January 03, 2005

Difference Between VoIP and File Sharing

Om mentions about a P2P application called Hamachi. It allows two computers to share files and other resources between the two computers. It can be summarized (may be oversimplified) to be consisting of the following three aspects:

  1. Hamachi clients register with Hamachi server, which facilitates in locating other Hamachi clients. Clients are identified by “Hamchi network address”.
  2. The server “enables peer-to-peer communications between two computers [in] bidirectional NAT traversal.”
  3. Hamachi clients provide application specific functions like user interface and encryption of data.

I am sure you have noticed by now, that the services provided by Hamachi is isomorphic to those provided by a VoIP system: Hamachi server is analogous to SIP proxy server; Hamachi network address is equivalent to SIP address; NAT traversal scheme is the same. Hamachi specific application routine is equivalent to a SIP client that follows SIP signaling protocol and voice codec and also provides a user interface. Cynically speaking then, Applied Networking can easily reposition itself to be a P2P VoIP provider and raise funding instantly.

Seriously though, the industry is developing multitude of software to do two basic functions that are fundamental to IP Communications – client identification and location; NAT/Firewall traversal. Not only it is sufficient to have a single way; but these multiple implementations are undesirable because they all require identity issued from separate entities. In other words, we need a Skype address, a FWD address, a Hamachi address etc. Since this is the only source of revenue, these entities will extract fee from us (protestations notwithstanding). So we need to devise an universal way to do the first two functions and an addressing scheme that is not beholden to one commercial entity. Then all these applications can be used for the specific purpose for which it is designed.

Posted by aswath at January 3, 2005 02:50 PM
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JXTA is a platform for p2p which has abstractions -- peers, rendevous peers, etc. It's easy to see how many p2p protocols, including SIP, fit the JXTA abstractions. See http://www.dsauder.com/weblog/archives/000241.html

Also interesting along these lines is Clay Shirky's chapter in the O'Reilly book _Peer to Peer_, in which he discusses how all p2p applications must solve the same basic problems: naming and identity, firewalls and NATs, etc. I found his comments interesting that naming in p2p is distinct from DNS, and that the winners in p2p will be those who can control the namespace.

Posted by: Doug Sauder at January 4, 2005 10:23 AM

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