Building Linux IPv6 DNS Server (Complete Soft Copy)

Building a Linux IPv6 DNS Server
1. INTRODUCTION
1.1 OVERVIEW TO OUR PROJECT
IPv6 is a key cutting Edge Technology and top 4th Technology all
around the world from EFY Magazine resources. It is a Top 6th Technology
of Computer Networks from Network Magazine website. The project mainly
deals with creating a Dual IP stack node with provision of complete support
for both IPV4 and IPV6 in hosts and servers. This can be achieved by
making a recursive copy of the kernel and configuring the necessary network
properties to support both IPv4 and IPv6. The kernel is configured by using
scripts in shell programming and C programming. The main idea of the
project is configure a DNS server in Linux with IPv6 name resolution
facility. The concept of encapsulation of IPv6 packets within IPv4 headers to
carry then an IPv4 network simply called as IPv6 over IPv4 tunneling.
Finally Resources are accessed in the network regardless of the platform.
1.2 PINPOINTS OF OUR PROJECT
• Creating a new kernel from the existing kernel through kernel
compilation.
• Making DNS server in Linux with IPv6 support.
• Providing backup of existing kernel in Linux.
• DNS server can be activated or deactivated through Interactive user
interface.
• To promote sharing of files from Windows to Linux or vice versa.
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1.3 DOCTRINE OF THE REPORT
Chapter 1 discusses about the Introduction, which includes overview
of the project, document conventions followed in the project and brief
description about the organization profile.
Chapter 2 discusses about the Literature Survey, which includes
details about the problem definition, existing system, and proposed
system of our project.
Chapter 3 discusses about the System Specification for our project.
Basically it consists of hardware and software requirements and
network service profiles for our project.
Chapter 4 discusses the System design for our project have the
following components such as data flow diagram and other design
considerations and issues while designing the system.
Chapter 5 discusses about the System Implementation for our project.
It consists of Brief account of project modules.
Chapter 6 discusses the System Testing for our project which have
testing strategies and errors which we have faced while designing the
system.
Chapter 7 discusses the Conclusion and scope for future
enhancement for our project.
Chapter 8 discusses about the References of our project having the
following criteria such as RFCs, Bibliography, Websites, HowTo
guides, FTP sites, Blogs, Forums, PPT’s and PDF’s.
Chapter 9 discusses the appendices of our project which consists of
source codes and snapshots for our project.
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1.4 DOCUMENT CONVENTIONS
MAIN SECTION TITLES
Font: Time New Roman Face: Bold Size: 16
SUB SECTION TITLES
Font: Times New Roman Face: Bold Size: 14
Other Text Explanations
Font: Times New Roman Face: Normal Size: 12
1.5 ORGANISATION PROFILE
Maze Net Systems has emerged as IT Solutions Company and today
it’s providing application migrations/solutions and re-engineering for turn
key projects. Maze Net’s offerings range from software development like
data warehousing, financial software services and enterprise system
management solutions, with a rich talent pool of about 25 associates. Maze
Net Systems has its corporate office and development centers in Chennai
(India).
To be a vibrant, customer-oriented, quality driven, state of the art
Technology Company Creating value to employees, customers, shareholders
and society Maze Net Systems has emerged as leading global IT Solutions
Company and is a leader in application migrations and application
reengineering. Maze Net’s offerings range from cross-platform migrations,
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software development, and outsourced product development to application
maintenance.
This consultative approach provides a risk-free, cost-effective way for
an organization to design, develop, and/or maintain cutting edge information
systems. Maze Net is a Quality conscious company there by assessed at
CMM LEVEL 4 Certification from Software Engineering Institute.
The customer focus is intended at contributing to the creation of
customer relationships that endure beyond the end of assignments while the
people focus aims at building a learning organization to manage the
demands of rapid technological changes.
The process focus will bring about process focus through well-
defined, institutionalized processes and finally, Maze Net would also work
towards improving the predictability of delivery time, effort and quality of
delivery. Maze Net is on its way to CMM Level 5.
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2. LITERATURE SURVEY
2.1 PROBLEM DEFINITION
LINUX kernels up to 2.3 do not support the incorporation of IPv6 into
it. Hence to build a kernel which has provision for both IPv4 and IPv6, we
use kernel version 2.4. In this project, we look closely at IPv6 name
resolution and provide technical support to help the user set up their own
IPv6 Linux DNS server to allow IPv6 name resolution using the latest
version of BIND Configuration tool.
2.2 EXISTING SYSTEM
The existing IPv4 system supports DNS configuration in RedHat
Linux 9 and its prior versions. The graphical tool BIND 9 and prior versions
support DNS configuration of IPv4. The kernel version 2.4 and prior
versions support IPv4 DNS configuration. The BIND tool was introduced to
configure the IPv4 DNS after Linux 6. The existing system namely RedHat
Linux 8 and BIND 8 does not support IPv6 configurations.
2.3 PROPOSED SYSTEM
The proposed system is aimed at removing the drawbacks of the
existing system. Our dual stack server can easily help a user to give IPv6
support to the Linux system. The project has configurations and tunneling is
established through coding written in JAVA. Also, the packets are
transferred from client to the server using the code and cross platform
resources are achieved.
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3. SYSTEM SPECIFICATION
3.1 HARDWARE REQUIREMENTS
SERVER MACHINE : Red Hat Enterprise / Workstation Linux v3.0
[Server Installation]
CLIENT MACHINE : MS-Windows / Fedora core v3.0
[Client Installation]
PROCESSOR : Intel / AMD Processors (> 533 MHz)
MAIN MEMORY : 32MB RAM
HARD DISK : Minimum 2GB
KEYBOARD : 101 keys
3.2 SOFTWARE REQUIREMENTS
PLATFORM USED : RedHat Enterprise / Workstation Linux 3
SOURCE LANGUAGE : Java, C, Shell Scripting
SHELL TYPE : Bash
KERNEL VERSION : 2.4 (Shrike)
KERNEL TYPE : Stable Kernel (Open)
BIND VERSION : 9.0
LANGUAGE TOOL KITS : J2SDK v 1.4, Gcc Compiler
PACKAGE FORMAT : .rpm for Linux, .exe format for
Windows families.
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3.3 SERVICE PROFILE
DNS (DOMAIN NAME SERVER)
Type : System V-Managed Service
Packages : bind, bind-utils
Daemons : named, rndc
Script : named
Ports : 53(domain), 953(rndc)
Configs : /etc/named.conf
/var/named/*
/etc/rndc.*
3.4 SOFTWARE DESCRIPTION
About Kernel
The kernel is the part of the operating system that handles the most
basic functions and control interactions with the computer hardware. The
Linux kernel is very modular. Each driver, for a file system or a piece of
hardware, needs to be compiled into the kernel, or inserted as a module. The
file /proc/file systems contain a list of all the file systems that the kernel
understands.
There are two ways to get IPV6 support. The simplest is to probe the
IPV6 module to the kernel (as root). If this fails, then your distribution didn’t
install the IPV6 module. The second way is to recompile the kernel,
yourself. This sounds like a lot of work, but isn’t that hard.
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Kernels, being the backbone of an operating system are of two types:
(i) Open Kernel
(ii) Closed Kernel
The open kernel is a free source and easily modifiable by any one
familiar with Linux. The closed kernel is a kernel of proprietary software
which cannot be modified by normal user.
The open kernel is again of two kinds:
(i) Stable Kernel (2.4.20.8)
(ii) Development Kernel (2.4.19.8)
If the third octet of Linux Kernel Version is Even, it is called as Stable
Kernel and if the third octet of Linux Kernel Version is Odd, it is known as
Development Kernel.
The kernel has release, version and volume specifications each
separated by a period. If the version of the kernel is even, then the kernel is
pointed as a stable kernel and can be used for implementation purposes. If
the version is Odd then the kernel is a development kernel and it is not
advisable for implementation purposes. The Development Kernel is used for
Benchmarking applications.
The Kernel versions prior to 2.3 did not have provisions for IPV6, so
a Program module has to be added by recompiling the kernel. But the
current versions from 2.4 have provisions to support IPv6 and are IPv6 ready
kernels. Appropriate RPMS has to be enabled in the kernel. Most users
won’t have to compile anything to enable IPV6 support.
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Almost every Linux distribution comes with IPv6 support out of the
box. For any RedHat 7.3 or RedHat 8.0 user, the user probably doesn’t have
to recompile the kernel. If there is an older version of RedHat, or other
distribution which doesn’t include IPv6 support, then the user has to
recompile the kernel.
Why Linux?
Linux is free. Like UNIX, it is very powerful and is a "real" operating
system. Also, it is fairly small compared to other UNIX operating systems.
Many UNIX operating systems require 500MB or more, whereas Linux can
be run on as little as 150MB of space, and it can run on as little as 2MB of
RAM. Realistically, though, you will want to have room for development
tools, data, and so on, which can take up 250MB or more, and your RAM
should be 16MB.
Here we go some of the Linux advantages:
• Full multitasking - Multiple tasks can be accomplished and multiple
devices can be accessed at the same time.
• Virtual memory - Linux can use a portion of your hard drive as
