Excerpts from William Herrin on Fri, Apr 03, 2009 02:46:55PM -0400:
> >> On Fri, Apr 3, 2009 at 11:21 AM, Scott Brim <[email protected]>
> >> wrote:
> >> > A locator names a point of attachment at a given layer. If an
> >> > endpoint changes its points of attachment at that layer,
> >> > associations between the endpoint and locators will change.
> Hi Scott,
>
> Your version sets the scope at the network layer boundary. The
> locator changes with my attachment at the layer boundary.
>
> But that's not right. The scope is arbitrary. Protocol and
> design-dependent.
>
> For example, I send a packet to 1.2.3.4 using a loose source route
> via 5.6.7.8. 5.6.7.8 is a locator. 5.6.7.8 serves as 1.2.3.4's point
> of attachment to the larger network.
>
> Once my packet gets to one of the routers which accepts packets to
> 5.6.7.8, the 5.6.7.8 locator loses scope and delivery proceeds based
> on the 1.2.3.4 address. But there's no layer change.
There are three things that may need naming. In order of increasing
generality:
1. A point of attachment, aka "PoA", for the ultimate destination
(at a given layer).
2. A "waypoint" which is on the path to the ultimate destination.
This may be considered by some to include #1.
3. Anything that is used to make a next_hop forwarding decision,
including other parts of packet headers, policy, whatever. This
may be considered by some to include #2.
We're stuck with "locator" as naming one of these. I was trying to
apply it to #1. I think that Bill is applying it to #2. Bill?
I would include "logical" PoAs such as anycast addresses in #2.
Because LISP is an encapsulation, I would include LISP RLOCs in #1,
not #2.
I don't know what to call #3 except "input to forwarding functions".
"Forwarding directive" came out of NewArch -- see
<http://www.isi.edu/newarch/DOCUMENTS/falk.FARADS.ppt>. It seems to
overlap our concepts of stackID and locator -- that's something to
think about.
But the big question is: which of these three do you think is the best
match for the way the rest of the I* is using "locator"?
Scott
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