At+t Corp.

Abhijit K Choudhury

Ellen L Hahne

Sanjoy Paul

Nicholas Frank Maxemchuk

Henning G Schulzrinne

A dynamic threshold system and method is disclosed for allocating memory among different output queues in a shared-memory ATM switch. The maximum permissible length for any individual queue at any instant of time is a function of the unused buffering in the switch. The dynamic threshold system and method deliberately reserves a small amount of buffer space, not allocating it to any currently active output queue, but attempts to equally share the remaining buffer space among the currently active output queues. The dynamic threshold system and method improve fairness and switch efficiency by guaranteeing access to the buffer space for all output queues, and by preventing any single output queue from monopolizing the memory at the expense of the others. The dynamic threshold system and method adapt to uncertain or changing load conditions. The packet losses that occur with dynamic thresholds tend to be clustered at a few offending queues, which is desirable in ATM systems, since it results in fewer messages being disturbed at higher protocol layers and, hence, fewer message retransmissions. The dynamic threshold system and method are also extendable to handle traffic with multiple space priorities.

Dynamic queue length thresholds in a shared memory ATM switch

A system for queueing and selective pushout and method are disclosed for a packet communications module such as a shared memory asynchronous transfer mode (ATM) switch. The shared memory stores packets in queues, each packet having a field and at most two pointers. Within each queue, the packets having respective space priorities are stored in subqueues each having the respective space priorities. The packets are stored in these priority subqueues using a first pointer pointing to the next packet of the same space priority in the queue. The second pointer associated with a stored packet points to the previous packet of greater than or equal space priority in the FIFO order in the queue. The field of a packet is used to store the priority value corresponding to the next packet in FIFO order in the queue, and this field is used by a processor to decide priority sub-queues to serve next. The packets are stored in the queues in a FIFO order using the two pointers and the fields of the packets. The processor controls the selective pushout to push out a packet and uses the two pointers and the fields of the packets to restore the FIFO order. A method is also disclosed including the steps of storing packets in a queue, with each of the queued packets associated with the two pointers and a field; serving the queue; pushing out packets from the queue; and maintaining queue-lengths and a state information table.

Implementation of selective pushout for space priorities in a shared

A method for protecting electronically published documents involves operating a computer system and network for electronic publication of documents, and includes the steps of receiving requests for documents from users having computers with display devices or printers, including with the requests unique user identification for each of the user; authenticating the requests with a copyright server; using the copyright server to direct a document server to act upon proper authentication of each request; using the document server to create uniquely encoded, compressed and encrypted documents for each authenticated request, where the documents have unique encoding corresponding to each of the users, and forwarding the documents to each authenticated request user through the network to corresponding agents of each authenticated request user, with each of the agents being selected from display agents and printer agents; and decrypting and uncompressing the documents at each of the agents and making the documents available for use only in response to receiving correct secret keys provided by the authenticated request user to the agents.

Method of protecting electronically published materials using

A method of regulating backpressure traffic in a packet switched network made up of a plurality of switching elements each having a local buffer memory identifies at least one switching element which succeeds at least one other switching element in a transmission path. The at least one succeeding switching element has a congested local buffer memory. A backpressure signal is transmitted to the at least one other switching element. Packets destined for the succeeding switching element are queued in the local buffer memory of the at least one other switching element. Next, it is determined when the occupancy of the local buffer memory for the other switching element has exceeded a predetermined threshold. In response to the exceeded predetermined threshold, the other switching element ignores the backpressure signal transmitted from the succeeding switching element and transmits the queued packets to the succeeding switching element.

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Scotch Plains, NJ, United States of America

Abhijit K Choudhury