virtual memory, which increases the efficiency of your system by
keeping active processes in RAM and placing less frequently used or
inactive portions of memory on disk. Virtual memory also utilizes all
your system's memory and doesn't allow memory segmentation to
occur.
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• The X Window System - The X Window System is a graphics
system for UNIX machines. This powerful interface supports many
applications and is the standard interface for the industry.
• Built-in networking support - Linux uses standard TCP/IP
protocols, including Network File System (NFS) and Network
Information Service (NIS, formerly known as YP). By connecting
your system with an Ethernet card or over a modem to another
system, you can access the Internet.
• Shared libraries - Each application, instead of keeping its own copy
of software, shares a common library of subroutines that it can call at
runtime. This saves a lot of hard drive space on your system.
• Compatibility with the IEEE POSIX.1 standard - Because of this
compatibility, Linux supports many of the standards set forth for all
UNIX systems.
• Nonproprietary source code - The Linux kernel uses no code from
AT&T, nor any other proprietary source. Other organizations, such as
commercial companies, the GNU project, hackers, and programmers
from all over the world have developed software for Linux.
• Lower cost than most other UNIX systems and UNIX clones - If
you have the patience and the time, you can freely download Linux
off the Internet. Many books also come with a free copy.
• GNU software support - Linux can run a wide range of free software
available through the GNU project. This software includes everything
from application development (GNU C and GNU C++) to system
administration (gawk, groff, and so on), to games (for example, GNU
Chess, GnuGo, NetHack).
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Why Preferably Red Hat?
Red Hat Linux is the leading platform for open source computing. It
runs on multiple system architectures, certified by top enterprise software
and hardware vendors, and is supported for seven years.
WHAT DOES IT DO?
Red Hat Linux creates a reliable, secure, high-performance platform
designed for today’s commercial environments—with capabilities that match
or surpass those of proprietary operating systems.
Red Hat Linux is the corporate Linux standard, already at work
running some of the world’s largest commercial, government, and academic
institutions. Red Hat is the world’s leading supplier of commercial-strength
Linux solutions. It delivers the highest levels of reliability and value -
coupling the innovation of open source technology and the stability of a true
enterprise-class platform.
BIND – A Quick Tour
BIND is the most widely used DNS server on the Internet. Red Hat
Linux Uses BIND 9. It provides a stable and reliable infrastructure on which
to base a domain's name and IP address associations.
BIND has gone through numerous revisions over years. The Most
common BIND used since about 1995 was version 8. BIND 9 was released
in September 2000. The development of BIND 9 made important
improvements in security and robustness. In addition it provides IPv6
support, allows eight-bit clean names, and better multi-threading.
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The Internet Software Consortium (isc.org), who all are the
maintainers of BIND recommend that all users of older versions Bind
upgrade to version 9 because of its greatly improved security.
An Outlook on Shell Scripting
The UNIX shell program interprets user commands, which are either
directly entered by the user, or which can be read from a file called the shell
script or shell program. Shell scripts are interpreted, not compiled. The shell
reads commands from the script line per line and searches for those
commands on the system, while a compiler converts a program into machine
readable form, an executable file – which may then be used in a shell script.
Apart from passing commands to the kernel, the main task of a shell is
providing a user environment, which can be configured individually using
shell resource configuration files.
BASH IN Nut Shell
Bash is a sh-compatible shell that incorporates useful features from
the Korn shell (ksh) and C shell (csh). It is intended to conform to the IEEE
POSIX P1003.2/ISO 9945.2 Shell and Tools standard. Bash stands for
Bourne Again Shell.
It offers functional improvements over sh for both programming and
interactive use; these include command line editing, unlimited size
command history, job control, shell functions and aliases, indexed arrays of
unlimited size, and integer arithmetic in any base from two to sixty-four.
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Bash can run most sh scripts without modification. Like the other
GNU projects, the bash initiative was started to preserve, protect and
promote the freedom to use, study, copy, modify and redistribute software. It
is generally known that such conditions stimulate creativity. This was also
the case with the bash program, which has a lot of extra features that other
shells can't offer.
Luxury of C
The programming language C was developed in 1972 by Dennis
Ritchie at AT & T Bell Laboratory, Murray Hill, New Jersy. It was mainly
influenced by the language by the languages BCPL and B. It was named as
C to present it as the successor B language which was designed earlier by
Ken Thompson in 1970 for the first UNIX system on the DEC PDP – 7
computer.
C proved to be an excellent programming language for writing system
programs; Hence, it got wide popularity especially among the programmers
in research in research centers, universities and colleges. The UNIX
operating system, C compiler and all UNIX applications software are written
in C.
Features / Characteristics of C
C is attractive and popular because of the following reasons.
• General purpose language.
• Structured Language.
• Flexible and Powerful language.
• System programming language.
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• Relatively low-level language.
• Machine independent and hence portable.
• Memory addresses are directly accessed by pointers.
• More Built-in functions.
• Free format language.
• Programs are made up of functions.
Java Unleashed
Java is a general-purpose, object-oriented programming language
developed by Sun Microsystems of USA in 1991. Originally call Oak by
James Gosling; one of the inventors of the language, Java was designed for
the development of software for consumer electronic devices like TVs,
VCRs, toasters and such other electronic machines. This goal has a strong
impact on the development team to make the language simple, portable and
highly reliable. The Java team, which included Patrick Naughton,
discovered that the existing language like C and C++ had limitations in
terms of both reliability and portability.
Java is a general purpose, object – oriented programming language.
We can develop two types of java programs:
• Stand alone applications
• Web applets
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Stand-alone applications are programs written in java to carry out
certain tasks on a stand-alone local computer. In fact, java can be used to
develop programs for all kinds of applications, which earlier, were
developed using languages like C and C++. As pointed out earlier, Hot Java
itself is java application program.
Executing a stand-alone java program involves two steps.
1. Compiling source code into byte code using javac compiler
2. Executing the byte code program using java interpreter.
Applets are small java programs developed for Internet applications. An
applet located on a distant computer can be downloaded via Internet and
executed on a local computer using a java-capable browser. We can develop
applets for doing everything from simple animated graphics to complex
games and utilities.
Java Features
The inventors of Java wanted to design a language, which could offer
solutions to some of the problems encountered in modern programming.
They wanted the language to be reliable, portable and distributed but also
simple, compact and interactive. Sun Microsystems officially describes java
with the following attributes:
Compiled and Interpreted
Platform-Independent and portable
Object-oriented
Robust and secure
Distributed
Familiar, Simple and small
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Multithreaded and Interactive
High Performance
Dynamic and Extensible
The most striking feature of the language is that it is a platform-
neutral language. Java is the first programming language that is not tied to
any particular hardware or operating system. Programs developed in java
can be executed anywhere on any system. We can call java as a
revolutionary technology because it has brought in a fundamental shift in
how we develop and use programs. Nothing like this has happened to the
software industry.
Swing Components
The Swing components conform to the Swing architecture, which
means that they are lightweight, have a pluggable look and feel and so on.
Despite the plethora of features, the components are easy to use. Swing
components and applications commonly present information to the user and
invite the user's interaction using a GUI.
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4. SYSTEM DESIGN
4.1 DATA FLOW DIAGRAM
Data flow diagram clearly tells about the pipeline and how the
modules are marshaled in the project.
Start
Kernel Compilation
Lookup module
(Registering the
clients with server and
checks the status)
Building Linux
DNS Server
Cross Platform
Resource Access
Configuring IPv6
over Ipv4
Stop
Diagram 1. Data flow diagram
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4.2 IPV4 HEADER
IPV4 is the internet protocol version 4, the protocol in current usage.
Thus, can be simply called as IP. IP is the transmission mechanism used by
the TCP/IP protocols. It is an unreliable and connectionless datagram
protocol – a best effort delivery service. The term best effort means that IP
provides no error checking or tracking. IP assumes the unreliability of the
