This standard is one of a group of national standards developed to facilitate the interconnection of computers and terminals on a local area network (LAN). It is related to other national standards of the Open Systems Interconnection Reference Model. GB/T 15629.2-1995 Information Processing Systems Local Area Networks Part 2: Logical Link Control GB/T15629.2-1995 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Information processing systems--Local area networks Part 2: Logical link control
GB/T 15629.2—1995
ISO 8802.2—1989
This standard adopts the international standard IS08802.2-1989 "Information processing systems--Local area networks Part 2: Logical link control". 1 Introduction
1.1 Subject matter and scope of application
This standard is one of the national standards formulated for the interconnection of computers and terminals on local area networks (LANs). It is related to other national standards of the open systems interconnection reference model. Note: The exact relationship between the layers described in this standard and the layers defined in the open systems interconnection (OSI) reference model is to be studied. Data Link Layer
Physical Layer
Figure 1-1 Relationship of LAN Reference Model
This standard describes the functions, features, protocols and services of the Logical Link Control (ILC) layer in the GB/T15629 series of standard LAN protocols. The ILC layer constitutes the sublayer on top of the Data Link Layer (see Figure 1-1) and is shared by various media access methods defined and supported by the GB/T15629 series of standards. Several independent national standards describe various media access methods and point out the additional features and functions provided by the Media Access Control (WAC)-F layer. In each case, the functionality of the data link is completed as defined in the LAN Reference Model.
This standard describes the ILC sublayer service specifications for the network layer (layer 3), MAC sublayer and LLC sublayer management functions. The service specifications provide a summary of various services for the network layer. From the perspective of the network layer, various services are services provided to the network layer by the ILC layer and the layers below it. The service specification provides the MAC layer with a description of the MAC sub-services required by the LLC layer. The purpose of these services is to be independent of the form of the media access method and the nature of the media itself. The service specification provides the LLC sub-layer management function with a description of the management services provided to the L1C sub-layer. All of the above service specifications are given in the form of primitives. Abstract methods are used to represent the logical exchange of information and control between the LLC sub-layer and the service functions (network layer, MAC sub-layer or ILC sub-layer management functions) identified by the State Administration of Technical Supervision on June 21, 1995. They do not specify or restrict the implementation of entities or interfaces. This national standard provides a description of peer-to-peer protocol procedures. These protocol procedures are defined for the transmission of information and control between any pair of data link layer service access points on a local area network. The I.LC procedures are independent of the type of media access method used in a specific local area network.
To cater for a wide range of possible applications, two types of data link control operations are included (see Chapter 4). The first type of operation (see Chapter 6) provides data link connectionless mode services over a data link with minimal protocol complexity. This type of operation is useful when the higher layers provide any necessary recovery and sequencing services, so that these services do not need to be repeated within the data link layer. In addition, this type of operation is useful in applications where it is not necessary to guarantee that every data link layer data unit is delivered. The term "logical data link" is used in this standard to describe this type of service. The second type of operation (see Chapter 7) provides data link connection mode services over a data link similar to existing data link control procedures provided in national standards, such as HDLC (see GB7575). This service includes support for sequential delivery of data link layer data units and a wide range of data link error recovery techniques. The term "data link connection" is used in this standard to describe the second type of service. This standard identifies two different "classes" of LLC operations. Class I provides data link connectionless mode services only. Class I provides data link connection mode services plus data link connectionless mode services. Any category of operations can be supported. The basic protocol described here is a peer-to-peer protocol for a multi-station, multi-access environment. Because it is a multi-station, multi-access environment, a station may be involved in exchanging data with multiple different stations on multiple different logical links and/or data link connections using multiple peer protocols, and the connections of these logical links and/or data links are established by a single physical layer (PHY) on a single physical medium. Each unique round-trip pairing at the data link layer should define an independent logical data link connection or a logical data link connection with independent logical parameters and variables. Unless otherwise specified, the procedures described in this standard will be related to each data link layer logical link or data link connection separately, and will not be related to any other logical data links or data link connections that may exist at the stations involved. 1.2 Standard Compatibility
The peer protocol procedures defined in Chapter 5 utilize certain concepts and principles, as well as commands and responses, in the balanced data link control procedures called asynchronous balanced mode defined in GB7421 (GB11595 Level 21.APB procedures are defined on the basis provided by the ABM procedures). The structure for the data link layer procedures defined as a whole is partly defined in Chapter 3 of this standard and partly defined in those national standards that define various media access control (MAC) procedures. In a local area network, the combination of the MAC sublayer address and the LLC sublayer address is unique to each service access point of the data link layer. Note: The division of the data link layer addressing space into independent MAC and LLC address fields is not currently part of any existing data link layer national standard.
