Thank you for support,
Are there any way to change this, such as 1 ack for 5 TCP segments sent from client (lwip)
What you referring to is a stretch ACK (where the ACK covers more than 1 full sized segment). This is not configurable and stretching more than the 2 maximum sized segments allowed by delayed ACKs algorithm is a violation of RFC 1122
(see 188.8.131.52 When to Send an ACK Segment).
If you’re trying to tune the TCP performance from the sender’s side, stretching ACKs (on the receiver) will not improve performance. Have you looked into tuning your send buffer (TCP_SND_BUF) given your bandwidth product delay?
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