Subject: [rrg] What is a locator ?/ was Re: Terminology straw poll

From: [email-masked]
Date: Fri, 11 Jun 2010 03:33:54 EDT

In einer eMail vom 10.06.2010 23:18:19 Westeuropäische Sommerzeit schreibt  
[email-masked]:

B) An  "Address" is an object that combines aspects of identity 
with  topological location.  IPv4 and IPv6 addresses are 
current  examples.

The postal letter address denotes a location (endpoint) to which the letter 
 is to be delivered based on this address. Who will open the letter is a  
different subject.
 
IPv4 and IPv6 addresses do not denote topological locations. We all know  
their historical and weird meanings and shouldn't ponder and wordsmith any  
further what "address" means. But the term Locator is not (yet) charged  with 
false/misleading understanding. Therefore:

C) A  "Locator" is a structured topology-dependent name that 
is not used  for node identification, and is not a path.  
Two related  meanings are current, depending on the class 
of things being  named:
1) The topology-dependent name of a node's  interface.
2) The topology-dependent name of a single  subnetwork
OR topology-dependent name of a group  of related 
subnetworks that share a single  aggregate.   An 
IP routing prefix is  a current example of this last.

A "Locator" is an attribute of a node which denotes its location.
 
Locator-based forwarding means forwarding packets to that node which is  
denoted by the 
destination/egress-locator (without evaluating its current IP address which 
 doesn't provide any topological location information). 
 
Locator values must be globally unique ( two different nodes must have two  
different locators).
Therefore I agree saying that a "locator" is a structured topology  de
pendent name, but I strongly disagree with saying "that is not used for  node 
identification". The endpoint of locator-based routing is still a node  
(similar to LISP's ETR), i.e. that router where Locator-based forwarding ends  and 
where  forwarding is continued classically.
 
Heiner