1.3 Reference standards
GB7421 Compilation of high-level data link control procedures for data communications in information processing systems GB.7575 Elements of high-level data link control procedures for data communications in information processing systems GB9387 Basic reference model for open systems interconnection in information processing systems GB11595 Interface between packet-type data terminal equipment (DTE) and data circuit-terminating equipment (DCE) connected to a public data network using dedicated circuits
CCITT Recommendation X.200 Open Systems Interconnection Reference Model for CCITT Applications 1.4 Abbreviations and definitions
1.4.1 Abbreviations
ABM Asynchronous balanced mode
ACK Acknowledgement
ADM Asynchronous disconnected mode
C Command
CCITT International Telegraph and Telephone Consultative Committee
C/R Command/Response
DA Address
DCE Data Circuit Terminating Equipment
Draft International Standard
DM Disconnect Mode
Destination Service Access Point
Data Terminal Equipment
F Termination
FCS Frame Check Sequence
FRMR Frame Rejection
High-Level Data Link Mode
1 Information
I Information Transfer Format
ISO International Organization for Standardization
1.AN Local Area Network
Balanced Link Access Procedure
LLC Logical Link Control||tt ||LSAP Link Layer Service Access Point
LSB Least Significant Bit
LSDU Link Layer Service Data Unit
M Modify Function Bit
MAC Media Access Control
Receive Sequence Number
Transmit Sequence Number
JSI Open Systems Interconnection
P Poll
Protocol Data Unit
Poll/Terminate
PHY Physical Layer
R Response
REI Reject
RNR Receive Not Ready
RR Receive Ready
S Monitoring Format
S Monitoring Function Bit
SA Source Address
GB/T 15629.2--1995
SABME extended asynchronous balancing mode
SAP service access point
SSAP source service access point
TEST test
U unnumbered format
UA unnumbered confirmation
UI unnumbered information
V(R) receiving state variable
V(S) sending state variable
XID exchange identifier
1.4.2 Definition
The following definitions apply to this standard:
Accept accept
GB/T 15629.2—1995
LLC accepts the correctly received PDU as a status for processing. Address fields (DSAP and SSAP) address fields (DASP and SSAP) An ordered pair of service access point addresses at the beginning of LLCPDU, which is used to identify the LLC that is designated to receive the PDU and the LLC that sends the PDU. The length of each address field is one octet. Basic status basic status
LLC's ability to send or receive PDUs containing information fields. Command command
In data communication, an instruction sent by the LLC represented by the control field of the PDU. It enables the addressed LLC to perform a specific data link control function.
Command PDUcommand PDU
All PDUs sent by the LLC, in which the C/R bits are equal to "o". Control field (C) controlfield (C) The field immediately following the DSAP and SSAP address fields of the PDU. The receiving destination LLC specified by the DSAP address field interprets the contents of the control field: a. as a command issued by the source LLC specified by the SSAP address field to instruct the execution of a specific function; b. as a response issued by the source LLC specified by the SSAP address field. Data linkdata link
A combination of two or more terminal devices and interconnected communication channels that operate in a specific way to exchange information; the term "terminal device" here does not include the data source and data sink. Data link layerdata linklayer
The conceptual layer of control or processing logic that exists in the hierarchy of a station and is responsible for maintaining control of the data link. The data link layer functions provide an interface between the higher-level logic of the station and the data link. These functions include interpretation of address/control fields, channel access, and generation, transmission, and interpretation of commands/responses. Exception conditionexception condition
The state presented when the LLC receives a command PDU that cannot be executed, which is caused by a transmission error or internal processing failure. Global (broadcasting) DSAP addressglobal (broadcasting) DSAPaddress uses the predefined LLCD DSAP address (all "1s") as the broadcast (party) address. It is never the address of a single LLC on the data link.
