Misunderstanding P2P

Mea Culpa. I have been guilty of some lazy thinking about P2P. And it is unforgivable because my own technology L3, relies greatly on P2P.

If I seem fixated on Joost, please forgive me; they just happen to be in the news a lot these days. Plus, I have used Joost (as well as Jaman) and so my examples often use them. However, Joost will not be alone in having problems with P2P; Vudu, Zattoo, UUSee (China) and a host of others will have similar issues. Jaman, on the other hand is at least technologically sounder (in my opinion), because they use download-and-play and P2P works great with that. But Jaman has some other weaknesses. By the way, I quite enjoyed the videos I have been watching on both Joost and Jaman.

But, I am getting ahead of myself. Lets back up.

A quick pop-quiz. Of the following count those you would classify as P2P:

Kazaa, Skype, Napster, BitTorrent, Joost, Hotmail, YouTube, AIM

If you said all, give yourself a pat on the back. Now, it may sound like semantics, but yes, Hotmail – most email for that matter – is a Peer-to-Peer application. When it is not, it is usually Spam. But I am trying to make a point here. There are P2P applications and there are P2P technologies. Email and to a lesser degree a site like YouTube, are P2P applications. BitTorrent is primarily a P2P technology. Of late, BitTorrent is positioning itself as a distributor of video so it is morphing towards being both – a P2P application as well as a P2P technology.

In my earlier post (7 reasons why Joost could fail), I had mentioned that the creators of Joost were P2P people and so they used it in Joost. In fact, Skype is a P2P application and Joost uses P2P technology – in a sense they are apples and oranges. Hence, I was guilty of intellectual laziness. However, I still stand by the point of the argument in that article – that people use what they know, and that sometimes blindsides them.

Now that we can tell a P2P application from a P2P technology, let us look at two types of P2P technologies that can be used for Internet Video.

P2P Downloads – this is what BitTorrent does. You exchange files with others through your Internet connection. You can download the files any time and watch the video whenever you want (except instantly) – aka download and play.

P2P Streaming – what can I say? This is dead before you can say “Peer”. I had not really given it a lot of thought when I wrote the aforementioned article, yet I could tell there was square-peg-round-hole problem there. Which is why I simply relied on someone else’s quote that they found significant overhead in P2P streaming. I was right, but guilty of not following the thought process through to its logical conclusion.

It is easy enough to do the math. A typical home broadband connection (Cable or DSL) is asymmetric. My connection at home is 1536x256kbps. Which means I can download six times faster than I can upload. For the sake of simplicity, assume that everyone has the same connectivity. This means that if I were to use my DSL connection to watch Joost it would take six peers to service my viewing! Joost freely admits in this presentation by Colm MacCarthaigh – Joosts Network Architect that

Joost servers “top-up” the DSL“bandwidth gap”

In other words Joost will never be a purely P2P application. They will always need servers providing a majority of the bandwidth. My guess is that they may be able to save about 10% of their bandwidth by using P2P (assuming there are peers).

Now this is why the Download and the Streaming models of P2P are very different. In P2P streaming this situation requires six peers as shown above, whereas in P2P downloading you can have as few as one peer – it will simply take six times as long as to get the file. But in the latter case, when you are done downloading you can watch a flawless playback. In the former, you have no guarantee of the quality.

Also, unlike other streaming video offerings, Joost cannot make effective use of CDNs (Content Delivery Networks) to improve quality or save bandwidth. From the same presentation:

We’re willing to peer, but is there much point? Only portions of the long-tail are
peerable.

And

Joost servers also handle the “longtail” (which is still pretty long)

I may be mistaken, but it sounds like they don’t want to peer into other ISPs and so a CDN (which does exactly that) would not be of use to them.

There is another problem with P2P streaming. Since it is streaming, and streaming is real time, other peers have to be watching the same content at the same time as you are. Okay, you can stagger it a little bit, and perhaps that will help the first problem mentioned above (that is, reduce the number of peers I need). Again, since I am familiar with Joost, I know they use a 2GB buffer on my hard disk. So, some of the stream (I would guess about an hour and a half based on the quality) can be saved locally and this could be used to help out all those peers who are watching the same content at the same time as you are. Wait! Stop the presses! That sounds suspiciously like prime time! I wonder if we can get a Walter Cronkite clone!

I hope I have convinced you that P2P works best with downloading. With streaming P2P works hardly at all and if some people are to believed, it is even counter-productive. In fact I am a big fan of Peer-to-Peer distribution, because used correctly it does address the Long Tail. That is what my next article will be about. Watch this space!

P.S. Do read about the Long Tail of Bollywood here.