[e2e] What if there were no well known numbers?

Joe Touch touch at ISI.EDU
Wed Aug 9 07:26:43 PDT 2006

Saikat Guha wrote:
> On Tue, 2006-08-08 at 10:26 -0700, Joe Touch wrote:
>> In a two-party system, "receiver open to input" always precedes "sender
>> issues message".
> When talking about the present Internet, does the "two-party system"
> refer to only the sending host and the receiving host?


> What about the
> corresponding middles -- the corporate firewall that most of us are
> behind, or the NAT that many home users are behind?

They masquerade as one of the two parties. When they succeed, they are
the receiver or sender, and the system ends up with multiple steps and
multiple directions of two-party communication.

> Agreed that the receiver must be "open to input" before the sender sends
> the message, but the receiver need not be open-to-input _for any and all
> possible senders_ -- it can be open-to-input for a trusted middle entity
> that can vet the sender's message and relay it to the receiver. (The
> middle entity here is open-to-input for all, and suitably protected.)

You have succeeded only in redefining one endpoint as the middlebox.
That middlebox still must be open to all senders or it won't be able to
figure out which ones to forward. It can't know who a message is from
until it reads it.

> Is it _necessary and required_ to be able to receive *from anyone and
> everyone* before someone can send to you?

When "someone" isn't locked in stone apriori, yes - by definition. The
point is that a closed system can be closed, but an open one cannot.


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