Group (multicast) DSAP addressgroup(multicast) DSAP addressA destination address assigned to a collection of LLCs so that they can be addressed collectively. Its least significant bit should be set to "1".higher layer
The conceptual layer of control or processing logic that exists in the hierarchy of stations, above the data link layer, and the performance of data link layer functions is related to the higher layers; for example: device control, buffer allocation, LLC station management, etc. Information field (I)information field (I)A sequence of octets that appears between the end of the LLCPDU and the control field. The contents of the I information field, the contents of TEST and UIPDUs are not interpreted at the LLC sublayer.
Invalid frame invalidframe
A PDU that is one of the following:
a does not contain an integer number of octets;
GB/T 15629.2—1995
does not contain at least two octets of address and one octet of control field;
identified by the physical layer or MAC sublayer, which contains data bit errors. LLC
A part of a data station that supports the logical link control function of one or more logical links. LLC generates command PDUs and response PDUs for transmission and interprets received command PDUs and response PDUs. Specific responsibilities assigned to LLC include: a. Initiate control number exchange;
h. Organize data flow:
C. Interpret received command PDUs and generate appropriate response PDUs; l. Perform relevant error control and error recovery functions within the LLC sublayer. MAC
The part of a data station that supports the media access control functions located below the I.LC layer. MAC: The procedures include framing/defragging data units, performing error checking, and obtaining the right to use the underlying physical medium. N-layer
The sub-section of an architecture consisting of subsystems at the same level (N). N-user
The N+1 entity that uses the services of layer N and communicates with another N+1 entity through the lower layer. Octet
A bit-oriented unit consisting of eight adjacent binary bits. Peer protocolbzxz.net
The sequence of messages exchanged between two entities in the same layer that achieve the successful transfer of data and/or control information from one location to another using the services below. Priority (use in primitives) Parameter used to convey a required or desired priority. Protocol Data Unit (PDU) protocoldata unit (PDU) A contiguous sequence of octets delivered to or from the MAC sublayer as a unit. A valid LLCPDU is at least two octets long and contains two address fields and a control field. A PDU may or may not contain additional information fields.
Responseresponse
In data communications, the answer represented by the control field of the response PDU. It informs the LLC of the action taken by the source I.LC to one or more command FDUs. Response PDUresponseFDU
Output All PDUs sent by the LLL in which the C/R bit is equal to 1\. Serviceservice
The capabilities and features provided by the N layer to the N user. ServiceClass (used in primitives)serviceclass (used in primitives)Parameters used by the factory to convey the required or expected service category. 2LLC Sublayer Service Specification
This chapter includes the services that the LLC sublayer is required to provide or that are required by the LLC sublayer at the logical interface with the network layer, MAC sublayer, and LLC sublayer management functions. 98
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Generally, the services of a layer (or sublayer) are service capabilities provided to users in an adjacent higher layer (or sublayer). In order to provide its services, a layer (or sublayer) needs to build its functionality on the services provided by the adjacent lower layer (or sublayer). Figure 2-1 represents this concept of a service hierarchy and shows the relative relationship between two corresponding N users and their associated N layer (or sublayer) peer protocol entities. SERVICE USER
REQUEST
CONFIRM
SERVICE PROVIDER
Figure 2-1 SERVICE PRIMITIVES
SERVICE USER
-INDICATION
-RESPONSE
Various services are specified by describing the information flow between N users and N layers (or sublayers). This information flow is represented by a model of discrete instantaneous events, which characterize the service provided. Each event consists of passing service primitives from one layer (or sublayer) to another layer (or sublayer) through N layers (or sublayers) of service access points associated with N users. Service primitives convey information needed to provide a particular service. These service primitives are an abstract concept that only specifies the service in the abstract without specifying the means of providing the service. The definition of the service is independent of the implementation of any particular interface.
Various services are specified by describing the service primitives and parameters that characterize each service. A service can have one or more associated primitives that constitute the activities associated with the particular service. Each service primitive can have zero or more parameters that convey the information needed to provide the service.
