RFC 2166 (rfc2166) - Page 3 of 34
APPN Implementer's Workshop Closed Pages Document DLSw v2
Alternative Format: Original Text Document
RFC 2166 APPN Implementer's Workshop June 1997 1. Introduction This document defines v2.0 of Data Link Switching (DLSw) in the form of a set of enhancements to RFC 1795. These enhancements are designed to be fully backward compatible with existing RFC 1795 implementations. As a compatible set of enhancements to RFC 1795, this document does not replace or supersede RFC 1795. The bulk of these enhancements address scalability issues in DLSw v1.0. Reason codes have also been added to the HALT_DL and HALT_DL_NOACK SSP messages in order to improve the diagnostic information available. Finally, the appendix to this document lists a number of clarifications to RFC 1795 where the implementation experience to- date has shown that the original RFC was ambiguous or unclear. These clarifications should be read alongside RFC 1795 to obtain a full specification of the base v1.0 DLSw standard. 2. HALT Reason codes RFC 1795 provides no mechanism for a DLSw to communicate to its peer the reason for dropping a circuit. DLSw v2.0 adds reason code fields to the HALT_DL and HALT_DL_NOACK SSP messages to carry this information. The reason code is carried as 6 bytes of data after the existing SSP header. The format of these bytes is as shown below. Byte Description 0-1 Generic HALT reason code in byte normal format 2-5 Vendor-specific detailed reason code The generic HALT reason code takes one of the following decimal values (which are chosen to match the disconnect reason codes specified in the DLSw MIB). 1 - Unknown error 2 - Received DISC from end-station 3 - Detected DLC error with end-station 4 - Circuit-level protocol error (e.g., pacing) 5 - Operator-initiated (mgt station or local console) The vendor-specific detailed reason code may take any value. Bryant & Brittain Informational
