ISO/IEC 4335:1993/Amd 6:1995

Information technology —- Telecommunications and information exchange between systems — High-level data link control (HDLC) procedures — Elements of procedures — Amendment 6: Extension of HDLC sequence number modulus beyond 128

This amendment increases the modulus number (i.e. the sequence number) in steps up to a maximum of 2147483648 which can be represented in 31 bits. This is done by the introduction of a new “Set Mode” command that can be used to negotiate or indicate the modulus in the absence of or to override a default value. This uses an optional information filed in the mode setting commands/responses.