what's the meaning of TTL=64?

Solution 1:

TTL is Time To Live. Each hop decrements this field by one, and if the value reaches 0, the packet is dropped (usually this happens only in loop situations). This makes sure that data packets are not congesting a network if there is an IP routing loop present. The sender of the packet can set the TTL to any value, up to 255.

Solution 2:

Another possibility is you're seeing packets that never even reach the network outside of your computer, i.e.

PING localhost (127.0.0.1): 56 data bytes
64 bytes from 127.0.0.1: icmp_seq=0 ttl=64 time=0.048 ms
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.134 ms
64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0.139 ms