Hi, We're using Nist Net to do some network impairment testing, one of the guys here has written a tcl wrapper for the nist net functions to allow for more automated testing setups; we're principally interested interested in doing b/w limiting right now (I haven't put in any drd parameters yet but I wouldn't think that should matter). We have a hardware/firmware remote imaging application that sends our own (proprietary imaging) protocol wrapped in an ESP header and we don't do packet retransmissions; our b/w utilization is averages about 25Mb although it can be pretty bursty. When I set a b/w limit of 500 Mb (which isn't limiting at all) everything is fine and operates as expected. However, when I set the b/w to 100Mb (which should still only run into the occasional burst limit) , I end up getting duplicate packets fairly consistently. (We do want to handle duplicate packets but that's not what this test should be exercising.) Any ideas as to why this might be occurring, has this problem been reported before? A few more details about our setup that was tweaked by one of the other discussion messages that I noticed. The traffic endpoints (call them client and host) are on different subnets and the machine running nistnet is also the router between those two subnets - running linux kernel 2.6.11-prep . The traffic is mainly ESP traffic so there are no port numbers visible, our working implementation uses an SPI of 0 for now. I'm not sure how nistnet interacts with the routing changes controlled by the linux route utility but it occurred to me that it might be possible that the 'regular' routing is still happening, with nistnet grabbing the packets to be delayed and then (when they've been sufficiently delayed) blindly sending them off without realizing that they've now been duplicated. The duplicate packets I'm capturing in t/ethereal are identical (down to the timestamps) but differ in frame/capture numbers (and they're not always back to back). Anybody have experience with this? Is this a possible explanation or am I way off base? Is there anything else in this setup that raises a flag?
Thanks in advance for any suggestions ... N --- Nou Dadoun [EMAIL PROTECTED] 604-628-1215
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