annex A Protocol Capabilities (PC) Annex B Frames Protocol Data Units (FR) Annex C System parameters (SP) History Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 2 of 31

3 nterface Specification Conventions The statement of compliance is abbreviated as follows: = mplemented, the function is implemented according to the relevant TU-T Recommendation, unless the "comment" field specifies a variation, NU = Not Used, the function is not implemented, NA = Not Applicable-- = Descriptive text or title in the recommendation, no comment necessary. Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 3 of 31

4 nterface Specification Contact Vodafone GmbH Ferdinand-Braun-Platz Düsseldorf Germany Telefon: +49 (0) Website: Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 4 of 31

5 nterface Specification 1 Scope The implementation of the DSS1 Layer 2 in EWSD is based on the specification produced by ETS and TU-T (previously CCTT) to support the services and Supplementary Services of the memorandum of understanding (MOU). This interface specification may be changed at any time. The user of this interface specification has to check for the newest version available from Vodafone GmbH. This interface specification may be superseded in total or in part by the terms of a contract between the individual network user and Vodafone GmbH. Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 5 of 31

6 nterface Specification 2 References n the case of a conflict between specific requirements in this document with requirements in any of the directly or indirectly referenced documents, the specific requirements of this document are applicable. 2.1 Normative References The publications listed hereafter form the basis for the DSS1 Layer 2 implementation in EWSD. Q.920 TU-T Rec. Q.920 (.440) (03/93) DGTAL SUBSCRBER SGNALLNG SYSTEM No. 1 (DSS1) SDN USER-NETWORK NTERFACE DATA LNK LAYER GENERAL ASPECTS. Q.921 TU-T Rec. Q.921 (.440) (03/93) SDN USER-NETWORK NTERFACE DATA LNK LAYER SPECFCATON X ETS Rec. prets X (09/1991) ntegrated Services Digital Network (SDN); User-network interface data link layer specification Application of CCTT Recommendations Q.920/.440 and Q.921/ Reference Acquisition European Telecommunications Standards nstitute: TU Recommendations: Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 6 of 31

7 nterface Specification 3.1 Definitions 3 Definitions and Abbreviations The definitions in the referenced standards apply. 3.2 Abbreviations The definitions in the referenced standards apply. 4 Tables n order to give information about the implemented messages, parameters and procedures, each relevant paragraph of the TU-T Rec. Q.92X is listed thereafter in tabular form. Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 7 of 31

8 nterface Specification TU-T Rec. Statement of Comment Q.920 DGTAL SUBSCRBER -- SGNALLNG SYSTEM No. 1 (DSS1) SDN USER-NETWORK NTERFACE DATA LNK LAYER GENERAL ASPECTS Q General The NOTE 1 is modified as follow: The physical layer is currently defined in Recommendations.430 [8] and.431 [9], and prets [14] and prets [15], respectively, and layer 3 is defined in Recommendations Q.930 (.450) [10], Q.931 (.451) [11] and ETS [16], ETS [17], and X.25 [4]. References should be made to these Recommendations for the complete definition of the protocols and procedures across the SDN user-network interface. The NOTE 2 is modified as follow: The term "data link layer" is used in the main text of this Recommendation. However, mainly in figures and tables, the terms "layer 2" and "L2" are used as abbreviations. Furthermore, in accordance with Recommendations Q.930 (.450) [10] and Q.931 (.451) [11], and ETS [16] and ETS [17], the term "layer 3" is used to indicate the layer above the data link layer. Q Concepts and terminology Clarification for basic access: Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 8 of 31 For point-to-point configurations, the layer 2 will support the data link (SAP = 0 (signalling), TE = 0) and (SAP = 16, (p-data conforming to X.25), TE = 0) and in addition one management link (SAP = 63, TE = 127 (broadcast)). The management link is only used in certain failure conditions. For point-to-multipoint configurations, the SAP-values 0, 16, 63 are supported. Note: SAP = 1 (P-data conforming to Q.931) is not supported, because only X.25-p- Data-Terminals can be connected via X.25-Terminal-adapters and the p-data are routed to the packet handler. The layer 2 will only support one link for SAP = 0 and TE = 0 is allocated for this purpose. Broadcast data link entities are not applicable. Q Overview description of LAPD -- functions and procedures Q General For point-to-point configurations, only point-to-point data link connections and layer management connections are applicable. Q Unacknowledged operation For point-to-point configurations, only point-to-point data link connections and layer management connections are applicable. Q Acknowledged operation Q Establishment of information transfer modes --

