[lwip-users] question about 4*MSS

[yueyue papa]

Hi All

I see the HTTP slow response email recently. 

This is my current  lwipopts.h
##############################
#define LWIP_TCP                1
#define TCP_TTL                 255

/* Controls if TCP should queue segments that arrive out of
   order. Define to 0 if your device is low on memory. */
#define TCP_QUEUE_OOSEQ         0    

/* TCP Maximum segment size. */
#define TCP_MSS                 1460    

/* TCP sender buffer space (bytes). */
#define TCP_SND_BUF             (TCP_MSS<<1)  

/* TCP sender buffer space (pbufs). This must be at least = 2 *
   TCP_SND_BUF/TCP_MSS for things to work. */
#define TCP_SND_QUEUELEN       (4 * TCP_SND_BUF/TCP_MSS)

/* TCP writable space (bytes). This must be less than or equal
   to TCP_SND_BUF. It is the amount of space which must be
   available in the tcp snd_buf for select to return writable */
#define TCP_SNDLOWAT           (TCP_SND_BUF/2)

/* TCP receive window. */
#define TCP_WND                 (TCP_MSS<<1) 

/* Maximum number of retransmissions of data segments. */
#define TCP_MAXRTX              8

/* Maximum number of retransmissions of SYN segments. */
#define TCP_SYNMAXRTX           8
######################################

Should I changed to


#define TCP_MSS                 1024
#define TCP_SND_BUF          (TCP_MSS<<2)  
#define TCP_WIN                   (TCP_MSS<<2)

i also meet the performance slow probelm.  The logical is very simple: TCP send and receive. (similar as HTTP. )

I always see the ACK and delay ACK discussed, is ther default suggest paramters.

Thanks