[BitTorrent] Re: Would it be possible to switch to UDP and STUN?

weezul_fenderson weasel at havoc.gtf.org
Sun Oct 3 16:35:01 EDT 2004

This message is a followup to my previous reply.

> UDP transfers are tricky to implement properly.

I now think I understand this comment a bit more fully, so I will ammend my previous 

Yes, it is obviously "technically trivial" to implement file transfers with UDP, via some form 
of error correction.  However, what I did not realize when I wrote that is the following:

When you have a high TCP load *and* a high UDP load, UDP packets appear to get dropped 
like crazy (under some network conditions).  Just try running BitTorrent and SIPphone 
simultaniously.  In addition, one would probably also need to more carefully manage the 
UDP load itself to ensure that it did not get to high.

So we might find ourselves in the "tricky" situation where some nodes needed to go all 
UDP and some all TCP, making those nodes unable to talk to one another.  In adddition, it 
is not 100% clear if managing the packet dropping problem in a pure UDP enviroment will 
require hosts to be more honest, and screw up tit-for-tat.

Of course, there might be some trivial way to fix many of these problem by making your 
UDP packets harder to drop or whatever.. and maybe the program SIPshare already does it.  
I would suggest that we wait and see how SIPshare develops.  It seems likely that someone 
will pick it up, do the obvious by adding STUN support, and try to mnake a go of it.  If UDP 
is unworkable for P2P, it will become obvious at that point.  It will also become obvious if 
it is impossible to run both BitTorrent and SIPshare simultaniously.. or even from the local 

> Even using UDP transfers and some kind of hole-punching trick for the 
> firewalls of two nodes, they can't necessarily talk directly to each other.

As far as I know, this is still only as true as it is for SIP products, i.e. most nodes can talk 


------------------------ Yahoo! Groups Sponsor --------------------~--> 
$9.95 domain names from Yahoo!. Register anything.

Yahoo! Groups Links

<*> To visit your group on the web, go to:

<*> To unsubscribe from this group, send an email to:
    BitTorrent-unsubscribe at yahoogroups.com

<*> Your use of Yahoo! Groups is subject to:

More information about the BitTorrent mailing list