TTL

Question

Which of the following is the purpose of TTL field in DNS record?

1) If a record is lost during transmission , it will not circulate endlessly

2) Cached copies of the record will expires automatically

3) Redundant servers can trace the record back to it's creation time so that it can be validated

4) None of these

Answer 1

Should be 2 cached copies expire automatically after sotme time.this is done to get fresh data ue updated data and not cached data

Comments

but what is the problem with (1)

TTL also for a packet not circulate endleessly in the network. Is it not right?

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The TTL you're talking about is the TTL field present in the header of an IP datagram that defines the lifetime of the datagram in the network and which is decremented by one at every router that forwards it so as to prevent the datagram from going into a loop.

But the TTL in the question is in context of DNS records in the DNS server which is the lifetime of that record in that server. The record is deleted after TTL expires and any host's request for that domain that belonged to that record will be forwared to the authoritative server.