TTL : Java Glossary
©1996-2017 Roedy Green of Canadian Mind Products
This acronym has three meanings depending on the context:
- TTL (Transistor-Transistor Logic) : a robust family of IC
chips often used by home experiments. You can build primitive computers with and
and or gates
- TTL (Time To Live) : The number of
hops a packet can take on the Internet before it is euthanised. Without this,
errors in the Internet’s routing tables might send a packet hopping from
place to place forever, like Charlie in the subway. On evey hop, this count in the
packet header is decremented. A packet may typically take 7 to 30 hops to get to
its destination. You can use tracert mindprod.com to see
the hops the packets from you to my website get here. Each hop typically takes
about 30 milliseconds.
- TTL : How long a
DNS (Domain Name Service) cache entry should be kept before it is considered
stale. DNS is the lookup of a human name like mindprod.com to its computer numeric ip 188.8.131.52
, much like
an automated phone book would look up human names to get their phone numbers.
refresh themselves as needed from an upstream name server, cascading all the way
back to the authorative source, a computer owned by the owner of the domain or
his ISP (Internet Service Provider). Typically entries are cached for a day.
Dynamically assigned names might have a TTL
as low as 30 seconds.