Apparatus and method for hardware creation of a DOCSIS header

• US 20030058862A1
• Filed: 08/15/2002
• Published: 03/27/2003
• Est. Priority Date: 09/27/2001
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Lansing, Shane P., Avakian, Heratch
• Granted Patent: US 7,586,914 B2
• Time in Patent Office: Days
• US Class Current: 370/392
• CPC Class Codes: H04L 69/12 Protocol engines
• CPC Class Codes: H04L 69/22 Parsing or analysis of headers
• CPC Class Codes: H04L 69/324 in the data link layer [OSI layer 2], e.g. HDLC
• CPC Class Codes: H04N 21/42676 for modulating an analogue carrier signal to encode digital information or demodulating it to decode digital information, e.g. ADSL or cable modem
• CPC Class Codes: H04N 21/437 Interfacing the upstream path of the transmission network, e.g. for transmitting client requests to a VOD server flow control in data networks H04L47/10; streaming protocols, e.g. RTP or RTCP, H04L65/65; scheduling or organising the servicing of application requests in data packet switching networks H04L67/60
• CPC Class Codes: H04N 7/17318 Direct or substantially direct transmission and handling of requests

Abstract

A media access controller (MAC) is configured with a DOCSIS Header creator circuit. The DOCSIS header creator circuit is configured with logic for receiving a data packet and determining whether the received data packet has an existing packet header prepended thereto. The DOCSIS header creator circuit is further configured to determine if the length of the received data packet includes a cyclic redundancy code. Still further, the DOCSIS header creator circuit is configured to determine a packet header length field value for the received data packet. If the DOCSIS header creator circuit determines that a cyclic redundancy code needs to be included in with the received data packet, then the DOCSIS header creator circuit is able to generate a CRC flag. If the data packet needs to be encrypted, then the DOCSIS header creator circuit will generate an encryption flag if it is determined that the received data packet should be encrypted. Finally, the DOCSIS header creator circuit generates a DOCSIS packet header having a plurality of fields.

Claims

1. An apparatus for generating a DOCSIS packet header in hardware, comprising:

a header creator control circuit configured with logic for

(i) receiving said data packet and determining whether said received data packet has an existing packet header prepended thereto,

(ii) determining if the length of said received data packet includes a cyclic redundancy code,

(iii) determining a packet header length field value for said received data packet,

(iv) generating a CRC flag if it determined that said cyclic redundancy code is not included,

(v) generating an encryption flag if it is determined that said received data packet should be encrypted, and

(vi) generating a DOCSIS packet header having a plurality of fields.

2. The apparatus of claim 1, wherein said plurality of fields includes a frame control field, a MAC control field, a packet header length field, and a header check sequence field.

3. The apparatus of claim 2, wherein said plurality of fields further includes an extended header field.

4. The apparatus of claim 2, wherein said header creator control circuit generates said DOCSIS packet header when it is determined that said received data packet does not have said existing packet header.

5. The apparatus of claim 2, wherein said packet header length field value is written into said DOCSIS packet header.

6. The apparatus of claim 2, further comprising a DES/HCS/CRC circuit.

7. The apparatus of claim 6, wherein said DES/HCS/CRC circuit is configured to generate a cyclic redundancy code, encrypt a data packet, and generate a header check sequence

8. The apparatus of claim 7, further comprising a circuit for fetching a DES key for use by said DES/HCS/CRC circuit.

9. The apparatus of claim 1, where a packet descriptor is prepended to said data packet prior to said data packet being received by said header creator control circuit.

10. The apparatus of claim 9, wherein said header creator control circuit is further configured to compare said existing packet header to said prepended packet descriptor to determine if a first set of fields and a first packet size associated with said prepended packet descriptor correspond to a second set of fields and a second packet size associated with said existing packet header.

11. The apparatus of claim 10, wherein said header creator control circuit is further configured to compare said existing packet header to a length field associated with said prepended packet descriptor.

21. The method of claim 1, wherein said DOCSIS header creator circuit adds one or more bytes to said received data packet for HCS.

12. A method for creating a DOCSIS packet header in hardware, comprising the steps of:

(a) receiving a data packet into a header creator control circuit and determining whether said received data packet has an existing packet header prepended thereto;

(b) determining if a length value of said received data packet includes a cyclic redundancy code;

(c) determining a packet header length field value for said received data packet;

(d) generating a CRC flag if it determined that said DES/HCS/CRC circuit should generate said cyclic redundancy code;

(e) generating an encryption flag if it is determined that said DES/HCS/CRC circuit should encrypt said received data packet; and

(f) generating a DOCSIS packet header having a plurality of fields.

13. The method of claim 12, wherein said plurality of fields includes a frame control field, a MAC control field, a packet header length field, and a header check sequence field.

14. The method of claim 13, wherein said plurality of fields further includes an extended header field.

15. The method of claim 12, wherein if it is determined that said length value of said received data packet does not include a cyclic redundancy code then one or more bytes are added to said received data packet and said length value of said received data packet is increased by the number of said one or more bytes added.

16. The method of claim 15, wherein said received data packet, said generated new packet header and if generated, said CRC flag and said DES flag, are transmitted for further processing.

17. The method of claim 16, wherein said generated new packet header and if generated, said CRC flag and said DES flag, are received at a DES/HCS/CRC circuit.

18. The method of claim 17, wherein said DES/HCS/CRC circuit determines if said CRC flag has been generated and if so, said DES/HCS/CRC circuit generates a CRC value.

19. The method of claim 18, wherein if said DES/HCS/CRC circuit generates said CRC value, then said one or more extra bytes are overwritten with said generated CRC value.

20. The method of claim 17, wherein said DES/HCS/CRC circuit determines if said DES flag has been generated and if so, said DES/HCS/CRC circuit encrypts said received data packet.