Ethereal-users: [Ethereal-users] libpcap and Gigabit ethernet

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From: Dinkar Bhat <dbhat@xxxxxxxxxxxxxxxxxx>
Date: Thu, 15 Apr 2004 17:41:19 -0400
Hello,

I have a question about libpcap library with Gigabit Ethernet. I have seen several discussions about Ethereal in the context of Gigabit ethernet which is also based on libcap, and hence I
am asking a couple of questions here:

a) I have read in a paper (by Luca Deri) that a basic packet capture loop:
pcap_open(); while(1) { captureAndDiscard(); } pcap_close() can handle Gigabit speed without any packet loss [assuming sufficiently fast processor]. There is no filter set.
So the question is the does packet loss (or rather
lack of it) depend on size of caplen? In other words, if I set caplen higher then does the probability
of packet loss increase?

2) If full-packet (caplen=1514) capture on a Gigabit interface results in loss, then does setting a filter (for instance only packets for one particular host) enable full-packet capture *without* any packet loss (at least with very very low loss)? In other words, does setting filter have any effect on packet loss with caplen set to 1514?

Thanks much
Dinkar.