IPV4 to IPV6: Addressing

<h2>
Hexadecimal Number System</h2>
Before introducing <a href="http://ipv4-ipv6.blogspot.com/" target="_blank">IPv6 Address format</a>, we shall look into 
Hexadecimal Number System.  Hexadecimal is positional number system 
which uses radix (base) of 16.  To represent the values in readable 
format, this system uses 0-9 symbols to represent values from zero to 
nine and A-F symbol to represent values from ten to fifteen.  Every 
digit in Hexadecimal can represent values from 0 to 15.<br />
<figure>
<img caption="Hexadecimal Conversion Table" src="http://www.tutorialspoint.com/ipv6/images/Hexadecimal_conversion_table.jpg" />
<figcaption align="center">[<i>Image: Conversion Table</i>]</figcaption>
</figure><h2>
Address Structure</h2>
An IPv6 address is made of 128 bits divided into eight 16-bits 
blocks.  Each block is then converted into 4-digit Hexadecimal numbers 
separated by colon symbol.<br />

For example, the below is 128 bit IPv6 address represented in binary format and divided into eight 16-bits blocks:<br />
<blockquote>
0010000000000001 0000000000000000 0011001000110100 1101111111100001 
0000000001100011 0000000000000000 0000000000000000 1111111011111011</blockquote>
Each block is then converted into Hexadecimal and separated by ‘:’ symbol:<br />
<blockquote>
2001:0000:3238:DFE1:0063:0000:0000:FEFB</blockquote>
Even after converting into Hexadecimal format, IPv6 address remains 
long.  IPv6 provides some rules to shorten the address.  These rules 
are:<br />
<b>Rule:1</b> Discard leading Zero(es):<br />
In Block 5, 0063, the leading two 0s can be omitted, such as (5th block):<br />
<blockquote>
2001:0000:3238:DFE1:63:0000:0000:FEFB</blockquote>
<b>Rule:2</b> If two of more blocks contains consecutive zeroes, omit
 them all and replace with double colon sign ::, such as (6th and 7th 
block):<br />
<blockquote>
2001:0000:3238:DFE1:63::FEFB</blockquote>
Consecutive blocks of zeroes can be replaced only once by :: so if 
there are still blocks of zeroes in the address they can be shrink down 
to single zero, such as (2nd block):<br />
<blockquote>
2001:0:3238:DFE1:63::FEFB</blockquote>
<h2>
Interface ID</h2>
IPv6 has three different type of Unicast Address scheme.  The second 
half of the address (last 64 bits) is always used for Interface ID.  MAC
 address of a system is composed of 48-bits and represented in 
Hexadecimal.  MAC address is considered to be uniquely assigned 
worldwide.  Interface ID takes advantage of this uniqueness of MAC 
addresses.  A host can auto-configure its Interface ID by using IEEE’s 
Extended Unique Identifier (EUI-64) format.  First, a Host divides its 
own MAC address into two 24-bits halves.  Then 16-bit Hex value 0xFFFE 
is sandwiched into those two halves of MAC address, resulting in EUI-64 
Interface ID.<br />

<img src="http://www.tutorialspoint.com/ipv6/images/interface_id.jpg" />
<br />
<figcaption align="center">[<i>Image: EUI-64 Interface ID</i>]</figcaption><b>Conversion of EUI-64 ID into IPv6 Interface Identifier</b><br />
To convert EUI-64 ID into IPv6 Interface Identifier, the most significant 7<sup><small>th</small></sup> bit of EUI-64 ID is complemented.  For example:<br />
<figure style="margin: 0px; padding: 0px;">
<img src="http://www.tutorialspoint.com/ipv6/images/eui_to_ipv6_id.png" />
<figcaption align="center">[<i>Image: IPV6 Interface ID</i>]</figcaption>
</figure><h2>
Global Unicast Address</h2>
This address type is equivalent to IPv4’s public address.  Global 
Unicast addresses in IPv6 are globally identifiable and uniquely 
addressable. <br />
<figure style="margin: 0px; padding: 0px;">
<img caption="Global Unicast Address" src="http://www.tutorialspoint.com/ipv6/images/global_unicast_address.jpg" />
<figcaption align="center">[<i>Image: Global Unicast Address</i>]</figcaption>
</figure>Global Routing Prefix: The most significant 48-bits are designated as
 Global Routing Prefix which is assigned to specific Autonomous System. 
 Three most significant bits of Global Routing Prefix is always set to 
001.<br />
<h2>
Link-Local Address</h2>
Auto-configured IPv6 address is known as Link-Local address.  This 
address always starts with FE80.  First 16 bits of Link-Local address is
 always set to 1111 1110 1000 0000 (FE80).  Next 48-bits are set to 0, 
thus:<br />
<figure style="margin: 0px; padding: 0px;">
<img caption="Link-Local Address" src="http://www.tutorialspoint.com/ipv6/images/link_local_address.jpg" />
<figcaption align="center">[<i>Image: Link-Local Address</i>]</figcaption>
</figure>Link-Local addresses are used for communication among IPv6 hosts on a
 link (broadcast segment) only.  These addresses are not routable so a 
Router never forwards these addresses outside the link.<br />
<h2>
Unique-Local Address</h2>
This type of IPv6 address which is though globally unique, but it 
should be used in local communication.  This address has second half of 
Interface ID and first half is divided among Prefix, Local Bit, Global 
ID and Subnet ID.<br />
<figure style="margin: 0px; padding: 0px;">
<img caption="Unique-Local Address" src="http://www.tutorialspoint.com/ipv6/images/unique_local_address.jpg" />
<figcaption align="center">[<i>Image: Unique-Local Address</i>]</figcaption>
</figure>
Prefix is always set to 1111 110.  
L bit, which is set to 1 if the address is locally assigned.  So far the meaning of L bit to 0 is not defined.
Therefore, Unique Local IPv6 address always starts with ‘FD’.
<br />
<h3>
Scope of IPv6 Unicast Addresses:</h3>
<figure>
<img caption="IPv6 Unicast Address Scope" src="http://www.tutorialspoint.com/ipv6/images/address_scope.jpg" />
<figcaption align="center">[<i>Image: IPv6 Unicast Address Scope</i>]</figcaption>
</figure>

