On the subject of infinite possibilities - given that there are an infinite number of of possible mistakes and only one correct solution, it is statistically impossible to do anything right. IP4 was definitely a mistake. Whatever replaces it will invariably also be a mistake. Besides, if everything was done correctly this forum would be very dull! -Michael C > ---------- > Van: David A Higginbotham[SMTP:[EMAIL PROTECTED]] > Verzonden: maandag 24 april 2000 13:22 > Aan: 'Anthony Atkielski'; [EMAIL PROTECTED] > Onderwerp: RE: IPv6: Past mistakes repeated? > > I agree! Why create a finite anything when an infinite possibility exists? > On another note, I have heard the argument that a unique identifier > already > exists in the form of a MAC address why not make further use of it? > > David H > > -----Original Message----- > From: Anthony Atkielski [mailto:[EMAIL PROTECTED]] > Sent: Monday, April 24, 2000 6:05 AM > To: [EMAIL PROTECTED] > Subject: IPv6: Past mistakes repeated? > > > What I find interesting throughout discussions that mention IPv6 as a > solution for a shortage of addresses in IPv4 is that people > see the problems with IPv4, but they don't realize that IPv6 will run into > the same difficulties. _Any_ addressing scheme that uses > addresses of fixed length will run out of addresses after a finite period > of > time, and that period may be orders of magnitude > shorter than anyone might at first believe. > > Consider IPv4. Thirty-two bits allows more than four billion individual > machines to be addressed. In theory, then, we should have > enough IPv4 addresses for everyone until four billion machines are > actually > online simultaneously. Despite this, however, we seem > to be running short of addresses already, even though only a fraction of > them are actually used. The reason for this is that the > address space is of finite size, and that we attempt to allocate that > finite > space in advance of actual use. > > It should be clear that IPv6 will have the same problem. The space will > be > allocated in advance. Over time, it will become obvious > that the original allocation scheme is ill-adapted to changing > requirements > (because we simply cannot foresee those requirements). > Much, _much_ sooner than anyone expects, IPv6 will start to run short of > addresses, for the same reason that IPv4 is running short. > It seems impossible now, but I suppose that running out of space in IPv4 > seemed impossible at one time, too. > > The allocation pattern is easy to foresee. Initially, enormous subsets of > the address space will be allocated carelessly and > generously, because "there are so many addresses that we'll never run out" > and because nobody will want to expend the effort to > achieve finer granularity in the face of such apparent plenty. This > mistake > will be repeated for each subset of the address space > allocated, by each organization charged with allocating the space. As a > result, in a surprisingly short time, the address space > will be exhausted. This _always_ happens with fixed address spaces. It > seems to be human nature, but information theory has a hand > in it, too. > > If you need further evidence, look at virtual memory address spaces. Even > if a computer's architecture allows for a trillion bits > of addressing space, it invariably becomes fragmented and exhausted in an > amazingly short time. The "nearly infinite space" allowed > by huge virtual addresses turns out to be very finite and very limiting > indeed. > > The only real solution to this is an open-ended addressing scheme--one to > which digits can be added as required. And it just so > happens that a near-perfect example of such a scheme is right in front of > us > all, in the form of the telephone system. Telephone > numbers have never had a fixed number of digits. The number has always > been > variable, and has simply expanded as needs have changed > and increased. At one time, a four-digit number was enough to reach > anyone. > Then seven-digit numbers became necessary. Then an > area code became necessary. And finally, a country code became necessary. > Perhaps a planet code will be necessary at some point in > the future. But the key feature of the telephone system is that nobody > ever > decided upon a fixed number of digits in the beginning, > and so there is no insurmountable obstacle to adding digits forever, if > necessary. Imagine what things would be like if someone had > decided in 1900 that seven digits would be enough for the whole world, and > then equipment around the world were designed only to > handle seven digits, with no room for expansion. What would happen when > it > came time to install the 10,000,000th telephone, or when > careless allocation exhausted the seven-digit space? > > Anyway, some keys to a successful addressing scheme, in my opinion, are as > follows (but the first is the only