Re: [Mldonkey-users] Investigation: No download for some, fulldownloads for the other

[MLdonkey]

>  I *do* understand that side of the story. However I always thought the
>  primary mechanism to obtain sources is by asking servers...? At least that's
>  the default behaviour of eDonkey, whose quirks I learnt and observed. If
>  your source re-emerges then it is going to publish on a server and
>  subsequently gets found again. If mldonkey does no UDP searches to all
>  server it knows, then I can see there is a problem. If I remember correctly,
>  the official eDonkey clients asks every 15 min or so a batch of servers to
>  obtain sources.

The problem is that UDP queries are not always replied by servers for
different reasons:
- the packet has been dropped
- the server has decided to drop the request because of the load
- the server never accepts UDP request

The last one seems to be more and more frequent, because servers
cannot accept 100000 clients sending each 20 queries for their files
every hour.

>  When I reemerge, my client connects to servers (even several at once, with
>  mldonkey...) and thus gets seen again. I see no problem therefor.
>  
>  I simply consider it rude networking behaviour, if a client consistently
>  tries to reach me even though every single time he gets a "he's gone"
>  message back. (As a side node, the afforementioned behaviour repeats itself
>  three times -> SYN  <--- SYN, RST, ---> SYN <---- SYN, RST,  ---> SYN <----
>  SYN, RST within one second. This is probably the TCP stack of the
>  originator. However the client comes back after 5 oder 10 minutes and
>  repeats) And of course it is not just one client, there are lots of clients
>  doing this ..... Would the timeout be shorter I'd look at it as "hammering"
>  but as for now, its just as I said: rude network behaviour.
>  
>  Most people probably don't know or see this, however I wouldn't mind if
>  mldonkey behaves nicely. If my system(s) say there's nothing there, then
>  there IS nothing there. I don't mind if mldonkey later gets my IP due to
>  source exchange and tries again ONE time. However repeated tries to reach
>  something that always tells you "not here" is just.... wrong.
>  
>  Also remember that all german T-DSL users lose their IP after 24 hours. So
>  the chances are high that you continue to pester entirely other people's
>  machines. (My IP is fixed, therefor I see them over days trying to reach me)

Yes, but trying to connect you every 6 hours is not big. If 20 000
clients do that(you have popular files), you have 1 connection per
second. Not a big deal, and this is probably by far the worst case.

>  >  So I don't think that remembering very old sources is such a bad
>  > thing, unless your file has already many good sources, or you are
>  
>  No remembering old sources is not bad at all. Simply not losing them when
>  they cease to exist is... maybe you want to add a counter and only lose a
>  source once you hit X tries which responded in a port closed message.
>  (Whereas X shouldn't be greater than 3 though... that's still enough tries
>  for port unreachables...) Add to that an exponential timeout and it will
>  behave much nicer (ie source gets asked after one hour, gets port
>  unreachable back -> requeued for asking in 2 hours. Then if again port
>  unreachable -> requeue for asking in 4 more hours -> if still port
>  unreachable, delete the source)
>  
>  > running out of memory.  The only thing that need to be to done is to
>  > delay such reconnection attempts, such as a few hours instead of the
>  > 10 minutes of good sources.
>  
>  Maybe. However if you always get a port unreachable back, you should stop
>  considering the source valid.
>  
>  Haha, to proof my point: I just sniffed on my connection. Within 5 minutes,
>  I've recieved 21 SYN packets on my mldonkey port. From 5 different source
>  IPs... I've last run mldonkey on that port 7 days ago.... (!!!)
>  
>  Go figure... I cannot say what type of clients that were, you don't see that
>  in their SYN. However, as I mentioned, I don't mind using a client of which
>  I know it behaves nicely with regard to networking behaviour.

Let's say we can try to connect every 6 hours, that was the old behavior
in fact. It should not hurt that much, and drop the source after 3 days...

- MLDonkey