Patent ID: 6711169
Filing Date: 2004-03-23
Classification: H04L,H04Q

Abstract:
A packet system operating in ATM, wherein each cell has a header to identify a connection or link, the system including a controller to ensure that rules are followed to ensure:i) ATM cells are delivered in the order transmitted, and ii) ATM cells are delivered with a consistent VP or VP/VC value said connection or link being either for a virtual path (VP), where cells are delivered with the same VP field but potentially different VC fields; or a virtual circuit (VC), where cells are delivered with the same VP and VC fields, the VP and VC fields being contained within the cell header and negotiated on a link by link basis but being static for a link, said ATM defining an adaptation layer for transmitting packets through a VC, whereby the adaptation layer ATM endpoints break packets into cells and the transmission of packets through the network relies on both of said rules for correct operation; the packet switching system further including a session protection system which disrupts the controller and employs a pseudo random number generator, located in a transmitting network element to break at least one of said rules by: (a) either delivering ATM cells in an order differing from that in which they were transmitted, (b) or delivering ATM cells with a non-consistent VP or VP/VC value, and which also employs a further pseudo random number generator located in a receiving network element either to reassemble the received ATM cells so that they are in the order of transmission, or so that they have a consistent VP or VP/VC value respectively, the session protection system providing said network elements with exchange keys to synchronise said pseudo random generators.