mandatory feature, I > think): > > 1. The number of digits used for addressing is not limited by the > addressing > protocol. > 2. Every machine in the network need only know in detail about other > points > in the network that have the same high-order digits in > their addresses. > 3. There is a distinction for every machine between "local" addresses > (those > that implicitly have the same high-order digits as the > address of the machine in question) and "remote" addresses (those that > have > different high-order digits). > > With such an address scheme, a single international body can allocate one > digit to each region of the world (the size of the regions > is irrelevant). Beneath that, other, more local bodies, one per initial > digit, can allocate more digits below that. There is no > need for anyone to allocate the entire address space in advance, so there > is > no need to worry about problems with the initial > allocation that will have to be fixed later. And since the actual number > of > digits in a machine address is unlimited, different > parts of the world, different companies, different organizations, etc., > can > expand addresses as needed. At any given time, the > maximum number of digits would be fixed at some very high number (128 > decimal digits, perhaps), but if this ever became too > limiting, it would be sufficient to simply up that number--no reallocation > or modification of the address space would be necessary. > > Imagine computers in the United States under such a scheme. All IPtNG > addresses (IPtNG=IP: the Next Generation--I have to call it > something, right?) for the U.S. would start with one. Since there are > lots > of computers in the U.S., you'd see addresses like: > > 14872883747534 for a machine in San Jose > 1487048377212 for a machine in Sacramento > 1412278987831 for a machine in Los Angeles > 1248819473 for a machine in Wyoming > 134875810869 for a machine in Boston > > ... and so on. Notice that the lengths vary based on the number of > machines > in a given region--if you need more address space, you > just add more digits. Wyoming has relatively few machines, so addresses > there are short. San Jose has a zillion machines, so > addresses there are long. > > Now picture the small country of Vulgaria, and its address space: > > 486174 for a machine in Vulgaria Minor (where most of the > population > lives) > 48631 for a machine in Vulgaria Major > > Vulgaria is a tiny country with only a few hundred machines. The 4 > designates the region of the world in which Vulgaria is found. > The 86 is allocated to all of Vulgaria. The remaining digits are > allocated > within Vulgaria itself. > > If you haven't already noticed, this pattern is essentially the one > already > in use for telephones. It works extremely well. > > Some might say that this ties the IP address to a geographical region. > Well, yes, it does. So what? If you want to use IP for > security (as in identifying individuals), you're making a mistake to begin > with. The address of a machine just locates it for > routing purposes; it does not authenticate its identity. If you want > identity information for machines, you give them a separate > "identity address" that follows them anywhere in the world, even if their > IPtNG address changes. And if you want identity > information for people (which is often the real goal), you give _them_ an > "identity address" that follows them anywhere in the > world. > > Here again, with respect to security, the telephone network sets the > pattern: if you move, your telephone number changes, but your > identity does not. Nobody calls a telephone number and simply assumes the > identity of the person who answers; normally an > authentication process is carried out ("Can I speak to Jane?"), because > everyone knows that a telephone number just gets you to a > specific telephone, but not to a specific person. Nobody lets you charge > purchases to a specific credit card just because you are > calling from a specific telephone--you still have to identify yourself. > > Anyway, I suppose it's too late to change anything in IPv6, but I'm > convinced that IPv6 will just show the same problems as IPv4, > and it will be more like 20-40 years down the road, and not the billions > of > years that some people seem to assume. I think that > history shows that the leading mistake of all engineers is to > underestimate > future capacity needs, and I see that happening with > IPv6, just as it did with IPv4 (and with Y2K, and with the IBM PC address > space, and so on, and so on). I just thought I'd add my > $0.02. Maybe I've overlooked something in IPv6, but I fear that I have > not. > > I'd be interested in hearing what others think of this potential problem. > (Or at least correct me if I've overlooked something in > IPv6 that will prevent the problems listed above from occurring.) > > -- Anthony >
