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CIT 361: Week 2

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This week we will cover chapter 2 from the textbook on IP addressing. Once again, for some of you this will be a review of concepts originally covered in earlier networking classes but I suspect some of this will be new to all of you. Chapter two covers one of the most basic and important of the TCP/IP protocols, namely network addressing primarily with IPv4 (Internet Protocol) addressing systems which is still the most prevalent addressing system on the Internet. However, this chapter also covers IPv6 addressing which is probably new to most if not all of you will be the dominant IP Addressing system of the future.

On a local, unrouted subnet the MAC (media access control) address, which is a unique, hard coded number embedded in the chip set of each network interface device, is used to direct traffic between network devices. However, since there is no logical structure to these MAC addresses that can be applied to even a small network much less something as large as the Internet, we need to have a more organized and hierarchical structure to network addressing. IPv4 has been used for decades to fill this need. However, we effectively ran out of IPv4 addresses in the late 1990s and have been operating with work arounds ever since. In chapter two we cover this current method of addressing but at the end of class we will cover the newer, much higher capacity, and far more secure IPv6 addressing system.

In IPv4 we often see an address that looks like 134.197.217.123, which happens to be the IP address for GBC's COT Dept web server. The devices on the Internet do not ever see a number that looks like this, they see 1000011011000101110110011111011 since all traffic on the Internet is actually sent in binary. Neither the "dotted decimal" nor the binary version of this number are very human friendly, so people use "words" to contact to Internet servers like "cot.gbcnv.edu" which is this same COT departmental web server. Unfortunately, these "words" do not mean anything to most Internet devices like routers, therefore they must be converted into a numerical address which is actually used to direct Internet traffic. The words to numbers conversion is done by another TCP/IP protocol called DNS (domain name service) which we will discuss in much greater detail in chapter seven.

When the Internet Protocol version 4 (IPv4) was first created it allowed for 4,294,967,296 addresses. Since there are now estimated to be over 8 billion people on Earth and many devices like routers and web servers need IP addresses even though nobody actually uses these to directly access the Internet, you can see why we have been out of address space for quite a while. We will investigate the protocols (NAT, DHCP, and others) that allow us to work around this problem in later chapters. For now, you need to understand how IP address space is organized. Briefly, it is divided into 5 classes, A through E, of which only A, B, and C can be assigned to network devices in normal configurations. Each class A license allows for 16,777,214 addresses, while class B allows 65,534, and class C allows for 256. Classes D and E, as well as some numbers within the other classes, are reserved for special purposes.

These numbers are arranged hierarchically on the Internet which allows for very fast and efficient routing and packet switching of data traffic between devices anywhere in the world. The book covers the concepts of addressing, subnetting, masking, and others required to make TCP/IP work on such a massive scale, as well as alternative methods such as supernetting, CIDR, etc. It also covers "public vs. private" IP addresses and other IP addressing issues very well. Therefore, I will not reiterate these topics here, but you should read about and must understand all these before we can proceed to more complex TCP/IP issues.

As always, I urge you to post your questions, thoughts, and concerns about anything in chapter 2 on this week's discussion board. If you think you can help clarify any of the issues posted then feel free to respond. I will monitor the discussion, answer posts, and correct responses as necessary during the week.