[e2e] About the primitives and their value

Joe Touch touch at ISI.EDU
Wed Aug 9 07:29:56 PDT 2006

Pekka Nikander wrote:
> Joe,
>> Receivers are inherently passive. To do otherwise makes them senders,
>> subject to sender rules. To plug their inputs renders them deaf, period.
> A communication network is as transparent as it is made to be.  It is
> not necessarily like "ether", open to anyone's noise.  Agreed, the
> original Internet used to be open for anyone to send anything to anyone,
> and that had great _value_ for the community.  However, that is only
> _one_ example of network design.
> If I take your "ether"-like fully transparent network, then I must agree
> with you.  In such a network a receiver is simply passive and must
> receive whatever any sender sends to it.
> However, put the first bridge or router there, and you have to make the
> choice of making the box fully transparent or _not_.  You can make the
> box a "firewall", allowing the "receiver" instruct the box of what
> information it wants to receive, by default, and what not.  Hence, once
> you give up your fully-open network abstraction, stating that "receivers
> are inherently passive" becomes a mere tautology.

If you deploy a firewall, how does it know who to let in? It has to read
the messages it receives. You have moved the triage problem to the
firewall, and redefined the receiver to be it.

> 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.

As others have pointed out, that's publish/subscribe. The pub/sub system
then becomes the thing that bootstraps communication.

Now show us a place to publish that is NOT open to all incoming pub/sub
messages. ;-)

Again, all this does is move the problem - and the opportunity for attack.


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