[e2e] What is the meaning of "end-to end"?

[Fred Baker]

At 02:05 PM 5/12/2001, Mirela Perusia wrote:
>Could you be so kind as to tell me what the meaning of "end-to-end" is?

As the term was originally coined, it is from the place that a message 
originates to the place it terminates - from application to application. In 
HTTP, from browser to web server application, or back again. In mail, at 
least from email application to email application, and perhaps from user to 
user.

The interesting thing here is that you can look at this at any layer, and 
so you will find:

  - the MPLambdaS crowd calling their solutions end to end when
    what they mean is "entirely through an optical domain",
  - IPSEC implementations (between IP and TCP) going "end to end"
    meaning "from originating computer to terminating computer"
  - similarly, TCP sessions that go from TCP implementation to TCP
    implementation.

One person's "edge" is another person's "end", and in some sense each is 
right - the principal can be applied at any layer, and in such a context 
refers to that layer's relationship with those below it.