Question 28/VII - Open Systems Interconnection (OSI) data link and physical Layers (continuation of part of Question 43/VII studied in 1985-1988 on OSI data link and physical layers) Considering (a) that Recommendation X.200 specifies the reference model of Open Systems Interconnection for CCITT applications; (b) that Recommendation X.210 specifies the layer service definition conventions of Open Systems Interconnection for CCITT applications; (c) that Recommendation X.211 specifies the physical service of Open Systems Interconnection for CCITT applications? (d) that Recommendation X.212 specifies the data link service of Open System Interconnection for CCITT applications; (e) that administrations and users in many countries are applying the Open Systems Interconnection family of Recommendations to public networks now existing or due to be available in the near future; (f) that close collaboration and liaison with other international bodies (e.g., ISO, IEC) studying Open Systems Interconnection is highly desirable, 1. Data link layer What refinements are required to the data link layer Recommendation X.212? In particular, studies should include: a) development of refinements and enhancements to Recommendation X.212; b) expansion of Appendix 3 of Recommendation X.212 to include additional data link layer protocols; c) consideration of data link management aspects of OSI (see Annex 1). 2. Physical layer What refinements are required to the physical layer Recommendation X.211? In particular, studies should include: a) development of refinements and enhancements to Recommendation X.211. This study should include relationships to other Recommendations; b) consideration of physical layer management aspects of OSI. 3. Liaison What is necessary to maintain cooperation with other international organizations (e.g., ISO/IEC JTC 1) in activities concerning the data link and physical layers for OSI? ANNEX 1 (to Question 28/VII) Data link management facilities Management services are provided to allow the local system management process to execute control of and to request certain test and statistical functions of the DLL. Note - This document makes no assessment as to whether the primitive action takes place at a DLSAP or at some service-access-point identified for management. This is a subject for urgent further study. (Editor's note: The potential need for the following services has been identified. Details of primitives, parameters and sequences are for further study.) Q.1 Data link service characteristics In order to effectively coordinate the choice of network protocol with the provision of data-link connectionless mode service, information relating to the characteristics of the service must be made available. Q.1.1 Function The data link service characteristics service conveys information from the DLS provider to the DLS user concerning those characteristics of the service available for a given pair of DLSAPs which are beyond the scope of those characteristics which can be expressed in a single invocation of the connectionless-mode DLS, or are optional features of the connection-mode DLS that are not negotiable during DLC establishment. Q.1.2 Types of primitives and parameters Table Q-1/X.212 illustrates the types of primitives and the parameters needed for the provision of this service. TABLE Q-1/X.212 Primitives and parameters + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + \PRIMITIVE DL-MGMT-FACILITY DL-MGMT-FACILITY PARAMETER\ Request Indication + - - - - - - - - - - - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - - + - - - - - - - - - - - - - - - - - - Destination address x x Service characteristic/ x QOS parameter + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + Q.1.2.1 Destination address The address referred to in Table Q-1/X.212 is a DLSAP address. The connection-mode and connectionless-mode DLSs both use the same DSLAP- addresses as described in sections 12.2.1 and 12.2.3 of the data link service definition. Q.1.2.2 Service characteristic/QOS parameter The value of the service characteristics/QOS parameter is a list of sub- parameters. For each sub-parameter, any value permitted according to the particular sub-parameter may be indicated. QOS parameters are described in sections 10 and 11 of this Recommendation. The following list of service characteristics is for further study. a) Congestion control: the congestion control parameter is concerned with whether a connectionless-mode DLS user is willing to accept indications from the DLS provider that transmission is refused. The specification of this parameter means that the DLS provider should not initiate discard operations (see section 16). b) Sequence preservation probability: the sequence preservation probability is the ratio of sequence-preserved transmissions to a total transmissions observed during a performance measurement. A sequence-preserved transmission is one in which the following rule is observed: for a given pair of DLSAPs, a DL-UNITDATA indication will not occur at a destination DLSAP after any other DL-UNITDATA indication corresponding to a later DL-UNITDATA request issued from the source DLSAP to the destination DLSAP. The specification of a sequence preservation probability of one (1) means that the DLS provider may not initiate change of order operations (see section 16). c) Maximum DLSDU size: this parameter defines the maximum number of octets that can be transferred in a single DLSDU. Q.1.3 Sequence of primitives The valid sequence of primitives are given in the time sequence diagrams in Figures Q-1 and Q-2/X.212. Q.2 Report service Q.2.1 Function The DL-REPORT indication conveys information about the failure of the DLS provider to provide the requested Quality of Service or service characteristic. In particular, this relates to a failure of the DLS provider to satisfy the constraints imposed upon a DL-UNITDATA request, given a particular destination DLSAP. Q.2.2 Types of primitives and parameters Table Q-2/X.212 illustrates the types of primitives and the parameters needed for the provision of this service. TABLE Q-2/X.212 Primitives and parameters + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + \PRIMITIVE DL-REPORT PARAMETER\ Indication + - - - - - - - - - - - - - - - - - - - - - - - - - + - - - - - - - - - - - - Destination address x Service characteristic/ x QOS parameter Reason for report x + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + Q.2.2.1 Destination address The address referred to in Table Q-2/X.212 is a DLSAP-address. The connection-mode and connectionless-mode DLSs both use the same DLSAP- addresses as described in sections 12.2.1 and 12.2.3 of the data link service definition. Q.2.2.2 Service characteristic/QOS parameter The value of the service characteristic/QOS parameter is a list of sub- parameters. For each sub-parameter, any value permitted according to the particular sub-parameter may be indicated. QOS parameters are described in section 10 of this Recommendation. The list of service characteristics is given in section I.1.2.2. Q.2.2.3 Reason for report The value of the reason for report parameter indicates the reason why the DL-REPORT indication was initiated by the DLS provider. Reason values may be: a) no reason specified; b) transit delay exceeded; c) DLS provider congestion; d) requested QOS/service characteristic unavailable. Q.2.3 Sequence of primitives The valid sequence of primitives are given in the time sequence diagram in Figure Q-3/X.212. Q.3 Test The test service allows a local management function to initiate a pre- defined test of a particular DLS provider including the local and remote DL entities and the underlying physical connection. Q.4 Statistics The statistics service is provided to require the DLS provider to maintain "accounts" of the retransmitted data units, total data units, and any other items that may be defined by parameters. Statistics primitives will probably include connect, disconnect and transfer. Q.5 Configure The configure service provides the local system manager with the ability to add and delete DL entities from a multi-link group.