IPNetInfo is a small freeware
utility that allows you to easily find all available information about
an IP address. It can fetch you the details like the owner of the IP
address, the country/state name, IP addresses range, contact information
(address, phone, fax, and email), and more. Now that the Internet is
moving towards IPv6 addresses, the new version of IPNetInfo, you can
even get the details of IPv6 addresses.
In
order to use this feature in the app, you have to check the ‘Detect
IPv6 Addresses’ option in the ‘Choose IP addresses’ window. This option
is disabled by default when you run the application. After enabling this
feature, you can type one or more IPv6 addresses in the addresses list
text-box, and then the result looks like in the image above.
The
IP address information is retrieved by sending a request to the whois
server. The program uses multiple Whois servers, so in case one is not
able to retrieve the information, the app uses the other ones available.
I'm not sure if IPv6 in Ubuntu 10.04 Lucid Lynx is still causing
issues with the Internet connection being slow and so on, but in case it
does here's how to disable it.
To check if IPv6 is disabled, run the following command:
cat /proc/sys/net/ipv6/conf/all/disable_ipv6
0 means it's enabled and 1 - disabled.
This tweak is thanks to an old comment from Stonecut
(this way you don't have to edit the GRUB). Basically, to disable IPv6
in Ubuntu 10.04 Lucid Lynx, you have to add the following lines to /etc/sysctl.conf:
To do it from the command line, paste this in a terminal:
echo "#disable ipv6" | sudo tee -a /etc/sysctl.conf
echo "net.ipv6.conf.all.disable_ipv6 = 1" | sudo tee -a /etc/sysctl.conf
echo "net.ipv6.conf.default.disable_ipv6 = 1" | sudo tee -a /etc/sysctl.conf
echo "net.ipv6.conf.lo.disable_ipv6 = 1" | sudo tee -a /etc/sysctl.conf
Then reboot and check if IPv6 has been disabled with the command in the beginning of the post.
If for some reason IPv6 still shows up as enabled in Ubuntu 10.04 Lucid Lynx, you can use the method described in THIS post.
This tweak (and others) will go into Ubuntu 10.04 Start script (I don't know why I didn't think of this before).
The practical guide to deploying IPv6 in campus,
WAN/branch, data center, and virtualized environments
IPv6
for Enterprise Networks brings together all the information you need to
successfully deploy IPv6 in any campus, WAN/branch, data center, or
virtualized environment. Four leading Cisco IPv6 experts present a
practical approach to organizing and executing your large-scale IPv6
implementation. They show how IPv6 affects existing network designs,
describe common IPv4/IPv6 coexistence mechanisms, guide you in planning,
and present validated configuration examples for building labs, pilots,
and production networks.
The authors first review
some of the drivers behind the acceleration of IPv6 deployment in the
enterprise. Next, they introduce powerful new IPv6 services for routing,
QoS, multicast, and management, comparing them with familiar IPv4
features and behavior. Finally, they translate IPv6 concepts into usable
configurations. Up-to-date and practical, IPv6 for Enterprise Networks
is an indispensable resource for every network engineer, architect,
manager, and consultant who must evaluate, plan, migrate to, or manage
IPv6 networks.
Shannon
McFarland, CCIE No. 5245, is a Corporate Consulting Engineer for Cisco
serving as a technical consultant for enterprise IPv6 deployment and
data center design with a focus on application deployment and virtual
desktop infrastructure. For more than 16 years, he has worked on
large-scale enterprise campus, WAN/branch, and data center network
design and optimization. For more than a decade, he has spoken at IPv6
events worldwide, including Cisco Live.
n Identify how IPv6 affects enterprises
n Understand IPv6 services and the IPv6 features that make them possible
n
Review the most common tranisition mechanisms including dual-stack
(IPv4/IPv6) networks, IPv6 over IPv4 tunnels, and IPv6 over MPLS
n Create IPv6 network designs that reflect proven principles of modularity, hierarchy, and resiliency
n Select the best implementation options for your organization
n Build IPv6 lab environments
n Configure IPv6 step-by-step in campus, WAN/branch, and data center networks
n Integrate production-quality IPv6 services into IPv4 networks
n Implement virtualized IPv6 networks
n Deploy IPv6 for remote access
n Manage IPv6 networks efficiently and cost-effectively
This
book is part of the Networking Technology Series from Cisco Press®,
which offers networking professionals valuable information for
constructing efficient networks, understanding new technologies, and
building successful careers.
I think everyone was thought about IPv4 and IPv6 but on internet are tones of articles about IPv6 and IPv4 and you should read more to understand this concept.
In this tutorial I will try to explain what is with IPv6 in few words.
How does IPv6 looks like?
First you should know that ipv6 is different from ipv4.
IPv4 Example: 81.21.211.234
IPv6 Example: 2001:0db8:85a3:0042:1000:8a2e:0370:7334
Does I have IPv6?
Well, the correctly question is: I’m connected to internet via IPv4 or IPv6?
Your IP is allocated by your internet provide, so they can give you an IPv4 or IPv6. To check what kind of IP you are connected through you can go here: Check IP Address – IPv4 or IPv6
Why IPv6?
Because the IPv4 have 32bits of address and can provide maximum 4.3
billion addresses. So in the whole world this number of addresses has
reached/will soon reached and we need more IP Addresses.
IPv6 have 128 bits and support approximately 2128 addresses.
