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Most common SONET/SDH data rates

트릭맨 2007. 6. 18. 18:33

The SONET/SDH Digital Hierarchy
The following table lists the hierarchy of the most common SONET/SDH data rates:
- Optical Level
- Electrical Level
- Line Rate (Mbps)
- Payload Rate (Mbps)
- Overhead Rate (Mbps)
- SDH Equivalent
OC-1      STS-1            51.840             50.112            1.728   -
OC-3      STS-3          155.520           150.336            5.184   STM-1
OC-12    STS-12       622.080            601.344         20.736   STM-4
OC-48    STS-48     2488.320          2405.376         82.944   STM-16
OC-192  STS-192   9953.280         9621.504       331.776   STM-64
OC-768  STS-768 39813.120       38486.016     1327.104   STM-256

Other rates (OC-9, OC-18, OC-24, OC-36, OC-96) are referenced in some of the standards documents but were never widely implemented. It is possible other higher rates (e.g. OC-3072) may be defined in in the future.
The "line rate" refers to the raw bit rate carried over the optical fiber. A portion of the bits transferred over the line are designated as "overhead". The overhead carries information that provides OAM&P (Operations, Administration, Maintenance, and Provisioning) capabilities such as framing, multiplexing, status, trace, and performance monitoring. The "line rate" minus the "overhead rate" yields the "payload rate" which is the bandwidth available for transferring user data such as packets or ATM cells.

The SONET/SDH level designations sometimes include a "c" suffix (such as "OC-48c"). The "c" suffix indicates a "concatenated" or "clear" channel. This implies that the entire payload rate is available as a single channel of communications (i.e. the entire payload rate may be used by a single flow of cells or packets). The opposite of concatenated or clear channel is "channelized". In a channelized link the payload rate is subdivided into multiple fixed rate channels. For example, the payload of an OC-48 link may be subdivided into four OC-12 channels. In this case the data rate of a single cell or packet flow is limited by the bandwidth of an individual channel.