Re: [Mldonkey-users] OT: P2P via SMTP and Open Relays

[René Gallati]

Hello,

>  I got request whats the clamour about. Well, basically SMTP contains 
> something comparable to multicast, which means you send it once through 
> your line to an SMTP-relay and that relay may resend it 10, 100 or 1000 
> times to different recipients. So e.g. your 128kBit/s uploadline is busy 
> for 15 hours sending a 700MB ISO to your relay, but then the relay resends 
> it using its full bandwidth of 100, 622 or 1000MBit/s to clients using a 
> downloadline of 768kBit, everyone of the eg 1000 receivers gets the full 
> buzz within two hours and so circumventing the small uploadlines usually 
> found at private homes.

That's no multicast. It is multi-single cast. If you use your provider's 
mailserver, then that mailserver needs to send x-times your mails to all 
your recipients. This means that it needs to store your mail x-times on 
the local harddisk (some recipient mailsservers might be 
unavailable/slow) not to mention that usually mailboxes are size limited 
on any ISP and massive bounces (including additional overhead) inccurs. 
This further causes a *huge* ressource usage on the sending mailserver. 
Multiply by 2 for Spam check. Multiply by 2 for anti-virus check. Add 
this usage on *any* transit mailserver.

The increase in size by 33% for the base64 encoding has already been 
mentioned. No, there is nothing to argue about this, using email for 
peer 2 peer is *not* clever. It will cause many net-admins instantly 
wanting to hang you on the next tree. You *don't* want to do this on a 
global scale (for a p2p network)

What you can do is use this scheme between you and your friends where 
everyone has his own mailserver. But that way you have a mailserver that 
is always reachable, so why don't you just run 
mldonkey/edonkey/overnet/emule directly and avoid the 33% size 
increase-overhead that mail has ?

When you use your ISPs Mailserver, you shift the load that p2p incurs 
(many parallel I/O operations) from your node upwards to your ISP. And 
if several people do this, you kill your ISPs mailservers. Since email 
is the most important application of the Internet (business!) such a 
DDoS would backfire very very quickly. Again, you don't want an angry 
mob of admins knocking at your door.

>  Thats right, in ideal cases 1000 users get the complete download within 
> two hours without blocking the precious uploadline!

YOUR uploadline, but not that of your ISP nor his mailserver which has 
to multiply the datastream and incurrs all of the penalty. There's no 
free lunch.

>  That was a simplification, but the rather complex total concept could be 
> contained in a nice programm hidding the complexity from the users. Also 

Sure. Be advised however that the admins will see their servers die and 
they will react and kick off the users that caused this DDoS to them. No 
matter if they knew what they were doing or not. You can hide the 
mechanisms from the enduser but not from the people who will ultimately 
have their systems killed because of that.

> this isn't really P2P but a rather complex Server-Client-System, but who 
> cares, its mostly about distributing incredible amounts of data in no time 
> and at no costs.

No costs for YOU. Extreme costs for the operator of the mailservers. Do 
it and you'll lose your connectivity. Amazingly fast.

But hey, don't be down now. Such a system does exist ! Have a look at a 
technology that is almost as old as email: It's called usenet. Right, 
nntp, port 119. You upload once, the nntp servers peer with each other 
and propagate the data for you. Everyone can download it. But you upload 
only once. Cool eh? Well the downside is that since people started to 
use it for binary files, the volume of usenet has grown to currently 
about 700GBytes/day for a full feed, so there is (almost) no free NSP, 
you have to pay for a full binary usenet feed (but it's not really 
expensive) If you're interested in that, have a look at 
http://www.slyck.com/ng.php which explains how it works.

By the way: Most new sharereactor releases come from usenet by 
individuals who grab it off usenet and then put it on the *donkey-net.

Usenet is often way faster and you usually can download from your (paid) 
NSP (= News service provider) at your full line speed. For example, I 
pay $9.95 for a limit of 50GBytes/Month. I have access to *all* 
newsgroups that exists and the speed limit is 600KBytes/sec total and I 
can have up to 8 concurrent connections. Since my local broadband 
connectivity is 1024kbit, I can flat out my usage at the physical limit.

And I don't even need to upload if I don't want, though I sometimes 
fetch stuff from usenet and make it available on donkey-net.

But the bottom line is: Forget using email for massive p2p. You can try 
of course, but don't say afterwards that nobody warned you.

And yes, I administer several systems and some are mailservers. The 
first one I see using such a scheme looses his internet access on the 
very same day, no matter if he is on the sending or recieving side. That 
I promise.