[chord] Chord and SIP

[Johnston, Alan]

Hi Emil,

Thanks for your reply.  I'm reading up on Twine - it looks interesting.
It seems CFS might also be useful to SIP as a lookup mechanism for
rendezvous.

SIP is an application layer protocol used to establish, modify, and
terminate media sessions over the Internet.  It has some built in
rendezvous capabilities that allow devices with dynamic IP addresses or
that change their point of attachment to the Internet to be reachable
using a SIP URI.

I'm interested in finding out about the Chord protocol "on the wire"
between peers over the Internet.  The documentation I've read so far
says that it uses sends RPCs over UDP using ephemeral ports.  Are there
any plans to use TLS as a transport?  Use of certificates for peer
authentication?

Transporting Chord over SIP would allow the use of some of SIP's
security and authentication mechanisms (such as TLS, S/MIME, etc.) but
I'm still not sure that it is a good justification.

Thanks for all your help.

Thanks,
Alan Johnston
sip:alan at sipstation.com

> -----Original Message-----
> From: Emil Sit [mailto:sit at MIT.EDU] 
> Sent: Tuesday, January 25, 2005 11:02 AM
> To: Johnston, Alan
> Cc: chord at amsterdam.lcs.mit.edu
> Subject: Re: [chord] Chord and SIP
> 
> 
> Alan,
> 
> On Tue, 25 January 2005 at 13:34 (+0000), Johnston, Alan wrote:
> > opinion with others looking into P2P.  I had assumed that SIP could 
> > utilize the Chord protocol for discovery (use a SIP URI as a search 
> > key and get back the IP address of the node that has the current 
> > address of that URI) then run as normally.  However, others are 
> > proposing that the Chord DHT algorithm be run *over* SIP.  That is, 
> > messages between peers used to establish, modify, and query peers 
> > would be carried over SIP messages.
> 
> I don't think any of us are very familiar with SIP and its 
> capabilities.
> 
> Chord provides a mechanism for providing rendezvous services 
> efficiently. If you needed, you could use Twine [1] for 
> service discovery.  Or you could build your own service to 
> layer on top of Chord so that you can provide the kinds of 
> performance and data availability that your application requires.
> 
> Whether Chord is run separately (for example, using our 
> implementation) or over SIP seems orthogonal to how it is 
> used by an application. I imagine there would be some loss of 
> efficiency in running the Chord protocols over SIP, depending 
> on how things are encoded.
> 
> [1] http://nms.lcs.mit.edu/projects/twine/
> 
> -- 
> Emil Sit / MIT CSAIL PDOS / http://pdos.lcs.mit.edu/chord/  
>