[Click] strange LinkUnqueue behaviour

[Peter De Cleyn]

Hi list,

I recently tried to implement some linkdelays within a Click
configuration and testing with the supplied script, I discovered some
strange behaviour. I checkout  the pre1.60 CVS release this morning to
verify.

When using a Queue->LinkUnqueue combination (as also suggested in the
documentation of LinkUnqueue) the packet forwarding stops regularly
for some seconds, flushes the queue contents afterwards at once and
resumes 'normal' operation, even when the offered packets rate does
not (by far) exceeds the defined linkrate. When only using a
LinkUnqueue element and no Queue, no excess shaping occurs.

To illustrate the problem and to reproduce it, I copied the testscript
I used, which sends 2 packets every second, with a 1000 bytes payload.
These packets get encapsulated with UDP/IP/Ethernet and are then sent
through a 512 kbps link. I expect only a 160 ms delay on every packet,
but no change in the interarrival time of the packets, as no shaping
should occur.  From the output of the script, the unexpected behaviour
will be clear, but I also attached a sequence graph resulting from the
tracefiles.

RatedSource(\<0800>, 2, 1000)
-> DynamicUDPIPEncap(1.0.0.1, 1234, 2.0.0.2, 1234, 1)
-> EtherEncap(0x0800, 1:1:1:1:1:1, 2:2:2:2:2:2)
-> ToDump("/tmp/pre")
-> IPPrint("From Source",TIMESTAMP true)

-> Queue()
-> LinkUnqueue(0.160,512 kbps)
-> IPPrint("Result",TIMESTAMP true)
-> ToDump("/tmp/res");



Replacing the LinkUnqueue element by -> BandwidthShaper(512 kbps)->
DelayUnqueue(0.160) in this script, results in the same behaviour.

I hope someone can point out how to solve this, I think it should not
remain in the 1.6 release.

kind regards

Peter De Cleyn
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