<br />
The scope of Link-local address is limited to the segment.  Unique 
Local Address are though locally global but are not routed over the 
Internet, limiting their scope to an organization’s boundary.  Global 
Unicast addresses are globally unique and recognizable.  They shall make
 the essence of Internet v2 addressing.<br />
<br />
<span style="background-color: #edf4ff; color: #888888; font-family: Arial, Helvetica, sans-serif; font-size: 13px;"><a href="http://ipv4-ipv6.blogspot.com/2014/07/address-types-formats-ipv6.html">http://ipv4-ipv6.blogspot.com/2014/07/address-types-formats-ipv6.html</a></span>

Address Types & Formats IPv6

Hexadecimal Number System Before introducing IPv6 Address format , we shall look into Hexadecimal Number System. Hexadecimal is position...

<a href="http://ipv4-ipv6.blogspot.com/" target="_blank">In computer networking</a>, addressing mode refers to the mechanism how 
we address a host on the network.  IPv6 offers several types of modes by
 which a single host can be addressed, more than one host can be 
addressed at once or the host at closest distance can be addressed.<br />
<h2>
Unicast</h2>
In unicast mode of addressing, an IPv6 interface (host) is uniquely 
identified in a network segment.  The IPv6 packet contains both source 
and destination IP addresses.  A host interface is equipped with an IP 
address which is unique in that network segment.  A network switch or 
router when receives a unicast IP packet, destined to single host, sends
 out to one of its outgoing interface which connects to that particular 
host.<br />
<figure>
<img caption="Unicast Messaging" src="http://www.tutorialspoint.com/ipv6/images/unicast.jpg" />
<figcaption align="center">[<i>Image: Unicast Messaging</i>]</figcaption>
</figure><h2>
Multicast</h2>
The IPv6 multicast mode is same as that of IPv4.  The packet destined
 to multiple hosts is sent on a special multicast address.  All hosts 
interested in that multicast information, need to join that multicast 
group first.  All interfaces which have joined the group receive the 
multicast packet and process it, while other hosts not interested in 
multicast packets ignore the multicast information.<br />

<figure>
<img caption="Multicast Messaging" src="http://www.tutorialspoint.com/ipv6/images/multicast.jpg" />
<figcaption align="center">[<i>Image: Multicast Messaging</i>]</figcaption>
</figure><h2>
Anycast</h2>
IPv6 has introduced a new type of addressing, which is called Anycast
 addressing.  In this addressing mode, multiple interfaces (hosts) are 
assigned same Anycast IP address.  When a host wishes to communicate 
with a host equipped with an Anycast IP address, sends a Unicast 
message.  With the help of complex routing mechanism, that Unicast 
message is delivered to the host closest to the Sender, in terms of 
Routing cost.<br />
<figure>
<img caption="Anycast Messaging" src="http://www.tutorialspoint.com/ipv6/images/anycast.jpg" />
<figcaption align="center">[<i>Image: Anycast Messaging</i>]</figcaption>
</figure>Let’s take an example of TutorialPoints.com Web Servers, located in 
all continents.  Assume that all Web Servers are assigned single IPv6 
Anycast IP Address.  Now when a user from Europe wants to reach 
TutorialsPoint.com the DNS points to the server which is physically 
located in Europe itself.  If a user from India tries to reach 
Tutorialspoint.com, the DNS will then point to Web Server physically 
located in Asia only.  Nearest or Closest terms are used in terms of 
Routing Cost.<br />

<br />
In the above picture, When a client computer tries to reach a Server,
 the request is forwarded to the Server with lowest Routing Cost.<br />
<br />
<span style="background-color: #edf4ff; color: #888888; font-family: Arial, Helvetica, sans-serif; font-size: 13px;"><a href="http://ipv4-ipv6.blogspot.com/2014/07/in-computer-networking-addressing-mode.html">http://ipv4-ipv6.blogspot.com/2014/07/in-computer-networking-addressing-mode.html</a></span>

IPv6 Addressing Modes

In computer networking , addressing mode refers to the mechanism how we address a host on the network. IPv6 offers several types of modes ...

Address Types & Formats IPv6

IPv6 Addressing Modes

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