Imagine the national interstate system built with dirt roads and cobblestones. It would defeat the whole purpose. The sheer expansiveness of the road network isn't enough. It has to support vehicles traveling at high speed, must endure rain, sleet, and snow, and be easy on the vehicles that ride over it.xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

            Good thing we have concrete slabs and blacktop. As much as anything else, modern road-paving techniques are responsible for the success of highways, parkways, and interstates. As it relates to the Internet, the analogy to modern paving techniques is known as Internet Protocol version 6 (IPv6), which was developed by the Internet Engineering Task Force (IETF; www.ipv6.org).

            IPv6, the successor to the currently entrenched IPv4 (there won't be a version 5 in between) will offer numerous benefits. It will increase the overall speed of the Internet, enhance the security of data transmissions, give priority to real-time voice and video traffic, and add an exponentially greater number of addresses for machines on the network. IPv4 wasn't analogous to mere dirt and cobblestones, but it's appropriate to say that IPv6 will do more than simply fix a few potholes.

Internet Protocol: What Is It?

Internet Protocol (IP) is part of the protocol stack commonly known as TCP/IP. (The TCP stands for Transmission Control Protocol.) Without IP, the Internet wouldn't work.

            Generally speaking, a protocol is a set of guidelines to be used when one computer is speaking with another. A good analogy in the real world would be social protocols. Do you bow to say hello or shake hands? Depending upon the social situation, a different protocol may apply. If two people are from different cultures, they may need an interpreter—someone who not only speaks both of their languages but who can help each party in the conversation understand the body language and gestures of the other. In essence, the interpreter acts as a protocol translator, as well.

            The Internet consists of a dizzying array of computers connected together. There are Windows computers and Macs, computers running UNIX, Linux, Solaris, and more. With their own applications, they can function however they want, but in public, they must all speak a common tongue, one that must be understood by all the routers, hubs, and switches that comprise the network itself. (At the risk of mixing our metaphors, think of these as traffic signs. Everyone must understand the same set of symbols in order for traffic to move smoothly.)

            For the Internet, IP is used to link up all these different types of computers, the traffic cop that makes sure everything gets where it's supposed to.

            Currently, the Internet operates on IP version 4. Although it has served well so far, it has certain limitations that will make it difficult to continue using IPv4 for the long term. These limitations include a limited number of global IP addresses, poor security, and poor support for data prioritization.

The Limits of IP Addressing

Although it's just one piece of the puzzle, the address problem is the one you're likely to hear most about. Besides its importance, it's the problem that's easiest to understand. In short, we're running out of addresses.

            Every computer on the Internet needs to have an IP address. This address is composed of four sets of numbers from 0 to 255 separated by dots. Using this scheme, over four billion distinct addresses are available. When you access a service on the Internet, you are doing it using these numbers. The names you type in (www.yahoo.com, for example) are matched up with the numbers—the IP address—by the Domain Name System (or Service), also known as DNS, the system that translates alphanumeric URLs into IP addresses.

            Four billion addresses may seem like a lot, but it's not enough. The problem comes from three separate developments. First, the Internet is growing exponentially. While four billion may have originally seemed sufficient, it hasn't taken long for that to be perceived as a limitation.

            Second, IP addresses are not doled out on a piecemeal basis, they are allocated in blocks. In the past, an organization that needed only a few hundred IP addresses might have actually been allocated many thousands because that organization fitted into a certain class definition. This system led to many addresses that were assigned but never used. This problem has been remedied somewhat with alterations to the way IPv4 is administered.

            Many companies and ISPs have been able to save addresses by allocating them on a temporary basis. When the user logs on, the computer is assigned a temporary IP address, good only for the duration of the session. The next time the user logs on, the computer is assigned a different IP address. Since it is not likely that all users will be logged on simultaneously, this system, called dynamic IP addressing, can help an administrator provide access to a large number of users with a smaller pool of IP addresses. (Permanent IP addresses, which can be leased from an ISP, are called static IP addresses.)

            This allocation of dynamic IP addresses is most common with dialup ISPs. It is not dependent on a modem connection. For example, Verizon uses dynamic IP allocation for its residential DSL service. Corporations can likewise use it for dialup access to the corporate LAN.

            Dynamic IP addressing has advantages and disadvantages. The temporary nature of the connections can be considered a security layer of sorts; it makes it more difficult for a cracker to find your machine when you're online. The dynamic scheme encourages users to log off when not active online, thereby freeing up IP addresses for other users. Dynamic addressing makes it difficult (though not impossible) for users to host services on their own computer. If the IP address of a Web server is always changing, it can be very difficult for visitors to find a Web site hosted on it a second time. This helps prevent users from setting up unauthorized Internet hosts on their own computers.

            As far as security is concerned, IPv4 does not actually include any native security (that is, authentication or encryption) support. It relies on add-ons such as Secure Sockets Layer (SSL) to provide security.

            The same goes for prioritization. Although certain modifications can be made to IPv4 to help it prioritize traffic, its fundamental way of looking at the Internet is that "a packet is a packet is a packet." However, very different types of traffic have emerged on the Internet, each with its own specific set of needs, and data packets can no longer be treated equally. Some require prioritization.

            For example, it does not much matter if the packets comprising an e-mail message are delayed by traffic. In fact, the recipient might not get around to reading the message for hours. However, the packets supporting voice communications and instant messaging must arrive immediately or the real-time nature of the activity is compromised.