underlying layers and does its best to get a transmission through to its
destination, but with no guarantees. The transmission along a physical
network can be destroyed by a number of reasons like bit errors due to noise,
discarding of a datagram because of congestion in routers etc.
The Components of IPv4 header are:
Version Number
This is a 4-bit field that contains the IP version number the
protocol software is using.
Diagram 2. IPv4 Header
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Header Length
This 4-bit field reflects the total length of the IP header built by
the sending machine; it is specified in 32-bit words.
Type of Service
The 8-bit (1 byte) Service Type field instructs IP how to
process the datagram properly.
Datagram Length (or Packet Length)
This field gives the total length of the datagram, including the
header, in bytes.
Identification
This field holds a number that is a unique identifier created by
the sending node.
Flags
The Flags field is a 3-bit field, the first bit of which is left
unused (it is ignored by the protocol and usually has no value written to
it).
Fragment Offset
This enables IP to reassemble fragmented packets in the proper
order.
Time to Live (TTL)
This field gives the amount of time in seconds that a datagram
can remain on the network before it is discarded.
Transport Protocol
This field holds the identification number of the transport
protocol to which the packet has been handed.
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Header Checksum
The number in this field of the IP header is a checksum for the
protocol header field (but not the data fields) to enable faster processing.
Sending Address and Destination Address
These fields contain the 32-bit IP addresses of the sending and
destination devices.
Options
The Options field is optional, composed of several codes of
variable length.
Padding
The content of the padding area depends on the options
selected. The padding is usually used to ensure that the datagram header
is a round number of bytes.
DF
It stands for don’t fragment, given as an order to the routers not to
fragment the datagram because the destination is incapable of putting
the pieces back together again.
MF
It stands for more fragments it is needed to know if all the fragments
of the datagram have arrived.
What‘s Wrong With IPv4 ?
• Address space exhaustion by year 2005
• Difficult (re-)configuration
• Sophisticated, structured header
• No integrated end-to-end security solution
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• NAT is no longer adequate
What Can IPv6 Do Better?
• Increased address space
– 128 bits = 340 trillion trillion trillion addresses
– (2128
=340,282,366,920,938,463,463,374,607,431,768,211,456)
– = 67 billion billion addresses per cm2 of the planet surface
• Hierarchical address architecture
– Improved address aggregation
• More efficient header architecture
• Neighbor discovery and autoconfiguration
– Improved operational efficiency
– Easier network changes and renumbering
• Integrated security features
Why Not IPv5 As Successor For IPv4?
On any IP header, the first 4 bits are reserved for protocol version. So
theoretically a protocol number between 0 and 15 is possible:
• 4: is already used for IPv4
• 5: is reserved for the Stream Protocol (STP, RFC 1819 /
Internet Stream Protocol Version 2) (which never really
made it to the public).
The next free number was 6. Hence IPv6 was born!
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IPv6 – Key Advantages
These are the prominent key advantages of IPv6
• Global addressing:
– Scaling well beyond 4 trillion public endpoints
– Stateless address auto-configuration
• Plug and play:
– Simple instant-on ad-hoc networking
• Efficient mobility:
– Mobile IPv6, unlike IPv4, does not need the Foreign Agent
• Secure:
– IPSec is a requirement and integral part of the IP layer
– Anonymous addresses ensure privacy
Summary of IPv6 Benefits
• Expanded addressing capabilities
• Structured hierarchy to manage routing table growth
• Server less auto configuration and reconfiguration
• Streamlined header format and flow identification
• Improved support for options / extensions
IPv6 Meets The Challenges
• Enables next generation network-based applications without
additional expense or expertise
• Enables deployment of these applications without major
investment in new network infrastructure
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4.3 IPV6 HEADER
The Figure 3. Portrays the IPv6 Header Format
Vers: 4-bit Internet Protocol version number: 6.
Traffic class: 8-bit traffic class value. The 8-bit traffic class field
allows applications to specify a certain priority for the traffic they
generate, thus introducing the concept of Class of Service.
Flow label: 20-bit field. IPv6 introduces the concept of a flow, which
is a series of related packets from a source to a destination that
requires a particular type of handling by the intervening routers.
Payload length: The length of the packet in bytes (excluding
thisheader) encoded as a 16-bit unsigned integer. If length is greater
than 64 KB, this field is 0 and an option header (Jumbo Payload)
gives the true length.
Next header: Indicates the type of header immediately following the
basic IP header. It may indicate an IP option header or an upper layer
protocol. The protocol numbers used are the same as those used in
IPv4
Hop limit: This is the IPv4 TTL field but it is now measured in hops
and not seconds. It was changed for two reasons:
• IP normally forwards datagrams faster than onehop per second
and the TTL field is always decremented on each hop, so, in
practice, it ismeasured in hops and not seconds.
• Many IP implementations do not expireoutstanding datagrams
on the basis of elapsed time.The packet is discarded once the
hop limit is decremented to zero.
Source address: A 128-bit address consists of sending address.
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Destination address: A 128-bit address consists of receiving address.
A comparison between the IPv4 and IPv6 header formats will show
that a number of IPv4 header fields have no direct equivalents in the IPv6
header.
4.4 IPV6 ADDRESSING
Like IPv4, IPv6 addresses can be split into network and host parts
using subnet masks.
Local host Address
This is a special address for the loopback interface, similiar to IPv4
with its "127.0.0.1". With IPv6, the localhost address is:
0000:0000:0000:0000:0000:0000:0000:0001 or compressed: ::1
Figure 1. IPv6 Header
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Packets with this address as source or destination should never leave the
sending host.
Unspecified Address
This is a special address like "any" or "0.0.0.0" in IPv4 . For IPv6 it's:
0000:0000:0000:0000:0000:0000:0000:0000 or: ::
These addresses are mostly used/seen in socket binding (to any IPv6
address) or routing tables.
IPv6 Address With Embedded IPv4 Address
There are two addresses which contain an IPv4 address.
• IPv4-Mapped IPv6 Address
• IPv4-Compatible IPv6 Address
IPv4-Mapped IPv6 Address
IPv4-only IPv6-compatible addresses are sometimes used/shown for
sockets created by an IPv6-enabled daemon, but only binding to an IPv4
address. These addresses are defined with a special prefix of length 96
(a.b.c.d is the IPv4 address):
0:0:0:0:0:ffff:a.b.c.d/96 or in compressed format ::ffff:a.b.c.d/96
For example, the IPv4 address 1.2.3.4 looks like this: ::ffff:1.2.3.4
IPv4-Compatible IPv6 Address
Used for automatic tunneling, which is being replaced by 6to4
tunneling.
0:0:0:0:0:0:a.b.c.d/96 or in compressed format :a.b.c.d/96
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4.5 TUNNELING
When IPv6 or IPv6/IPv4 systems are separated from other similar
systems that they wish to communicate with by older IPv4 networks, then
IPv6 packets must be tunneled through the IPv4 network.IPv6 packets are
tunnelled over IPv4 very simply; the IPv6 packet is encapsulated in an IPv4
datagram, or in other words, a complete IPv4 header is added to the IPv6
packet. The presence of the IPv6 packet within the IPv4 datagram is
indicated by a protocol value of 41 in the IPv4 header.
There are two kinds of tunneling of IPv6 packets over IPv4 networks:
• Automatic Tunneling
• Configured Tunneling
Automatic Tunneling
Automatic tunneling relies on IPv4-compatible addresses. The
decision to when to tunnel is made by an IPv6/IPv4 host that has a packet to
send across an IPv4-routed network area.
Configured Tunneling
Configured tunneling is used for host-router or router-router tunneling
of IPv6-over-IPv4. The sending host or the forwarding router is configured
so that the route, as well as having a next hop, also has a tunnel end address
(which is always an IPv4-compatible address).
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Overview of Socket Programming
A socket is nothing more than a convenient abstraction. It represents a
connection point into a TCP/IP network, much like the electrical sockets in
your home provide a connection point for your appliances. When two
computers want to converse, each uses a socket. One computer is termed the
server--it opens a socket and listens for connections. The other computer is
termed the client--it calls the server socket to start the connection. To
establish a connection, all that's needed is a server's destination address and
port number.
Each computer in a TCP/IP network has a unique address. Ports
represent individual connections within that address. Each port within a
computer shares the same address, but data is routed within each computer
by the port number. When a socket is created, it must be associated with a
specific port--this process is known as binding to a port.
Socket Transmission Modes
Sockets have two major modes of operation:
• Connection-oriented mode
• Connectionless mode
Connection-Oriented Mode
Connection-oriented sockets operate like a telephone: they must
establish a connection and then hang up. Everything that a flow between
these two events arrives in the same order it was sent.
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Connection-oriented operation uses the Transport Control Protocol
