This directory hosts P4 implementation of TCP RTT measurement running on the Barefoot Tofino programmable switch.
We used register arrays to implement a hash table, with each entry saving a record for an outgoing TCP packet with its expected acknowledgment number and a timestamp. When the incoming ACK packet arrived, we fetch the entry and calculate the time difference. The entries in the table are lazily expired: they are consider expired when the timestamp is too old, but only overwritten upon hash collisions.
For more details, please refer to our paper: Measuring TCP Round-Trip Time in the Data Plane (To appear in SIGCOMM'20 SPIN workshop).
The current version of the implementation posted here uses a two-stage hash table.
The P4 program receives mirrored bi-directional traffic and automatically guesses if a packet is a data packet or ACK response, based on packet size. For data packet, no output will be given. For ACK packet, if it matched with an earlier record, we successfully produce a RTT sample, and it will be written in the payload section of the output report.
The output report is in IPv4+UDP format, with the original packet appended after the report.
To compile, run bf-p4c p4src/RTT.p4.
Please use bf-p4c version 9.1.0 or higher to compile the program.
If you find this implementation or the discussions in our paper useful, please consider citing:
@article{chen2020rtt,
title={Measuring TCP Round-Trip Time in the Data Plane},
author={Chen, Xiaoqi and Kim, Hyojoon and Aman, Javed M and Chang, Willie and Lee, Mack and Rexford, Jennifer},
journal={ACM SIGCOMM 2020 Workshop on Secure Programmable Network Infrastructure (SPIN 2020)},
year={2020},
publisher={ACM}
}
Copyright 2019 Xiaoqi Chen, Princeton University.
The project's source code are released here under the GNU Affero General Public License v3. In particular,
- You are entitled to redistribute the program or its modified version, however you must also make available the full source code and a copy of the license to the recipient. Any modified version or derivative work must also be licensed under the same licensing terms.
- You also must make available a copy of the modified program's source code available, under the same licensing terms, to all users interacting with the modified program remotely through a computer network.
(TL;DR: you should also open-source your derivative work's P4 source code under AGPLv3.)