The four generic types of primitives are:
REQUEST: The request primitive is passed from N users to the N layer (or sublayer) to request the initiation of a service. INDICATION: The indication primitive is passed from the N layer (or sublayer) to the N users to indicate an internal event of the N layer (or sublayer) that is valid for the N users. The event may be logically related to a remote service request, or may be caused by an event internal to the N layer (or sublayer).
RESPONSE: A response primitive is passed from the N user to the N layer (or sublayer) to complete a procedure previously initiated by an indication primitive. CONFIRM: A confirmation primitive is passed from the N layer (or sublayer) to the N user to convey one or more results associated with a previous service request.
The timing diagram shown in Figure 2-2 illustrates the possible relationships between the various primitive types. The diagram also indicates the logical relationships of the various primitive types. Primitive types that occur earlier in time are logical prerequisites for subsequent primitive types, and they are connected within the diagram by dashed lines. 2.1 Network Layer/LLC Sublayer Interface Service Specification This clause specifies the services that the network layer requires the LLC sublayer to provide, from the perspective of the network layer, in order to allow local network layer entities to exchange packets with remote peer network layer entities. The abstract way in which these services are described does not imply any specific implementation or any stated interface.
REQUEST
REQUEST
INDIGATON
GB/T15629.2—1995
INDICATION
INDICA TION
INDICATION
INDICATION
REQUEST
CONFIRM
RESPONSE
REQTEST
CONFIRM
REQUEST
CONFIRM
Figure 2-2 Sequence Diagram
Two forms of service are provided: unconfirmed connectionless mode and connected mode:INDICATION
RESPONSE
INLATION
HESPONSE
Unconfirmed Connectionless Mode Services—Unconfirmed connectionless data transfer services provide the means to enable network entities to exchange link service data units (LSDUs) without establishing a data link level connection. This data transfer can be point-to-point, multicast or broadcast. Connection Mode Services—This group of services provides the means to establish, use, reset and terminate data link layer connections. These connections are point-to-point connections between LSAPs.
The connection establishment service provides the means by which a network entity can request the establishment of a data link layer connection, or can notify a network entity of the establishment of a data link layer connection.
The connection oriented data transfer service provides the means by which a network entity can send or receive LSDUs on a data link layer connection. This service also provides data link layer sequencing, flow control, and error recovery. The connection reset service provides the means by which an established connection can be returned to its initial state. The connection termination service provides the means by which a network entity can request the termination of a data link layer connection, or can notify a network entity of the termination of a data link layer connection.
The connection flow control service provides the means by which the flow of data across the network layer/data link layer interface associated with a particular connection can be controlled.
2.1.1 Overview of Interactions
2.1.1.1 Unconfirmed Connectionless Mode Services
2.1.1.1.1 Unconfirmed Connectionless Mode Data Transfer The primitives associated with unconfirmed connectionless mode data transfer are: DL--UNITDATA request
DL--UNITDATA indication
The DL--UNITDATA request primitive is passed to the LLC sublayer to request the transmission of an LSDU using the unconfirmed connectionless mode procedure. The DL--UNITDATA indication primitive is passed from the LLC sublayer to indicate the arrival of an LSDU. 1
2.1.1.2 Connection Mode Services
2.1.1.2.1 Connection Establishment
The service primitives associated with connection establishment are: DL--CONNECT request
DL--CONNECT indication
DL--CONNECT response
DL--CONNECT confirm
GB/T 15629.2-1995
The DL-CONNECTrequest primitive is passed to the LLC sublayer to request the establishment of a data link connection between the local LSAP and the remote LSAP. The DL-CONNECTindication primitive is passed from the LLC sublayer to indicate that the remote entity requests the establishment of a connection to the local LSAP. The DL-CONNECTresponse primitive is passed to the LLC sublayer to report the acceptance of the connection. The DL--CONNECTconfirm primitive is passed from the LLC sublayer to convey the results associated with the previous DL-CONNECT request primitive. 2.1.1.2.2 Connection-mode data transfer
