Bridging

The ITU, or International Telecommunications Union (formerly known as the CCITTÑthe Consultative Committee on International Telegraph and Telephone) incorporated the SONET standard into its Synchronous Digital Hierarchy (SDH) recommendations, which address differences between the European and North American transmission standards. The ITU sets standards for international communications (except for nations adhering to ANSI standards). SDH is a world standard, and as such, the SONET standard is considered a subset within it.

The SDH transmission hierarchy uses the STM-1 (Synchronous Transfer Module Level 1) as its basic building block signal (transmitted at 155.52 Mbps). Again, there are STM-N signals, which are STM-1 signals that have been multiplexed into a higher signaling rate.

Table 2-1. SONET/SDH Transmission Hierarchies

SONET

Bit Rate

SDH

 

STS-1/OC-1

51.84 Mbps

Ñ

 

 

 

 

 

STS-3/OC-3 (supports

155.52 Mbps

STM-1 (supports

 

FE-100Sx and APIM-2x

 

FE-100Sx and APIM-2x

 

in SONET operational

 

in SDH operational

 

mode)

 

mode)

 

 

 

 

 

STS-12/OC-12

622.08 Mbps

STM-4

 

 

 

 

 

STS-24/OC-24

1244.16 Mbps

Ñ

 

 

 

 

 

STS-48/OC-48

2588.32 Mbps

STM-16

 

 

 

 

 

STS-192/OC-192

9953.28 Mbps

STM-64

 

 

 

 

You should be sure that the operational mode for both the local and remote ends of the SONET connection is set appropriately for your region. Setting the wrong operational mode may cause errors to be generated during transmission, since there are slight differences in framing SONET and SDH signals.

To access the SONET/SDH ConÞguration window from the Bridge Status

window:

1.Click on the desired Port button () to display the Port menu.

2.Click on SONET/SDH Configuration. The SONET/SDH Configuration: Port X window, Figure 2-25, will appear.

To access the SONET/SDH ConÞguration window from the Chassis View window:

1.Click on the appropriate port index to access the Port menu.

2.Click on SONET/SDH Configuration. The SONET/SDH Configuration: Port X window, Figure 2-25, will appear.

2-78

SONET Port Configuration

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Cabletron Systems 2.2 manual Sonet