Digital telecommunication link for efficiently transporting mixed classes of packets

• US 5,497,371 A
• Filed: 02/16/1995
• Issued: 03/05/1996
• Est. Priority Date: 10/26/1993
• Status: Expired due to Term

• Current Assignee: Avaya Holdings Corporation (Avaya Incorporated)
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Ellis, John G., Dysart, Keith C., Commons, Douglas N.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): BLUM, RUSSELL
• Application Number:
  US08/389,449
• Time in Patent Office: 383 Days
• Field of Search: 370/60, 370/61, 370/79, 370/85.1, 370/85.6, 370/58.2, 370/58.3, 370/110.1, 370/100.1, 371/48, 371/52, 371/53, 371/54, 371/30
• US Class Current: 370/412
• CPC Class Codes: H04L 12/64 Hybrid switching systems
• CPC Class Codes: H04L 12/6418 Hybrid transport
• CPC Class Codes: H04L 2012/563 Signalling, e.g. protocols, reference model
• CPC Class Codes: H04L 2012/5651 Priority, marking, classes
• CPC Class Codes: H04L 2012/5671 Support of voice
• CPC Class Codes: H04L 2012/5678 Traffic aspects, e.g. arbitration, load balancing, smoothing, buffer management
• CPC Class Codes: H04L 2012/6464 Priority
• CPC Class Codes: H04L 2012/6489 Buffer Management, Threshold setting, Scheduling, Shaping
• CPC Class Codes: H04L 47/245 using preemption
• CPC Class Codes: H04L 47/34 ensuring sequence integrity, e.g. using sequence numbers
• CPC Class Codes: H04L 49/20 Support for services
• CPC Class Codes: H04L 49/30 Peripheral units, e.g. input or output ports
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

An efficient packet transport system for mixed traffic in which a packet fragmentation protocol allows traffic of different classes to occupy a single physical link. In one embodiment, packet fragmentation gives delay sensitive traffic priority over non-sensitive traffic. This allows both traffic types to coexist on a single data link. The protocol eliminates software overheads associated with mis-ordered packets and efficiently transports both cell and frame formatted data using encapsulation.

Claims

1. A digital telecommunication system for serially transmitting in packets of various sizes digital data of two or more different priorities from a source card to a destination card over a link, in transmitting the digital data the digital telecommunication system routinely using frame slips to adjust differences among clocks in the system, comprising:

the link connecting the cards;

each of the cards having two or more buffers and two or more queues, each queue and buffer being connected to each other and being assigned with a priority for individually storing packets or fragmented packets of digital data of any number of bytes according to their priority;

a link controller at the source card serving the buffers for transmission of a packet therein to the destination card according to their priorities so that a packet of higher priority in its assigned buffer is able to interrupt at any time the transmission of a packet of lower priority from its assigned buffer and to fragment it to one or more packet fragments of any number of bytes;

the link controller adding to each packet and fragmented packet, priority bits, sequence bits, CRC bits and a complete bit to indicate respectively the priority, sequence number, CRC, and completeness of each packet and fragmented packet; and

a protocol checker at the destination card for monitoring the sequence numbers of packets for skipped or replicated packet fragments which may have been caused by the frame slips.

2. The digital telecommunication system according to claim 1, wherein the link controller comprises:

a priority encoder connected to the queues for reading the priority of packets stored therein;

a header generator for adding to each of the packets and the packet fragments a flag, priority bits, sequence bits, a complete bit and CRC bits; and

a transmission control for coordinating the priority encoder and the header generator.

3. The digital telecommunication system according to claim 2 further comprising a common memory on each card which is properly partitioned to be used for the queues and buffers, each assigned to a different priority.

4. The digital telecommunication system according to claim 2 wherein a packet length is of any size within the respective maximum length for each priority, which maximum length is determined by the speed of the link.

5. In a digital telecommunication system, a method of serially transmitting in packets of various sizes, digital data of two or more different priorities from a source card to a destination card over a link, in transmitting the digital data the digital telecommunication system routinely using frame slips to adjust differences among clocks in the system, comprising steps of:

at each card, individually storing packets of digital data of any number of bytes according to their priority in two or more respectively assigned queues;

at each card, individually transferring from each queue and buffering packets of digital data of any number of bytes according to their priority in two or more respectively assigned buffers;

serving the buffers at the source card for transmission of packets according to their priorities so that a higher priority packet in a higher priority buffer interrupts at any time the transmission of a lower priority packet from a lower priority buffer by fragmenting the lower priority packet into one or more packet fragments of any number of bytes;

adding to each packet and packet fragment, priority bits, sequence bits, CRC bits, and a complete bit to indicate respectively the priority, sequence number, error check and completeness of each packet and fragmented packet;

receiving serially at the destination card packets transmitted over the link;

individually buffering received packets and packet fragments according to their priority at their respectively assigned buffers; and

monitoring the sequence bits of the packet fragments for the correct sequence of the packet fragments and for skipped or replicated packet fragments which may have been caused by the frame slips.

6. The method of serially transmitting digital data according to claim 5, wherein the step of serving the buffers at the source card for transmission of a higher priority packet is performed whenever there is a packet to send in the respective buffer, thus interrupting the transmission of a lower priority packet each time a higher priority packet is transmitted and fragmenting it into one or more packet fragments of any size.

7. The method of serially transmitting digital data according to claim 6, further comprising a step of:

storing packets of digital data in respective queues according to their priority prior to the step of individual buffering.