p2psp team mailing list archive

[Cristóbal Medina López <cristobalmedinalopez@xxxxxxxxx>]

Hi,

Yes, I mean the first one (N = (n - 1) * (n - 2) / 2 ). I still don't get
why N is the number of possible permutations in the attacker's peer list.
For a simple example where the team size is 4 (n=4). Could you write down
the 3 possible permutations?

Thank you very much,
You're doing a great work.

Regards.

PS: We prefer work with pull requests on github ;)

El mar., 31 de marzo de 2015 a las 12:10, Ilshat Shakirov (<
im.shakirov@xxxxxxxxx>) escribió:

> Could you explain at length the previous formula? (anyway we think that it
>> also works perfectly)
>
> Sorry, I didn't understand your question. Do you mean
>
>> *N = (n - 1) * (n - 2) / 2*
>>
> or
>
>> http://p2psp.org/en/p2psp-protocol?cap=indexsu11.xht#x20-160004.11
>>
>  ?
>
> If you mean *N = (n - 1) * (n - 2) / 2* so it's a simply combination
> (n-1, 2).
> Btw, n is size of the team without splitter.
>
> 2015-03-31 14:33 GMT+05:00 Cristóbal Medina López <
> cristobalmedinalopez@xxxxxxxxx>:
>
>> Hi Ilshat,
>>
>> We think that the formula is fine. Only one question (see bellow):
>>
>> El lun., 30 de marzo de 2015 a las 14:58, Ilshat Shakirov (<
>> im.shakirov@xxxxxxxxx>) escribió:
>>
>>> Hello!,
>>>
>>> I got a new results from experiments with new parameters (2 trusted and
>>> one attacker), and it doesn't match with expected results from
>>> http://p2psp.org/en/p2psp-protocol?cap=indexsu11.xht#x20-160004.11
>>> (formula 11)
>>> But I deduced new formula (only for these params for now (T=2, A=1)):
>>>
>>> ​
>>> , where n is team size.
>>> ​Let me explain it:
>>> It just a formula for expected value for discrete random variable. So
>>> let describe our discrete variable:
>>> We have n peers, 2 trusted peers and one attacker. Size of each node's
>>> peer list is* n - 1*. Number of possible permutations for 2 trusted
>>> peers in attacker's peer list is *N = (n - 1) * (n - 2) / 2.*
>>>
>>
>> Could you explain at length the previous formula? (anyway we think that
>> it also works perfectly)
>>
>>
>>>
>>> The probability for getting only one poisoned chunk in the netowrk is *P(1)
>>> = (n - 2) / N*; (because we're getting only one poisoned chunk when
>>> trusted peer is the first in attacker's peer list, so there is n-2 variants
>>> of this situation).
>>> Next, *P(2) = (n - 3) / N*, P(x) =* (n - x - 1) / N*
>>> The max possible number of poisoned chunks in network with 2 trusted
>>> peer and one attacker is n - 2 (n - attacker - trusted);
>>> So, we must only to compute expected value as sum of *P(x)*x*.
>>>
>>> Formula can be easily generalized to different numbers of attackers and
>>> trusted peers, but first I want to know your opinion about it.
>>> What do you think? =)
>>> <https://en.wikipedia.org/wiki/Discrete_random_variable>
>>>
>>>
>> Please, check that the following python code implements your formula:
>>
>> x = 0.0
>> n = 10
>> for i in range(1,n-2):
>>     y=2.0*i*(n-i-1)/((n-1)*(n-2))
>>     print y, i
>>     x+=y
>> print x
>>
>> Thanks,
>> Regards.
>>
>>
>>
>>>
>>> 2015-03-29 1:43 GMT+05:00 Ilshat Shakirov <im.shakirov@xxxxxxxxx>:
>>>
>>>> Hello!,
>>>>
>>>> Sorry for the delay in the response.
>>>> I have just improved the Peersim impl of P2PSP:
>>>> - malicious peer connects to the team after some delay (magic constant
>>>> :))
>>>> - *CHUNK *message have 4 times more delay than other messages (hello,
>>>> goodbye, etc.)
>>>> - trusted and malicious peers are chosen randomly at the begin of
>>>> simulation
>>>>
>>>> I have performed new experiments with these improvements, it can be
>>>> accessed at the same doc - https://docs.google.com/spreadsheets/d/
>>>> 1pc6yb87xJy8gNkWSWvvCvjAjR6WBFdOzCbPvO-zEooU/edit#gid=0 - it has 2 new
>>>> tabs - raw2 and result2.
>>>> *raw2 *tab have 2 sets of data - the first one was performed without
>>>> different latencies, and the second one was performed with different
>>>> latencies.
>>>> Could you please evaluate results? What the next steps you want to see