9 TU-T Rec. Statement of Comment Q Data link connection identification Clarification for basic access: Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 9 of 31 nterface Specification For point-to-point configurations, the layer 2 will support the data links (0, 0) and (16, 0) and in addition one management link (63, 127). The layer 2 will only support one link for SAP1 = 0, and TE = 0 is allocated for this purpose. Q Data link states Clarification for basic access: For point-to-point configurations, the data link entities are never in the TE-unassigned state, because the TE-value=0 is reserved for this case. Please refer to our comments to Annex B.2. Q TE administration This clause is Not Applicable for primary rate access. For point-to-point configurations, the TE procedures are not supported. Q Establishment of multiple frame operation Q Service characteristics -- Q General Q Services provided to layer 3 Q Unacknowledged information transfer service This clause is Not Applicable for primary rate access. The network does not use U-frames for transmission of messages. On receipt of an U-frame, the network treats the frame according to Q This clause is Not Applicable for primary rate access. The network does not send U-frames. Q Acknowledged information transfer service Q Services provided to layer management Q Administrative services Data link connection parameter passing is not supported. This clause is not used for primary rate access. Q Model of the data link service - Q General Clarification for basic access:

10 nterface Specification TU-T Rec. Statement of Q Data link layer representation as - seen by layer 3 Q Data link connection endpoint states Q Broadcast data link layer connection services Comment For point-to-point configuration, a broadcast information (i.e. TE=127) transfer mode is not applicable for data link connections. A broadcast information (i.e. TE = 127) transfer mode is not applicable. Table 1/Q.920: DL-UNT DATA is not supported. Clarification for basic access: For point-to-point configurations, a broadcast data link layer connection is not applicable for data link connections. This clause is Not Applicable for primary rate access. Q Point-to-point data link connection endpoint services Clarification for basic access: For point-to-point configurations: Layer 2 will support the data links (0, 0) and (16, 0) and in addition one management link (63, 127) Layer 2 in the link connection established state, if the layer 2 is permanently activated via MML-command (for SAAP=0) or if layer 2 layer 3 are established for a connection. Q Q Sequences of primitives at one point-to-point data link connection endpoint Services required from the physical layer The network does not use U-frames for transmission of messages. On receipt of an U-frame, the network treats the frame according to Q of this specification. Layer 2 will only support one link for SAP = 0 and TE = 0 is allocated for this purpose. Layer 2 is under normal operation conditions in the link connection established state, but the other states are implemented and used when the data link connection is established, re-established or released. The last part of paragraph is modified as follow: The primitives between management entities and the physical layer are: Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 10 of 31

11 TU-T Rec. Q Data link layer - Management structure Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 11 of 31 Statement of Comment Q Data link procedure Q Multiplex procedure Clarification for basic access: nterface Specification iv) activation: MPH-ACTVATE-NDCATON This primitive is used to indicate that the physical layer connection has been activated. v) deactivation: MPH-DEACTVATE-REQUEST/NDCATON These primitives are used to request deactivation of the physical layer connection and to indicate that the physical layer connection has been deactivated. The REQUEST is used at the network side only. vi) MPH-NFORMATON-NDCATON: This primitive is used to indicate to user management entities information regarding the physical layer condition. Two parameters are defined: connected and disconnected. For point-to-point configurations, the broadcast data link entity is not applicable. Parameter initialisation procedures are not supported. For point-to-point configurations, layer 2 will support the data links (0, 0) and (16, 0) and in addition one management link (63, 127). Layer 2 will only support one link for SAP = 0, and TE = 0 is allocated for this purpose. Q Structure of the data link procedure For point-to-point configurations, the broadcast data link entity is not applicable. Q Overall data link layer functional diagram - Q General Q Enhanced functional block diagram and block interaction diagram Q.921. SDN USER-NETWORK NTERFACE-DATA LNK LAYER -- Clarification for basic access: For point-to-point configurations, layer 2 will support the data links (0, 0) and (16, 0) and in addition one management link (63, 127). Broadcast data link entities are not applicable. Layer 2 will only support one link for SAP = 0, and TE = 0 is allocated for this purpose.

12 TU-T Rec. Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 12 of 31 Statement of Comment nterface Specification SPECFCATON Q General The third sentence of NOTE 1 is modified as follows: Furthermore, in accordance with Recommendations Q.930 (.450) [2] and Q.931 (.451) [3], and ETS [9] and ETS [10], the term "layer 3" is used to indicate the layer above the data link layer. Q Frame structure for peer-to-peer -- communication Q General Q Flag sequence The last sentence is modified as follows: See SDN User-Network nterfaces: Layer 1 Recommendations.430 [4] and.431 [5], and prets [7] and prets [8], respectively, for applicability. Q Address field The LAPB data link connection is not supported, because the LAPB address field is not sufficient for SDN (it cannot contain SAP plus TE). f the network receives a LAPB-frame, the frame is treated as an invalid frame as described in Q Q Control field Q nformation field Q Transparency Q Frame check sequence (FCS) field Q Format convention Q Numbering convention Q Order of bit transmission Q Field mapping convention Q nvalid frames Q Frame abort Q Elements of procedures and formats -- of fields for data link layer peer-topeer communication Q General Q Address field format Q Address field variables -- Q Address field extension bit (EA) Q Command/response field bit (C/R) Q Service access point identifier (SAP) Clarification for basic access: The network only accepts frames which have one of the following SAP values: 0, 16, 63. Note: SAP=1 (p-data conforming to Q.931) is not supported, because only X.25-p-