(TCP). A socket in this mode must connect to the destination before sending
data. Once connected, the sockets are accessed using a streams interface:
open-read-write-close. Connection-oriented operation is less efficient than
connectionless operation, but it's guaranteed.
Connectionless Mode
Connectionless sockets operate like the mail: delivery is not
guaranteed, and multiple pieces of mail may arrive in an order distinct from
that in which they were sent.
Connectionless operation uses the User Datagram Protocol (UDP). A
datagram is a self- contained unit that has all the information needed to
attempt its delivery. The UDP protocol promises only to make a best-effort
delivery attempt. Connectionless operation is fast and efficient, but not
guaranteed.
Overview of Java Network Cafe
The following sections give a short overview of the capabilities and
limitations of the different network classes provided in the java.net package.
The overview can help to pick the Java classes that best fit your networking
application.
The URL Class
The URL class is an example of what can be accomplished using the
other, lower-level network objects. The URL class is best suited for
applications or applets that have to access content on the World Wide Web.
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If all you use Java for is to write Web browser applets, the URL and
URLConnection classes, in all likelihood, will handle your network
communications needs.
The Socket Class
The Socket class provides a reliable, ordered stream connection (that
is, a TCP/IP socket connection). The host and port number of the destination
are specified when the Socket is created.
The connection is reliable because the transport layer (the TCP
protocol layer) acknowledges the receipt of sent data. If one end of the
connection does not receive an acknowledgment within a reasonable period
of time, the other end re-sends the unacknowledged data (a technique known
as Positive Acknowledgment with Retransmission, often abbreviated as
PAR). Once you have written data into a Socket object, you can assume that
the data will get to the other side (unless you receive an IOException, of
course).
The reliable stream connection provided by Socket objects is well
suited for interactive applications. Examples of protocols that use TCP as
their transport mechanism are Telnet and FTP. The HTTP protocol used to
transfer data for the Web also uses TCP to communicate between hosts.
The Server socket Class
The ServerSocket class represents the thing with which Socket-type
connections
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communicate. Server sockets listen on a given port for connection requests
when their accept() method is called. The ServerSocket offers the same
connection-oriented, ordered stream protocol (TCP) that the Socket object
does. In fact, once a connection has been established, the accept() method
returns a Socket object to talk with the remote end.
The Datagram socket Class
The DatagramSocket class provides an unreliable, connectionless,
datagram connection (that is, a UDP/IP socket connection).
Unlike the reliable connection provided by a Socket, there is no
guarantee that what you send over a UDP connection actually gets to the
receiver. The TCP connection provided by the Socket class takes care of
retransmitting any packets that get lost. Packets sent through UDP simply
are sent out and forgotten, which means that if you need to know that the
receiver got the data, you will have to send back some sort of
acknowledgment.
Table 1. Classes of the java.net package
Class Purpose
URL Represents a Uniform Resource Locator.
URLConnectio
n
Retrieves content addressed by URL objects
Socket Provides a TCP (connected, ordered stream) socket
ServerSocket Provides a server (listening) TCP socket.
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DatagramSock
et
Provides a UDP (connectionless datagram) socket.
DatagramPac
ket
Represents a datagram to be sent using a DatagramSocket
object.
InetAddress Represents a host name and its corresponding IP number or
numbers.
4.6 DNS IN NUT SHELL
These are the some of the noteworthy features for DNS server.
• DNS stands for Domain Name System.
• It translates (or "maps" as the jargon would have it) from name to
address and from address to name, and some other things.
• Allow machines to be logically grouped by name Domains.
• Provides email routing Information.
The structure of the DNS database, shown in Figure 2., is very similar
to the structure of the UNIX file system. The whole database (or file system)
is pictured as an inverted tree, with the root node at the top. Each node in the
tree has a text label, which identifies the node relative to its parent.
This is roughly analogous to a "relative pathname" in a filesystem,
like bin. Onelabel - the null label, or "" - is reserved for the root node. In
text, the root node is written as a single dot ("."). In the UNIX filesystem, the
root is written as a slash ("/").
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Each node is also the root of a new subtree of the overall tree. Each of
these subtrees represents a partition of the overall database - a "directory" in
the UNIX filesystem, or a domain in the Domain Name System. Each
domain or directory can be further divided into additional partitions, called
subdomains in DNS, like a filesystem's "subdirectories." Subdomains, like
subdirectories, are drawn as children of their parent domains.
Figure 2. The DNS database versus a UNIX file system
Figure 3. DNS upside-down tree structure
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The Figure 3. Portraits the DNS upside down tree structure which is in
a hierarchical manner. Every domain has a unique name, like every
directory. A domain's domain name identifies its position in the database,
much as a directory's "absolute pathname" specifies its place in the file
system. In DNS, the domain name is the sequence of labels from the node at
the root of the domain to the root of the whole tree, with "." separating the
labels.
DNS Lookups
DNS have a couple of lookups, one is forward lookup and the other is
reverse of forward lookup.
Forward Lookup
- It Resolves Hostname into IP address.
Reverse Lookup
- It Resolves IP address into Host Name.
DNS Server Functions
These are the some of the notable key points in DNS server.
• Internet Domain Support
- Accessing servers through remote network.
• Local Name Resolution
- Resolve the hostnames of systems on your LAN.
• Internet Name Resolution
- Most often used for ISP's DNS server.
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Name Server Hierarchy
According to name server hierarchy the prominent features are
• Master Name Server
Contains the master copy of data for a zone.
• Slave Name Server
Provides a backup to the master name server.
• Caching Name Server
Provides a backup of queries and answers
DNS Message Format and Resource Records
All communications inside of the domain protocol are carried in a
single format called a message. The top level format of message is divided
into 5 sections (some of which are empty in certain cases) shown below:
• Header
• Question
• Answer
• Authority
Figure 4. Graphical Representation of DNS Configuration
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• Additional
The header section is always present. The header includes fields that
specify which of the remaining sections are present, and also specify
whether the message is a query or a response, a standard query or some other
opcode, etc.
The names of the sections after the header are derived from their use
in standard queries. The question section contains fields that describe a
question to a name server. These fields are a query type (QTYPE), a query
class (QCLASS), and a query domain name (QNAME). The last three
sections have the same format: a possibly empty list of concatenated
resource records (RRs).
The answer section contains RRs that answer the question; the
authority section contains RRs that point toward an authoritative name
HEADER
QUESTION
ANSWER
AUTHORITY
ADDITIONAL
RRs answering the question
the question for the name server
RRs holding additional information
RRs pointing toward an authority
Diagram 3. DNS Message Format
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server; the additional records section contains RRs which relate to the query,
but are not strictly answers for the question.
DNS Configuration Files
The default configuration file for BIND is /etc/named.conf,
There are couples of zones in BIND.
• Master Zone
• Slave zone
Master zones are the central player in BIND configuration. Slave
zones look similar to their master counterparts. These are the typical zone
configuration files in our project.
zone "mahendra.com" {
type master;
file "mahendra.com.zone"
};
zone "kernel.org" {
type slave;
masters { 192.168.192.168; };
file "kernel.org.zone";
};
The file directive specifies the text file that holds the zone's database.
The name of the zone file is arbitrary be common examples include:
mahendra.com.zone
mahendra.com.db
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db.mahendra.com
mahendra.com
Zone files usually reside in /var/named/ directories. All zone files
must start with a TTL directive. Every zone file must have the following
components such as serial number, refresh time, retry time, and expire time
and TTL parameters.
Installing a Rpm Package in Linux
The modules from the enhanced version cannot be loaded into the
prior versions, because the facilities in the prior versions are restricted and
the modules attached to the degraded version will not cope up with each
other. So for a version which has no support for IPv6 a patch up rpm
corresponding to the kernel version has to be downloaded from the net and
run in the root using the command.
# rpm –ivh <RPM Package>
For e.g. # rpm –ivh j2sdk1.4.0.1-arch-x86.rpm
The switch options in rpm command are explained as follows:
i - Stands for Installation.
v - Stands for Verbose mode.
h - Stands for Hash display while installation.
Through this RPM command we can install goodies of software's in
Linux boxes.
Page 37

