Is there an optimal byte size for sending data over a network?

Question

I assume 100 bytes is too small and can slow down larger file transfers with all of the writes, but something like 1MB seems like it may be too much. Does anyone have any sugge

Answer 1

No, there is no universal optimal byte size.

TCP packets are subject to fragmentation, and while it would be nice to assume that everything from here to your destination is true ethernet with huge packet sizes, the reality is even if you can get the packet sizes of all the individual networks one of your packets takes, each packet you send out may take a different path through the internet.

It's not a problem you can "solve" and there's no universal ideal size.

Feed the data to the OS and TCP/IP stack as quickly as you can, and it'll dynamically adapt the packet size to the network connections (you should see the code they use for this optimization - it's really, really interesting. At least on the better stacks.)

If you control all the networks and stacks being used and inbetween your clients/servers, though, then you can do some hand tuning. But generally even then you'd have to have a really good grasp of the network and the data your sending before I'd suggest you approach it.

-Adam

Answer 2

If you can, just let the IP stack handle it; most OSes have a lot of optimization already built in. Vista, for example, will dynamically alter various parameters to maximize throughput; second-guessing the algorithm is unlikely to be beneficial.

This is especially true in higher-order languages, far from the actual wire, like C#; there are enough layers between you and actual TCP/IP packets that I would expect your code to have relatively little impact on throughput.

At worst, test various message sizes in various situations for yourself; few solutions are one-size-fits-all.

Answer 3

If you are using TCP/IP over Ethernet, the maximum packet size is about 1500 bytes. If you try to send more than that at once, the data will be split up into multiple packets before being sent out on the wire. If the data in your application is already packetized, then you might want to choose a packet size of just under 1500 so that when you send a full packet, the underlying stack doesn't have to break it up. For example, if every send you do is 1600 bytes, the TCP stack will have to send out two packets for each send, with the second packet being mostly empty. This is rather inefficient.

Having said that, I don't know much of a visible impact on performance this will have.