Conclusion
You know a little but more about your connection and about your IP Addresses.
If you want more you should go to Wikipedia and read more documentation.
When a host is connected to one link or network, it acquires an IP
address and all communication happens using that IP address on that
link. As soon as, the same host changes its physical location, that is,
moves into some different area / subnet / network / link, its IP
address changes accordingly and all communication happening on the host
using old IP address, goes down.
IPv6 mobility provides a mechanism which equips a host with an
ability to roam around among different links without losing any
communication/connection and its IP address.
Multiple entities are involved in this technology:
Mobile Node: The device which needs IPv6 mobility.
Home Link: This link is configured with the home subnet prefix and this is where the Mobile IPv6 device gets its Home Address.
Home Address: This is the address which Mobile Node
acquires from Home Link. This is permanent address of Mobile Node. If
the Mobile Node remains in the same Home Link, the communication among
various entities happens as usual.
Home Agent: This is a router which acts as registrar for
Mobile Nodes. Home Agent is connected to Home Link and maintains
information about all Mobile Nodes, their Home Addresses and their
present IP addresses.
Foreign Link: Any other Link which is not Mobile Node’s Home Link.
Care-of Address: When a Mobile Node attaches to a Foreign
Link, it acquires a new IP address of that Foreign Link’s subnet. Home
Agent maintains the information of both Home Address and Care-of
Address. Multiple Care-of addresses can be assigned to Mobile Node, but
at any instance only one Care-of Address has binding with Home Address.
Correspondent Node: Any IPv6 enable device which intends to have communication with Mobile Node.
Mobility Operation
When Mobile Node stays in its Home Link, all communications happen on its Home Address. As shown below: [Image: Mobile Node connected to Home Link]When Mobile Node leaves its Home Link and is connected to some
Foreign Link, the Mobility feature of IPv6 comes into play. After
connecting to Foreign Link, Mobile Node acquires an IPv6 address from
Foreign Link. This address is called Care-of Address. Mobile Node
sends binding request to its Home Agent with the new Care-of Address.
Home Agent binds Mobile Node’s Home Address with Care-of Address,
establishing a Tunnel between both.
Whenever a Correspondent Node tries to establish connection with
Mobile Node (on its Home Address), the Home Agent intercepts the packet
and forwards to Mobile Node’s Care-of Address over the Tunnel which was
already established. [Image: Mobile Node connected to Foreign Link]
Route Optimization
When a Correspondent Node initiate communication by sending packets
to Mobile Node on Home Address, these packets are tunneled to Mobile
Node by Home Agent. In Route Optimization mode, when the Mobile Node
receives packet from Correspondent Node, it does not forward replies to
Home Agent. Rather it sends its packet directly to Correspondent Node
using Home Address as Source Address. This mode is optional and not
used by default. http://ipv4-ipv6.blogspot.com/2014/07/when-host-is-connected-to-one-link-or.html
In IPv4, addresses were created in classes. Classful IPv4 addresses
clearly defines the bits used for network prefixes and the bits used for
hosts on that network. To subnet in IPv4 we play with the default
classful netmask which allows us to borrow hosts bit to be used as
subnet bits. This results in multiple subnets but less hosts per
subnet. That is, when we borrow host bit to create a subnet that costs
us in lesser bit to be used for host addresses.
IPv6 addresses uses 128 bits to represent an address which includes
bits to be used for subnetting. Second half of the address (least
significant 64 bits) is always used for Hosts only. Therefore, there is
no compromise if we subnet the network. [Image: IPv6 Subnetting]16 Bits of subnet is equivalent to IPv4’s Class B Network. Using
these subnet bits an organization can have more 65 thousands of subnets
which is by far, more than enough.
Thus routing prefix is /64 and host portion is 64 bits. We though,
can further subnet the network beyond 16 bits of Subnet ID, borrowing
hosts bit but it is recommended that 64 bits should always be used for
hosts addresses because auto-configuration requires 64 bits.
IPv6 subnetting works on the same concept as Variable Length Subnet Masking in IPv4.
/48 prefix can be allocated to an organization providing it the
benefit of having up to /64 subnet prefixes, which is 65535
sub-networks, each having 264 hosts. A /64 prefix can be assigned to a
point-to-point connection where there are only two hosts (or IPv6
enabled devices) on a link.
IPv4 since 1982, has been an undisputed leader of Internet. With
IPv4’s address space exhaustion IPv6 is now taking over the control of
Internet, which is called Internet2.
IPv4 is widely deployed and migration to IPv6 would not be easy. So
far IPv6 could penetrate IPv4’s address space by less than 1%.
The world has celebrated ‘World IPv6 Day’ on June 08, 2011 with a
purpose to test IPv6 address over Internet in full. On June 06, 2012
the Internet community officially launched IPv6. This day all ISPs who
were offering IPv6 were to enable it on public domain and were to keep
it enable. All the device manufacturer also participated to offer IPv6
by-default enabled on devices.
This was a step towards encouraging Internet community to migrate to IPv6.
Organizations are provided plenty of ways to migrate from IPv4 to
IPv6. Also organization, willing to test IPv6 before migrating
completely can run both IPv4 and IPv6 simultaneously. Networks of
different IP versions can communicate and user data can be tunneled to
walk to the other side.
