ports_range.md

Socket's IP and Port

One socket connection's address have the quadruple :

{SrcIP, SrcPort, DstIP, DstPort}

One socket original address combine with {SrcIP, SrcPort}:

• M avaliable SrcIPs
• N avaliable SrtPorts
• you can create (M * N) connections

Available ports range

You should know some details about the ports range in Linux/Unix. The Port (short int variable) value range is 1 ~ 65535, and the 1 ~ 1024 just for the root apps. You should check the available ports range with sysctl command:

sysctl -a | grep "ip_local_port_range"

You can set ports range:

sysctl -w net.ipv4.ip_local_port_range="1024 65535"
sysctl -p

Now you have 65535-1024 ≈ 64000 availabe ports.

Available IP & Ports

• You have N available IPs
• Now, the number of total available ports: N * 64000

Some details you should know

• The one TCP's tcp_snd_buffer & tcp_rcv_buffer is 32KB by default, maybe think 1 TCP consumes 100KB memory.
• You want to simulator 100k users, you should have the 100000*100/1000/1000 = 10G memory at least.
• Maybe you should set the tcp_snd_buffer & tcp_rcv_buffer for 16KB.
• Maybe you should use the hibernate option to reduce the memory usage for idle connections.