In einer eMail vom 03.07.2008 21:47:51 Westeuropäische Normalzeit schreibt [EMAIL PROTECTED]:
On Thu, Jul 3, 2008 at 3:49 AM, <[EMAIL PROTECTED]> wrote: > In einer eMail vom 02.07.2008 23:43:24 Westeuropäische Normalzeit schreibt > [EMAIL PROTECTED]: > >> Layer-3 addresses presently describe two characteristics of the >> endpoint: its network location and its identity. In a clean slate >> environment, it is not obvious to me that path-selection need know >> anything about the identity part; it need only know about one of the >> network locations. > > Right. I'd call it "learning from the postman".A letter isn't checked at the > ingress postal office whether it is deliverable or not (whether the receiver > has or has not moved to some other place). Instead it is forwarded to the > egress postal office without such checking. No attempt is made neither as to > inform, world-wide, any postal office when someone moves to another > place. Every year many new residential areas are going to be developed, but > no postman has ever complained about an (increasing) scalability problem. Heiner, I'm not sure that speaks to the question. Let me borrow your analogy: Line 1: William Herrin Line 2: 3005 Crane Drive Line 3: Falls Church, VA 22042 Line 4: United States Your point is that a post office in Dublin need not know about 3005 Crane Drive. It need only get the mail to the US. The first post office in the US need not know about Crane Drive either; it need only get the mail to the post office for 22042. The post office for 22042 does, however, need to know how to get to 3005 Crane Drive. Correct While that's undoubtedly true, all of lines 2 through 4 are used for path selection at various stages of the letter's trip. As Noel said, they are inherently inseparable from the path selection process.. I could not, for example, tell the post office in Dublin to deliver a letter to "3005 Crane Drive, United States" or "Falls Church VA, United States." It wouldn't reach me. Correct -MY- point was that Line 1 need not be there at all. It is an identifier which serves no role in the routing. If you get line 1 wrong or leave it off entirely your letter will still get to me. And this is precisely MY point, too:-) Ignore line 1 before the letter hasn't reach the egress post office. (maybe we should "invent" MPLS-2 :-). Line 1 is valuable for other purposes. I generally round-file letters addressed to "Current Resident" and I wouldn't want to accidentally open someone else's mail. However, there is no inherent reason that "William Herrin" must be a part of the address. It would be just as functional if I found it on a second envelope enclosed in the first. This is important, because as it turns out, letters address to: Line 1: William Herrin Line 2: 6857 Lafayette Park Drive Line 3: Annandale, VA 22003 Line 4: United States will ALSO get to me, albeit a little more slowly. The person with my identity is reachable at multiple locations each of which can be described in a manner close enough to a hierarchy to be efficient. I can imagine similar situations:Routing to the egress node based on lines 2-4 combined with line 1 ="to all residents there" Heiner
