Measuring and Characterising Inbound Sessions in Residential DSL Traffic
It has been assumed that the need for successful NAT traversal discourages
residential DSL users from running services or applications that require them
to accept connections from remote hosts. However, there are now numerous
approaches for NAT traversal but there have been no studies measuring the
prevalence of DSL users accepting inbound sessions. This paper presents an
analysis of TCP and UDP flows initiated by remote clients to a group of
residential DSL users, using packet traces captured from a New Zealand ISP
between 2009 and 2011. Our analysis reveals that over half of all measured
users accepted at least one inbound TCP or UDP session. There was no dominant
port being used to accept sessions and port usage was spread over thousands of
different ports. Skype and BitTorrent were the most popular application
protocols observed and had increased in popularity over time. We also report
on the use of dual SYNs to perform TCP NAT traversal in our data.
Published at ATNAC 2011, Melbourne, Australia.