Future of IPv6
IPv6 enabled Internet version 2 will replace todays IPv4 enabled
Internet. When Internet was launched with IPv4, developed countries
like US and Europe took the larger space of IPv4 for deployment of
Internet in their respective countries keeping future need in mind. But
Internet exploded everywhere reaching and connecting every country of
the world increasing the requirement of IPv4 address space. As a
result, till this day US and Europe have many IPv4 address space left
with them and countries like India and China are bound to address their
IP space requirement by means of deployment of IPv6.
Most of the IPv6 deployment is being done outside US, Europe. India
and China are moving forward to change their entire space to IPv6.
China has announced a five year deployment plan named China Next
Generation Internet.
After June 06, 2012 all major ISPs were shifted to IPv6 and rest of them are still moving.
IPv6 provides ample of address space and is designed to expand
today’s Internet services. Feature-rich IPv6 enabled Internet version 2
may deliver more than expected.
Routing concepts remain same in case of IPv6 but almost all routing
protocol have been redefined accordingly. We have seen in Communication
in IPv6 segment, how a host speaks to its gateway. Routing is a
process to forward routable data choosing best route among several
available routes or path to the destination. A router is a device which
forwards data which is not explicitly destined to it.
There exists two forms of routing protocols
Distance Vector Routing Protocol: A
router running distance vector protocol advertises its connected routes
and learns new routes from its neighbors. The routing cost to reach a
destination is calculated by means of hops between the source and
destination. A Router generally relies on its neighbor for best path
selection, also known as “routing-by-rumors”. RIP and BGP are Distance
Vector Protocols.
Link-State Routing Protocol: This protocol acknowledges
the state of a Link and advertises to its neighbors. Information about
new links is learnt from peer routers. After all the routing
information has been converged, Link-State Routing Protocol uses its own
algorithm to calculate best path to all available links. OSPF and
IS-IS are link state routing protocols and both uses Djikstra’s Shortest
Path First algorithm.
Routing protocols can be divided in two categories:
Interior Routing Protocol: Protocols in
this categories are used within an Autonomous System or organization to
distribute routes among all routers inside its boundary. Examples: RIP,
OSPF.
Exterior Routing Protocol: Whereas an Exterior Routing
Protocol distributes routing information between two different
Autonomous Systems or organization. Examples: BGP.
Routing protocols
RIPng
RIPng stands for Routing Information Protocol Next Generation. This
is an Interior Routing Protocol and is a Distance Vector Protocol.
RIPng has been upgraded to support IPv6.
OSPFv3
Open Shortest Path First version 3 is an Interior Routing Protocol
which is modified to support IPv6. This is a Link-State Protocol and
uses Djikrasta’s Shortest Path First algorithm to calculate best path to
all destinations.
BGPv4
BGP stands for Border Gateway Protocol. It is the only open standard
Exterior Gateway Protocol available. BGP is a Distance Vector protocol
which takes Autonomous System as calculation metric, instead of number
of routers as Hop. BGPv4 is an upgrade of BGP to support IPv6 routing.
Protocols changed to support IPv6:
ICMPv6: Internet Control Message Protocol
version 6 is an upgraded implementation of ICMP to accommodate IPv6
requirements. This protocol is used for diagnostic functions, error and
information message, statistical purposes. ICMPv6’s Neighbor Discovery
Protocol replaces ARP and helps discover neighbor and routers on the
link.
DHCPv6: Dynamic Host Configuration Protocol version 6 is
an implementation of DHCP. Though IPv6 enabled hosts do not require any
DHCPv6 Server to acquire IP address as they can be auto-configured.
Neither do they need DHCPv6 to locate DNS server because DNS can be
discovered and configured via ICMPv6 Neighbor Discovery Protocol. Yet
DHCPv6 Server can be used to provide these information.
DNS: There has been no new version of DNS but it is now
equipped with extensions to provide support for querying IPv6 addresses.
A new AAAA (quad-A) record has been added to reply IPv6 query
messages. Now DNS can reply with both IP versions (4 & 6) without
any change in query format.
Before introducing IPv6 Address format, 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. [Image: Conversion Table]
Address Structure
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.
For example, the below is 128 bit IPv6 address represented in binary format and divided into eight 16-bits blocks:
Each block is then converted into Hexadecimal and separated by ‘:’ symbol:
2001:0000:3238:DFE1:0063:0000:0000:FEFB
Even after converting into Hexadecimal format, IPv6 address remains
long. IPv6 provides some rules to shorten the address. These rules
are: Rule:1 Discard leading Zero(es):
In Block 5, 0063, the leading two 0s can be omitted, such as (5th block):
2001:0000:3238:DFE1:63:0000:0000:FEFB
Rule:2 If two of more blocks contains consecutive zeroes, omit
them all and replace with double colon sign ::, such as (6th and 7th
block):
2001:0000:3238:DFE1:63::FEFB
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):
2001:0:3238:DFE1:63::FEFB
Interface ID
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. [Image: EUI-64 Interface ID]Conversion of EUI-64 ID into IPv6 Interface Identifier
To convert EUI-64 ID into IPv6 Interface Identifier, the most significant 7th bit of EUI-64 ID is complemented. For example: [Image: IPV6 Interface ID]
Global Unicast Address
This address type is equivalent to IPv4’s public address. Global
Unicast addresses in IPv6 are globally identifiable and uniquely
addressable. [Image: Global Unicast Address]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.
Link-Local Address
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: [Image: Link-Local Address]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.