The primitives associated with connection-mode data transfer are:DL--DATA request
DL--DATA indication
The DL-DATArequest primitive is passed to the LLC sublayer to request the transmission of an LSDU using connection-mode procedures. The DL-DATAindication primitive is passed from the LLC sublayer to indicate the arrival of an LSDU. 2.1.1.2.3 Connection termination
The primitives associated with connection termination are:
DL--DISCONNECT request
DL--DISCONNECT indication
The DL-DISCONNECTrequest primitive is passed to the LLC sublayer to request the immediate termination of the data link connection. The DL-DISCONNECTindication primitive is passed from the LLC sublayer to indicate to the network layer that the connection has been terminated. 2.1.1.2.4 Connection reset
The primitives related to connection reset are:
DL--RESET request
DL--RESET indication
DL-RESET response
DL.--RESET confirm
The DL-RESTE request primitive is passed to the LLC sublayer to request that the connection be immediately reset to the initial state. The DL-RESET indication primitive is passed from the LLC sublayer to indicate that the remote entity or the local LLC sublayer is attempting to reset the connection. The DL-RESET response primitive is passed to the LLC sublayer to report acceptance of the reset status. The DL-RESET confirm primitive is passed from the LLC sublayer to convey the result associated with the previous DL-RESET request primitive. 2.1.1.2.5 Connection flow control
The primitives associated with connection flow control are: DI --CONNECTION --FLOWCONTROL request DL --CONNECTION-FLOWCONTROL indication The DL-CONNECTION --FLOWCONTROL request primitive is passed to the LLC sublayer to control the flow of DL --DATA indication primitives associated with the connection from the LLC sublayer. The DL_CONNECTION_FLOWCONTROLindication primitive is passed from the LLC sublayer to control the flow of the DL_DATA request primitive associated with the connection from the network layer.
2.1.2 Detailed service specification
This clause describes in detail the primitives and parameters associated with the identification service. Note that these parameters are specified in an abstract sense. The information specified in these parameters 101
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must be available to the receiving entity. As for the method of generating this available information, it does not restrict the entity implementation. The \source-address\ and \destination-address\ parameters shall at least provide the logical concatenation between the MAC address field (SA and/or DA) and the LLC address field (SSAP and/or DSAP). The implementation of the connection mode service may use the locally significant connection identifier to imply the source address and destination address parameters. The "data" parameter may be provided by actually passing the link service data unit, passing a pointer, or passing other means. The "priority" parameter provides the priority associated with the data unit transmission. The "priarity" parameter is passed transparently to the underlying MAC sublayer via the appropriate LLC/MAC primitives, see clause 2.2. The "reason" parameter provides an explanation of the disconnection, including a request by the remote entity, or an error internal to the LLC sublayer. The "amount" parameter provides information about the amount of data the LLC entity is allowed to transfer. 2.1.2.1 DL--UNITDATA request 2.1.2.1.1 Function
This primitive is a service request primitive for the unconfirmed connectionless data transfer service. 2.1.2..2 Semantics of service primitives
This primitive shall provide the following parameters:
DL-UNITDATA request (
source-address,
destination-address,
priority
The "source-address" and \destination-address\ parameters specify the local and remote LSAPs involved in the transfer of the data unit. The destination-address may specify a single address or a group address. The "data" parameter specifies the link service data unit to be transferred by the data link layer entity. The \priority parameter specifies the priority level required for the transfer of the data unit. Priority. 2.1.2.1.3 Conditions for Generation
This primitive is passed from the network layer to the LLC sublayer to request that an LSDU be sent using the unacknowledged connectionless mode procedure to one or more remote LSAPs.
