sure a you i um for yeah i why um i a we oh okay oh right and a uh you no i no a yeah i i and oh oh a you a and uh i oh well i oh oh a was i oh i i and two and i i and ah a i oh right a yeah uh oh where uh i a a yeah like that yeah one i for a but right i i right the moment i so oh a thank Q um and hands and use was that can be enforced and then any moment in time as both the server as a klein i'm going to model this in the following way i'm going to assume that i have a client which can quest a file of some form of service a server which are is an upload quest and and i'm going to assume that um i can model this as shown in here and i going to call is a gift giving game so i'm going to assume that the client has no action he just a request at some content and the set that has an action he can choose to serve and i'd thus that of is to the client or not to serve i'm going to assume that it the step but decided to set the clan to get the if you don't be and otherwise is this that but it and i to serve you to get the benefit of zero so clearly thus client has the benefit from being served by the server a set on the other hand in the cost of C so has a to do would be minus C and the um in the case of doesn't serve the cost will be zero so that a yeah why actually can action a one prime in that action there would be no incentive for the server to a to to to two to of and hands she would like to not serve and fear so what is important in this context is to try to bring some form of incentives to can is the users to serve each other and that is the goal of the proper design of let's call or than that design yeah are many ways to implement incentives to not lex the most studied within the out of engineering a a see propagation for example in P two P a was people assume of his study of past see propagation out that users how about in the current and vitamin we can see that that is not a good model because i may not have a his study of past see propagation of the particular person so i know a couple of you in the audience but moment ready to of you i don't know however i may be interested in getting some content from you and you might be interested in getting some content from somebody else but because of that fast see the of interest as as well as the that of being dynamic can use of starting and going i may not be able to have a he story of few are particular um a personal his story of reciprocation has in such situations we use social of um if C propagation and this also reciprocation skins so a from based on reputation and going to discuss that in know to do that so like a like less you will is you are going to implement this source show all if you provocation in a rigorous way as follows i'm going to assume that the of code design or would try to design a social norm and he's going to do that the by introducing the following elements for he's going to a to and you here were every agent a set of imputation labels L but number of L would be part of the design um then a peer cannot but the a G a web are given a particular reputation a label for the so that for the client with from seen that that he be can decide to starve not this uh that the protocol designer can design a social norm as follows she can sell like the set of reputation label she can determine i mean the social strategy what you would like to see it in that actions and merging so given the reputation of the sort of a and the reputation of the client be if i'd upon be a at the G to start models that or and if the agent was a P D and he's its reputation would be increased otherwise it would be decrease not to though that we deal with that of fish agent here so they may decide that it's not in the set of interest to form of this also um so i'm with don't you one more thing and went to assume that you can though maybe somebody comply with the social norm that maybe be a i the reporting errors or something has happened and i i'm a not product the update this reputation um let give an example of a source of i'm going to use in the talk um i'm having to san ninety as i'm going to have a and a to you are going to consider a for base or shows that they G which has a service to old age if the server has a class hold below age and the kind and has a reputation of by of age i'm going to assume always that that was that of so we've one condition or not that happened that would serve well yeah at hand they are not going to serve if the server has a reputation that is higher than that of the plot uh yeah you and this type of test whole base also of the G uh i i can have much more sophisticated social that i give a talk earlier today day which can that's a more sophisticated strategies but that makes a noise is more difficult so here and once the ring just a simple they G if they you was that's are going to follow the social strategy that put patient is going to increase an and went to assume a marketing a passionate stations if at any moment in find somebody body all bay it's going to be punished or the way the reputation um so they the use that have on the ability to decide that you want to solve all this type of um that's for based scheme so what if you doing kids optimization one so the not would be its own reputation label um reputation distribution of the community which i'm going to consider consider i'm going to call let's community configuration and also the a one and a quotation you may want how that all this information is known well this information could be no maybe there is a track you can come up with distributed versions of the but they are more complicated to to really formal lies and and come up with a eighty percent you oh or going to introduce a simple belief that users are going to hold so the use that's are going to assume that use as that are at a reputation zero