Unique-Local Address
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. [Image: Unique-Local Address]
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’.
Scope of IPv6 Unicast Addresses:
[Image: IPv6 Unicast Address Scope]
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.
In computer networking, 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.
Unicast
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. [Image: Unicast Messaging]
Multicast
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. [Image: Multicast Messaging]
Anycast
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. [Image: Anycast Messaging]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.
In the above picture, When a client computer tries to reach a Server,
the request is forwarded to the Server with lowest Routing Cost.
The wonder of IPv6 lies in its header. IPv6 address is 4 times
larger than IPv4 but the IPv6 header is only 2 times larger than that of
IPv4. IPv6 headers have one Fixed Header and zero or more Optional
(Extension) Headers. All necessary information which is essential for a
router is kept in Fixed Header. Extension Header contains optional
information which helps routers to understand how to handle a
packet/flow.
[Image: IPv6 Fixed Header]IPv6 fixed header is 40 bytes long and contains the following information.
S.N.
Field & Description
1
Version (4-bits): This represents the version of Internet Protocol, i.e. 0110.
2
Traffic Class (8-bits): These 8 bits are
divided into two parts. Most significant 6 bits are used for Type of
Service, which tells the Router what services should be provided to this
packet. Least significant 2 bits are used for Explicit Congestion
Notification (ECN).
3
Flow Label (20-bits): This label is used to
maintain the sequential flow of the packets belonging to a
communication. The source labels the sequence which helps the router to
identify that this packet belongs to a specific flow of information.
This field helps to avoid re-ordering of data packets. It is designed
for streaming/real-time media.
4
Payload Length (16-bits): This field is used
to tell the routers how much information this packet contains in its
payload. Payload is composed of Extension Headers and Upper Layer data.
With 16 bits, up to 65535 bytes can be indicated but if Extension
Headers contain Hop-by-Hop Extension Header than payload may exceed
65535 bytes and this field is set to 0.
5
Next Header (8-bits): This field is used to
indicate either the type of Extension Header, or if Extension Header is
not present then it indicates the Upper Layer PDU. The values for the
type of Upper Layer PDU is same as IPv4’s.
6
Hop Limit (8-bits): This field is used to
stop packet to loop in the network infinitely. This is same as TTL in
IPv4. The value of Hop Limit field is decremented by 1 as it passes a
link (router/hop). When the field reaches 0 the packet is discarded.
7
Source Address (128-bits): This field indicates the address of originator of the packet.
8
Destination Address (128-bits): This field provides the address of intended recipient of the packet.
Extension Headers
In IPv6, the Fixed Header contains only information which is
necessary and avoiding information which is either not required or is
rarely used. All such information, is put between the Fixed Header and
Upper layer header in the form of Extension Headers. Each Extension
Header is identified by a distinct value.
When Extension Headers are used, IPv6 Fixed Header’s Next Header
field points to the first Extension Header. If there is one more
Extension Header, then first Extension Header’s ‘Next-Header’ field
point to the second one, and so on. The last Extension Header’s
‘Next-Header’ field point to Upper Layer Header. Thus all headers from
point to the next one in a linked list manner.
If the Next Header field contains value 59, it indicates that there’s no header after this header, not even Upper Layer Header.
The following Extension Headers must be supported as per RFC 2460:
The sequence of Extension Headers should be:
These headers:
1. Should be processed by First and subsequent destinations.
2. Should be processed by Final Destination.
Extension Headers are arranged one after another in a Linked list manner, as depicted in the diagram below:
Internet Protocol version 6, is a new addressing protocol designed to
incorporate whole sort of requirement of future internet known to us as
Internet version 2. This protocol as its predecessor IPv4, works on
Network Layer (Layer-3). Along with its offering of enormous amount of
logical address space, this protocol has ample of features which
addresses today’s shortcoming of IPv4.
Why new IP version?
So far, IPv4 has proven itself as a robust routable addressing
protocol and has served human being for decades on its
best-effort-delivery mechanism. It was designed in early 80’s and did
not get any major change afterward. At the time of its birth, Internet
was limited only to a few Universities for their research and to
Department of Defense. IPv4 is 32 bits long which offers around
4,294,967,296 (232) addresses. This address space was
considered more than enough that time. Given below are major points
which played key role in birth of IPv6:
Internet has grown exponentially and the address space allowed by
IPv4 is saturating. There is a requirement of protocol which can
satisfy the need of future Internet addresses which are expected to grow
in an unexpected manner.
Using features such as NAT, has made the Internet discontiguous
i.e. one part which belongs to intranet, primarily uses private IP
addresses; which has to go through number of mechanism to reach the
other part, the Internet, which is on public IP addresses.
IPv4 on its own does not provide any security feature which is
vulnerable as data on Internet, which is a public domain, is never safe.
Data has to be encrypted with some other security application before
being sent on Internet.
Data prioritization in IPv4 is not up to date. Though IPv4 has
few bits reserved for Type of Service or Quality of Service, but they do
not provide much functionality.
IPv4 enabled clients can be configured manually or they need some
address configuration mechanism. There exists no technique which can
configure a device to have globally unique IP address.
Why not IPv5?
Till date, Internet Protocol has been recognized has IPv4 only.
Version 0 to 3 were used while the protocol was itself under development
and experimental process. So, we can assume lots of background
activities remain active before putting a protocol into production.