Path setting for java's bin directory can be achieved by /etc/profile
configuration file by passing certain parameters.
Page 38

5. SYSTEM IMPLEMENTATION
5.1 OUR PROJECT MODULES
In Our Project we divided the process into five Modules:
Kernel Compilation and Creation of Patch Work.
Lookup Module.
Configuring IPv6 over IPv4.
DNS Configuration Settings by editing the /etc based config. files.
Cross Platform Resource Access.
Kernel Compilation and Creation of Patch Work
In this module we are creating a new kernel to execute our project. So
we are surmounting the accidental damages to the already existing
kernel.
Building a new kernel providing some benefits as follows:
• Additional drivers.
• Enabling additional features (security patch for example).
• Use a more recent kernel than prebuilt kernels.
• Optimization
"Lower" memory footprint.
Speed, compiled for your hardware.
We can configure the new kernel in two ways.
• Text based configuration – make config , make menuconfig
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• GUI basedconfiguration – make xconfig, make gconfig
In our project the necessary files to build a new kernel are kept under the
loading.sh file.
The following commands are used to customize the kernel
• Kernel level commands
These are the kernel commands which are included in our shell program
loading.sh to build, compile, installing the kernel modules.
# make dep >> for dependency checks.
# make clean >> parameter checks.
# make bzImage >> Extracting Kernel image.
• Modules level commands
These are the commands to install modules in the kernel
# make modules >> configuring kernel modules.
# make modules_install >> installing modules.
Lookup Module
The main goal of this module is to check the status of the server by
the client. Initially the server is enabled by specifying a port number which
is greater than 1024 [i.e. it should not be a default port number as assigned
by ICANN].
Then all the clients are registered with the server in the same port
number that is assigned previously at the server side programs by clicking
Page 40