13 TU-T Rec. Statement of Comment nterface Specification Data-Terminals can be connected via X.25-Terminal-adapters and the p-data are routed to the packet handler. n EWSD also the SAP=32 is used for loop tests in the NT. The Terminal Equipment only use SAP=0, 16, 63. Table 2/Q.921: Only SAP = 0 is supported. Q Terminal endpoint identifier (TE) Clarification for basic access: Q TE for broadcast data link connection For point-to-point configurations, layer 2 will support the data links (0, 0) and (16, 0) and in addition one management link (63, 127). Layer 2 will only support one link for SAP = 0, and TE = 0 is allocated for this purpose. For point-to-point configurations, broadcast data link connection is not supported. This clause is Not Applicable for primary rate access. Q TE for point-to-point data link connection Q Control field formats Q nformation transfer () format Q Supervisory (S) format Q Unnumbered (U) format Q Control field parameters and associated state variables Q Poll/Final (P/F) bit Q Multiple frame operation variables -- and sequence numbers Q Modulus Q Send state variable V(S) Q Acknowledge state variable V(A) Q Send sequence number N(S) Q Receive state variable V(R) Q Receive sequence number N(R) Q Unacknowledged operation variables and parameters Q Frame types -- For point-to-point configurations, only TE=0 is used. Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 13 of 31

14 Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 14 of 31 nterface Specification TU-T Rec. Statement of Comment Q Commands and responses The XD command/response frame is not supported (according to Appendix V.4). f the network receives a XD frame, no action is taken. Parameter negotiation procedures are not supported, the parameter values are fixed in the exchange and cannot be changed. Q nformation () command Q Set asynchronous balanced mode extended (SABME) command Q Disconnect (DSC) command For point-to-point configurations, the network does normally not initiate the termination of multiple frame operation. However, mechanisms for terminating the multiple frame operation are implemented for failure conditions. Q Unnumbered information (U) command The network does not support U-frames for transmission of messages. On receipt of an U-frame, the network treats the frame according to Q Q Receive ready (RR) command/response Q Reject (REJ) command/response The optional procedure for the retransmission of an REJ response frame (see Appendix ) is not supported. Q Receive not ready (RNR) command/response Q Unnumbered acknowledgement (UA) response Q Disconnected mode (DM) response Q Frame reject (FRMR) response NA The network does never send the Frame reject (FRMR) response frame, because not all terminals can handle FRMR. f the network receives a FRMR frame, actions according to Q of this specification, are taken. On receiving of an incorrect frame, the exchange resets layer 2 by SABME. Q Exchange identification (XD) NU Exchange identification is not supported (refer to Appendix V). command/response Q Elements for layer-to-layer -- communication Q General Q Generic names -- Q DL-ESTABLSH Q DL-RELEASE Q DL-DATA Table 6/Q.921: DLU-UNT DATA, MDL-UNT DATA and MDL-XD are not supported.

15 TU-T Rec. Statement of Comment Q DL-UNT DATA Q MDL-ASSGN Q MDL-REMOVE Q MDL-ERROR Q MDL-UNT DATA Q MDL-XD Q PH-DATA Q PH-ACTVATE Q PH-DEACTVATE Q MPH-ACTVATE (see Appendix ) Q MPH-DEACTVATE (see Appendix ) Q MPH-NFORMATON Q Primitive types -- Q request Q indication Q response Q confirm Q Parameter definition -- Q Priority indicator Q Block interaction diagram of the data link layer Q Definition of the peer-to-peer procedures of the data link layer Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 15 of 31 nterface Specification This clause is Not Applicable for primary rate access. t is only relevant for TE side (user side). Q Parameter data Q Primitive procedures -- Q General Q Layer 3 Data link layer interactions For point-to-point configurations, the broadcast data link connection endpoint is not applicable. Layer 2 is in the link connection established state, if the layer 2 is permanently activated via MML-command (for SAP=0) or if layer 2 and layer 3 are established for a connection, but the other states are implemented and used during establishment, reestablihment or release of the data link connection. The XD command/response frame is not supported. f the network receives a XD frame no action is taken (please refer to our clarification to Q ).