Similarly, protocol version 5 was used while experimenting with stream
protocol for internet. It is known to us as Internet Stream Protocol
which used Internet Protocol number 5 to encapsulate its datagram.
Though it was never brought into public use, but it was already used.
Here is a table of IP version and their use:
Brief History
After IPv4’s development in early 80s, the available IPv4 address
pool begun to shrink rapidly as the demand of addresses exponentially
increased with Internet. Taking pre-cognizance of situation that might
arise IETF, in 1994, initiated the development of an addressing protocol
to replace IPv4. The progress of IPv6 can be tracked by means of RFC
published:
1998 – RFC 2460 – Basic Protocol
2003 – RFC 2553 – Basic Socket API
2003 – RFC 3315 – DHCPv6
2004 – RFC 3775 – Mobile IPv6
2004 – RFC 3697 – Flow Label Specification
2006 – RFC 4291 – Address architecture (revision)
2006 – RFC 4294 – Node requirement
June 06, 2012 some of Internet giants chose to put their Servers on
IPv6. Presently they are using Dual Stack mechanism to implement IPv6
parallel with IPv4.
Features
The successor of IPv4 is not designed to be backward compatible.
Trying to keep the basic functionalities of IP addressing, IPv6 is
redesigned entirely. It offers the following features:
Larger Address Space:
In contrast to IPv4, IPv6 uses 4 times more bits to address a device on
the Internet. This much of extra bits can provide approximately
3.4×1038 different combinations of addresses. This address can
accumulate the aggressive requirement of address allotment for almost
everything in this world. According to an estimate, 1564 addresses can
be allocated to every square meter of this earth.
Simplified Header:
IPv6’s header has been simplified by moving all unnecessary information
and options (which are present in IPv4 header) to the end of the IPv6
header. IPv6 header is only twice as bigger than IPv4 providing the
fact the IPv6 address is four times longer.
End-to-end Connectivity:
Every system now has unique IP address and can traverse through the
internet without using NAT or other translating components. After IPv6
is fully implemented, every host can directly reach other host on the
Internet, with some limitations involved like Firewall, Organization’s
policies, etc.
Auto-configuration:
IPv6 supports both stateful and stateless auto configuration mode of its
host devices. This way absence of a DHCP server does not put halt on
inter segment communication.
Faster Forwarding/Routing:
Simplified header puts all unnecessary information at the end of the
header. All information in first part of the header are adequate for a
Router to take routing decision thus making routing decision as quickly
as looking at the mandatory header.
IPSec:
Initially it was decided for IPv6 to must have IPSec security, making it
more secure than IPv4. This feature has now been made optional.
No Broadcast:
Though Ethernet/Token Ring are considered as broadcast network because
they support Broadcasting, IPv6 does not have any Broadcast support
anymore left with it. It uses multicast to communicate with multiple
hosts.
Anycast Support:
This is another characteristic of IPv6. IPv6 has introduced Anycast
mode of packet routing. In this mode, multiple interfaces over the
Internet are assigned same Anycast IP address. Routers, while routing,
sends the packet to the nearest destination.
Mobility:
IPv6 was designed keeping mobility feature in mind. This feature
enables hosts (such as mobile phone) to roam around in different
geographical area and remain connected with same IP address. IPv6
mobility feature takes advantage of auto IP configuration and Extension
headers.
Enhanced Priority support:
Where IPv4 used 6 bits DSCP (Differential Service Code Point) and 2 bits
ECN (Explicit Congestion Notification) to provide Quality of Service
but it could only be used if the end-to-end devices support it, that is,
the source and destination device and underlying network must support
it.
In IPv6, Traffic class and Flow label are used to tell underlying routers how to efficiently process the packet and route it.
Smooth Transition:
Large IP address scheme in IPv6 enables to allocate devices with
globally unique IP addresses. This assures that mechanism to save IP
addresses such as NAT is not required. So devices can send/receive data
between each other, for example VoIP and/or any streaming media can be
used much efficiently.
Other fact is, the header is less loaded so routers can make forwarding decision and forward them as quickly as they arrive.
Extensibility:
One of the major advantage of IPv6 header is that it is extensible to
add more information in the option part. IPv4 provides only 40-bytes
for options whereas options in IPv6 can be as much as the size of IPv6
packet itself.
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 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.
Unicast
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. [Image: Unicast Messaging]
Multicast
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. [Image: Multicast Messaging]
Anycast
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. [Image: Anycast Messaging]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.
In the above picture, When a client computer tries to reach a Server,
the request is forwarded to the Server with lowest Routing Cost.
Address Types
Hexadecimal Number System
Before introducing IPv6 Address format, 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. [Image: Conversion Table]
Address Structure
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.
For example, the below is 128 bit IPv6 address represented in binary format and divided into eight 16-bits blocks:
Each block is then converted into Hexadecimal and separated by ‘:’ symbol:
2001:0000:3238:DFE1:0063:0000:0000:FEFB
Even after converting into Hexadecimal format, IPv6 address remains
long. IPv6 provides some rules to shorten the address. These rules
are: Rule:1 Discard leading Zero(es):
In Block 5, 0063, the leading two 0s can be omitted, such as (5th block):
2001:0000:3238:DFE1:63:0000:0000:FEFB
Rule:2 If two of more blocks contains consecutive zeroes, omit
them all and replace with double colon sign ::, such as (6th and 7th
block):
2001:0000:3238:DFE1:63::FEFB
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):
2001:0:3238:DFE1:63::FEFB
Interface ID
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 64-bit
Interface ID. [Image: EUI-64 Interface ID]
Global Unicast Address
This address type is equivalent to IPv4’s public address. Global
Unicast addresses in IPv6 are globally identifiable and uniquely
addressable. [Image: Global Unicast Address]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.
