G.709
Encyclopedia
ITU-T Recommendation G.709 "Interfaces for the Optical Transport Network
(OTN)" describes a means of communicating data over an optical network. It is a standardized method for transparent transport of services over optical wavelengths in DWDM systems.
It also known as Optical Transport Hierarchy (OTH) standard.
The G.709 OTUk signal is positioned as a server layer signal for various client signals, e.g. SDH/SONET
, ATM
, IP
, Ethernet
, Fibre Channel
and OTN
ODUk (where k=0, 1, 2, 2e, 3, 3e2, 4 or flex). Work on support for InfiniBand
and Common Public Radio Interface
client signals is currently in progress.
The frame structure defined in G.709 is constructed of 4 areas:
G.709 offers advanced OAM&P
capabilities such as Tandem Connection Monitoring (TCM), End to End performance monitoring, connectivity monitoring, signal quality supervision and General Communication Channel
(GCC).
Unlike SDH/SONET, the line rate is increased by maintaining the G.709 frame structure (4 rows x 4080 columns) and decreasing the frame period (in SDH/SONET the frame structure is increased and the frame period of 125 µs is maintained).
Optical Transport Network
ITU-T defines an Optical Transport Network as a set of Optical Network Elements connected by optical fibre links, able to provide functionality of transport, multiplexing, switching, management, supervision and survivability of optical channels carrying client signals...
(OTN)" describes a means of communicating data over an optical network. It is a standardized method for transparent transport of services over optical wavelengths in DWDM systems.
It also known as Optical Transport Hierarchy (OTH) standard.
The G.709 OTUk signal is positioned as a server layer signal for various client signals, e.g. SDH/SONET
Synchronous optical networking
Synchronous Optical Networking and Synchronous Digital Hierarchy are standardized multiplexing protocols that transfer multiple digital bit streams over optical fiber using lasers or highly coherent light from light-emitting diodes . At low transmission rates data can also be transferred via an...
, ATM
Asynchronous Transfer Mode
Asynchronous Transfer Mode is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that...
, IP
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
, Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
, Fibre Channel
Fibre Channel
Fibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards , an American National Standards Institute –accredited standards...
and OTN
Optical Transport Network
ITU-T defines an Optical Transport Network as a set of Optical Network Elements connected by optical fibre links, able to provide functionality of transport, multiplexing, switching, management, supervision and survivability of optical channels carrying client signals...
ODUk (where k=0, 1, 2, 2e, 3, 3e2, 4 or flex). Work on support for InfiniBand
InfiniBand
InfiniBand is a switched fabric communications link used in high-performance computing and enterprise data centers. Its features include high throughput, low latency, quality of service and failover, and it is designed to be scalable...
and Common Public Radio Interface
Common Public Radio Interface
The Common Public Radio Interface standard defines the interface of base stations between the Radio Equipment Controllers in the standard, to local or remote radio units, known as Radio Equipment ....
client signals is currently in progress.
The frame structure defined in G.709 is constructed of 4 areas:
- OPUk is the area in which payload is mapped.
- ODUk contains the OPUk with additional overhead bytes (e.g. TTI, BIP8, GCC1/2, TCM etc.).
- OTUkOptical Transport NetworkITU-T defines an Optical Transport Network as a set of Optical Network Elements connected by optical fibre links, able to provide functionality of transport, multiplexing, switching, management, supervision and survivability of optical channels carrying client signals...
is the section and includes framing , TTI, BIP8 and GCC0 bytes. - FECForward error correctionIn telecommunication, information theory, and coding theory, forward error correction or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels....
- The standard FEC code (described in G.975) is a Reed-Solomon coding calculated across the payload (OPU) columns. This allows detection and correction of bit errors due to signal impairments during transmission. The FEC code also extends the distance the optical signal can travel before requiring regeneration.
G.709 offers advanced OAM&P
OAMP
OAMP, traditionally OAM&P, stands for operations, administration, maintenance, and provisioning. The addition of 'T' in recent years stands for troubleshooting, and reflects its use in network operations environments...
capabilities such as Tandem Connection Monitoring (TCM), End to End performance monitoring, connectivity monitoring, signal quality supervision and General Communication Channel
General Communication Channel
The General Communication Channel was defined by G.709 is an in-band side channel used to carry transmission management and signaling information within Optical Transport Network elements.Two types of GCC are available:...
(GCC).
Typical client signals and corresponding G.709 rates
| Client Signal Type | Client Signal | OTUk Line Rate (kbit/s) | |OTUk frame period (µs) | SONET/SDH | STS-48 STS-48 -Mission parameters:*Mass:**Orbiter landing with payload: **Payload: *Perigee: *Apogee: *Inclination: 57.0°*Period: 96.2 min-Mission highlights:... /STM-16 |
OTU1 | 2,666,057 | 2,488,320 | 48.971 | ± 20 | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| SONET/SDH | STS-192/STM-64 | OTU2 | 10,709,225 | 10,037,629 | 12.191 | ± 20 | |||||
| Ethernet Ethernet Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies.... /Fibre Channel Fibre Channel Fibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards , an American National Standards Institute –accredited standards... |
10GBASE-R/10GFC | OTU2e | 11,095,727 | 10,356,012 | 11.766 | ±100 | |||||
| SONET/SDH | STS-768/STM-256 | OTU3 | 43,018,413 | 40,150,519 | 3.034 | ±20 | |||||
| Ethernet Ethernet Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies.... |
Up to 4 10GBASE-R | OTU3e2 | 44,583,355 | 41,611,131 | 2.928 | ±100 | |||||
| Ethernet Ethernet Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies.... |
100GBASE-R | OTU4 | 111,809,973 | 100,376,298 | 1.167 | ±20 | |||||
Unlike SDH/SONET, the line rate is increased by maintaining the G.709 frame structure (4 rows x 4080 columns) and decreasing the frame period (in SDH/SONET the frame structure is increased and the frame period of 125 µs is maintained).
External links
- The G.709 Optical Transport Network - An Overview - Application note 153 by EXFO
- OTN interfaces for IP over DWDM - Juniper White Paper that describes the evolution and reasoning of IP-over-ATM-over-SONET/SDH-over-DWDM towards IP-over-OTN-over-DWDM. It clearly describes what problem OTN tries to solve (and how)
- Value of OTN for Network Convergence White Paper
- Download the G.709 Recommendation