Re: Help with timestamp

[Yuchung Cheng <ycheng () cs ucsd edu>]

On 07-14-2003, Marcos Paredes Farrera wrote:
> So if we have a tcpdump output with information  of every packet in the
> interface, the timestamping is different between the outgoing and incoming
> packets in that interface. I really need to confirm that because I've been
> some performance test with Instantaneous Throughput and I have noticed that
> the way how tcpdump make the timestamping is critical for this analysis and
> in the other hand if there is a high traffic the way how is time stamped
> become more notorious.
libpcap only provides at most millisecond information.  either u timestamp the
first bit or the last bit does not matter unless it will take 1 ms to send
the buffer. Moreover, if you want to know the _accurate_ time the network
card receives the packet or send to the wire, you are using the wrong tool,
libpcap can't do that because it depends on OS-specific bpf implementation.
At least Linux can't give you that information either. You probably want to
use something else.

Yu-chung
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