16 TU-T Rec. Statement of Comment Q Procedure for the use of the P/F bit -- Q Unacknowledged information transfer Q Acknowledged multiple frame Note is not supported, i.e. LAPB is not supported. information transfer Q Procedures for unacknowledged -- information transfer Q General Q Q Q Transmission of unacknowledged information Receipt of unacknowledged information Terminal endpoint identifier (TE) management procedures Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 16 of 31 This clause is Not Applicable for primary rate access. The network does not support U-frames for transmission of messages. nterface Specification At the network side, the system management entity provides that the PH- DEACTVATE-NDCATON primitive will be issued only, if persistent deactivation has occurred. However, at the user side, the conditions to issue a PH-DEACTVATE- NDCATON primitive depend on the implementation of the physical layer. This clause is Not Applicable for primary rate access. The network does not support U-frames for transmission of messages. This clause is Not Applicable for primary rate access. f an U-frame is received, the frame will be discarded. -- Layer Management: There will be no TE management procedures (no TE assignment procedures, TE removal, TE check, TE dentify verify, because only the TE value 0 is used (Refer to our clarification to Q.921/Annex A). Q General Q TE assignment procedure The network selects a TE value from a map of the full range of automatic TE values (64-126), or, if some TE values are currently in use, from an updated list of all automatic TE values available for assignment.

17 TU-T Rec. Statement of Comment Q Expiry of timer T202 Q TE check procedure -- Q Use of the TE check procedure Q Operation of the TE check procedure Q TE removal procedure Q Action taken by the data link layer entity receiving the MDL-REMOVE request primitive Q Conditions for TE removal Q TE identity verify procedure -- Q General Q Operation of the TE identity verify procedure nterface Specification f the exchange receives an D verify with A equal to an unassignment TE (i.e. a request from the terminal, whether is TE (=A) is correct), the exchange responds with an D remove message with the same A value. Exch. TE TE-unassign. U (SAP, TE) (D verify,a) 1) 2) 3) U (SAP, TE) (D remove,a) U (SAP, TE) (D remove,a) TE-unassign. SAP = 63, TE = 127 n frame 1: A = A TE value which is not marked assigned in the Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 17 of 31

18 nterface Specification TU-T Rec. Statement of Comment Network. n frame 2 and 3:A = The same A value as in frame 1. Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 18 of 31 The user side layer management entity receiving any identity check message shall compare the content of the A field to is TE value requested being verified and to the value 127 (indicating that all TE values are to be checked). t shall stop timer T202 if there is a match. n any case, it has to respond on an identity check message according to the TE check procedure as defined in Q Q Expiry of Timer T202 Q Formats and codes -- Q General Q Layer management entity identifier Q Reference number (Ri) Q Message type Q Action indicator (Ai) Q nitialization of data link layer - parameters Q General Please refer to comments to Appendix V. Q Parameter initialization Please refer to comments to Appendix V. Q nternal parameter initialization Please refer to comments to Appendix V. Q Automatic negotiation of data link Please refer to comments to Appendix V. layer parameter values Q Procedures for establishment and -- release of multiple frame operation Q Establishment of multiple frame Only modulo 128 is implemented operation Q General

19 nterface Specification TU-T Rec. Statement of Comment Q Establishment procedures Q Procedure on expiry of timer T200 Q nformation transfer Q Termination of multiple frame operation -- For point-to-point configurations, the network does normally not initiate the termination of multiple frame operation. However, mechanisims for terminating the multiple frame operation are implemented for failure conditions. Q General The persistent layer 1 deactivation is assumed to be a port, that is barred in layer 1; this means, that an awake-signal from the user is ignored. The state persistent layer 1 deactivation does not exist. The primitive PH-DEACTVATE-NDCATON is used to acknowledge a layer 1 deactivation to layer 2. Q Release procedure Q Procedure on expiry of timer T200 Q TE-assigned state Clarification for basic access: An unsolicited DM response with the F-bit set to 0 is ignored, because LAPB operation is not supported. Q Collision of unnumbered commands -- and responses Q dentical transmitted and received commands Q Different transmitted and received commands Q Unsolicited DM response and SABME or DSC command NU Q Procedures for information transfer in multiple frame operation Q Transmitting frames Q Receiving frames Q P bit set to 1 Q P bit set to 0 Q Sending and receiving -- Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 19 of 31 This case is a relic from LAPB-procedures, to be able to request a layer 2- establishment from the slave in the unbalanced mode. The exchange/terminal requests a layer 2 establishment with SABME (i.e. balanced mode), so the establishment according to Table 9/Q.921 (DM response, F=0/TEassigned) is not applicable. A LAPB operation is not supported (please refer to our clarification to Q ).

