Some problems about packet size

[辛文飞]

1, inside the virtual machine (ns3.26, linuxmint18.1) When the size of the packet is set relatively large (more than 30,000) when the receiving end can still receive data, but when it is set more than 40000, the program will not work, according to the TCP transmission Mechanism, when the packet size exceeds the ipv4 layer maximum transmission unit, the packet will be fragmented, ns3 TCP send buffer has a total of over 1.31 million bytes, when a packet size is over more than 40,000, which should not be a problem

2, I started on a physical machine (Lubuntu17.1, ns3.27 / ns3.26),when the packet size  exceeds 2288 bytes, the build system gives me an error, suggesting that the size of the packet sent exceeds the maximum physical unit transmission unit, to be fair to say that these data Once the packet is too large in the transport layer began to fragment, how does the following physical layer  MTU error occurs?

3, when the packet size is less than 2288, it is divided into several different levels, in the range of 2100-2288, send 8 packets, received 5, at 1300-2100, send 8, received 6, at 1100-1300 when sending eight received seven, less than 1100 received eight, each packet sent interval has been set relatively large, can anyone explain this phenomenon