Basics of Time To Leave (TTL)

Basics of  Time to Live (TTL)

Many times we have seen this word ttl during any ping request to any device or router. The output comes as;

Reply from xx.xx.xx.xx: bytes=32 time=1ms TTL=255 

Reply from xx.xx.xx.xx: bytes=32 time=1ms TTL=255 

Reply from xx.xx.xx.xx: bytes=32 time=1ms TTL=255 

Reply from xx.xx.xx.xx: bytes=32 time=1ms TTL=255 

So this may be wonder that, what is this TTL actually. Here is the basic info on TTL,

Time-to-live (TTL) is a system generated value ranging from (1-255) in an Internet Protocol (IP) packet that, used during communication. When you use the ping request to any network device from a network tool or through command lines. It states a router either the packet is in the network for a long time and need to be discarded or communicated. Notifies the time for packet reachability. 

Each router receives the packet deducts at least 1 from the count; if the count remains greater than 0, the router forwards the packet, otherwise it discards it and sends an ICMP message back to the source host. After that a resend can be performed.

The ping and the traceroute functions both use the TTL value to attempt to reach a given host computer or to trace a route to that host. 

It prevents data packets circulating randomly in the network.  As a general it have 8 bit time to live (TTL) for IPV4 system and called Hop count for IPV6 system.

-DR