Link-Local Address
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: [Image: Link-Local Address]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.
Unique-Local Address
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. [Image: Unique-Local Address]
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’.
Scope of IPv6 Unicast Addresses:
[Image: IPv6 Unicast Address Scope]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.
Special Addresses
Version 6 has slightly complex structure of IP address than that of
IPv4. IPv6 has reserved few addresses and address notations for special
purposes. See the table below:
Special Addresses:
As shown in the table above 0:0:0:0:0:0:0:0/128 address does not
specify to anything and is said to be an unspecified address. After
simplifying, all 0s are compacted to ::/128.
In IPv4, address 0.0.0.0 with netmask 0.0.0.0 represents default
route. The same concept is also applie to IPv6, address 0:0:0:0:0:0:0:0
with netmask all 0s represents default route. After applying IPv6
simplying rule this address is compressed to ::/0.
Loopback addresses in IPv4 are represented by 127.0.0.1 to
127.255.255.255 series. But in IPv6, only 0:0:0:0:0:0:0:1/128 address
represents Loopback address. After simplying loopback address, it can
be represented as ::1/128.
Reserved Multicast Address for Routing Protocols:
The above table shows reserved multicast addresses used by interior routing protocol.
All addresses are reserved in similar IPv4 fashion
Reserved Multicast Address for Routers/Node:
These addresses helps routers and hosts to speak to available
routers and hosts on a segment without being configured with an IPv6
address. Hosts use EUI-64 based auto-configuration to self-configure an
IPv6 address and then speaks to available hosts/routers on the segment
by means of these addresses.
Headers
The wonder of IPv6 lies in its header. IPv6 address is 4 times
larger than IPv4 but the IPv6 header is only 2 times larger than that of
IPv4. IPv6 headers have one Fixed Header and zero or more Optional
(Extension) Headers. All necessary information which is essential for a
router is kept in Fixed Header. Extension Header contains optional
information which helps routers to understand how to handle a
packet/flow.
Fixed Header
[Image: IPv6 Fixed Header]IPv6 fixed header is 40 bytes long and contains the following information.
S.N.
Field & Description
1
Version (4-bits): This represents the version of Internet Protocol, i.e. 0110.
2
Traffic Class (8-bits): These 8 bits are
divided into two parts. Most significant 6 bits are used for Type of
Service, which tells the Router what services should be provided to this
packet. Least significant 2 bits are used for Explicit Congestion
Notification (ECN).
3
Flow Label (20-bits): This label is used to
maintain the sequential flow of the packets belonging to a
communication. The source labels the sequence which helps the router to
identify that this packet belongs to a specific flow of information.
This field helps to avoid re-ordering of data packets. It is designed
for streaming/real-time media.
4
Payload Length (16-bits): This field is used
to tell the routers how much information this packet contains in its
payload. Payload is composed of Extension Headers and Upper Layer data.
With 16 bits, up to 65535 bytes can be indicated but if Extension
Headers contain Hop-by-Hop Extension Header than payload may exceed
65535 bytes and this field is set to 0.
5
Next Header (8-bits): This field is used to
indicate either the type of Extension Header, or if Extension Header is
not present then it indicates the Upper Layer PDU. The values for the
type of Upper Layer PDU is same as IPv4’s.
6
Hop Limit (8-bits): This field is used to
stop packet to loop in the network infinitely. This is same as TTL in
IPv4. The value of Hop Limit field is decremented by 1 as it passes a
link (router/hop). When the field reaches 0 the packet is discarded.
7
Source Address (128-bits): This field indicates the address of originator of the packet.
8
Destination Address (128-bits): This field provides the address of intended recipient of the packet.
Extension Headers
In IPv6, the Fixed Header contains only information which is
necessary and avoiding information which is either not required or is
rarely used. All such information, is put between the Fixed Header and
Upper layer header in the form of Extension Headers. Each Extension
Header is identified by a distinct value.
When Extension Headers are used, IPv6 Fixed Header’s Next Header
field points to the first Extension Header. If there is one more
Extension Header, then first Extension Header’s ‘Next-Header’ field
point to the second one, and so on. The last Extension Header’s
‘Next-Header’ field point to Upper Layer Header. Thus all headers from
point to the next one in a linked list manner.
If the Next Header field contains value 59, it indicates that there’s no header after this header, not even Upper Layer Header.
The following Extension Headers must be supported as per RFC 2460:
The sequence of Extension Headers should be:
These headers:
1. Should be processed by First and subsequent destinations.
2. Should be processed by Final Destination.
Extension Headers are arranged one after another in a Linked list manner, as depicted in the diagram below: [Image: Extension Headers Connected Format]
Communication
In IPv4, a host which wants to communicate with some other host on
the network, needs first to have an IP address acquired either by means
of DHCP or by manual configuration. As soon as a host is equipped with
some valid IP address, it is now able to speak to any host on the
subnet. To communicate on layer-3, a host also must know the IP address
of the other host. Communication on a link, is established by means of
hardware embedded MAC Addresses. To know the MAC address of host whose
IP address is known, a host sends ARP broadcast and in revert the
intended host sends back its MAC address.