2.1.2.1.4 Effect on Receipt
Receipt of this primitive causes the LLC sublayer to attempt to send an LSDU using the unacknowledged connectionless mode procedure. 2.1.2.1.5 Additional Comments
This primitive is not associated with any connection that is transported to a remote LSAP. The possible logical sequence of primitives associated with achieving successful unacknowledged connectionless mode data unit delivery is shown in Figure 2-2(c). 2. 1.2.2 DL -- UNITDATA indication 2.1.2.2.1 Function
This primitive is a service indication primitive for the unacknowledged connectionless mode data unit transfer service. 2.1.2.2.2 Semantics of service primitive
This primitive shall provide the following parameters:
DI.. UNITDATA indication (
source-address,
destination-address,
data,
Priority
The "source-address" and "destination-address" parameters specify the local and remote LSAPs involved in the data unit transfer. The "sourceaddress" may be the address of a local LSAP or may be a group address specifying a number of LSAPs, including the address of the local LSAP. The "data" parameter specifies the link service data unit that has been received by the LLC sublayer entity and the "priority" parameter specifies the priority level requested for the data unit transfer. 2.1.2.2.3 Generation Conditions
GB/T 15629. 2—1995
This primitive is passed from the LLC sublayer to the network layer to indicate the arrival of an LSDU from a specified remote entity. 2.1.2.2.4 Effects on Receipt
The effect of receiving this primitive at the network layer is unspecified. 2.1.2.2.5 Additional Notes
This primitive is not associated with any connection to a remote LSAP. In the absence of errors, the content of the "data" parameter is logically complete and unchanged relative to the "data" parameter in the related DL-UNITDATArequest primitive. 2.1.2.3 DL--CONNECT request 2.1.2.3.1 Function
This primitive is a service request primitive for the connection establishment service. 2.1.2.3.2 Semantics of service primitive
This primitive shall provide the following parameters:
DL-CONNECT request (
source-address,
destination-address ,
priority
The "source-address\ and \destination-address" parameters specify the local and remote LSAPs to be connected. The "priority" parameter specifies the priority required for the connection.
2.1.2.3.3 Generation Conditions
This primitive is passed from the network layer to the LLC sublayer when the network layer entity wishes to establish a logical link connection with a remote LSAP at a given priority.
2.7.2.3.4 Effects Upon Receipt
Receipt of this primitive by the LLC sublayer causes the local LLC entity to initiate connection establishment with the remote LLC entity. 2.1.2.3.5 Additional Notes
The possible logical sequence of primitives associated with achieving a successful connection establishment is shown in Figure 2-2(f). 2. 1.2. 4 DL-CONNECT indication2.1.2.4.1 Function
This primitive is a service indication primitive for the connection establishment service. 2.1.2.4.2 Semantics of service primitive
This primitive shall provide the following parameters:
DL--CONNECT indication (
source-address,
destination-address,
priority
The "source-address" and "destination-address" parameters specify the local and remote LSAPs to be connected. The "priority" parameter indicates the priority requested for the connection.
2.1.2.4.3 Generation conditions
This primitive is sent from the LILC sublayer to the network layer to indicate that a connection of a certain priority is being requested. 2.1.2.4.4 Effect
GB/T 15629.2—1995
The network layer entity shall send a DL-CONNECT request primitive to accept the connection or shall send a DL-DISCONNECT request primitive to reject the connection. 2.1.2.4.5 Additional Notes
None.
2.1.2.5 DL--CONNECT response 2.1.2.5.1 Function
This primitive is the service response primitive for the connection establishment service. 2.1.2.5.2 Semantics of service primitive
This primitive shall provide the following parameters:
DL--CONNECT response (
source-address,
destination-address,
priority
“The source-address\ and \destination-address\ parameters specify the local and remote LSAPs to be connected. “The priority\ parameter indicates the priority offered for the connection.
2.1.2.5.3 Generation conditions
This primitive is passed from the network layer to the LLC sublayer to indicate acceptance of the requested connection. 2.1.2.5.4 Effects upon receipt
Receipt of this primitive by the LLC sublayer causes the local LLC entity to accept a connection with the remote LLC entity. 2.1.2.5.5 Additional notes
The network layer entity may return and DL-CONNECT The same priority as given in the indication primitive, or it may choose a lower priority. After returning the DL-CONNECTresponse primitive, the network layer entity considers the connection established. 2.1.2.6 DL-CONNECT confirm 2.1.2.6.1 Function
This primitive is the service confirmation primitive for the connection establishment service. 2.1.2.6.2 Semantics of service primitive
This primitive shall provide the following parameters:
DL---CONNECT confirm (
source-address,
destination-address,
priority
The "source-address" and "destination-address" parameters specify the local and remote LSAPs to be connected. The "priority" parameter indicates the priority offered for the connection.
