Juniper Networks, Inc. Juniper Networks, Inc. This document specifies a mechanism referred to as "Intent Driven Service Mapping". The mechanism uses BGP to express intent based association of overlay routes with underlay routes having specific Traffic Engineering (TE) characteristics satisfying a certain Service Level Agreement (SLA). This is achieved by defining new constructs to group underlay routes with sufficiently similar TE characteristics into identifiable classes (called "Transport Classes"), that overlay routes use as an ordered set to resolve reachability (Resolution Schemes) towards service endpoints. These constructs can be used, for example, to realize the "IETF Network Slice" defined in TEAS Network Slices framework. Additionally, this document specifies protocol procedures for BGP that enable dissemination of service mapping information in a network that may span multiple cooperating administrative domains. These domains may be administered either by the same provider or by closely coordinating providers. A new BGP address family that leverages RFC 4364 procedures and follows RFC 8277 NLRI encoding is defined to advertise underlay routes with its identified class. This new address family is called "BGP Classful Transport", a.k.a., BGP CT.