Hardware Specifications | Hardware Configuration and Overview of Functions |
|
|
|
|
Line Cards
A line card is composed of a line interface unit and a line buffer.
Basically, the line interface unit physically terminates the lines. The line interface unit takes ATM cells from the ATM line signals and sends the cells to the line buffer. In addition, the line interface unit inserts the ATM cells from the line buffer into the ATM line signals and sends the cells to the opposing hardware. In addition, the line interface unit multiplexes and demultiplexes the ATM cells from a number of lines.
The principal functions performed by the line interface unit are as follows:
■Conversion of electric signals and optical signals and detection of optical reception signal disconnection.
■Serial/parallel conversion.
■Encode/decode or termination of each line frame.
■Cell alignment and clock change (adjusts cell speed to line speed).
The line buffer converts into address number the data housed in the header of the ATM cell received from the line interface unit and sends the cell to the ATM switch. At the same time, the line buffer unit is equipped with an input buffer (IXB) that stores ATM cells according to the BP (back pressure) from the switch engine. Furthermore, the line buffer converts the address number in the header of the ATM cell received from the ATM switch into data used by the opposing hardware and sends the cell to the line terminating block. The line buffer is also equipped with an output buffer (OXB) that stores ATM cells that are input in excess of the line speed.
The principal functions performed by the line buffer are as follows:
■Valid VP bit count: 14 bits
■
■Congestion control (BP and EFCI functions)
■Priority control (QoS 5 class, loss 2 class)
■UPC control (GCRA)
■OAM control
■Shaping (PCR & SCR guarantee type)
■Frame discard (EPD)
Centillion 1200N ATM Switch User Manual | |
NTP |
|
