G is a series of recommendations (standards) from Study Group 15 (Transport, Access and Home) of the International Telecommunication Union (ITU-T). The G series concerns "Transmission systems and media, digital systems and networks".
| Specification Range | Specification Type |
|---|---|
| G.100 - G.199 | International Telephone Connections and Circuits |
| G.200 - G.299 | General Characteristics Common to all Analogue Carrier Transmission Systems |
| G.300 - G.399 | Individual Characteristics of International Carrier Telephone Systems on Metallic Lines |
| G.400 - G.449 | General Characteristics of International Carrier Telephone Systems on Radio-Relay or Satellite Links and Interconnection with Metallic Lines |
| G.450 - G.499 | Coordination of Radiotelephony and Line Telephony |
| G.600 - G.699 | Transmission Media and Optical Systems Characteristics |
| G.700 - G.799 | Digital Terminal Equipments |
| G.800 - G.899 | Digital Networks |
| G.900 - G.999 | Digital Sections and Digital Line System |
| G.1000 - G.1999 | Quality of Service and Performance – Generic and User-Related Aspects |
| G.6000 - G.6999 | Transmission Media Characteristics |
| G.7000 - G.7999 | Data Over Transport – Generic Aspects |
| G.8000 - G.8999 | Packet over Transport Aspects |
| G.8000 - G.8099 | Ethernet over Transport aspects |
| G.8100 - G.8199 | MPLS over Transport aspects |
| G.8200 - G.8299 | Quality and availability targets |
| G.8600 - G.8699 | Service Management |
| G.9000 - G.9999 | Access Networks |