| 摘要 |
<p>According to the invention, an ATM switch is used for returning signalling cells to their input side and to an apparatus which is located there for processing signalling cells and which performs SAR functions. The apparatus (56) processing signalling cells is connected to the ATM layer circuit (52) using a UTOPIA interface according to the standard. Seen from the ATM layer circuit, the processing apparatus does not hereby in any way differ from those physical layer circuits (PHY) connected to it through the UTOPIA interface which connect the optical fibres to the ATM node. Through the ATM switch (52) the signalling cells circulate back to the input side, and in the output buffer a modification of cell headings is done wherein the VPI/VCI data is replaced with a tag of that physical circuit through which the signalling cell has arrived and the old tag is replaced with a new tag by which the ATM layer circuit directs the modified signalling cells through the UTOPIA interface to the apparatus processing signalling cells.</p> |