on Register button .The client name and the port name are entered on their
preferred text boxes.
Successively any client system can be added in the network with the
server by checking the server status through lookup button. A clear
indication will be shown to the user regarding the server status whether it is
active or inactive.
Configuring IPv6 over IPv4
At present we have IPv4 all around the globe. We can’t change the
entire IPv4 network to IPv6 network suddenly. In order to come over this
problem we encapsulated the IPv6 packet support over the IPv4 packets.
This process is known as “IPv6 Tunneling”. It can be accomplished by
writing proper BIND script for our project.
In our project, we created our network name as “Mahendra.com” with
specified IP address. The file db.mahendra.com contains the essential
functional parameters that are needed to configure the server. The forward
lookup contains the zone name as mahendra.com and the reverse lookup
contains IP address as a zone name. All the server and client names and their
IP addresses are configured in BIND script.
DNS Configuration Settings by editing the /etc Based Configuration
Files
The following commands are used to trigger the server / reconfigure.
• # Service named start - The command indicates to start the
named service in Linux network services.
Page 41

• # Service named stop - The command indicates to stop the
• # Service named restart - The command indicates to restart the
• # Chkconfig named on - The command indicates to start the
named service while booting Linux.
DNS panel consists of three components.
• Control panel
• IPv6 address
• IPv4 address
In the control panel dialog box, we can activate the server through
start / restart buttons and deactivated through stop button. Additionally the
close button is used to exit from the control panel if the user clicks on it.
Both IPv6 and IPv4 address panels consists of following components:
• Domain name – represents the name of the entire network.
• Host name - represents the name of the particular client.
• IPv6/IPv4 address- represents the hexadecimal address format and
classful addressing.
Also the user can add the new clients in the network by clicking on the
add button.
Page 42

