US 9,178,789 B2Granted

System and method for transmission control protocol slow-start

AssigneeFuturewei Technologies, Inc.

InventorsYan Zhang, Nirwan Ansari, Mingquan Wu, Hong Heather Yu

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Abstract

An embodiment of a system and method that uses inline measurements to probe available bandwidth for a transmission control protocol, and adaptively sets a slow-start threshold according to the available bandwidth. The method includes initializing a congestion window “cwnd,” sending cwnd packets, estimating an available bandwidth for the cwnd packets. The congestion window cwnd is set to a higher number, and the higher number of further packets is sent if the available bandwidth is greater than a first threshold level. The available bandwidth is re-estimated for the higher number of the further packets, and a soft start threshold “ssthresh” is set to the re-estimated available bandwidth. A statistical measure is calculated for the re-estimated available bandwidth, and the congestion window cwnd is set equal to ssthresh if a ratio of the statistical measure to the re-estimated available bandwidth is less than a second threshold level.

Claims22

Dependent claims

A method of operating a an adaptive fast (AF) time slow-start phase of a transmission control protocol system, the method comprising:

initializing a congestion window (cwnd) in the AF time slow-start phase, the cwnd is equal to a number of packets less than a first threshold corresponding to a number of packets designated per round trip time (RTT);
sending a quantity of cwnd packets;
performing, for an initial RTT, a first estimation of available bandwidth for the quantity of cwnd packets, wherein the first estimation is based on evaluating per RTT a delay of acknowledgement from a receiver in response to sending the quantity of cwnd packets;
determining the available bandwidth for the cwnd packets is greater than a first threshold level;
in accordance with determining the available bandwidth is greater than the first threshold level, adjusting the cwnd to a higher number of packets;
sending a quantity of adjusted cwnd packets;
repeating per each next RTT during the AF time slow-start phase and until an elapsed time is greater than a number of RTTs, performing a second estimation of available bandwidth, wherein the second estimation per each next RTT is based on dividing the quantity of adjusted cwnd packets into a plurality of successive subranges of packets, sending the packets in each successive subrange assuming a higher bandwidth, and evaluating the available bandwidth by considering delay of acknowledgement for each one of the subranges;
setting a slow-start threshold (ssthresh) to the available bandwidth obtained by the second estimation;
and
adjusting the cwnd based on the ssthresh.

7 more elements

A system comprising:

a central processing unit configured to execute a software application program;
and
a network interface unit configured to
initialize a congestion window (cwnd) to communicate data produced by the software application program in packets in a slow-start phase to a remote system;
send a quantity of cwnd packets;
perform, for an initial round tri time RTT, a first estimation of available bandwidth for the quantity of cwnd packets, wherein the first estimation is based on evaluating per RTT a delay of acknowledgement from a receiver in response to sending the quantity of cwnd packets;
determine the available bandwidth for the cwnd packets is greater than a first threshold level;
in accordance with determining the available bandwidth is greater than a first threshold level, adjust the cwnd to a higher number of packets;
send a quantity of adjusted cwnd packets;
repeat per each next RTT during the AF time slow-start phase and until an elapsed time is greater than a number of RTTs, performing a second estimation of available bandwidth, wherein the second estimation per each next RTT is based on dividing the quantity of adjusted cwnd packets into a plurality of successive subranges of packets, sending the packets in each successive subrange assuming a higher bandwidth, and evaluating the available bandwidth by considering delay of acknowledgment for each one of the subranges;
set a slow-start threshold (ssthresh) to the available bandwidth obtained by the second estimation;
and
adjust the cwnd based on the ssthresh.

10 more elements

Dependencies are inferred from the claim text.

Facts

Application: 13/340,354Filed 29 Dec 2011 · us provisional application
Priority: 19 Aug 2011
Published: US 2013/0044598 A121 Feb 2013
Granted: 3 Nov 2015
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

H04L 43/0882
Network utilisation, e.g. volume of load or congestion level: utilisation of link capacity
H04L 47/27
Flow control; Congestion control: evaluation or update of window size, e.g. using information derived from acknowledged [ACK] packets
H04L 47/29
Flow control; Congestion control: using a combination of thresholds
H04L 43/16
Arrangements for monitoring or testing data switching networks: threshold monitoring