Benefits of IPv6:
Solving the Problems

The solution to the address problem is very straightforward: add more. IPv6 uses a new addressing scheme that offers many more addresses than IPv4. IPv4 offered 232 addresses, whereas IPv6 offers 2128 addresses. (In technical language, this is known as a 128-bit addressing scheme instead of a 32-bit addressing scheme.) The number of new possible addresses is staggering: 340,282,366,920,938,463,463,
374,607,431,768,211,456.

            If this seems like overkill to you, let us add something more to the equation. As the Internet reaches out to more and more computers around the globe, it will be necessary to simultaneously connect wireless laptops, handheld computers, and cell phones. If Voice over IP (VoIP) makes the inroads some people expect it will, it will be necessary to give additional IP addresses to IP phones, too. Furthermore, futuristic scenarios in which refrigerators and toasters are Net-connected may not be that far off; they'll also need IP addresses if they're going to communicate information to the network. (A common scenario suggested here is that the device can notify a repair facility when it needs servicing, or the refrigerator can automatically order more milk.)

            The current addressing scheme doesn't offer built-in support for mobile devices. The original designers thought that IP addresses would be allocated based on geography. After all, devices were connected by wires; no one thought they would move around that much.

            Today, laptop computers have made it commonplace for users to relocate their computer many times a week, if not many times per day. The computer goes from the dialup connection at your friend's house (dynamic IP) to a CDPD connection on the road (static IP) to the LAN at work (may be static or dynamic IP) and back to your home-office DSL connection (dynamic IP). The same goes for devices that are meant to be wireless all the time, such as a wireless Palm i705 handheld. Ideally, they would have the same IP address whether it's in the home range in New York or roaming in California. IPv6 includes support for such mobility.

            On the security front, IPv6 includes protocol-level support for both authentication and encryption of your data so that only its legitimate recipient can read it.

            The security built into IPv6 is known as IPsec. In addition to authentication and encryption, IPsec includes support for compression of traffic. Overall, IPsec effectively moves the handling of security away from individual applications and over to the computers and the networks.

            Imagine an office building with 30 different companies located inside. The IPv4 situation is analogous to companies in this building hiring their own security guards. Naturally, the guards will watch over the assets of only the company that hired them. A guard for one company might inadvertently allow a perpetrator inside another.

            Similarly, guards for one company might give a false sense of security to companies that, while inside the same facility, actually have no guards at all. IPv6 will provide a single security operation that covers the whole building and all the companies located inside it. It's more centralized and more secure.

            For prioritization, IPv6 includes protocol-level support for giving precedence to some packets and not to others. The demands of real-time traffic like VoIP and IP videoconferencing are quite different from those of streaming media and instant messaging. Streaming media has the bandwidth needs of VoIP and IP videoconferencing, but it can be buffered so that any transmission delays are not noticed. The real-time demands of instant messaging, on the other hand, mean it can't be buffered—but the text-only nature (i.e., very low bandwidth requirements) of the application nevertheless makes it viable over IPv4. VoIP and IP videoconferencing, however, require the highest priority, since any delay in transmission is apparent and detracts from the user's experience.

Installation Timeline

It's impossible to simply upgrade the Internet overnight the way you might upgrade a word processing package on an office network. The task of migrating from IPv4 to IPv6 is a daunting one. As a result, a number of initiatives have begun to help expedite this migration. One is called 6bone (www.6bone.net), which is an experimental backbone that tests IPv6 features, related protocols, and transition scenarios.

            Since IPv4 and IPv6 are not compatible, 6bone uses an interesting method to get it all to work. It is built as an overlay infrastructure on top of IPv4 using tunneling. Tunneling is a well-known technology used in many different contexts, including VPNs. This gives people around the world who are experimenting with 6bone the opportunity to set up machines to operate with IPv6. The goals of gaining experience with IPv6 through 6bone have been achieved, and there are some IPv6 networks in place all over the world.

            IPv6 migration will take many years. The pitfalls inherent in any migration and the benefits of the existing network will dissuade operators from moving quickly.

            In addition to IPv6 support in many versions of UNIX and other operating systems popular with network administrators, Windows XP includes support for the new protocol, as well.

The User Experience

An Internet built on IPv6 will in some ways be radically different from the current one, while in other ways it will be exactly the same. IPv6 is not going to be of tremendous help to users logging on via 56-Kbps modems. The modems themselves act as the weak link in the chain, potentially undermining most of the benefits that IPv6 will provide.

            Business users with robust connections, on the other hand, may find the Internet a much more hospitable place for VoIP and videoconferencing applications over the LAN and VPN. There are, of course, other benefits to IPv6 that are too complex to deal with here. They include support for multiple addresses on individual machines, as well as a different type of support for multicasting information—that is, simultaneously sending the same information to more than one recipient.

            The biggest question, however, is when? When will corporations roll out IPv6 on their networks? When will IPv6 be firmly established on the Internet? When will we start to see the direct benefits of the new Internet Protocol?

            Unfortunately, it's up to the entire industry—no one person or company is completely in charge. That's part of the Internet's beauty, but it makes it frustratingly difficult to predict.

            In the 1950s, the planners of the Eisenhower Interstate Highway System thought their new roads would dramatically improve traffic flow nationwide. Time has proven the theory that clutter expands to fill any available space, and in many parts of the country the interstates are clogged with cars moving at a snail's pace. The Internet designers of today may have the best of intentions, but the future is always a wily opponent to anticipate.