
Customizing an ATM Line
114056 Rev. A 5-3
Modifying ATM FRE2 Physical Attributes
The physical attributes of the ATM line include framing information, transmission
checks, and how ATM treats the line under certain conditions (for example, when
the line is idle).
Assigning the Framing Mode
You can assign an ATM line to use either SONET or SDH framing mode.
By default, the ATM line uses SONET framing. This method uses a 51.84 Mb/s
synchronous transport signal (STS-1) as a basic building block to provide the
OC-3 frame (for example, the STS-3/OC-3 frame has a rate of 3 x 51.84 Mb/s or
155.52 Mb/s).
The SONET frame format consists of 90 x 9 bytes and is divided into two main
areas -- the synchronous payload envelope (SPE) and the transport overhead
(TOH). The SPE contains the core data that the frame is transporting. The TOH
contains the enhanced operations, administration, maintenance, and provisioning
(OAM&P) information.
Synchronous Digital Hierarchy (SDH) provides the framing format required for
ATM in Europe.
Site Manager: Framing Mode: page A-7
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