On Sat, Mar 28, 2009 at 1:23 AM, Tony Li <[email protected]> wrote: > locator A locator is a name that has topological sensitivity and > must change if the point of attachment changes.
Hi Tony, That soft-sells it a little. A locator specifies an entity's current attachment within the network topology. Types of locators include: * Local Locator - a set of names and/or numbers which specifies the point of attachment of a host, interface or service within the network topology of the local administrative zone. * Remote Locator - a set of names and/or numbers which specifies the point of attachment of an administrative zone within the network topology of the Internet. Since I've tied these definitions to "administrative zones," I'd better define that term too: * Administrative zone - a portion of the network in which a single entity holds some combination of access, authority and ownership which grants said entity full control over that portion of the network. That's a little fuzzy, so let me clarify it with some examples: 1. The computers on Tony's network have static IP addresses and connect to an ISP. Tony's network is a separate administrative zone from the ISP's because the ISP has neither access to change Tony's network settings nor ownership of Tony's equipment. 2. Brian's computer gets a dynamic IP address from his cable Internet provider. Brian's computer is within the ISP's administrative zone because the ISP has the access and authority to change Brian's IP address at its discretion. 3. Tony's wife has has her own computer. It get's a DHCP address from Tony's computer. Her computer is part of Tony's administrative zone. 4. Tony's wife has a static IP address and she forbids Tony from touching her computer. Her computer is a separate administrative zone from Tonys because Tony lacks access and authority to change her computer's IP address. 5. XYZ corp has an email team, a web team and a network team which operate independently under the CTO. XYZ corp is a single administrative zone because XYZ corp owns the whole thing and the CTO can compel changes to the network across all three teams at his discretion. 6. XYZ corp outsources it's spam filtering to ABC corp. ABC corp is a separate administrative zone from XYZ corp. Though XYZ's contract presumably allows it to have ABC change it's network to match XYZ's, no one at XYZ has the access, ownership or authority to directly change ABC's network. > identifier An identifier is the name of an endpoint. It has no > topological sensitivity. That is, the identifier will not > change, even if the endpoint changes its attachment within > the topology. Identifiers may have other properties, such > as the scope of their uniqueness (global or local) and the > probability of their uniqueness (absolute or statistical). Types of identifiers include: * Host identifier - a name or number expected to be attached to a specific computer for it's entire service life. Example: "minax" is my web server. * Globally unique host identifier - Same plus is unique within the scope of the Internet. Example: "minax.dirtside.com" is my web server. * Service identifier - a set of names and/or numbers which designate a service provided by a host or cluster of hosts. A service identifier is expected to remain constant for as long as the service is offered to the Internet and must be unique within the scope of the Internet. Example: www.whitehouse.net protocol http on IPv4 TCP port 80 * Transport identifier - a set of names and/or numbers which designate a particular transport connection or associated set of packets between an initiator and a service. A transport identifier is expected to remain constant for the duration of the connection and must be unique within the scope of the two communicating endpoints. Example: the combination of source and destination IP address plus source and destination port is a TCP transport identifier. * Session identifier - a set of names and/or numbers which associate a single communications session which occurs over multiple invocations of one or more transport protocols. A session identifier must be unique within the scope of the associated user and service. Example: a web login cookie. To clarify some of the above, I think I should also define two new terms: * Initiator - the computer which starts a communication session between itself and a service on the internet. Computers on the Internet don't just happen to bump into each other. One end or the other initiates that communication. Example: A PC with a web browser. * Service - some presumably useful communication provided by an Internet-connected computer upon receiving a request from an initiator. Example: The results of the various URLs under http://www.cnn.com/ The purpose of routing is, of course, to move packets from the initiator to a computer providing the service and then back to the initiator. > address An address is a name that is both a locator and an > identifier. An address is a number used by the networking protocols to implement one or more types of locators and identifiers. In deployed IPv4, the "IP address" is overloaded with the following semantics: 1. The remote locator 2. Part of the local locator (the MAC address also plays a role in the local locator) 3. The host identifier 4. Possibly part of the service identifier. Depends on how the application interacts with the DNS. For example, because of "DNS pinning" the IPv4 address is bound to an http or https service identifier for the duration of each web session, even if the session is anonymous (not identified). On the other hand, if you telnet to a hostname, then the IP address is not part of the service identifier because the service name is translated to a host identifier after which the service identifier plays no further role. 5. Part of the transport identifier (the other parts are the remote IP address and the local and report protocol ports) Finally, we should define (or at least clarify) two additional terms: * Route - The path from the current entity through the network topology to the destination locator. Alternately: the next hop in said path. * Map - The association between an identifier and the current set of locators at which the identifier is found. Regards, Bill Herrin -- William D. Herrin ................ [email protected] [email protected] 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004 _______________________________________________ rrg mailing list [email protected] http://www.irtf.org/mailman/listinfo/rrg
