Abstract: Invalid transmissions in an ATM network (200) are identified by maintaining a user profile (304) relating to network use for each participating node of the network (200) and detecting potentially invalid transmissions based on a deviation (312) from the user profile. In a preferred embodiment, the user profile is continuously updated by monitoring transmissions within the ATM network (200), taking advantage of information included in defined fields of the transmitted ATM cells. When a detected deviation exceeds a predetermined threshold (314), the source node of the transmission is investigated to verify the identity of the source node user. The investigation is accomplished prior to establishing a security link between the source node and a secured node (202), thereby increasing availability of the secured node (202) for use by authorized network users.

Abstract: Detection of the packet type of information packets received at a node in a packet based communications network is accomplished by comparing information from each received packet to a table (62) of possible packet types. After packet type has been identified, the corresponding packet is routed for processing based on type. For increased processing speed, the comparison with each of the entries in the table (62) can be performed substantially simultaneously. In one embodiment, a content addressable memory (CAM, 48) is utilized to store the table (62) information and to perform the required comparisons. In addition, wired OR means (50) is provided for use in reducing the total number of entries in the table (62). In a preferred embodiment, the cell types of asynchronous transfer mode (ATM) cells are detected.