From Single Lane to Highways: Analyzing the Adoption of Multipath TCP in the Internet

TL;DR

This paper provides a comprehensive analysis of MPTCP adoption in the Internet, revealing growth in MPTCP-enabled hosts, the impact of middleboxes, and the current low traffic share despite increased usage.

Contribution

It offers the first large-scale measurement of MPTCP deployment, examines middlebox effects, and analyzes real-world traffic to understand MPTCP's adoption and challenges.

Findings

Over 9,000 MPTCP-enabled IPv4 hosts detected

Middleboxes often mirror TCP options, affecting MPTCP perception

MPTCP traffic has increased 20-fold but remains a small share of total traffic

Abstract

Multipath TCP (MPTCP) extends traditional TCP to enable simultaneous use of multiple connection endpoints at the source and destination. MPTCP has been under active development since its standardization in 2013, and more recently in February 2020, MPTCP was upstreamed to the Linux kernel. In this paper, we provide the first broad analysis of MPTCPv0 in the Internet. We probe the entire IPv4 address space and an IPv6 hitlist to detect MPTCP-enabled systems operational on port 80 and 443. Our scans reveal a steady increase in MPTCP-capable IPs, reaching 9k+ on IPv4 and a few dozen on IPv6. We also discover a significant share of seemingly MPTCP-capable hosts, an artifact of middleboxes mirroring TCP options. We conduct targeted HTTP(S) measurements towards select hosts and find that middleboxes can aggressively impact the perceived quality of applications utilizing MPTCP. Finally, we analyze two complementary traffic traces from CAIDA and MAWI to shed light on the real-world usage of MPTCP. We find that while MPTCP usage has increased by a factor of 20 over the past few years, its traffic share is still quite low.