Monday, September 29, 2008

Welcome to 39 peers!

I have launched an open-source project named "39 peers". From the web site:

"The 39 Peers project aims at implementing an open-source peer-to-peer Internet telephony software using the Session Initiation Protocol (P2P-SIP) in the Python programming language. The software is still incomplete -- especially the P2P part.

Peer-to-peer systems inherently have high scalability, fault tolerance and robustness against catastrophic failures because there is no central server and the network self-organizes itself. Internet telephony can be an application of peer-to-peer architecture where the participants locate and communicate with each other without relying on expensive or managed service providers. 39 peers project is an attempt to provide a open source and free-for-all peer-to-peer network targeted towards open standards based real-time communication.

The 39 peers project is developed for student developers and researchers to experiment with new ideas. It is written in Python scripting language. It supports open protocols such as IETF SIP and RTP. It is licensed under GNU/GPL license."

Thursday, June 05, 2008

memcached

Recently I got a chance to look at memcached a distributed in-memory cache.

There are two ways of scaling databases: (1) replicating with master-slave such that reads can be done from any slave database whereas writes needs to be done in master, and (2) distributing the data among segments such that accessing a data needs to access only a particular segment instead of the whole database. The first technique doesn't work well for scaling SIP-related contact data, because number of writes (login/logout, presence updates) are significant compared to number of reads (call routing, IM delivery). Distributing the data among segments has been done before, and my thesis also describes it in the context of SIP telephony.

The memcached system uses this second technique, hence has much better performance in certain cases. It is targeted towards web applications that generate dynamic web content by accessing the database at the back-end. One could run memcached on several servers, potentially co-located with the web servers in the server farm. The dynamic web service (e.g., written in PHP) is then modified to first look in the cache, and if not found then query the actual database (and update the cache as well). The cache provides a distribute hash-table (DHT) interface.

When the data is updated in the cache, it gets stored in the appropriate memcached instance based on some hash of the data key. When a query is done, that instance is queried for the data. Each cache instance can be configured with a limit of memory size, typically 1-3GB based on the available memory in the system. The distributed nature of the cache allows you to linearly scale the cache by just adding more instances of the cache on different machines.

At first glance this looks very promising for use in a P2P-SIP application. However, there are some serious limitation. Although memcached has built-in hashing mechanism for data storage, there is no automatic replication of data (hence no fail-over), the hashing needs to be implemented by the client itself (hence no recursive queries). In particular, memcached implements only one part of a full P2P data storage application such as OpenDHT. Because of this limitation, it cannot be used effectively for P2P-SIP client implementations without adding a lot of additional software. Nevertheless, memcached can potentially be used for P2P-SIP proxy server farm.

As a new project idea, it would be interesting to try to use memcached in openser SIP proxy server to readily build a P2P SIP server farm without much overhead! If you are project student willing to work on this, I will be happy to mentor you.

Wednesday, January 02, 2008

Business out of P2P-SIP

Here are some of my thoughts on how to make (or save) money with P2P-SIP.

There are two points to note: (1) an end-user doesn't know (or care) whether he communicates using client-server or peer-to-peer as long as he gets all the features (audio, video, text, conferencing, offline message, etc), security and speed. (2) unlike service infrastructure where the provider can make money out of user base (either charging per call or per minute as in Skype-out or via advertisements as in youtube?), there is no solid business model for P2P-SIP. Since it is open protocol, anyone can develop a client and break free from the provider. This of it as a email client technology -- how many vendors make money selling email clients?

There are some alternatives to this ideal view of P2P-SIP though. For example, one could control the user base -- keep the enrollment of the user controlled by the provider and allow communication among the clients of the same provider. This requires that the implementation be proprietary (at least the security and validation part), otherwise anyone may write an alternate implementation to bypass the validation. Thus the protocol doesn't remain open and is not P2P-SIP.

Alternatively, one could build a server-farm of SIP proxies using P2P technology so that the maintenance cost of the servers is reduced. However, this still requires dedicated set of servers (electricity, bandwidth, call centers, etc), hence the cost saving is very low. Even though you may be using P2P-SIP you won't save much money.

Thirdly, one could build and sell P2P-SIP software, e.g., for enterprises, that doesn't require expensive call managers or central servers. This works well, but has one problem. People have come to expect that communication, at least PC to PC, is free. Unless the client software provides tons of new features, which cannot be easily done by another vendor, selling such a client software is also difficult.

So, how do you make money? You don't. Instead, you can save money.

You can save money that you would otherwise be spend on maintaining the server infrastructure or you can enable new businesses that were earlier not possible because of close systems. Most of the current communication mechanisms have evolved in a tightly controlled environment, e.g., Mobile phones, Skype, Yahoo, etc. Instead what we need is an open mechanism similar to emails and web. An email client is not tied to a single server. A web client (browser) is not tied to a single server or web site. A communication client should not be tied to a single provider.

Consider an open system where anyone can call anyone else without paying to a provider beyond the Internet connection fees. This opens door for a whole new set of businesses. For example a small time vendor, consultant or topic expert can lend his service in real-time for a small fee without going through the hassle of setting up agreement with a provider. Existing systems such as social network sites or content distribution networks can have additional feature that allows a user to interact with his friends, or other users on the same site, or other users watching the same content, irrespective of the attachment of the user to the provider. There is a huge potential for innovations in the communication client space, similar to how web browsers have evolved.

So, who can do this? I don't think it will come from existing businesses who have large user base -- this includes the likes of Yahoo, MSN, AIM, or Skype. The reason is that they wouldn't want to open up their users to others. I also don't think it will come from existing businesses that are targeted for selling advertisements -- the likes of Youtube, Google, etc.

The question to ask is who benefits from ubiquitous P2P-SIP? Media companies and content owners should invest in making P2P-SIP ubiquitous so that their existing system is improved or becomes more appealing to end users. Such companies can probably sponsor open source projects for P2P-SIP. If there is a better and free communication infrastructure, all sorts of new innovations are possible. For example, people would like to talk with their friends while watching a TV series online, a cricket match online or a movie online.

In conclusion, I feel that big companies that can benefit from real-time communication, but don't have an existing solution to work with, should invest in open-source P2P-SIP technologies. If you are interested in talking about it, feel free to drop me an email.