IP Address Management

Principles and Practice

Timothy Rooney

• Publisher: Wiley-IEEE Press
• Year: 2011
• Print ISBN: 9780470585870
• eBook ISBN: 9781118099551
• Edition: 1
• Topic: Computer Science
• Subtopic: Cyber Security
• Index: Computer Science

This book will be the first covering the subject of IP address management (IPAM). The practice of IPAM includes the application of network management disciplines to IP address space and associated network services, namely DHCP (Dynamic Host Configuration Protocol) and DNS (Domain Name System). The consequence of inaccurately configuring DHCP is that end users may not be able to obtain IP addresses to access the network. Without proper DNS configuration, usability of the network will greatly suffer as the name-to-address lookup process may fail. Imagine having to navigate to a website or send an email or an instant message by IP address instead of by name! It's equally important that these DHCP and DNS configurations be based on a common IP address plan, which maps out the IP address hierarchy, subnets, address pools, and domains.

IPAM applies management disciplines to these core services, including configuration, change control, auditing, reporting and so on, and they are necessary given the absolute requirement for properly managing IP space and DHCP and DNS servers. The linkages among an IP address plan, DHCP server configuration and DNS server configuration are inseparable; a change of an IP address will affect DNS information and perhaps DHCP as well. These functions provide the foundation for today's converged services IP networks, so they need to be managed using a rigorous approach.

Today, there is no single book that covers the management of these linkages and services they provide; IP Address Management Principles and Practice will fill that gap. While several books are available for leading vendors' DHCP and DNS services implementations, few exist for IP address planning, and none exist that unifies these three topics.

To obtain a free copy of the IPAM Configuration Guide please send an email to:

[email protected]

Part I

Ip Addressing

Part I begins our discussion of the first IPAMcornerstone: IP addressing. This part covers IPv4 and IPv6 protocols as well as address block management techniques.

Chapter 1

The Internet Protocol

1.1 Highlights of Internet Protocol History

The Internet Protocol (IP) has changed everything. In my early days at AT&T Bell Laboratories in the mid-1980s when we used dumb terminals to connect to a mainframe, the field of networking was just beginning to enable the distribution of intelligence from a centralized mainframe to networked servers, routers, and ultimately personal computers. Now that I've dated myself, a little later, many rival networking technologies were competing for enterprise deployments with no clear leader. Deployment of disparate networking protocols and technologies inhibited communications among organizations, until during the 1990s the Internet Protocol, thanks to the widespread embrace of the Internet, became the world's de facto networking protocol.

Today, the Internet Protocol is the most widely deployed network layer¹ protocol worldwide. Emerging from a U.S. government sponsored networking project for the U.S. Department of Defense begun in the 1960s, the Transmission Control Protocol/Internet Protocol (TCP/IP) suite has evolved and scaled to support networks from hundreds of computers to hundreds of millions today. In fact, according to Internet Systems Consortium (ISC) surveys, the number of devices or hosts² on the Internet exceeded 730 million as of early 2010 with average annual additions of over 75 million hosts per year over each of the past 6 years (see Figure 1.1). The fact that the Internet has scaled rather seamlessly from a research project to a network of over 730 million computers is a testament to the vision of its developers and robustness of their underlying technology design.

Figure 1.1 Growth of Internet hosts during 1993–2010 [3].

Source: ISC.

The Internet Protocol was “initially” defined in 1980 in Request for Comments (RFC³) 760 [1] and 791 [2], edited by the venerable Jon Postel. We quote “initially” because as Mr. Postel pointed out in his preface, RFC 791 is based on six earlier editions of the ARPA (Advanced Research Projects Agency, a U.S. Department of Defense agency) Internet Protocol, though it is referred to in the RFC as version 4 (IPv4). RFC 791 states that the Internet Protocol performs two basic functions: addressing and fragmentation. While this may appear to trivialize the many additional functions and features of the Internet Protocol implemented then and since, it actually highlights the importance of these two major topics for any protocol designer. Fragmentation deals with splitting messages into a number of IP packets so that they can be transmitted over networks that have limited packet size constraints, and reassembly of packets at the destination in the proper order. Addressing is of course one of the key topics of this book, so assuring unique addressability of hosts requiring reachability is critical to basic protocol operation.

The Internet has become an indispensable tool for daily personal and business productivity with such applications as email, social networking, web browsing, wireless access, and voice communications. The Internet has indeed become a key element of modern society. And in case you're interested, the term “Internet” evolved from the lower case form of the term used by the early developers of Internet technology to refer to communications among interconnected networks or “internets.”

Today, the capitalized “Internet,” the global Internet that we use on a daily basis, has become a massive network of interconnected networks. Getting all of these networks and hosts on them to cooperate and exchange user communications efficiently requires adherence to a set of rules for such communications. This set of rules, this protocol, defines the method of identifying each host or endpoint and how to get information from point A to point B over a network. The Internet Protocol specifies such rules for communication using the vehicle of IP packets, each of which is prefixed with an IP header.

1.1.1 The IP Header

The IP layer within the TCP/IP protocol suite adds an IP header to the data it receives from the TCP or UDP transport layer. This IP header is analyzed by routers along the path to the final destination to ultimately deliver each IP packet to its final destination, identified by the destination IP address in the header. RFC 791 defined the IP address structure as consisting of 32 bits comprised of a network number followed by a local address. The address is conveyed in the header of every IP packet. Figure 1.2 illustrates the fields of the IP header. Every IP packet contains an IP header, followed by the data contents within the packet, including higher layer protocol control information.

Figure 1.2 IPv4 header fields [1].

Version. The Internet Protocol version, 4 in this case.

Header Length (Internet Header Length, IHL). Length of the IP header in 32-bit units called “words.” For example, the minimum header length is 5, highlighted in Figure 1.2 as the lightly shaded fields, which consists of 5 words × 32 bits/word = 160 bits.

Type of Service. Parameters related to the packet's quality of service (QoS). Initially defined as ToS (type of service), this field consisted of a 3-bit precedence field to enable specification of the relative importance of a particular packet, and another 3 bits to request low delay, high throughput, or high reliability, respectively.

The original ToS field has been redefined via RFC 2474, “Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Header” (177). The DS field, or differentiated services field, provides a 6-bit code point (DSCP, differentiated services code point) field with the remaining 2 bits unused. The code point maps to a predefined service, which in turn is associated with a level of service provided by the network. As new code points are defined with respective services treatment by the Internet authorities, IP routers can apply the routing treatment corresponding to the defined code point to apply higher priority handling for latency-sensitive applications, for example.

Total Length. Length of the entire IP packet in bytes (octets).

Identification. Value given to each packet to f...

Table of contents

• Cover
• Title Page
• Copyright
• Dedication
• Preface
• Acknowledgments
• Part I: Ip Addressing
• Part II: DHCP
• Part III: DNS
• Part IV: Ipam Integration
• Bibliography
• Glossary
• Rfc Index
• Index