In IPv6, there’s no broadcast mechanism. It is not a must for an
IPv6 enabled host to obtain IP address from DHCP or manually configured,
but it can auto-configure its own IP. Then, how would a host
communicates with others on IPv6 enabled network?
ARP has been replaced by ICMPv6 Neighbor Discovery Protocol.
Neighbor Discovery Protocol
A host in IPv6 network is capable of auto-configuring itself with a
unique link-local address. As soon as it is equipped with an IPv6
address, it joins a number of multicast groups. All communications
related to that segment happens on those multicast addresses only. A
host goes through a series of states in IPv6:
Neighbor Solicitation: After configuring all IPv6’s either
manually, or by DHCP Server or by auto-configuration, the host sends a
Neighbor Solicitation message out to FF02::1/16 multicast address for
all its IPv6 addresses in order to know that no one else occupies same
addresses.
DAD (Duplicate Address Detection): When the host does not
listen from anything from the segment regarding its Neighbor
Solicitation message, it assumes that no duplicate address exists on the
segment.
Neighbor Advertisement: After assigning the addresses to
its interfaces and making them up and running, the host once again sends
out a Neighbor Advertisement message telling all other hosts on the
segment, that it has assigned those IPv6 addresses to its interfaces.
Once a host is done with the configuration of its IPv6 addresses, it does the following things:
Router Solicitation: A host sends a Router Solicitation
multicast packet (FF02::2/16) out on its segment to know the presence of
any router on this segment. This helps the host to configure the
router as its default gateway. If its default gateway router goes down,
the host can shift to a new router and makes it the default gateway.
Router Advertisement: When a router receives a Router Solicitation message, it responses back to the host advertising its presence on that link.
Redirect: This may be the situation where a Router
receives a Router Solicitation request but it knows that it is not the
best gateway for the host. In this situation, the router sends back a
Redirect message telling the host that there is a better ‘next-hop’
router available. Next-hop is where the host will send its data
destined to a host which does not belong to the same segment.
Subnetting
In IPv4, addresses were created in classes. Classful IPv4 addresses
clearly defines the bits used for network prefixes and the bits used for
hosts on that network. To subnet in IPv4 we play with the default
classful netmask which allows us to borrow hosts bit to be used as
subnet bits. This results in multiple subnets but less hosts per
subnet. That is, when we borrow host bit to create a subnet that costs
us in lesser bit to be used for host addresses.
IPv6 addresses uses 128 bits to represent an address which includes
bits to be used for subnetting. Second half of the address (least
significant 64 bits) is always used for Hosts only. Therefore, there is
no compromise if we subnet the network. [Image: IPv6 Subnetting]16 Bits of subnet is equivalent to IPv4’s Class B Network. Using
these subnet bits an organization can have more 65 thousands of subnets
which is by far, more than enough.
Thus routing prefix is /64 and host portion is 64 bits. We though,
can further subnet the network beyond 16 bits of Subnet ID, borrowing
hosts bit but it is recommended that 64 bits should always be used for
hosts addresses because auto-configuration requires 64 bits.
IPv6 subnetting works on the same concept as Variable Length Subnet Masking in IPv4.
/48 prefix can be allocated to an organization providing it the
benefit of having up to /64 subnet prefixes, which is 65535
sub-networks, each having 264 hosts. A /64 prefix can be assigned to a
point-to-point connection where there are only two hosts (or IPv6
enabled devices) on a link.
IPv4 to IPv6
One problem in transition from IPv4 to IPv6 completely is that IPv6
is not backward compatible. This results in a situation where either a
site is on IPv6 or it is not. Unlike an implementation of new
technology where the newer one is backward compatible so the older
system can still work with the newer without any additional changes.
To overcome this short-coming, there exist few technologies which can be used in slow and smooth transition from IPv4 to IPv6:
Dual Stack Routers
A router can be installed with both IPv4 and IPv6 addresses
configured on its interfaces pointing to the network of relevant IP
scheme. [Image: Dual Stack Router]In above diagram, a Server which is having IPv4 as well as IPv6
address configured for it now can speak with all hosts on IPv4 network
and IPv6 network with help of Dual Stack Router. Dual Stack Router, can
communicate with both networks and provides a medium for hosts to
access Server without changing their respective IP version.
Tunneling
In a scenario where different IP versions exist on intermediate path
or transit network, tunneling provides a better solution where user’s
data can pass through a non-supported IP version. [Image: Tunneling]The above diagram depicts how two remote IPv4 networks can
communicate via Tunnel, where the transit network was on IPv6. Vice
versa is also possible where transit network is on IPv6 and remote sites
which intends to communicate, are on IPv4.
NAT Protocol Translation
This is another important method of transition to IPv6 by means of a
NAT-PT (Network Address Translation – Protocol Translation) enabled
device. With help of NAT-PT device, actual conversion happens between
IPv4 and IPv6 packets and vice versa. See the diagram below: [Image: NAT - Protocol Translation]A host with IPv4 address sends a request to IPv6 enabled Server on
Internet which does not understand IPv4 address. In this scenario,
NAT-PT device can help them communicate. When IPv4 host sends a request
packet to IPv6 Server, NAT-PT device/router, strips down the IPv4
packet, removes IPv4 header and adds IPv6 header and passes it through
the Internet. When a response from IPv6 Server comes for IPv4 host, the
router does vice versa.