20 TU-T Rec. Statement of Comment nterface Specification acknowledgements Q Sending acknowledgements Q Receiving acknowledgements Q Receiving REJ frames Q Receiving RNR frames f the peer layer 2 enters the Busy State, this condition will be scanned with the timer T200 till N2X4 times. f no release of the peer busy state will be advised after the last inquiry, then the layer 2 connection will be reestablished. Q Data link layer own receiver busy condition Q Waiting acknowledgement Q Re-establishment of multiple frame -- operation Q Criteria for re-establishment Clarification for basic access: An unsolicited DM response with the F-bit set to 0 is ignored, because LAPB operation is not supported. This case is a relic from LAPB-procedures, to be able a layer 2-establishment from the slave in the unbalanced mode. The exchange/terminal requests a layer 2 establishment with SABME (i.e. balanced mode), so the establishment according to Table 9/Q.921 (DM response, F=0/TEassigned) is not applicable. Q Procedures Q Exception condition reporting and recovery Q N(S) sequence error The optional procedures of Appendix are not supported. Q N(R) sequence error The information field contained in an frame which is correct in sequence and format is delivered to layer 3 by means of the DL-DATA-NDCATON primitive. Q Timer recovery condition Q nvalid frame condition Q Frame rejection condition ncorrect length means more than 6 octets between the flags for supervisory frames or more than 5 octets between the flags for unnumbered frames, or more than 265 octets between the flags for U-frames. Frame rejection condition means: sending a REJ-frame. Q Receipt of an FRMR response frame Q Unsolicited response frames Replace Establish by gnore in the matrix-field: DM response, F=0 TE assigned. Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 20 of 31 LAPB is not supported by Siemens; therefore a layer 2-establishment with DM from TE is not applicable in the state TE assigned (refer to 5.5.6). The data link layer will always be established with SABME.

21 TU-T Rec. Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 21 of 31 Statement of Comment Note: We assume an inconstancy in ETS (Table 9/Q.921 Q ). Q Duplicate assignment of a TE value Q List of system parameters Parameter negotiation is not supported (please refer to Appendix V.4). Q Timer T200 Default value T200 = 1 s is used. Q Q Q Maximum number of retransmissions (N200) Maximum number of octets in an information field (N201) Maximum number of transmissions of the TE dentity request message (N202) NA Default value N200 = 3 is used. Default value N201 = 260 octets is used. Not applicable in the network side. Q Maximum number of outstanding The default values are used for the window size. frames (k) Q Timer T201 Default value T201 = 1s is used. nterface Specification Q Timer T202 NA Not applicable in the network side. Q Timer T203 Default value T203 = 10s is used. Q Data link layer monitor function -- Q General The paragraph is modified as follows: The procedural elements defined in 5 allow for the supervision of the data link layer resource. This section describes procedures which may be used to provide this supervision function. The use of this function is mandatory for network side data link layer entities in European networks but optional for a user side data link layer entity. Q Data link layer supervision in the multiple-frame-established state Q Connection verification procedures -- Q Start timer T203 Q Stop timer T203 Q Expiry of timer T203 Q.921.A Provision of point-to-point signalling connections Q.921.B SDL for point-to-point procedures - Q.921.B.1 General The following paragraph is added: n European networks, the TE value 0 is reserved for NT2 in point-to-point configurations using a single data link connection (that is, only one point-to-point data link connection is supported within each SAP), in addition to this, the broadcast data link connection, (TE = 127) between the NT2 and the network may be supported within each SAP.

22 TU-T Rec. Q.921.B.2 Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 22 of 31 Statement of Comment An overview of the states of the point-to-point data link layer entity Q.921.B.3 Cover notes Q.921.B.4 The use of queues Q.921.B.5 SDL representation Q.921.C SDL representation of the broadcast procedures States 2 and 3 are not supported (user function) nterface Specification -frames are never used as supervisory commands. Only -commands with P-0 are supported. Not for point-to-point configurations Q.921.D State transition table of the point-topoint - Refer to comments to Q procedures of the data link layer Q.921.D.1 The state transition table presented in... Q.921.D.2 Key to the state transition table - Q.921.D.2.1 Definition of a cell of the state transition table Q.921.D.2.2 Key to the contents of a cell Q.921.E Protocol mplementation Conference Statement (PCS) to Recommendation Q.921 for Basic Rate (User-side) Q.921.E.1 General For the answer please refer to Appendix A Q.921.E.2 Abbreviations and special symbols Q.921.E.3 nstructions for completing for PCS Proforma Q.921.E.4 Global statement of conformance Q.921.E.5 Protocol Capabilities (PC) Refer to Appendix A Q.921.E.6 Frames Protocol Data Units (FR) Refer to Appendix A Q.921.E.7 System parameters (SP) Refer to Appendix A Q.921. Retransmission of REJ response -- Please refer to comments to Q frames Q ntroduction NU Q Procedure NU