um will higher than zero will follow the social more and you data reputation zero they do not provide them now in in order to determine whether a user should for this sort of thought that are not i need to determine not only the for kind a D V D of the user but also the long-term utility of are we use a given the community configuration and the specify social norm you can this actually i yet or not and keep data is that based on its performance in the long term in that you could would be just one shot did you need to go to T decided nobody will comply everybody will feel i so this is the um a problem of that values use that needs to solve so you can use to decide actually what be its best response at every period in time that maximise is it's a long time at that it is a can used to select this at signal which is to leading to the optimal long term that data no that's not from a system point of view what they would like to her so from a system point of view what they would like to have is he would like to have an a me go back to to this first setting with like to have a problem was that is source should the optimal so that we would like is that is not a code design of cell X that's also one that's so long as form on what time by the set of degradation label the reputation update scheme and the social strategy so is to send that this and i mean that such that the community are rice at the unique stochastic a stable like will there is i want to have something like that is if i don't have a unique a key the community make over to different and it different um types of configurations some of which may be efficient and in part because can that i would like that this unique a Q blue which i'm going to define in just one second is corporate so in this unique i Q label everybody will cooperate with the job what you talk i speak at least a be like in meets up quite complicated concept you why there no with already you word this would be kind of a very small somebody you of it but the idea here is is that um i have a strategy at you provide sick to get together with a comedy configuration you and this should be a stochastic a least table like you do if and only if when the at is update errors of excitation go to zero seek my is that that's this response of the use as against the overall population configuration and use new is time-invariant then is that points than i make in do by this particular signal and more than that that the community stay set me with a positive for about okay now that you look so this is a protocol design a problem i'm going to go back to it all the way the end for now let me concentrate on the use and you know what that for this again to be a stochastic a least like you leave room the best is one dynamic when need to ended cold first to decision able actually i for this that to sort is best response then i mean in to solve an in P yeah or finding me with and P the only thing i want to point out here is that we can see that in this and D that this state is the reputation of the user and the configuration of the components given that at additional of they was so best on this big for lies the of a to functions such that we can do that best response than i mean and we want to now look at a given that this and and what that the structural properties of these test is point by not and if is that we have which is very important is that the solution of the previous and be problem in this type of social norm governed all um community is that that's all they the G this is the optimal strategy selected what it means is actually that given the configuration of the client which which i mean that acting i'm going to have a a S for age a that as for than going to start the users and below and not therefore in order to determine the optimal point see we can only it's sufficient to determine the optimal test hold at at very um state yeah so the optimal set service test for that age yeah i can be formulate this and D and and if i do that based on this information is structured is desired i can come up with one more or out also also some form of structure which is that this that's for of remote point has the following property i will now a one two of some body a but have the source norm so the source norm that is me go to so that of people have a bad reputation five i would never go and set some by they shall for that's a first thing a not that is that the service is user provides one one only increases with a but you can think about that as some to think it'd the above a certain and that's about but as the reputation increase is you don't want to get in the start this you have in the system it becomes increasingly that you meant for you to to cheap no that's a look do you this type of structure properties how as the community of or because you would like to solve this from a proper code design a point of view so for thing is we can prove that the community of all following a markov of chain and that is that's these phones and i'm mean of the user in each state of the markov chain is a community configuration more of what we can show is that is not of jane P as the following properties that exist actually is T you are shown we have stability and a D and i in a some of that just to be able to define a early meeting configuration is if you are shown which i'm going to court it all make a hat to which the community will oh four to as this at all oh reputation errors then the words your so that has a configuration is stochastic least stable when it's probability in on that data star or or make a on had well my um bar should say is a larger than zero that's one i'm going to say that the configuration is to classical state you that what i can can in terms of gorgeous of the community the following first is that the limit in configuration