High performance protocol for an interconnect system of an intermediate network node

• US 6,973,072 B1
• Filed: 02/22/2001
• Issued: 12/06/2005
• Est. Priority Date: 02/22/2001
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Muntz, Gary S.
• Primary Examiner(s): Sam, Phirin
• Application Number:
  US09/791,062
• Time in Patent Office: 1,748 Days
• Field of Search: 370/351, 370/352, 370/353, 370/354, 370/356, 370/359, 370/389, 370/392, 370/397, 370/399, 370/395.31, 370/400, 370/401, 370/419, 370/465, 370/474, 370/516, 370/517, 370/518, 370/519, 370/329, 370/412
• US Class Current: 370/351
• CPC Class Codes: H04L 45/60 Router architectures
• CPC Class Codes: H04L 69/12 Protocol engines

Abstract

An interconnect protocol enables encoding of packets for transmission over an interconnect system used to couple a plurality of line cards to at least one performance routing engine of an aggregation router. The protocol manifests as a unique encoding and encapsulation technique for data transmitted over point-to-point links of the interconnect system. The encapsulation technique includes an interconnect header which is attached to each packet. Framer logic is provided at a transmitter of the system to generate encoded frames from a stream of packet data for transmission over the links and at a receiver to recover the transmitted data from the frames.

Claims

1. A method for encoding packet data for transmission over an interconnect system used to couple a plurality of line cards to a routing engine of an intermediate network node, the method comprising the steps of:

generating an interconnect packet from the packet data received at a line card, the interconnect packet including a data payload appended to a header, the header comprising a length field and a channel field;

encoding frames from a stream of interconnect packets for transmission over the interconnect system, each encoded frame including a plurality of start of packet (SOP) indicators arranged to substantially reduce latency associated with transmission of the interconnect packets;

recovering the encoded frames and stream of interconnect packets from the interconnect system; and

determining an end of each interconnect packet within the recovered stream using a length content of the length field.

2. The method of claim 1 wherein the step of encoding comprises the step of apportioning each interconnect packet into a plurality of encoded frames.

3. The method of claim 2 wherein the step of recovering comprises the step of reassembling the encoded frames into an interconnect packet.

4. The method of claim 3 wherein the step of recovering further comprises the step of referencing a beginning of each interconnect packet using the SOP indicators.

5. The method of claim 1 wherein the step of determining comprises the step of checking the length content to insure it is within a supportable range.

6. The method of claim 1 wherein the step of determining comprises the step of comparing the length content with minimum and maximum values to determine whether the interconnect packet has a length of supportable size.

7. The method of claim 6 further comprising the step of, if the length is of a supportable size, examining a channel number content of the channel field to determine a destination of the interconnect packet.

8. A method for encoding packet data for transmission over an interconnect system used to couple a plurality of line cards to a routing engine of an intermediate network node, the method comprising the steps of:

generating an interconnect packet from the packet data received at a line card, the interconnect packet including a data payload appended to a header, the header comprising a length field and a channel field;

encoding frames from a stream of interconnect packets for transmission over the interconnect system, each encoded frame including a plurality of start of packet (SOP) indicators arranged to substantially reduce latency associated with transmission of the interconnect packets;

determining an end of each interconnect packet within the recovered stream using a length content of the length field;

recovering the encoded frames and stream of interconnect packets from the interconnect system;

comparing the length content with minimum and maximum values to determine whether the interconnect packet has a length of supportable size; and

discarding the interconnect packet if the length is of an unsupportable size.

9. A system for encoding packet data for transmission over an interconnect system used to couple a plurality of line cards to a routing engine of an intermediate network node, the system comprising:

interface circuitry of the routing engine and each line card, the interface circuitry adapted to generate an interconnect packet from the packet data initially received at the line card, the interconnect packet including a data payload appended to a header, the header comprising a length field and a channel field;

means, coupled to the interface circuitry, for (i) encoding frames from a stream of interconnect packets for transmission over the interconnect system and (ii) recovering the encoded frames and stream of interconnect packets from the interconnect system, each encoded frame including a plurality of start of packet (SOP) indicators arranged to substantially reduce latency associated with transmission of the interconnect packets; and

a length check circuit coupled to the interface circuitry and configured to determine an end of each interconnect packet within the recovered stream using a length content of the length field.

10. The system of claim 9 wherein the interface circuitry functions as a translator that converts a packet data format received at the line card to a protocol format of the interconnect packet.

11. The system of claim 9 wherein the means for encoding comprises a transmitter cooperatively coupled to framing logic and adapted to transmit the encoded frames over the interconnect system.

12. The system of claim 11 wherein the transmitter comprises:

a forwarded clock register configured to generate a forwarded clock signal for transmission over a clock wire of the interconnect system;

a plurality of data registers configured to stage data prior to transmission over respective data wires of the interconnect system; and

a clock source configured to generate a local clock signal used to enable the forwarded clock and data registers.