23 nterface Specification TU-T Rec. Statement of Comment Q Recovery state variable V(M) NU Q N(S) sequence error supplementary NU procedure Q.921. Appendix Occurrence of MDL- -- ERROR indication within the basic states and actions to be taken by the management entity Q ntroduction Q Layout of Table.1 Clarification for basic access: Q Preferred management actions The terms remove TE and TE removal are interpreted in the following way: Remove TE : cancel the TE values in the DLC table TE removal procedure : Send an dentity Remove to the TE. n both cases the result will be a transition to the state TE unassigned. Clarification for basic access: a) Error log The specified error flags are implemented in the system. The evaluation, counting, storage of the error flags will be included in a further step. For Error code C and D, the TE check procedure shall be used. tems b), c) and d) are not supported for point-to-point configurations. Error log: Specific counters are implemented for error logging. The evaluation of data link errors will be included in a further step. Q.921. Appendix Optional basic access -- deactivation procedures Q ntroduction Following text replaces the first section: This appendix provides an example of a deactivation of the user-network interface at reference point S or T. Figure -1/Q.921 provides a conceptual model of the interactions which are required for this deactivation procedure. Q Description of the Conceptual Model Q Deactivation procedure with MPH- DEACTVATE indication Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 23 of 31 A function that initiates the deactivation of the user-network interface at the S-interface point is implemented. The functionality is similar to the procedure shown in Appendix. However, the deactivation timer (TM01 in Appendix ) is set to 30 s.

24 nterface Specification TU-T Rec. Statement of Q Deactivation procedure without MPH-DEACTVATE indication Q.921.V Appendix V Automatic negotiation -- of data link layer parameters Q.921.V.1 General Q.921.V.2 Automatic negotiation of data link layer parameter values Comment Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 24 of 31

25 nterface Specification Annex A Protocol Capabilities (PC) ndex Protocol Feature Status Reference (subclause,appendix) Support PC 1.1 PC 1.2 s the CPE of the non-automatic TE assignment category? s the CPE of the automatic TE assignment category? O Yes:X No:_ X:_ O Yes:X No: _ X:_ PC 2 Does the CPE support the broadcast data link? M 5.2 Yes:X No:_ X:_ PC 4 Does the CPE support data link nonitor function? O 5.10 Yes:X No:_ X:_ PC 5 Does the CPE support reject retransmission procedure O Appendix Yes:_ No:X X:_ PC 6.1 PC 6.2 PC 7 PC 8 PC 9 Does the DLE support automatic negotiation of data link layer parameters? Does the DLE support internal parameter initialization? Does the CPE permit concurrent LAPB data link connection within the D-channel Service Access Point dentifier (SAP) f the CPE supports Layer 3 call control procedures, is SAP = 0 supported? f the CPE supports X.25 Layer 3 packet procedures on D-channel, is SAP = 16 supported? O.2 Appendix V Yes:X No:_ X:_ O Yes:X No:_ X:_ O 2.3 Yes:_ No:X X:_ M Yes:X No:_ X:_ M Yes:_ No:X X:_ PC 10 s SAP = 63 supported M Yes:X No:_ X:_ PC 11.1 Does the implementation support the association of a given TE with all SAPs which the CPE supports? O 3.3.4, /Q.920 Yes:X No:_ X:_ PC 11.2 f the CPE is an X.31 type of packet mode terminal equipment, is a given TE for point-to-point data link connection (<127) associated with all SAPs which the CPE supports? M 3.3.4, /Q.920 Yes:X No:_ X:_ PC 12 Does the implementation support modulus 128 for frames numbering? M , Yes:X No:_ X:_ Peer-to-peer procedures Unacknowledged nformation Transfer PC 13 PC 14 Does the CPE support U-command? s the P/F bit set to 0? M M Yes:X No:_ X:_ Yes:X No:_ X:_ TE Management PC 15 Does the CPE transmit management entity messages in U frames with DLC = (63, 127)? M Yes:X No:_ X:_ Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 25 of 31

