計算機網絡專業譯文,來自CCNA,主要内容是介紹IPv6。
适合計算機專業網絡方向的大學畢業生。
專業譯文
原文：《Cisco Certified Network Associate Study Guide.Sixth Edition》的第740-747頁
(作者：Todd Lammle 出版社：Wiley Publishing, Inc.)
英語原文：
I hope you're ready to learn about the nuts and bolts of Internet Protocol version 6 (IPv6), because you're going to get the rub on it in this chapter!
You should have a solid hold on IPv4 by now, but if you think you could use a refresher, just page back to Chapter 3, "Subnetting, Variable Length Subnet Masks (VLSMs), and Troubleshooting TCP/IP." And if you're not crystal clear on the address problems inherent to IPv4, you really should review Chapter 11, "Network Address Translation (NAT)”
People refer to IPv6 as "the next-generation Internet protocol," and it was originally created as the answer to IPv4's inevitable, looming address-exhaustion crisis. Though you've probably heard a thing or two about IPv6 already, it has been improved even further in the quest to bring us the flexibility, efficiency, capability, and optimized functionality that can truly meet our ever increasing needs. The capacity of its predecessor, IPv4, pales in comparison-and that's the reason it will eventually fade into history completely.
The IPv6 header and address structure has been completely overhauled, and many of the features that were basically just afterthoughts and addendums in IPv4 are now included as full-blown standards in IPv6. It's seriously well equipped, poised, and ready to manage the mind-blowing demands of the Internet to come.
I promise-really-to make this chapter pretty painless. In fact, you might even find your self actually enjoying it-I definitely did! Because IPv6 is so complex yet elegant, innovative and chock-full of features, it fascinates me like some weird combination of a brand-new Lamborghini and a riveting futuristic novel. Hopefully you'll experience this chapter as the cool ride that I did writing it!
Why Do We Need IPv6?
Well, the short answer is, because we need to communicate, and our current system isn't really cutting it anymore-kind of like how the Pony Express can't compete with airmail. Just look at how much time and effort we've invested in coming up with slick new ways to conserve bandwidth and IP addresses. We've even come u p with Variable Length Subnet Masks (VLSMs) in our struggle to overcome the worsening address drought It's reality-the number of people and devices that connect to networks increases each and every day. That's not a bad thing at all-we're finding new and exciting ways to communicate to more people all the time, and that's a good thing. In fact, it's a basic human need. But the fore cast isn't exactly blue skies and sunshine because, as I alluded to in this chapter's introduction, IPv4, upon which our ability to communicate is presently dependent, is going to run out of addresses for us to use. IPv4 has only about 4.3 billion addresses available-in theory, and we know that we don't even get to use all of those. There really are only about 250 million addresses that can be assigned to devices. Sure, the use of Classless Inter-Domain Routing (CIDR) and Network Address Translation (NAT) has helped to extend the inevitable dearth of addresses, but we will run out of them, and it's going to happen within a few years. China is barely online, and we know there's a huge population of people and corporations there that surely want to