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.Receipt of a UI frame with an unrecognized encoding shall be signalled to the control function as a protocol violation.NOTE2-Cases marked as (solicited) represent proper protocol operation.8.2.4.12 Frame reject (FRMR) responseThe FRMR unnumbered response may be received by an error-correcting entity as a report of an error condition not recoverable by retransmission of the identical frame, i.e.at least one of the following error conditions resulting from the receipt of a valid frame:a) the receipt of a command or response control field that is undefined or not implemented;b) the receipt of a supervisory or unnumbered frame with incorrect length;c) the receipt of an invalid N(R); ord) the receipt of a frame with an information field which exceeds the maximum established length.An undefined control field is any of the control-field encodings not identified in Table 8.A valid N(R) value is one that is in the range V(A) " N(R) " V(S).An information field which immediately follows the control field and consists of five octets is returned with this response and provides the reason for the FRMR response.This information field format is given in Figure 10.87654321OctetRejected frame control field45V(S)6V(R)C/R7ZYXW8NOTE1-Rejected frame control field is the control field of the received frame which caused the frame reject.When the rejected frame is an unnumbered frame, the control field of the rejected frame is positioned in octet4, with octet 5 set to 00000000.NOTE2-V(S) is the current send state variable value of the error-correcting entity reporting the rejection condition.NOTE3-C/R is set to 1 if the frame rejected was a response and is set to 0 if the frame rejected was a command.NOTE4-V(R) is the current receive state variable value of the error-correcting entity reporting the rejection condition.NOTE5-W set to 1 indicates that the control field received and returned in octets 4 and 5 was undefined or not implemented.NOTE6-X set to 1 indicates that the control field received and returned in octets 4 and 5 was considered invalid because the frame contained an information field which is not permitted with this frame or is a supervisory or unnumbered frame with incorrect length.Bit W must be set to 1 in conjunction with this bit.NOTE7-Y set to 1 indicates that the information field received exceeded the maximum established information field length (N401) of the error-correcting entity reporting the rejection condition.NOTE8-Z set to 1 indicates that the control field received and returned in octets 4 and 5 contained an invalidN(R).NOTE9-Octet 6, bit 1 and octet 8, bits 5 through 8 shall be set to 0.Figure 10/V.42 - FRMR information field format8.2.4.13 Exchange identification (XID) command/responseXID frames are used to exchange general identification information.No sequence numbers are contained within the confrol field of an XID frame.The P/F bit of an XID frame is set to 0.Within the scope of this Recommendation, the information field of XID frames is used for negotiation/indication of parameter values and optional procedures.The encoding of this information field is given in 12.2.8.2.4.14 Test (TEST) commandImplementation of the TEST command frame is optional.When implemented, it is used to conduct a loop-back test between the two control functions.No sequence numbers are contained within the control field of a TEST frame.The Pbit of a TEST command frame is set to 0.An information field, not specified by this Recommendation, is also included in the frame.The control function initiating a loop-back test chooses the contents of the information field.The control function responding to a loop-back test returns the information field received from the initiator.8.2.5 Use of timersFor various functions in the following subclauses, timers are used to ensure proper operation of the protocol [ Pobierz całość w formacie PDF ]
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.Receipt of a UI frame with an unrecognized encoding shall be signalled to the control function as a protocol violation.NOTE2-Cases marked as (solicited) represent proper protocol operation.8.2.4.12 Frame reject (FRMR) responseThe FRMR unnumbered response may be received by an error-correcting entity as a report of an error condition not recoverable by retransmission of the identical frame, i.e.at least one of the following error conditions resulting from the receipt of a valid frame:a) the receipt of a command or response control field that is undefined or not implemented;b) the receipt of a supervisory or unnumbered frame with incorrect length;c) the receipt of an invalid N(R); ord) the receipt of a frame with an information field which exceeds the maximum established length.An undefined control field is any of the control-field encodings not identified in Table 8.A valid N(R) value is one that is in the range V(A) " N(R) " V(S).An information field which immediately follows the control field and consists of five octets is returned with this response and provides the reason for the FRMR response.This information field format is given in Figure 10.87654321OctetRejected frame control field45V(S)6V(R)C/R7ZYXW8NOTE1-Rejected frame control field is the control field of the received frame which caused the frame reject.When the rejected frame is an unnumbered frame, the control field of the rejected frame is positioned in octet4, with octet 5 set to 00000000.NOTE2-V(S) is the current send state variable value of the error-correcting entity reporting the rejection condition.NOTE3-C/R is set to 1 if the frame rejected was a response and is set to 0 if the frame rejected was a command.NOTE4-V(R) is the current receive state variable value of the error-correcting entity reporting the rejection condition.NOTE5-W set to 1 indicates that the control field received and returned in octets 4 and 5 was undefined or not implemented.NOTE6-X set to 1 indicates that the control field received and returned in octets 4 and 5 was considered invalid because the frame contained an information field which is not permitted with this frame or is a supervisory or unnumbered frame with incorrect length.Bit W must be set to 1 in conjunction with this bit.NOTE7-Y set to 1 indicates that the information field received exceeded the maximum established information field length (N401) of the error-correcting entity reporting the rejection condition.NOTE8-Z set to 1 indicates that the control field received and returned in octets 4 and 5 contained an invalidN(R).NOTE9-Octet 6, bit 1 and octet 8, bits 5 through 8 shall be set to 0.Figure 10/V.42 - FRMR information field format8.2.4.13 Exchange identification (XID) command/responseXID frames are used to exchange general identification information.No sequence numbers are contained within the confrol field of an XID frame.The P/F bit of an XID frame is set to 0.Within the scope of this Recommendation, the information field of XID frames is used for negotiation/indication of parameter values and optional procedures.The encoding of this information field is given in 12.2.8.2.4.14 Test (TEST) commandImplementation of the TEST command frame is optional.When implemented, it is used to conduct a loop-back test between the two control functions.No sequence numbers are contained within the control field of a TEST frame.The Pbit of a TEST command frame is set to 0.An information field, not specified by this Recommendation, is also included in the frame.The control function initiating a loop-back test chooses the contents of the information field.The control function responding to a loop-back test returns the information field received from the initiator.8.2.5 Use of timersFor various functions in the following subclauses, timers are used to ensure proper operation of the protocol [ Pobierz całość w formacie PDF ]