2.1.2.6.3 Generation conditions
The LLC sublayer transmits this primitive to the network layer to convey the connection established with a previous DL-CONNECT request primitive. The result indicates that the connection attempt was successful and specifies the priority obtained. 2.1.2.6.4 Effect after receipt
The network layer entity can use the connection to transfer data units. 2.1.2.6.5 Additional notes
This primitive indicates that the remote network layer entity has received and accepted the connection attempt. 2. 1.2.7 DL--DATA request
2.1.2.7.1 Function
GB/T 15629.2-—1995
This primitive is a service request primitive for the connection mode data unit transfer service. 2.1.2.7.2 Semantics of service primitive
This primitive should provide the following parameters:
DL--DATA request (
source-address,
destination-address,
The "source-address" and "destination-address\ parameters specify the local and remote LSAPs for the connection. The "data" parameter specifies the link service data unit to be transmitted by the LLC sublayer entity. 2.1.2.7.3 Generation Conditions
This primitive is passed from the network layer to the LLC sublayer to request that an LSDU be transmitted to a remote LSAP over an existing connection. 2.1.2.7.4 Effects Upon Receipt
Receipt of this primitive by the LLC sublayer causes the LLC sublayer to transmit the LSDU over the specified connection using connection-mode procedures. 2.1.2.7.5 Additional Remarks
Because the priority must be consistent for all DL--DATA requests in a particular connection, the DL--DATA request primitive does not contain a priority parameter.
The possible logical sequence of primitives associated with achieving a successful connection-mode data unit transmission is shown in Figure 2-2(c). 2.1.2.8 DL -- DATA indication 2.1.2.8.1 Function
This primitive is the service indication primitive used for the connection mode data unit transfer service. 2.1.2.8.2 Semantics of service primitive
This primitive shall provide the following parameters:
DL---DATA indication (
source-address,
destination-address,
The "\source-address" and "\destination-address" parameters specify the local and remote LSAPs for the connection. The "data" parameter specifies the link service data unit that has been received by the LLC sublayer entity. 2.1.2.8.3 Generation conditions
The LLC sublayer passes this primitive to the network layer to indicate the arrival of an LSDU from a specified remote network layer entity on a particular connection.
2.1.2.8.4 Effect on receipt
The effect of receipt of this primitive by the network layer is unspecified. 2.1.2.8.5 Additional comments
In the absence of errors, the contents of the "\data" parameter are logically complete and are consistent with the relevant DL-DATA The "data\ parameter in the request primitive is unchanged. 2.1.2.9DL--DISCONNECT request 2.1.2.9.1 Function
This primitive is a service request primitive for the connection termination service. 2.1.2.9.2 Semantics of the service primitive
priority
The "source-address" and "destination-address" parameters specify the local and remote LSAPs to be connected. The "priority" parameter indicates the priority provided for the connection.
2.1.2.6.3 Generation conditions
The LLC sublayer transmits this primitive to the network layer to convey the result related to the previous DL-CONNECT request primitive. The result indicates that the connection attempt is successful and specifies the priority obtained. 2.1.2.6.4 Effect after receipt
The network layer entity can use this connection for data unit transmission. 2.1.2.6.5 Additional comments
This primitive indicates that the remote network layer entity has received and accepted the connection attempt. 2. 1.2.7 DL--DATA request
2.1.2.7.1 Function
GB/T 15629.2-1995
This primitive is the service request primitive for the connection mode data unit transfer service. 2.1.2.7.2 Semantics of service primitives
This primitive shall provide the following parameters:
DL--DATA request (
source-address,
destination-address,
The "source-address" and "destination-address\ parameters specify the local and remote LSAPs for the connection. The "data" parameter specifies the link service data unit to be transmitted by the LLC sublayer entity. 2.1.2.7.3 Generation Conditions
This primitive is passed from the network layer to the LLC sublayer to request that an LSDU be transmitted to a remote LSAP over an existing connection. 2.1.2.7.4 Effects
Receipt of this primitive by the LLC sublayer causes the LLC sublayer to transmit the LSDU using connection-mode procedures over the specified connection. 2.1.2.7.5 Additional Remarks
Because the priority must be consistent for all DL--DATA requests in a particular connection, the DL--DATA request primitive does not contain a priority parameter.
