[e2e] About the primitives and their value (was: What if there were no well known numbers?)

Henning Schulzrinne hgs at cs.columbia.edu
Wed Aug 9 06:07:35 PDT 2006

> I have seen network designs where "to receive" is an active  
> primitive:  the "senders" are "passively" offering data or services  
> in the network, and a "receiver" must actively ask for such a piece  
> of data or service in order to get it.  The point is that the  
> "receiver" can only send the request to the "network", not to the  
> "sender".  End-to-end data transfer will only take place if there  
> is both a willing sender and a willing receiver.  That is, unless  
> there is already someone willing to provide the piece of data or  
> service, the request to receive will go nowhere.  In other words,  
> such a network is _not_ designed to support the "send this datagram  
> to this recipient" primitive, but on two primitives like: "I am  
> willing to send/offer/distribute this <whatever>" and "I want to  
> receive/get/consume this <whatever>".
> [You can argue that in the previous paragraph I've got the roles  
> wrong, that the data or service providers are "receivers" willing  
> to receive requests and the clients are "senders" sending the  
> requests.  Sure, one can see the situation as such if one wills,  
> but it doesn't change the point:  the requests are only delivered  
> if there is someone actively willing to act upon them.]
> Sure, such a design would not be the Internet as we used to know it  
> nor as we know it today.

This seems remarkably similar to the model used by IP multicast and,  
at the application level, for mailing lists and presence (or any  
PUBLISH-SUBSCRIBE system for that matter), so this model is not all  
that new. (I probably need to qualify the IP multicast analogy, since  
DVMRP offers more of a first-packet-is-free model in flood-and-prune.)

If you want, you can consider the classical radio/TV model in the  
same spirit: a receiver has to explicitly tune to a station to  
receive the data and the FCC will make sure that only one station can  
use that frequency in any particular place. While the other  
frequencies reach the receiver, they have no negative impact, leaving  
issues of neighbor interference aside.


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