[p2p-hackers] A Question about user awareness in p2p

[Markus Kern]

On Tuesday, March 22, 2005, 8:46:09 PM Anoop Mavilaveettil <anoopsmv at gmail.com> wrote:

> Well it is not that simple.
> 1)First, it is not necessary or mandatory that "two people are always
> in each other's buddy list". A user might have added another user in
> his buddy list, but not the other way. In this case when the second
> guy comes online, the first guy would never get a notification.

It is not necessary for the list to be the buddy list of course. You
could keep a list at each user where you add people to be notified
automatically.

> 2)Second. One major issue, that I have to point out, is that  I'm not
> talking about peers, I am talking about users. A user can connect to
> the p2p net using any peers.

> Let me explain a common scenario
> a) User1 connects to the p2p net using peer1.
> b)User2 connects to the p2p net using peer2.
> c)User1 using common message mechanisms add user2(NOT PEER2) as his
> buddy. But the main thing to note, is that User2 doesn't even
> know/don't care to know about user1 adding him to buddy list and user2
> never adds user1 in his buddy lists.
> d)User2 disconnects from the p2p net. At this time, we can possibly
> have some notification mechanisms, which will notify user1 at peer1 about
> the disconnection of user2.
> e)User2 connects to the p2p net from peer3. ---> And here lies my
> issue. How would user1 at peer1 would know about the arrival of
> user2 at peer3( without structured or limited flooding?)
> NAT traversal and all other issues are lower level ones, and solutions
> for those issues are well documented and easily available on the web.

It is not entirely clear to me what distinguishes a user from a peer
in your case but I assume it is that the user cannot maintain a state
between connections to peers. In this case the best place to store the
list of people to be notified when the user comes online is probably
the DHT (where the buddy list would be anyway?).

If you want some sort of event notification you will naturally need a
list of event sinks. Where you store this list is largely irrelevant
but it makes sense to store it close to the event source.

-- 
Markus Kern