distribution diffusion unique has the comedy converges to early make it's a top of the degradations in the long down so i just i want give a small set of configuration and this is very good because otherwise the design space will explode a second the and says that the set of stochastic least able configuration and the set of configuration be long it to this stochastic take a like people are the fame what does that really mean it means that we can and otherwise only the stochastic or stable like you be a we can use yeah like the stochastic least able it can either by analysing think the that of stochastic least stable configuration quotations okay so i can have a weight to conduct that i Z school version of the community what i want to do about when they want to do the design no for we can cut that i've barely meetings set all of this stochastic stable configuration and if we do that we have a first you're that which says well as anything in this network will converge i that two zero which means never cooperate operate everybody here writing or or always corpora and thing in the middle of from one to a minus one it's not going to get a present so i that everybody serves or nobody sir yeah the question becomes of the proper up design of or how what he design this type of interaction between users how should he determined the social strategy the G that it could station a a data would and the set of excitation to let use that as she as the competitive out other then the defect about for that what he is to do is to set that that's hold in the also at depending on the pot i'm it that's of the form and is to set it in such a weighting which depending on the cost of the benefit ratio as well as the discount factor of the on utility of the users this test is smaller than is about so the design becomes mainly focus on the H well as that really em you know what that is by as let's look at that in in state of result what actually in here is the following thing first i show that how the social well if there very is for a community as the cost increase as the cost of service okay that as increases i assume a i peak the network with the following parameters and what i want to show with the following first let's look at the blue lines what used the blue as is you optimal corporation this is something like a network utility maximization of do if i have self less use that's for be the end user they would always but it they were always feel a protocol and this is the best i can do that is in is goes down is because the cost increase so even we user corporate the cost increases as well hence what i want to show here is if you have a B D and is that everything goes fine one yeah hand if i need to determine the optimal um um talk which is sustainable meaning the optimal protocol which is oh bait by D set interested users is what i'm getting is this to be an bar see here so what is see that to be a design two things happen for is the cost becomes too high but one want to out that it that a will collapse you cannot apply to that interested users to in is high cost relative to the band i se a thing is you can see a as the cost increases you are starting to have gap then if you have this gap with as opposed to the optimal cooperation is because you have a trade between one hand optimality the that was incentive so in order to make this protocols protocol sustainable about you need to give a something in terms of form that we say well this optimization is that in ask and that it difficult what with i why would i go out that of this very difficult um a complicated optimization problem can and not just to was a particular fixed so shows that they using the particular that's for which makes sense if you do that to see that is that in red so what you would see is first the network community will collapse much faster because of the cost increasing and this stuff that you being chosen randomly well so you we see that as the cost increases is that gap to the optimal corporation a what we take away from here is to messages and this would be the last thing and not even going to show the crucial the that's the thing i like to to see is that you can not talk yet about a network to delete the optimization need to talk about sustainable that the direct optimization because the one type problems cannot piece really a really for forty used in this type of environment that is that a selfish and secondly if you want to go well a head and just to something a hall like a lot of the literature are currently in engineering is trying to do to cut people up social strategies and policies is for that but they up the that that ad hoc you performance with for a lot thank you that yeah no i i have every bite your bus has some information some knowledge let's say and we change with each other so i mean change it with you you make change it that on a make change changes if you can and so on no so what happens in here is because we don't have the few story of fife the see location what i had is i have a blob his study you're are study in the that so you don't have a for his study will need that i in the beauty of this work so in an that that it which i that i with the all the time this will not be that i model but an an use dynamic users coming go in the use of have been in different things i would not have the P and to necessarily have met to before and and be a the his study with you so it is a they she's a global level of reputation after it in that action you will have a different excitation of course you can come up with a reputation scheme or maybe be are part of a club of the signal processing a and we should behave in a signal processing cost but there we moved to the information that the club we only to behave was we don't meet these people very often that would be extended i