The possible logical sequence of primitives associated with achieving a successful connection-mode data unit transmission is shown in Figure 2-2(c). 2. 1.2.8 DL--DATA indication 2.1.2.8.1 Function
This primitive is a service indication primitive for the connection mode data unit transfer service. 2.1.2.8.2 Semantics of service primitive
This primitive shall provide the following parameters:
DL---DATA indication (
source-address,
destination-address,
The "\source-address" and "\destination-address" parameters specify the local and remote LSAPs for the connection. The "data" parameter specifies the link service data unit that has been received by the LLC sublayer entity. 2.1.2.8.3 Generation conditions
The LLC sublayer passes this primitive to the network layer to indicate the arrival of an LSDU from a specified remote network layer entity on a particular connection.
2.1.2.8.4 Effect upon receipt
The effect of receipt of this primitive by the network layer is unspecified. 2.1.2.8.5 Additional Notes
In the absence of errors, the contents of the "\data" parameter are logically complete and unchanged relative to the "data\" parameter in the associated DL-DATA request primitive. 2.1.2.9 DL--DISCONNECT request 2.1.2.9.1 Function
This primitive is a service request primitive for the connection termination service. 2.1.2.9.2 Semantics of the service primitive
priority
The "source-address" and "destination-address" parameters specify the local and remote LSAPs to be connected. The "priority" parameter indicates the priority provided for the connection.
2.1.2.6.3 Generation conditions
The LLC sublayer transmits this primitive to the network layer to convey the result related to the previous DL-CONNECT request primitive. The result indicates that the connection attempt is successful and specifies the priority obtained. 2.1.2.6.4 Effect after receipt
The network layer entity can use this connection for data unit transmission. 2.1.2.6.5 Additional comments
This primitive indicates that the remote network layer entity has received and accepted the connection attempt. 2. 1.2.7 DL--DATA request
2.1.2.7.1 Function
GB/T 15629.2-1995
This primitive is the service request primitive for the connection mode data unit transfer service. 2.1.2.7.2 Semantics of service primitives
This primitive shall provide the following parameters:
DL--DATA request (
source-address,
destination-address,
The "source-address" and "destination-address\ parameters specify the local and remote LSAPs for the connection. The "data" parameter specifies the link service data unit to be transmitted by the LLC sublayer entity. 2.1.2.7.3 Generation Conditions
This primitive is passed from the network layer to the LLC sublayer to request that an LSDU be transmitted to a remote LSAP over an existing connection. 2.1.2.7.4 Effects
Receipt of this primitive by the LLC sublayer causes the LLC sublayer to transmit the LSDU using connection-mode procedures over the specified connection. 2.1.2.7.5 Additional Remarks
Because the priority must be consistent for all DL--DATA requests in a particular connection, the DL--DATA request primitive does not contain a priority parameter.
The possible logical sequence of primitives associated with achieving a successful connection-mode data unit transmission is shown in Figure 2-2(c). 2. 1.2.8 DL--DATA indication 2.1.2.8.1 Function
This primitive is a service indication primitive for the connection mode data unit transfer service. 2.1.2.8.2 Semantics of service primitive
This primitive shall provide the following parameters:
DL---DATA indication (
source-address,
destination-address,
The "\source-address" and "\destination-address" parameters specify the local and remote LSAPs for the connection. The "data" parameter specifies the link service data unit that has been received by the LLC sublayer entity. 2.1.2.8.3 Generation conditions
The LLC sublayer passes this primitive to the network layer to indicate the arrival of an LSDU from a specified remote network layer entity on a particular connection.
2.1.2.8.4 Effect upon receipt
The effect of receipt of this primitive by the network layer is unspecified. 2.1.2.8.5 Additional Notes
In the absence of errors, the contents of the "\data" parameter are logically complete and unchanged relative to the "data\" parameter in the associated DL-DATA request primitive. 2.1.2.9 DL--DISCONNECT request 2.1.2.9.1 Function
This primitive is a service request primitive for the connection termination service. 2.1.2.9.2 Semantics of the service primitive
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