Posts Tagged ‘TCP’

TCP Auto-Tuning

November 17th, 2014 No comments

There is a field in each TCP segment called the “receive window”.  The receiver is essentially signalling the amount of data that it can accept, or is willing to accept.  This post describes the metrics and overhead.

The overhead is: window/2^tcp_adv_win_scale (tcp_adv_win_scale default is 2) So for linux default parameters for the recieve window (tcp_rmem):
87380 – (87380 / 2^2) = 65536. Read more…

Categories: linux Tags:

Long Fat Pipes: TCP WSCALE, TCP SACK and Time Stamp Options

October 14th, 2013 No comments

Long Fat Pipes
High-capacity packet satellite channels are LFN’s  (Delay 4 x 35‘800 km = 470ms RTT) and modern terrestrial long-haul fibre-optic paths will also fall into the LFN class. There are three fundamental performance problems with the current TCP  over LFNs:

• Window Size Limit (2^16 or max 65k bytes) – Remedy: TCP option “Window scale”
• Recovery from Segment Losses – Remedy: TCP option “selective acknowledgement”
• Round-Trip Measurement – Remedy: TCP option “Time stamp” Read more…