Upstream physical interface for modular cable modem termination system

• US 20050265397A1
• Filed: 05/17/2005
• Published: 12/01/2005
• Est. Priority Date: 06/27/2001
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Chapman, John T., Bernstein, Alon S., Youngman, Eric, Crocker, Daniel W.
• Granted Patent: US 7,639,617 B2
• Time in Patent Office: Days
• US Class Current: 370/490
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 12/4633 Interconnection of networks using encapsulation techniques, e.g. tunneling

Abstract

A modular Cable Modem Termination System (CMTS) includes a packet shelf operating a Data Over Cable Service Interface Specifications (DOCSIS) Media Access Control (MAC) framer. One or more downstream Physical Interface (PHY) shelves receive DOCSIS data from the packet shelf over a packet switched network and modulate the DOCSIS data for sending on a downstream path of a cable plant. One or more upstream PHY shelves send DOCSIS data received from an upstream path of the cable plant over the packet switched network to the packet shelf. By separating the PHY components from the MAC and from the system software, the PHY components for a Hybrid Fiber Coax (HFC) plant may be replaced with different PHY components for other access technologies such as wireless, Digital Subscriber Lines (DSL), Ethernet-to-the-Home, Fiber-to-the-Home, or fiber Passive Optical Networks (PONs).

Claims

1. An upstream cable Physical Interface (PHY), comprising:

one or more cable Physical Interfaces (PHYs) containing Quadrature Amplitude Modulation (QAM) demodulators for demodulating Data Over Cable Service Interface Specifications (DOCSIS) frames received over an upstream path of a cable plant into DOCSIS Media Access Control (MAC) PHY Interface (DMPI) blocks; and

a DOCSIS Remote PHY Interface (DRPI) framer configured to convert the DMPI blocks into packets and send the packets over a packet switched network.

2. The upstream PHY according to claim 1 wherein the DRPI framer encapsulates multiple DMPI blocks together in a same DOCSIS packet and sends the packet over a tunnel in the packet switched network.

3. The upstream PHY according to claim 2 wherein the DRPI framer encapsulates the DMPI blocks received from different upstream channels into the same packets and sends the packets over the tunnel to a DOCSIS MAC operating in a packet shelf.

4. The upstream PHY according to claim 3 wherein the DRPI framer inserts a domain header in the DMPI blocks that identifies an upstream domain and upstream logical channel associated with the DMPI blocks.

5. The upstream PHY according to claim 4 wherein the DRPI framer sends a DMPI timestamp snapshot block in some of the packets that identifies a timestamp value, mini-slot number, and a mini-slot frame number.

6. The upstream PHY according to claim 1 wherein the DRPI framer forms the packet by:

encapsulating the DMPI blocks into a payload of a UDP packet;

attaching an IP header to the UDP packet; and

attaching an Ethernet header to the IP header.

7. The upstream PHY according to claim 1 including multiple Quality of Service (QoS) queues used by the DRPI framer to format the DMPI blocks into different QoS tunnels.

8. The upstream PHY according to claim 7 including a Service Identifier (SID) to Quality of Service (QoS) table used by the DRPI framer to map SID values associated with the DMPI blocks to associated QoS values in the table and then transport the DMPI blocks over the QoS tunnels in the packet switched network corresponding with the associated QoS values.

9. The upstream PHY according to claim 8 wherein SID to QoS values in the table are dynamically varied according to SID to QoS values in MAP packets received over the packet switched network from a DOCSIS MAC in a remote packet shelf.

10. The upstream PHY according to claim 1 wherein the PHYs identify request messages in the DOCSIS frames received over the cable plant and the DRPI framer generates separate request packets for the identified request messages.

11. The upstream PHY according to claim 10 wherein the DRPI framer sends the same request message in a first request packet and in a second packet that encapsulates multiple other DMPI blocks, the DRPI framer inserting a notification in one or both of the first or second packet notifying a receiving DOCSIS MAC that the same request message has been sent in two different packets.

12. The upstream PHY according to claim 10 wherein the DRPI framer attaches a high Quality of Service to the first request packet.

13. The upstream PHY according to claim 10 wherein the DRPI framer combines the DMPI block containing the request message with other DMPI blocks in a same packet but sends the packet over the packet switched network as soon as the request message is encapsulated in the packet.

14. A method for operating a Physical Interface (PHY) for a cable plant, comprising:

demodulating data from an upstream path of a cable plant into blocks; and

formatting the blocks into packets and sending the packets over a packet switched network.

15. The method according to claim 14 including encapsulating multiple blocks together in the same packets and sending the packets over a tunnel in the packet switched network to a Data Over Cable Service Interface Specifications (DOCSIS) Media Access Control (MAC).

16. The method according to claim 15 including encapsulating the blocks received from different upstream channels into the same packets and sending the packets over the tunnel.

17. The method according to claim 16 including inserting a domain header in the blocks to identify an upstream domain and upstream local channel associated for the blocks.

18. The method according to claim 15 including inserting a timestamp snapshot block in some of the packets, or in a separate control message, that identifies a timestamp value, mini-slot number, and a mini-slot frame number to the DOCSIS MAC.

19. The method according to claim 14 including sending the blocks in packets over the packet switched network over different Quality of Service (QoS) tunnels.

20. The method according to claim 19 including selecting the QoS tunnels for sending the blocks according to an Service Identifiers (SIDs) associated with the Data Over Cable Services Interface Specification (DOCSIS) frames received over the cable plant.

21. The method according to claim 20 including receiving a map message over the packet switched network containing SID to QoS mappings and dynamically selecting the QoS tunnels for the blocks according to the SID to QoS mappings in the map message.

22. The method according to claim 14 including identifying request messages in the data demodulated from the cable plant and sending the blocks containing the request messages in request packets separate from other packets carrying the data blocks.

23. The method according to claim 22 including sending the same request message in a first request packet and in a second packet that encapsulates multiple other blocks and inserting a notification in one or both of the first or second packet notifying a receiving packet shelf that the same request message has been sent in two different packets.

24. The method according to claim 22 assigning a high Quality of Service value to the request packet.

25. The method according to claim 22 including encapsulating the blocks containing the request message with other blocks in a same packet and sending the packet over the packet switched network as soon as the block containing the request message is encapsulated in the packet.

26. A modular Cable Modem Termination System (CMTS), comprising:

a packet shelf operating a Data Over Cable Service Interface Specifications (DOCSIS) Media Access Control (MAC) framer; and

one or more upstream cable Physical Interface (PHY) shelves receiving DOCSIS data from a cable plant, formatting the DOCSIS data into packets, and sending the packets over a packet switched network to the packet shelf.

27. The modular CMTS according to claim 26 wherein the upstream PHY shelves include one or more Quadrature Amplitude Modulation (QAM) demodulators for demodulating the DOCSIS data received over the cable plant and the packet shelf does not contain any QAM demodulators.

28. The modular CMTS according to claim 26 including one or more downstream PHY shelves receiving DOCSIS data from the packet shelf over the packet switched network and modulating the DOCSIS data for sending on a downstream path of the cable plant.

29. The modular CMTS according to claim 28 wherein the packet shelf is configured to format Internet Protocol (IP) packets into Data Over Cable Service Interface Specifications (DOCSIS) frames and encapsulate multiple DOCSIS frames into a common payload in a tunneling packet for sending to the downstream or upstream PHY shelves.

30. The modular CMTS according to claim 29 wherein the upstream PHY shelves are configured to encapsulate multiple DOCSIS frames demodulated from the cable plant into a common payload in a tunneling packet and send the tunneling packet to the packet shelf