Cross Platform Resource Access
In our project, the server is configured under Linux platform and the
clients may under Windows / Linux platform.
We created the interactive java network programs to get connection
between the client and the server. Initially the server is in ON state. Then the
client sends the domain name and port number (default: 2995) as a run time
parameter while executing. Then through SAMBA server we can access the
windows files and directories in Linux or vice versa…We can enable IPv6
support for samba server by installing the preferred patches.
5.2 THE BOTTOMLINE OF THE PROJECT
At Present situation, suddenly we can’t change the entire IPv4
network into IPv6 network. That’s why we chose to select the concept of IP
v6 over IPv4 Tunneling. The above diagram represents the Bottom line of
the Project that resolves the name and IP address for both IPv6 and IPv4
components. The main concept involved in our Project IPv6 over IPv6
Figure 5. The Bottom Line of the Project
Page 43

Tunneling. The principal function for this concept is encapsulating the IPv6
packets within IPv4 packets.
Page 44

6. SOFTWARE TESTING
6.1 AN INTRODUCTION
Testing is done to make sure that all processes are executed properly
in order to avoid unprecedented errors and bugs under various
circumstances.
In our Project following testing procedures are followed.
Unit Testing
Integration testing
Validation testing
Output testing
User Acceptance testing
White box testing
Unit Testing
Unit testing focuses verification effort on the smallest limit of
software design. Using the unit test plan prepared in the design phase of the
system, important control paths are tested to uncover the errors within the
module. This testing was carried out during the coding itself. In this testing
each module is going to be working satisfactorily as the expected output
from the module.
Integration Testing
Integration testing is the systematic technique for constructing the
program structure while at the same time conducting test to uncover errors
associated with the interface. The objective is to take tested modules and
Page 45

build the program structure that has been dictated by design. All modules are
combined in this testing step. Then the entire program is tested as a whole. If
a set of errors is encountered correction is difficult because the isolation of
causes is complicated by vastness of the entire program. Using integrated
test plans prepared in the design phase of the system developed as a guide,
the integration was carried out. All the errors found in the system were
corrected for the next testing steps.
Validation Testing
At the end of the integration testing, software is completely assembled
as a package, interfacing errors have been uncovered and corrected and final
series of software validation testing begins. Validation testing can be defined
in many ways, but a simple definition is that validation succeeds then the
software functions in a manner that can be reasonably accepted by the user.
Software validation is achieved through a series of black box tests that
demonstrate conformity the requirements. Thus, the proposed system under
consideration has been tested by using validation testing and found to be
working satisfactory.
Output Testing
After performing the validation testing the next step is to perform the
output testing of the proposed system. Since no system could be useful if it
does not produce the required output in the specified format. The output
generated by the system under consideration is compared with the format
required by the user. Here the output format is considered in two ways. One
is onscreen and other is printed format. The output format on the screen is
found to be correct as the system design phase according to the user needs
Page 46