>>>> with peersim impl of p2psp? =) I want to perform experiments with different
>>>> numbers of trusted peers and attackers, in order to confirm theroretical
>>>> analysis given in paper.
>>>>
>>>> Also, I want to store all the logs from each experiment in the same
>>>> place. I want to use dropbox for this (shared dir). What do you think? =)
>>>>
>>>> Currently, Im preparing scripts (bash and bat) to run simulation, so
>>>> there will be possible to perform experiments without setting up IDE.
>>>>
>>>> ps Could you please include me to sim project on github? Or we will
>>>> work with pull requests? =)
>>>>
>>>> Thanks in advance!
>>>>
>>>>
>>>> 2015-03-20 18:48 GMT+06:00 Vicente Gonzalez <
>>>> vicente.gonzalez.ruiz@xxxxxxxxx>:
>>>>
>>>>>
>>>>>
>>>>> 2015-03-20 9:59 GMT+01:00 Ilshat Shakirov <im.shakirov@xxxxxxxxx>:
>>>>>
>>>>> I don't know the procedure you are using to add peers to a team (how
>>>>>>> the peers contact the splitter, receives the list of peers of the splitter
>>>>>>> and send the [hello] message to the peers that are in the list), but I
>>>>>>> suppose that this procedure is similar to one used in a real team.
>>>>>>
>>>>>> Yes, the peers are added to team as it described in DBS of rules (new
>>>>>> peer sends HELLO to splitter, splitter sends list of peers, peer sends
>>>>>> HELLO to rest of team).
>>>>>>
>>>>>
>>>>> OK.
>>>>>
>>>>>
>>>>>> I have new hypothesis - how much time is spent for sending chunks?
>>>>>> and for sending simple messages, like HELLO/GOODBYE. In peersim
>>>>>> implementation there is no difference in times between these two types of
>>>>>> message. If it's able to send 2 or more simple messages while one chunk is
>>>>>> sending, then simulation results will match with expected results.
>>>>>>
>>>>>
>>>>> When a peer is introducing himself to the rest of the team only sends
>>>>> [hello]s. To interlace [hello]s and chunks, the splitter should send first
>>>>> to it a chunk, and this is done after receiving the list of peers from the
>>>>> splitter. This does not happen.
>>>>>
>>>>> In my opinion, a better result (not only for this experiment) could be
>>>>> obtained if you assign a latency to each message that depends on the
>>>>> message's length.
>>>>>
>>>>>
>>>>>> This means that if the peer 34 were the trusted peer, the attacker
>>>>>>> would send only one poisoned chunk before it is reported. For this reason,
>>>>>>> I think that the order of the peers in the lists should have some influence
>>>>>>> in the average number of poisoned chunks.
>>>>>>
>>>>>> There is such results already. I.e. cell D43 in google sheet
>>>>>> <https://docs.google.com/spreadsheets/d/1pc6yb87xJy8gNkWSWvvCvjAjR6WBFdOzCbPvO-zEooU/edit#gid=0>.
>>>>>>
>>>>>>
>>>>>
>>>>> I see :-)
>>>>>
>>>>>
>>>>>>
>>>>>> Also, I can remove the latency for simple messages (like hello and
>>>>>> goodbye), and (I suppose) results will match with expected results.
>>>>>>
>>>>>
>>>>> No. Please, consider first my idea (longer messages will take more
>>>>> time traveling that shorter ones).  And, randomize, if possible, the order
>>>>> (or time) in which peers join the team.
>>>>>
>>>>>
>>>>>>
>>>>>> An accurate P2PSP simulator is very interesting for researching the
>>>>>>> performance of the P2PSP. Any kind of advance/facility in this direction is
>>>>>>> really appreciated :-)
>>>>>>
>>>>>>
>>>>>
>>>>>> Ok, I will begin to write readme file about performing experiments =)
>>>>>>
>>>>>
>>>>> Again, thanks. Your work will be very helpful!!
>>>>>
>>>>> Best,
>>>>> Vi.
>>>>>
>>>>> --
>>>>> Vicente González Ruiz
>>>>> Depto de Informática
>>>>> Escuela Técnica Superior de Ingeniería
>>>>> Universidad de Almería
>>>>>
>>>>> Carretera Sacramento S/N
>>>>> 04120, La Cañada de San Urbano
>>>>> Almería, España
>>>>>
>>>>> e-mail: vruiz@xxxxxx
>>>>> http://www.ual.es/~vruiz
>>>>> tel: +34 950 015711
>>>>> fax: +34 950 015486
>>>>>
>>>>
>>>>
>>>
>

Attachment: CodeCogsEqn(2).gif
Description: GIF image