On Apr 2, 2009, Tony Li wrote:
locator A locator is a name that has topological sensitivity at a given layer and changes if the point of attachment at that layer changes. [...]identifier An identifier is the name of an object at a given layer; identifiers have no topological sensitivity, and do not have to change, even if the object changes its point(s) of attachment within the network topology. [...]
Hi Folks - Since "topological sensitivity" is key to distinguishing identifiers and locators in these definition, I believe we should be more specific with respect to what we mean by it. Much of the previous discussion was, IMHO, due to people having different understandings, as exemplified by the discussion on whether MAC addresses are identifiers or locators. In particular, "topological sensitivity" could be defined as either or both of the following: (1) as the property of being used in path selection. (2) as the property of encoding a path, strictly or loosely. If we use definition (1), the categorization of a name as identifier or locator depends on the use of the name. Overloading, e.g., can turn an identifier into a locator. On the other hand, if we use definition (2), the categorization of a name is independent of the use of the name. The earlier discussion between Tony and Dino on whether MAC addresses are identifiers or locators exemplifies the need for more specificity of what we mean by topologial sensitivity. Dino argued that a MAC address has topological sensitivity, and hence is a locator, because MAC addresses are used for path selection in switches. He is absolutely correct if we define topolocial sensitivity as in (1) and consider switched Ethernet. Tony argued that MAC addresses should be considered identifiers because they were originally not used for path selection. He is absolutely correct if we use definition (2), or if we use definition (1) and consider traditional, non-switched Ethernet. To avoid misunderstandings, I would hence suggest defining "topological sensitivity" -- either as a separate definition, or by making existing definitions more specific. Personally, I am in favor of definition (2) because it provides terminology that remains stable independent of usage and overloading. Obviously, other folks' mileage may vary. - Christian _______________________________________________ rrg mailing list [email protected] http://www.irtf.org/mailman/listinfo/rrg
