[tor-dev] Statistics on fraction of connections used uni-/bidirectionally

[Florian Tschorsch]

Hi Karsten,

we still believe that the statistics are useful. However we also agree
with Rob that since more and more relays report data the scatter plot
becomes confusing. I think some kind of aggregation would be helpful.

In one of our previous papers we assessed the performance impact of
simultaneous TCP connections in overlay networks [1]. There we found
that the occurring performance degradation is hard(er) to solve when
connections are used bidirectionally -- which is the motivation for
these statistics. From the current results I would presume that this is
the case in Tor most of the time.

In Future developments the statistics could become helpful.

Cheers,
Florian.

[1] D. Marks, F. Tschorsch, and B. Scheuermann, "Unleashing Tor,
BitTorrent Co.: How to relieve TCP deficiencies in overlays," in 35th
IEEE Conference on Local Computer Networks (LCN'10), 2010, pp. 320–323.



On 16/12/13 05:34, Rob Jansen wrote:
> Hey Karsten,
> 
> I think the statistics could be useful, though I don't currently utilize them. I think the current presentation is somewhat confusing. Perhaps we can try to brainstorm some alternative ways to present the data if the decision is that we should keep it around.
> 
> Best,
> Rob
>  
> On Dec 9, 2013, at 12:43 PM, Karsten Loesing wrote:
> 
>> Björn, Florian,
>>
>> a few years back (in 2010, to be precise) we added statistics to
>> little-t-tor reporting what fraction of connections is used
>> uni-/bidirectionally.  Quoting dir-spec.txt:
>>
>> "conn-bi-direct" YYYY-MM-DD HH:MM:SS (NSEC s) BELOW,READ,WRITE,BOTH NL
>>    [At most once]
>>
>>    Number of connections, split into 10-second intervals, that are
>>    used uni-directionally or bi-directionally as observed in the NSEC
>>    seconds (usually 86400 seconds) before YYYY-MM-DD HH:MM:SS.  Every
>>    10 seconds, we determine for every connection whether we read and
>>    wrote less than a threshold of 20 KiB (BELOW), read at least 10
>>    times more than we wrote (READ), wrote at least 10 times more than
>>    we read (WRITE), or read and wrote more than the threshold, but
>>    not 10 times more in either direction (BOTH).  After classifying a
>>    connection, read and write counters are reset for the next
>>    10-second interval.
>>
>> These statistics are disabled by default, but when they are enabled,
>> relays publish them in their extra-info descriptors.  And quite a few
>> relays do that.  Here's a (bad) visualization (that used to be slightly
>> less bad when fewer relays published these statistics):
>>
>> https://metrics.torproject.org/performance.html#connbidirect
>>
>> Here's the question: Is there still value in having these statistics?  I
>> recall that they were useful in 2010, but will that still be the case in
>> 2013?
>>
>> If the answer is "yes", never mind.
>>
>> If the answer is "no", I'd create a ticket and submit a patch to remove
>> code parts from little-t-tor, and I'd remove the not-really-useful graph
>> from the metrics website.
>>
>> Cc'ing Rob, Aaron, and Roger as the people who typically have an
>> interest in these kinds of statistics.  If other tor-dev@ people have an
>> opinion on this, please raise your voice!
>>
>> All the best,
>> Karsten
>