13. The system of claim 9 wherein the means for recovering comprises a receiver cooperatively coupled to framing logic and adapted to receive the encoded frames and stream of interconnect packets from the interconnect system.

14. The system of claim 9 wherein the length check circuit comprises logic circuitry organized to compare the length content with minimum and maximum values to determine whether a length of the packet is of a supportable size.

15. The system of claim 9 wherein the intermediate network node is an aggregation router.

16. The system of claim 15 wherein the routing engine is a performance routing engine of the aggregation router.

17. A system for encoding packet data for transmission over an interconnect system used to couple a plurality of line cards to a routing engine of an intermediate network node, the system comprising:

interface circuitry of the routing engine and each line card, the interface circuitry adapted to generate an interconnect packet from the packet data initially received at the line card, the interconnect packet including a data payload appended to a header, the header comprising a length field and a channel field;

means, coupled to the interface circuitry, for (i) encoding frames from a stream of interconnect packets for transmission over the interconnect system and (ii) recovering the encoded frames and stream of interconnect packets from the interconnect system, each encoded frame including a plurality of start of packet (SOP) indicators arranged to substantially reduce latency associated with transmission of the interconnect packets;

a length check circuit coupled to the interface circuitry and configured to determine an end of each interconnect packet within the recovered stream using a length content of the length field;

a receiver cooperatively coupled to framing logic and adapted to receive the encoded frames and stream of interconnect packets from the interconnect system;

the receiver has,

first and second data registers configured to receive data from respective data wires of the interconnect system; and

a clock receiver for receiving a forwarded clock signal from a clock wire of the interconnect system, the clock receiver configured to feed a non-inverted copy of the received clock signal to the first data register and an inverted copy of the received clock signal to the second data register.

18. The system of claim 17 wherein the framing logic comprises a plurality of shift registers adapted to store the receive data provided by the first and second data registers.

19. The system of claim 18 wherein each encoded frame comprises a group of bits that is repeated within a framing pattern and wherein the framing logic further comprises a boolean logic circuit coupled to the shift registers, the boolean logic circuit configured to search for the framing pattern.

20. The system of claim 19 wherein the framing logic further comprises

a frame cycle counter that is activated in response to detection of the framing pattern.

21. Apparatus adapted to process packet data for transmission over an interconnect system used to couple a plurality of line cards to a muting engine of an intermediate network node, the system comprising:

interface circuitry of the routing engine and each line card, the interface circuitry adapted to generate an interconnect packet from the packet data initially received at the line card, the interconnect packet including a data payload appended to a header, the header comprising a length field and a channel field;

framing logic cooperatively coupled to (i) a transmitter to encode frames from a stream of interconnect packets for transmission over the interconnect system and (ii) a receiver to recover the encoded frames and stream of interconnect packets from the interconnect system, each encoded frame including a plurality of start of packet (SOP) indicators arranged to substantially reduce latency associated with transmission of the interconnect packets; and

a length check circuit coupled to the interface circuitry and configured to determine an end of each interconnect packet within the recovered stream using a length content of the length field.

22. A method for encoding packet data for transmission over an interconnect system used to couple a plurality of line cards in a network device, comprising:

generating an interconnect packet from the packet data received at a line card, the interconnect packet including a data payload appended to a header;

encoding frames from a stream of interconnect packets for transmission over the interconnect system, each encoded frame including a plurality of start of packet (SOP) indicators;

recovering the encoded frames and stream of interconnect packets from the interconnect system; and

determining an end of each interconnect packet within the recovered stream using a length content of a length field in the header.

23. The method as in claim 22, further comprising:

using 8 bits to represent a byte of the packet data and using a 9 th bit for the SOP.

24. A network device, the network device having a plurality of line cards coupled by an interconnect, comprising:

means for generating an interconnect packet from the packet data received at a line card, the interconnect packet including a data payload appended to a header;

means for encoding frames from a stream of interconnect packets for transmission over the interconnect system, each encoded frame including a plurality of start of packet (SOP) indicators;

means for recovering the encoded frames and stream of interconnect packets from the interconnect system; and

means for determining an end of each interconnect packet within the recovered stream using a length content of a length field in the header.

25. The network device as in claim 24, further comprising:

means for using 8 bits to represent a byte of the packet data and using a 9 th bit associated with each byte for the SOP.

26. A network device, comprising:

a plurality of line cards coupled by an interconnect;

interface circuitry to generate an interconnect packet from the packet data received at a line card of the line cards, the interconnect packet including a data payload appended to a header;

sending transceiver logic to encode frames from a stream of interconnect packets for transmission over the interconnect system, each encoded frame including a plurality of start of packet (SOP) indicators;

receiving transceiver logic to recover the encoded frames and stream of interconnect packets from the interconnect system; and

length determining circuitry to determine an end of each interconnect packet within the recovered stream using a length content of a length field in the header.

27. The network device as in claim 26, further comprising:

a frame having 8 bits to represent a byte of the packet data and using a 9 th bit for the SOP.