Fibre Channel (SAN)

Posts: 47
Registered: ‎07-21-2009

Question about tcp window size for FCIP channels

Does anyone know if there is a way to find out the tcp window size used by the Brocade switch for FCIP tunnels using the Fx8-24 blade. Also, if that tcp window size is configureable or not. If it is, how can that be done .





Brocade Moderator
Posts: 185
Registered: ‎03-29-2011

Re: Question about tcp window size for FCIP channels

Hi Moeen,


are you looking for the actual window size (for TCP a connetion)?  For some background information concerning, see 


"The TCP header has a 16-bit field to report the receive window size to the sender. Therefore, the largest window that can be used is 216 = 64 KB. To circumvent this problem, “Window Scale” was defined to allow windows larger than 216. This option defines an implicit scale factor, used to multiply the window size value found in each TCP header in order to obtain the true window size. The scale factor
is negotiated during the TCP three-way handshake connection origination. The maximum possible value is 1 GB; however, for the sender and receiver to use such a large window, they also have to have this much buffer space. The cwnd on the Brocade 7840/7800/ FX8-24 is negotiated with a value of 9 to 20 MB per TCP session."

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