RE: [RAM] some draft proposed definitions

Joel,

With the term topology you bring up the issue. A location can actually be specified in at least two different ways. With a

1) topology-bound locator (better term welcome), which is 
- only valid together with a certain topology (examples are IP address, postal address, ..).
- is structured, looking into part of the address you are able to get nearer to the destination (country, city, street, street number, ...)
- you don't need to know the detailed global topology (e.g., internet)

2) coordinate-bounded locator, which is
- a location in a coordinate system (like the 2-dimensional geographic coordinates)
- requires the map/other positioning systems to find the place where you are and a system to find out what direction to go 
- some ad-hoc routing system propose geographic routing

Kind regards,

Marcus

---------------------------------------------------

Dr. Marcus Brunner
Network Laboratories

> -----Original Message-----
> From: Joel M. Halpern [mailto:jmh@joelhalpern.com] 
> Sent: Monday, June 11, 2007 3:40 PM
> To: ram@iab.org
> Subject: Re: [RAM] some draft proposed definitions
> 
> Looking at these definitions, and trying to think through 
> more cases, I don't think that this actually captures the 
> distinction, at least as I think of it.
> And I suspect that issue is why people react differently to 
> various proposals in which IDs are also used for forwarding.
> 
> Lets look at two closely related examples:
> Is an IEEE 48 bit "address" really an identifier, a locator, 
> or a hybrid.  As far as I can tell, it is strictly an 
> identifier.  It is assigned to a particular thing in a way 
> that has no regard to where that thing is in any topology.  
> However, being excessively clever engineers, we have then 
> built solutions which allow us to forward packets based on 
> that identiifers.  Sometimes even very large solutions.  
> (bridging in all its myriad forms.)  That usage does not 
> change the nature of the field.
> And before one argues that the MAC was layer 2, not layer 3, 
> remember that OSI routing did exactly the same thing with the 
> lower bytes of the NSAP within an area.  That potion was an 
> identifier.  It stayed the same when the system moved (even 
> if it moved between areas.)
> 
> Hence, I think the difference between an Identifier and a 
> Locator is in the semantics, not in whether it can be used to 
> deliver packets.  It doesn't seem to me that an identifier 
> suddenly becomes a locator if in some region we choose to 
> keep track of where the identifier can be found.  To take the 
> extreme case, some researchers have proposed systems that 
> would use topologically insensitive identifiers for routing 
> on systems of the scale of the 
> internet.   Without regard to the actually usability of  the specific 
> solutions, I think those things used for the end-points would 
> still be identifiers, even if the entire system were 
> forwarding packets based on them. The bit strings in that 
> case have no location semantics in any topology that I can find.
> 
> Yours,
> Joel M. Halpern
> 
> At 12:12 PM 6/10/2007, RJ Atkinson wrote:
> >Identifier:     An object that is used only for identification,
> >                 never for forwarding packets or determining 
> location.
> >
> >ID:             Abbreviation for Identifier.
> >
> >Locator:        An object that is used only for forwarding packets
> >                 or determining location, never for identification.
> 
> 
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