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TOPIC: basic questions

basic questions 10 years 8 months ago #25202

* what is the use of TTL in a ip packet ?
shathriyan
Infrastructure Manager

Re: basic questions 10 years 8 months ago #25204

It defines the number of router hops the packet is allowed to make before it gets discarded. At each hop the counter gets lowered by one until the final router notes that the counts are all gone and discards the packet. The mecanism is there to prevent packets rattling aroung the routing infrastructure/internet forever when for some reason (such as a routing loop for example) they don't get delivered to a destination.

Re: basic questions 10 years 8 months ago #25221

My Server 2003 book also says that the TTL will decrease by 1 if the packet takes longer than 1 second to reach it's next router. Is this true? I've never heard of that but I suppose it would make sense.

Re: basic questions 10 years 8 months ago #25227

I've never heard of that, can any one else clarify?

Re: basic questions 10 years 8 months ago #25233

That doesn't sound right to me. How would router 2 know what time the packet left router 1? Unless I'm missing something about regular data packets having timestamps in them...

Re: basic questions 10 years 8 months ago #25237

TCP and UDP packets do not have timestamps in them. I know RTP does. Or at least that seems the reason VoIP uses RTP over UPD because it requires a timestamp.
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