Re: [lwip-users] socket option TCP_NODELAY: not implemented???

[Jonathan Larmour]

Piero 74 wrote:
> 
> Do you think usefull disable it if want short delay in packet exchange
> between pc application and lwip board? band is not a problem (packet
> will have size <600 bytes)

That sounds like the sort of time it is useful yes.

> For the same reason (time performance), i'm thinking to use MSG_MORE
> flag in send function... do you think that i could have some strange
> problem?

I didn't think MSG_MORE would help time performance. Instead it is to
reduce ack traffic, especially for small writes. Obviously you have to
remember not to set it on the last write before you want to send something.

> And the last question:
> i used setting above for lwip, and i obtained a very good performance
> using a simple test. Do you think are they correct?
> 
> 
> #define TCP_MSS                         1460
> #define TCP_SND_BUF                     (TCP_MSS<<1)
> #define PBUF_POOL_BUFSIZE               LWIP_MEM_ALIGN_SIZE(128)
> #define PBUF_POOL_SIZE                  20
> 
> #define IP_OPTIONS_ALLOWED              1
> 
> #define IP_REASSEMBLY                   1
> #define IP_FRAG                         0

Sure, although whether it's the best performance depends on your
application, and of course, available memory.

> the last two setting, follows this my idea:
> i used a big MSS and a MTU ot 1536. If pc application send packet to my
> lwip board throght different routers, or internet connection, it could
> possible that path mtu will be smaller than my MTU, and IP packets will
> be fragmented, so, lwip needs to reassemble packets. packets transmitted
> from lwip board will be not fragmented and will have maximum size of 1536.
> What do you think?

Yep.

Jifl
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