Cable modem termination system control of cable modem queue length
View Patent ↗Buffer bloat continues to cause latency problems for all kinds of network traffic, e.g., internet protocol traffic. Implementing network based control of packet upstream packet discards enables a scheduler of packets to manage congestion, instead of the network element with bloat. In embodiments, a cable modem termination system may schedule delivery of packets and, after receiving the scheduled packets, discarding packets. The cable modem termination system may determine when to discard a packet based on a detected backlog of data in a cable modem upstream flow queue. For example, a late discard of such packets may be based on information in a schedule request received from the network element.
1. A method for managing transmission control protocol (TCP) forward buffering in a cable modem, the method comprising:
scheduling time to receive a packet on an upstream channel from the cable modem;
receiving, at a cable modem termination system, at least one upstream packet from the cable modem during the scheduled time and at least one scheduling request from the cable modem; and
discarding based on information in the scheduling request, by the cable modem termination system, the at least one received upstream packet,
wherein the cable modem termination system detects a backlog of data in a cable modem upstream flow queue, and
wherein the cable modem termination system modifies or removes a Maximum Sustained Rate (MSR) Type-Length Value (TLV) parameter of a cable modem configuration file to enable the cable modem to make bandwidth requests in excess of a configured MSR TLV.
2. The method of claim 1 , wherein the method for controlling a cable modem queue length is performed solely by the CMTS.
3. A method for managing transmission control protocol (TCP) forward buffering in a cable modem, the method comprising:
scheduling time to receive a packet on an upstream channel from the cable modem;
receiving, at a cable modem termination system, at least one upstream packet from the cable modem during the scheduled time and at least one scheduling request from the cable modem; and
discarding based on information in the scheduling request, by the cable modem termination system, the at least one received upstream packet,
wherein the at least one received upstream packet is a received upstream TCP packet, and the information in the at least one scheduling request from the cable modem that the cable modem termination system uses as the basis to discard the received upstream TCP packet is a size of a cable modem upstream service flow queue reported from the cable modem or is information used by the cable modem termination system to estimate the size of the cable modem upstream service flow queue.
4. The method of claim 3 , wherein the cable modem termination system estimates the size of the upstream service flow queue by counting consecutive piggybacked bandwidth requests from the cable modem.
5. The method of claim 3 , wherein the cable modem termination system detects a backlog of data in a cable modem upstream flow queue.
6. The method of claim 5 , wherein the cable modem termination system detects the backlog of data in the cable modem upstream service flow from a backlog parameter of a DOCSIS Continuous Concatenation and Fragmentation bandwidth request received from the cable modem.
7. The method of claim 5 , wherein the cable modem termination system detects the backlog of TCP payload packets on the cable modem upstream flow queue by snooping upstream and downstream packets to recognize TCP streams.
8. The method of claim 5 , wherein detecting the backlog of data comprises identifying excessive buffering of transmission control protocol (TCP) payload packets in the cable modem upstream flow queue.
9. The method of claim 5 , wherein the cable modem termination system modifies or removes a Maximum Sustained Rate (MSR) Type-Length Value (TLV) parameter of a cable modem configuration file to enable the cable modem to make bandwidth requests in excess of a configured MSR TLV.
10. The method of claim 3 , wherein non-TCP traffic shares the same buffer as the TCP traffic.
11. A method for managing transmission control protocol (TCP) forward buffering in a cable modem, the method comprising:
scheduling time to receive a packet on an upstream channel from the cable modem;
receiving, at a cable modem termination system, at least one upstream TCP packet from the cable modem during the scheduled time and at least one scheduling request from the cable modem; and
discarding based on information in the scheduling request, by the cable modem termination system, the at least one received upstream TCP packet,
wherein after an initial discard of the at least one received upstream TCP packet, the cable modem termination system disables discarding for a cable modem upstream service flow for a time interval.
12. The method of claim 11 , wherein the time interval is at least one of fixed, configured, or dynamically calculated via an algorithm.
13. A method for managing transmission control protocol (TCP) forward buffering in a cable modem, the method comprising:
scheduling time to receive a packet on an upstream channel from the cable modem;
receiving, at a cable modem termination system, at least one upstream TCP packet from the cable modem during the scheduled time and at least one scheduling request from the cable modem;
selecting the at least one received upstream TCP packet for discarding, wherein an upstream TCP packet of only a particular format is selected for discarding; and
discarding based on information in the scheduling request, by the cable modem termination system, the at least one received upstream TCP packet.
14. The method of claim 13 , wherein the particular format for selecting the upstream packet for discarding is a particular format of a TCP payload packet.
15. A method for managing transmission control protocol (TCP) forward buffering in a cable modem, the method comprising:
scheduling time to receive a packet on an upstream channel from the cable modem;
receiving, at a cable modem termination system, at least one upstream packet from the cable modem during the scheduled time and at least one scheduling request from the cable modem; and
discarding based on information in the scheduling request, by the cable modem termination system, the at least one received upstream packet,
wherein each cable modem between TCP endpoints buffers at least a bandwidth delay product (BDP) of a desired TCP payload bandwidth multiplied by an uncongested round trip time (RTT).
16. A method of using a cable modem termination system as a cable modem proxy for managing transmission control protocol forward buffering in a cable modem, the method comprising:
identifying, at the cable modem termination system, a maximum sustained rate (MSR) Type-Length-Value (TLV) parameter configured for the cable modem;
removing or modifying the MSR TLV signaled to the cable modem in a cable modem configuration file read via TFTP to enable the cable modem to make bandwidth requests in excess of the configured Maximum Sustained Rate TLV; and
discarding at least on received upstream packet.
17. The method of claim 16 , further comprising recalculating a Message Integrity Code (MIC) before sending the MIC to the cable modem.
18. The method of claim 16 , wherein the cable modem termination system is a TFTP proxy for the cable modem.
19. The method of claim 16 , wherein removing the MSR TLV enables the cable modem to make unlimited MSR requests.
20. The method of claim 16 , wherein the cable modem termination system identifies a backlog based on a removed or modified MSR TLV and a cable modem request to schedule delivery of an upstream packet.
21. The method of claim 16 , wherein removing MSR TLVs signaled to the cable modem forces the cable modem to send a scheduling request to the cable modem termination system when it has an enqueued packet.
22. A method for discarding packets by a cable modem termination system, the method comprising:
monitoring a state regarding connections through a network element;
maintaining the state regarding the connections through the network element;
determining that excessive buffering occurs along the path between a sender and a receiver, and
discarding a packet of the connection,
wherein excessive buffering is determined by noting a difference between a last forward sequence number in a packet from the sender to the receiver on a transmission control protocol (TCP) connection, and a last acknowledgement of that sequence number in a packet from receiver to sender.
23. The method of claim 22 wherein the connections comply with the TCP.