FTP server sending lower sized segments randomly

[pradeepss]

I am troubleshooting a wireshark log and have stumbled upon this FTP behavior, FTP server sends a single lower segment after multiple MSS sized segments.

I dont know why this is happening. This is consistent once it starts like 11*MSS sized segments followed by 1 small segment.

Receiver window is almost empty (64k) and acks all the transmissions.

Any clues?

 

[Noway2]

I apologize for the lack of real details, but I recall reading something about this subject recently, but I am having trouble recalling the specifics. From what I remember, there are multiple (two?) buffers and counters associated with determining how big of a packet will be sent. The purpose was to avoid network congestion and there are a couple of different "named" algorithms that govern the packet size behavior to this effect. The net result is that even if the receiver can accept a larger packet, there are several conditions under which smaller ones will be transmitted. You may want to try searching for TCP/IP congestion prevention or a similar set of keywords for more information.