Time To Live (TTL) in IP protocol)

Time to live, sometimes TTL, is a computer network term that describes how a data packet is transmitted between a computer and a network device before it can be discarded, the maximum number of devices that can be experienced.

 

In IPv4, TTL is a header of an eight-bit binary IP protocol. this value can be considered as the maximum number of packets that can be jumped in the internet system. TTL is set by the sender of the data packet. This value is reduced for each host or device that passes through the destination. if the TTL value is reduced to 0 before the packet arrives at the destination, the packet will be discarded as an ICMP error packet.

 

TTL prevents unlimited transmission of data packets that cannot reach the destination in the network, forming an "undead packet ".

 

Different protocols have different settings for the TTL initial value. We can see that the TTL value set by the ping command is 128.

 

 

 

Usage

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In the ping command, observe the TTL value to understand the logical distance from the machine that sent the ping command to the destination.

 

When analyzing the network package in a structure such as NLB (one machine has an nlb ip address and one local IP address), even if the IP address of the same NLB is sent, you can also check through TTL. If these two values are different, it means that even if you send data packets to the same IP address, they are also different hosts.

 

Source:

Time to live

Http://en.wikipedia.org/wiki/Time_to_live