Embodiments of the present invention relate to a method for providing ATM cells at an interface arranged between a first and a second node of a transmission system, in an order according to ATM channels. Embodiments of the method comprise determining address information for a specific ATM cell; verifying, whether the address information has already been recorded in a table, in which the address information is mapped onto a channel ID (CH), by providing the address information to a CAM memory; if the address information has already been recorded in the table assigning the channel ID (CH) output from the CAM memory to the ATM cell for further processing; and if the address information has not yet been recorded in the table, indicating that the address information has not yet been recorded, assigning a free channel ID (CH) to the address information, recording said channel ID (CH) or the address information in the table; and providing the ATM cells, in an order according to channel IDs (CH), for further processing. Also provided is an apparatus comprising a processor and a CAM memory connected together to implement the present method.