Do you have any specification of the communication speed of esp8266?

[RayPhon]

I tried to transmit jpeg image(less than 10KB) via esp8266 with web socket, but it has taken over 1 second!

So I tried to check the speed of web socket, and it was less than 5KB with 2048 Bytes packet size(less packet size, slower speed)

Is it the right result? and I couldn't find any spec about communication speed in the datasheet, am I miss something?

If you have any idea about this, show me please.