for the hard copy also, the output comes out as a specified requirement by
the user. Hence, the output testing does not result in any correction in the
system.
User Acceptance Testing
User acceptance of a system is a key factor to the success of any
system. The system under consideration was tested for user acceptance by
constantly keeping in touch with the prospective system user at the time of
developing and making changes wherever required.
This is done with regard to the following points:
• Input screen design.
• Output screen design.
• Online message to guide the user.
• Event driven system.
• Format of the reports and other output.
Black Box Testing
Knowing the specified function that a product has been designed to
platform, test can be conducted at each function is fully operational. Black
box test is carried out to test that input to a function properly accepted and
output is correctly produced. A black box test examines some aspects of a
system with little regard for the internal logical structure of the software.
Errors in the following categories were found through Black Box testing:
• Incorrect or missing functions.
• Interface errors.
• Performance error.
Page 47

• Initialization and termination errors.
White Box Testing
White box testing of software is predicted on a close examination of
procedural detail. The status of the program may be tested at various points
to determine whether the expected or asserted status corresponding to the
actual status.
Using these following test cases can be derived:
• Exercise all logical conditions on their true and false side.
• Execute all loops within their boundaries and their operation bounds.
• Exercise internal data structure to ensure their validity.
6.2 FEATURES TO BE TESTED
There are certain modules to be tested to make the project to be
qualitative and will be effective in certain circumstances.
We divided the testing strategy into two counter parts:
• Generic test
• Security test
Generic Test Conditions
Table 2. Generic Test Conditions
Conditions to be tested Expected results
Click on all links System display appropriate screen.
No error message saying ‘not found’
is given
Use of wrong data type values Display error: Enter numeric or alpha
according to the entry
Page 48

Security Test Conditions
Table 3. Security Test Conditions
Conditions to be tested Expected results
Provide wrong port no Displays exception : Improper Port
number
If Port number is string Displays Number format Exception
If String is a number Displays Illegal argument Exception
If port number differs between client
and server
Displays "Server not active message"
Page 49

7. CONCLUSION
Our Project would resolve both IPv4 and IPv6 names, since we have
created a dual stack which supports both kinds of name resolution. The
project also includes the tunneling mechanism through name resolution by
the code developed by the code developed in JAVA.
Though the system has been successfully working with the currently
developed modules, it is planned to upgrade the system to accommodate the
IPv6 name server too. These ideas are under consideration and ground work
for further development is on.
These are the Pointers that we have chosen IPV6 as academic Project.
• Long-term solution, Scalable, Reliable, Manageable
• Secure and High-performance IP networks.
Scope of Future Enhancement
The Future Enhancement for our project involves:
• Implementation of IPv6 Name Server.
• Implementation of DHCP Name Server.
• Implementation of SAMBA Server.
Page 50

8. REFERENCES
Supported RFC’s For Our Project
The Supported RFC’s for our projects are
• RFC1886: DNS extension for IPv6
• RFC2373: IPv6 addressing architecture
• RFC2428: FTP extensions for IPv6 & NATs
• RFC2452: IPv6 MIB: TCP
• RFC2463: ICMP for IPv6
• RFC2464: IPv6 over ethernet
• RFC2466: IPv6 MIB: ICMP
• RFC2553: Basic socket API for IPv6
Books Referred
1. M.Beck, H.Bome, M, Dziadzka, U.Kunitz, R.Manus, D,Verwomer
“LINUX Kernal Internals” Addison Wesley Longman (Singapore )
Pvt. Ltd. Indian Branch 482 FIE , Delhi -110092, pp.54-123.
2. Craig Hunt “Linux Network Servers” BPB publications , B-14
connaught place, New Delhi-01, pp.67-78.
3. Kerry Cox “Red Hat Linux administrator’s guide” Prentice Hall of
India pte Ltd, New Delhi -01, pp.101-222.
4. Christopher Negus “Red Hat Linux 9 Bible” WILEY – dreamtech
India Pvt Ltd, New Delhi-01, pp.36-63.
5. Douglas E.Comer “Internetworking with TCP/IP” forth edition,
Pearson Education pte Ltd, New Delhi-92, pp.92-134.
Page 51

Websites
1. www.ietf.org
2. www.6bone.net
3. www.linuxkernel.org
4. www.sourceforge.net
5. www.ipv6.org
6. www.linux.org
7. www.linuxquestions.org
8. www.desktoplinux.com
9. www.realvnc.com
10. www.redhat.com
Forums
1. www.IPv6forum.com
Blogs
1. www.blogger.com
FTP Sites
1. ftp://tsx-11.mit.edu/pub/linux
How To Guides
1. Linux IPv6 guide from tldp.org
2. Linux DNS guide from tldp.org
Page 52

Power Point Presentations (PPT) And PDF’s
1. IPv6 Router Experience and Plans, July 2001, Naoya Ikeda,
Enterprise Server Division Hitachi, Ltd. Power Point Presentation
(PPT).
2. Cisco IPv6 status, Tony Hain, Cisco Systems Technical Leader -
IPv6. Power Point Presentation (PPT).
3. IPv6 market status, Yolonda Lamilla, Consulting System Engineer,
Cisco Systems. (PDF).
4. IPv6 on Linux: A Tutorial Approach, Ibrahim Haddad, IP
Network branch at Ericsson Research.(PDF).
Page 53

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