ASON is the combination of the first letters of Automatically Switched Optical Network. Actually, we might interpret ASON as a concept for the evolution of transport networks which allows for dynamic policy-driven control of an optical or SDH network based on signaling between a user and components of the network. The aim of ASON is to automate the resource and connection management within the network. ASON is defined as an alternative/supplement to network management system based connection management by IETF.
ASON uses the Generalized MPLS (GMPLS) signalling protocol to set up and monitor edge-to-edge transport connections. ASON concentrates on the optical backbone network. The related ASTN (Automatic switched-transport network) is used in the access networks and metropolian area networks, so called city rings. GMPLS consist of several protocols, including routing protocols (OSPF-TE or ISIS-TE), link management protocols (LMP), and a reservation/label distribution protocol (RSVP-TE). The reservation/label distribution protocol CR-LDP has now been deprecated by the IETF in RFC 3468 and IETF GMPLS working group decided to focus purely on RSVP-TE.