IETF RFC 3038 PDF

The Asynchronous Transfer Mode Label Switching Router (ATM-LSR) is one of the major applications of label switching. Because the ATM layer labels (VPI and VCI) associated with a VC rewritten with new value at every ATM switch nodes, it is not possible to use them to identify a VC in label mapping messages. The concept of Virtual Connection Identifier (VCID) is introduced to solve this problem. VCID has the same value at both ends of a VC. This document specifies the procedures for the communication of VCID values between neighboring ATM-LSRs that must occur in order to ensure this property.