26 nterface Specification ndex Protocol Feature Status TE Assignment Procedures Reference (subclause, appendix) Support PC 16.1 PC 16.2 PC 17 PC 18 Does the CPE initiate TE assignment upon powerup? Does the CPE initiate TE assignment at the time an incoming or an outgoing call is handled, if there is no TE assigned? f the CPE is of the non-automatic category, does the CPE side management entity assign a TE value? f the CPE is of the automatic category: Does the CPE side management entity initiate TE assignment? O Yes:X No:_ X:_ O Yes:X No:_ X:_ M Yes:X No:_ X:_ M Yes:X No:_ X:_ PC 19 s the Ri randomly generated? M Yes:X No:_ X:_ PC 20 PC 21 PC 22 PC 23.1 PC 23.2 PC 23.3 PC 24 PC 25 PC 26 s the Ai value in an dentity Request message always equal to 127? Does the CPE retransmit an dentity Request message upon timer T202 expiry? Does the CPE use a new value of Ri in the above instance (PC 21)? TE Check Response/Removal/dentity Verify Does the CPE send a single dentity Check Response message, if the Ai value in the received dentity Check Request message is equal to 127? Does the CPE send an individual denty Check Response message, for each TE which is assigned to it, if the Ai value in the received dentity Check Request message is equal to 127? Does the CPE send any combination of (multiple) single and individual dentity Check Response messages in order to report all the TEs assigned to it, if the Ai value in the received dentity Check Request message is equal to 127? Does the CPE support transmitting one dentity Check Response message in response to an dentity Check Request message with Ai 127, if the TE value being checked is in use? Does the DLE enter the TE Unassigned state, upon removal of an automatic TE? Does the CPE send an dentity Request message upon removal of an automatic TE? M Yes:X No:_ X:_ M Yes:X No:_ X:_ M Yes:X No:_ X:_ O Yes:X No:_ X:_ O Yes:X No:_ X:_ O Yes:X No:_ X:_ M Yes:X No:_ X:_ M 5.3 Yes:X No:_ X:_ M Yes:X No:_ X:_ ndex Protocol Feature Status Reference (subclause, appendix) Support Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 26 of 31

27 nterface Specification f an dentity Request message is outstanding: PC 27.1 Does the CPE remove the TE from the DLE on receipt of an dentity Assigned message containing a TE value which is already in use? O Yes:X No:_ X:_ PC 27.2 Does the CPE initiate TE identity verify procedure on receipt of an dentity Assigned message containing a TE value which is already in use? O Yes:X No:_ X:_ f the CPE is of the non-automatic TE category, PC 28 Does the CPE notify to the equipment user the need for corrective action after non-automatic TE removal? M Yes:X No:_ X:_ f the CPE checks the TE of all dentity Assign messages: PC 29.1 Does the CPE remove TE from the DLE on receipt of an dentity Assigned message containing a TE value which is already in use? O Yes:X No:_ X:_ PC 29.2 PC 30 PC 31 Does the CPE initiate TE identity verify procedure on receipt of an dentity Assigned message containing a TE value which is already in use? f the CPE initiates a TE dentity Verify procedure, does the Ai contain the own TE which has been assigned by ASP (automatic TE) or entered (nonautomatic TE), respectively? f the CPE initiates the TE identity verify procedure, Does the CPE remove the TE from the DLE, if no dentity Check Request message with an Ai 127 or an Ai value equal to Ai value in the dentity Verify Request message has been received when timer T202 (again) expired after retransmission of the dentity Verify Request message upon expiry of timer T202? Establishment and Release of Multiple Frame Operation O Yes:X No:_ X:_ M Yes:X No:_ X:_ M Yes:X No:_ X:_ PC 32 Does the CPE support multiple frame operation? M 5.5 Yes:X No:_ X:_ Does the DLE initiate multi-frame establishment PC 33.1 a) immediately after TE assignment? O Yes:X No:_ X:_ PC 33.2 b) when there is an incoming or an outgoing call? PC 34.1 c) Does the DLE remain in TE Assigned state when the multiple frame operation is released? PC 34.2 d) Does the DLE initiate immediate reestablishment when the multiple frame operation is released? O Yes:X No:_ X:_ O Yes:X No:_ X:_ O Yes:X No:_ X:_ ndex Protocol Feature Status Unsolicited Commands and Responses Reference (subclause, appendix) Support Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 27 of 31

28 nterface Specification f the CPE is of the automatic TE assignment category PC 35.1 Does the CPE initiate TE identity verify procedure on the receipt of an unsolicited UA response in the Multiple Frame Established State? O.9 Appendix Yes:X No:_ X:_ PC 35.2 Does the CPE remove the TE from the DLE on the receipt of an unsolicited UA response in the Multiple Frame Established State? O.9 Appendix Yes:X No:_ X:_ PC 36.1 Does the CPE initiate TE identity verify procedure on the receipt of an unsolicited UA response in the Timer Recovery State? O.10 Appendix Yes:X No:_ X:_ PC 36.2 Does the CPE remove the TE from the DLE on the receipt of an unsolicited UA response in the Timer Recovery State? O.10 Appendix Yes:X No:_ X:_ PC 37.1 PC 37.2 PC 38.1 PC 38.2 Does the CPE remove the TE from the DLE, after N200 unsuccessful retransmissions of SABME? Does the CPE initiate the TE identity verify procedure, after N200 unsuccessful retransmissions of SABME? Does the CPE remove the TE from the DLE, after N200 unsuccessful retransmissions of DSC? Does the CPE initiate the TE identity verify procedure, after N200 unsuccessful retransmissions of DSC? O.11 Appendix Yes:X No:_ X:_ O.11 Appendix Yes:X No:_ X:_ O.12 Appendix Yes:X No:_ X:_ O.12 Appendix Yes:X No:_ X:_ O.1 = Support of at least one of these items is required. O.2 = Support of at least one of these items is required. O.3 = Support of at least one of these items is required. O.4 = Support of one, and only one, of these items is required. O.5 = Support of one, and only one, of these items is required. O.6 = Support of one, and only one, of these items is required. O.7 = Support of at least one of these items is required. O.8 = Support of at least one of these items is required. O.9 = Support of one, and only one, of these items is required. O.10 = Support of one, and only one, of these items is required. O.11 = Support of one, and only one, of these items is required. O.12 = Support of one, and only one, of these items is required. Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 28 of 31

