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An Analysis of TCP Maximum Segment Sizes (Technical Report)




The Maximum Segment Size (MSS) is a basic yet critical property of any TCP
connection. Yet surprisingly, there have been no recent studies examining the
MSS values that are announced and utilised by TCP senders in any detail. This
paper analyses packet traces from several different locations and investigates
the advertised and observed MSS values for each captured TCP connection. In
particular, this study focuses on the range of MSS values that are announced by
TCP endpoints and the relationship between the advertised MSS value and the MSS
used by TCP senders. We find that although 1460 bytes remains the most commonly
announced MSS, it accounts for less than half of all MSS advertisements.
Instead, slightly smaller MSS values are increasing in popularity due to the
rise in PPPoE and VPN technologies. We also find that many
TCP sessions do not utilise either of the announced MSS values, possibly due to
application behaviour, and that a small but not insignificant number of TCP
senders transmit segments larger than permitted by the MSS announced to them.

This is a technical report - it has not been published in any peer-reviewed publications. Please cite the publisher as the University of Waikato, 2010.

Shane Alcock
Richard Nelson
mss_ict11.pdf412.37 KB