IPv4 Header Fields (TTL)
Total Len
Fragment ID
Source Address
Destination Address
Header
checksum
Frag Offset
TTL
protocol
TOS
ver
IHL
(options)
32 bits wide
TTL: “time to live”
each router must
decrement by 1
and discard if zero.
Also decremented
if router holds for
longer than 1 sec.
Prevents immortal
datagrams.
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