ITU-T recommendations

ITU-T Recommendations are the names given to telecommunications and computer protocol specification documents published by the Telecommunication Standardization Sector (ITU-T) on behalf of the International Telecommunication Union.

Series	Description
A	Organization of the work of ITU-T
B	Means of expression: definitions, symbols, classification
C	General telecommunication statistics
D	General tariff principles
E	Overall network operation, telephone service, service operation and human factors
F	Non-telephone telecommunication services
G	Transmission systems and media, digital systems and networks
H	Audiovisual and multimedia systems
I	Integrated services digital network
J	Cable networks and transmission of television, sound programme and other multimedia signals
K	Protection against interference
L	Construction, installation and protection of cables and other elements of outside plant
M	Telecommunication management, including TMN and network maintenance
N	Maintenance: international sound programme and television transmission circuits
O	Specifications of measuring equipment
P	Telephone transmission quality, telephone installations, local line networks
Q	Switching and signalling
R	Telegraph transmission
S	Telegraph services terminal equipment
T	Terminals for telematic services
U	Telegraph switching
V	Data communication over the telephone network
X	Data networks, open system communications and security
Y	Global information infrastructure, Internet protocol aspects and next-generation networks
Z	Languages and general software aspects for telecommunication systems

G Series Recommendations[]

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

Y Series Recommendations[]

Global Information Infrastructure, Internet Protocol Aspects And Nextgeneration Networks

Specification Range	Specification Type
GLOBAL INFORMATION INFRASTRUCTURE
Y.100–Y.199	General
Y.200–Y.299	Services, applications and middleware
Y.300–Y.399	Network aspects
Y.400–Y.499	Interfaces and protocols
Y.500–Y.599	Numbering, addressing and naming
Y.600–Y.699	Operation, administration and maintenance
Y.700–Y.799	Security
Y.800–Y.899	Performances
INTERNET PROTOCOL ASPECTS
Y.1000–Y.1099	General
Y.1100–Y.1199	Services and applications
Y.1200–Y.1299	Architecture, access, network capabilities and resource management
Y.1300–Y.1399	Transport
Y.1400–Y.1499	Interworking
Y.1500–Y.1599	Quality of service and network performance
Y.1600–Y.1699	Signalling
Y.1700–Y.1799	Operation, administration and maintenance
Y.1800–Y.1899	Charging
NEXT GENERATION NETWORKS
Y.2000–Y.2099	Frameworks and functional architecture models
Y.2100–Y.2199	Quality of Service and performance
Y.2200–Y.2249	Service aspects: Service capabilities and service architecture
Y.2250–Y.2299	Service aspects: Interoperability of services and networks in NGN
Y.2300–Y.2399	Numbering, naming and addressing
Y.2400–Y.2499	Network management
Y.2500–Y.2599	Network control architectures and protocols
Y.2700–Y.2799	Security
Y.2800–Y.2899	Generalized mobility