Re: [P2PSIP] Peer protocol, DHT and running code

On 20-Jun-07, at 06:17 , Enrico Marocco wrote:

> Philip Matthews wrote:
>> Furthermore, using a transport protocol other that TCP or UDP  
>> means that
>> we have to do all the work to define
>> how SIP and other protocols get transported over this transport
>> protocol. I don't think we should underestimate
>> how much time that would take.

First, a small correction.
SCTP transport of SIP has already been defined:  RFC 4168.

Now on to the main discussion...

>
> Actually, I don't think we really need to tunnel SIP over the peer
> protocol.  In the PCAN draft
> (http://tools.ietf.org/id/draft-marocco-p2psip-xpp-pcan-00.txt) we
> address the issue of NAT traversal the following way:
>
> 1) clients that need to do so would keep sip-outbound connections with
>    peers.
> 2) peers that handle sip-outbound flows for some clients would store
>    routing records containing the full path to the client.
>
> Here's an example: imagine client C registers with peer B and
> establishes an outbound flow with it. C's routing record (inserted in
> the overlay by B) will contain two hops: B's contact and C's
> contact/gruu.  In case B is also suffering restricted connectivity,  
> this
> would mean that it too would have an outbound flow with another peer,
> say A. In this case (which is pretty unlikely, because if B is
> restricted it probably won't be able to receive REGISTER requests form
> C), C's routing record would contain three hops.
>
> Having said that, it's probably worth noting that we have not yet
> decided whether this approach is better compared to routing SIP  
> messages
> inside the overlay. Both are easily implementable with XPP and XPP- 
> PCAN
> so I guess we'd need to discuss this further before we really made up
> our minds.

I assume that your peers have public IP addresses.
If so,  this is "superpeer" approach that is discussed in the "NATs  
and Overlays"  draft
and in my NAT traversal presentation in Prague. Dean has also suggested
a similar approach.

We have had some discussions of the pros and cons of this approach vs  
the approach
that Eric and I have been advocating of routing messages through a  
partial mesh of connections.

The whole goal of draft-matthews-p2psip-nats-and-overlays-01 is to  
discuss these two approaches
and their pros and cons.  Feedback on that draft would be much  
appreciated, and would help
the  WG decide on a direction.

- Philip

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