Optimum string size for InternetReadFile

Hi,

I am using the FTPOpenFile and InternetReadFile API calls for FTPing a file across a network. What would be the optimum size for the string I declare to be the buffer? Does it vary or is something like 4096 a good size?

I ask because it does seem that this generic FTP class I have is a bit slower at FTPing files than an actual FTP control. And if you are wondering why I am not using an FTP control, it is a long story but basically, I can not add any OCXs or DLLs to the existing system so I decided to use the API.

Thanks in advance.
Matt

Well, according to the network-types where I work, it seems the optimal size would correspond to the network packet size. They tell me that each network sends information in what is called a packet, the size of which varies with each network. Transmitting data in a chunk smaller (or greater) than the network packet size can cause the system to transmit more packet than necessary.

There example was as follows: Say you are transmitting 8K of data, and each packet size is 4K. If you send the data in 4K chunks, it takes 2 packets to get data across. If you transmit in 3K chunks, it takes 3 packets (3K, then 3K, then the final 2K). If you transmit in 5K chunks, then it still takes 3 packets (4K, then 1K, then the remaining 3K).

Personally, it's all greek to me. But that's what our "egg-sperts" tell me...find your network packet size, and use that as your optimum.

Thanks for the info. But I do have a question about that last 5K packet...why wouldn't it send a 5K packet, and then a 3K packet?

Matt

Because the packet cannot send more than 4K at a time. If your program tells it to send 5K, it sends 4K (max packet size), then 1K to finish the 5K request, then a 3K packet to finish the transmittal.

I think I follow what you are saying...if my packet size for the network is 4K, but I set my buffer to be 5K, then I have the 3 packets. If my network packet size was 5K though, then I would get one 5K packet and one 3K packet. Now that I think I have that understood, do you know how to determine the network packet size??

Thanks again.
Matt

The word from MY network people is to ask YOUR network people, since each is dependent on the network hardware and software you have...sorry...