29 nterface Specification Annex B Frames Protocol Data Units (FR) ndex Protocol Feature Status Reference Support FR 1 Frame Format A M 2.1 Yes:X No:_ X:_ FR 2 Frame Format B M 2.1 Yes:X No:_ X:_ FR 3 Flag Sequence Opening flag M 2.2 Yes:X No:_ X:_ FR 4 Flag Sequence Closing flag M 2.2 Yes:X No:_ X:_ Address Field FR 5 Two octets M 2.3 Yes:X No:_ X:_ FR 6 f the DLE permits concurrent LAPB data link connection within the D-channel, is the one octet address field recognized? Control Field Unacknowledged operation M 2.3 Yes:X No:_ X:_ FR 7 Single octet M 2.4 Yes:X No:_ X:_ Multiple frame operation FR 8 Two octets M 2.4 Yes:X No:_ X:_ FR 9 Single octet (unnumbered frame) M 2.4 Yes:X No:_ X:_ Order of Bit Transmission FR 10 Ascending numerical order M Yes:X No:_ X:_ Field Mapping Convention FR 11 Lower bit number = Lowest order value M Yes:X No:_ X:_ Do all transmitted frames contain the following fields? FR 12.1 Flag M 2.2 Yes:X No:_ X:_ FR 12.2 Address M 2.3 Yes:X No:_ X:_ FR 12.3 Control M 2.4 Yes:X No:_ X:_ FR 12.4 FCS M 2.7 Yes:X No:_ X:_ FR 13 s the CPE capable of accepting the closing flag as the opening flag of the next frame? M 2.2 Yes:X No:_ X:_ FR 14 Does the CPE generate a single flag as above? O 2.2 Yes:X No:_ X:_ FR 15 Does the CPE ignore one flag, or two or more consecutive flags that do not delimit frames? M 2.2 Yes:X No:_ X:_ FR 16 Are all invalid frames discarded and no action taken? M 2.9 Yes:X No:_ X:_ FR 17 FR 18 Are seven or more contiguous 1 bits interpreted as an abort and the associated frames ignored? f the CPE supports the automatic negotiation of data link layer parameters, does the CPE support XD frames? M 2.10 Yes:X No:_ X:_ M Appendix V Yes:X No:_ X:_ Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 29 of 31

30 nterface Specification Annex C System parameters (SP) ndex System parameters Status Reference Support/Range f the DLE supports multiple frame operation SP 1 Retransmission time (T200) M Yes:X No:_ Value:1 SP 2 Maximum number of retransmissions (N200) M Yes:X No:_ Value:3 Maximum number of octets in information field (N201) SP 3 for SAP supporting signalling M Yes:X No:_ Value:260 SP 4 for SAP supporting packet on the D-channel M Yes:X No:_ Value:260 Maximum number of outstanding frames (K) SP 5 for SAP supporting basic access signalling M Yes:X No:_ Value:1 SP 6 for SAP supporting basic access packet on the D- channel M Yes:X No:_ Value:3 SP 7 SP 8 SP 9 f the CPE is of the automatic TE assignment category, Maximum number of transmissions of TE dentity Request message (N202) Minimum time between the transmission of TE dentity Request message (T202) f the CPE supports the data link monitor function, Maximum time allowed without frames being exchanged (T203) f the CPE supports the automatic negotiation of data link parameters, M Yes:_ No:X X:_ M Yes:_ No:X X:_ M Yes:X No:_ Value:10 SP 10 Retransmission time of XD frame (TM20) M Appendix V.2 Yes:X No:_ Value:2.5 SP 11 Maximum number of retransmissions of XD frame (NM20) M Appendix V.2 Yes:X No:_ Value:3 Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 30 of 31

31 nterface Specification History Document history V st of July 1999 DL2 2.0-L-T V th of July 2016 Update Layout, Contact nformation, Small adjustments to Table in Appendix B to fit new Layout Vodafone DSS1 Layer 2 TU-T-L nterface Specification Date: Page 31 of 31