p2psp team mailing list archive

[Ilshat Shakirov <im.shakirov@xxxxxxxxx>]

ok, n = 4.
Formula is for exactly 2 trusted peer. It shows the number of permutations
of 2 trusted peers in node's peer list.
So the size of peer list is n - 1 = 3;
So the permutations will be
p, T, T
T, p, T
T, T, p


2015-03-31 16:46 GMT+05:00 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
>>>>>>
>>>>>
>>>>>
>>>>
>>