Mobility
When a host is connected to one link or network, it acquires an IP
address and all communication happens using that IP address on that
link. As soon as, the same host changes its physical location, that is,
moves into some different area / subnet / network / link, its IP
address changes accordingly and all communication happening on the host
using old IP address, goes down.
IPv6 mobility provides a mechanism which equips a host with an
ability to roam around among different links without losing any
communication/connection and its IP address.
Multiple entities are involved in this technology:
Mobile Node: The device which needs IPv6 mobility.
Home Link: This link is configured with the home subnet prefix and this is where the Mobile IPv6 device gets its Home Address.
Home Address: This is the address which Mobile Node
acquires from Home Link. This is permanent address of Mobile Node. If
the Mobile Node remains in the same Home Link, the communication among
various entities happens as usual.
Home Agent: This is a router which acts as registrar for
Mobile Nodes. Home Agent is connected to Home Link and maintains
information about all Mobile Nodes, their Home Addresses and their
present IP addresses.
Foreign Link: Any other Link which is not Mobile Node’s Home Link.
Care-of Address: When a Mobile Node attaches to a Foreign
Link, it acquires a new IP address of that Foreign Link’s subnet. Home
Agent maintains the information of both Home Address and Care-of
Address. Multiple Care-of addresses can be assigned to Mobile Node, but
at any instance only one Care-of Address has binding with Home Address.
Correspondent Node: Any IPv6 enable device which intends to have communication with Mobile Node.
Mobility Operation
When Mobile Node stays in its Home Link, all communications happen on its Home Address. As shown below: [Image: Mobile Node connected to Home Link]When Mobile Node leaves its Home Link and is connected to some
Foreign Link, the Mobility feature of IPv6 comes into play. After
connecting to Foreign Link, Mobile Node acquires an IPv6 address from
Foreign Link. This address is called Care-of Address. Mobile Node
sends binding request to its Home Agent with the new Care-of Address.
Home Agent binds Mobile Node’s Home Address with Care-of Address,
establishing a Tunnel between both.
Whenever a Correspondent Node tries to establish connection with
Mobile Node (on its Home Address), the Home Agent intercepts the packet
and forwards to Mobile Node’s Care-of Address over the Tunnel which was
already established. [Image: Mobile Node connected to Foreign Link]
Route Optimization
When a Correspondent Node initiate communication by sending packets
to Mobile Node on Home Address, these packets are tunneled to Mobile
Node by Home Agent. In Route Optimization mode, when the Mobile Node
receives packet from Correspondent Node, it does not forward replies to
Home Agent. Rather it sends its packet directly to Correspondent Node
using Home Address as Source Address. This mode is optional and not
used by default.
Routing
Routing concepts remain same in case of IPv6 but almost all routing
protocol have been redefined accordingly. We have seen in Communication
in IPv6 segment, how a host speaks to its gateway. Routing is a
process to forward routable data choosing best route among several
available routes or path to the destination. A router is a device which
forwards data which is not explicitly destined to it.
There exists two forms of routing protocols
Distance Vector Routing Protocol: A
router running distance vector protocol advertises its connected routes
and learns new routes from its neighbors. The routing cost to reach a
destination is calculated by means of hops between the source and
destination. A Router generally relies on its neighbor for best path
selection, also known as “routing-by-rumors”. RIP and BGP are Distance
Vector Protocols.
Link-State Routing Protocol: This protocol acknowledges
the state of a Link and advertises to its neighbors. Information about
new links is learnt from peer routers. After all the routing
information has been converged, Link-State Routing Protocol uses its own
algorithm to calculate best path to all available links. OSPF and
IS-IS are link state routing protocols and both uses Djikstra’s Shortest
Path First algorithm.
Routing protocols can be divided in two categories:
Interior Routing Protocol: Protocols in
this categories are used within an Autonomous System or organization to
distribute routes among all routers inside its boundary. Examples: RIP,
OSPF.
Exterior Routing Protocol: Whereas an Exterior Routing
Protocol distributes routing information between two different
Autonomous Systems or organization. Examples: BGP.
Routing protocols
RIPng
RIPng stands for Routing Information Protocol Next Generation. This
is an Interior Routing Protocol and is a Distance Vector Protocol.
RIPng has been upgraded to support IPv6.
OSPFv3
Open Shortest Path First version 3 is an Interior Routing Protocol
which is modified to support IPv6. This is a Link-State Protocol and
uses Djikrasta’s Shortest Path First algorithm to calculate best path to
all destinations.
BGPv4
BGP stands for Border Gateway Protocol. It is the only open standard
Exterior Gateway Protocol available. BGP is a Distance Vector protocol
which takes Autonomous System as calculation metric, instead of number
of routers as Hop. BGPv4 is an upgrade of BGP to support IPv6 routing.
Protocols changed to support IPv6:
ICMPv6: Internet Control Message Protocol
version 6 is an upgraded implementation of ICMP to accommodate IPv6
requirements. This protocol is used for diagnostic functions, error and
information message, statistical purposes. ICMPv6’s Neighbor Discovery
Protocol replaces ARP and helps discover neighbor and routers on the
link.
DHCPv6: Dynamic Host Configuration Protocol version 6 is
an implementation of DHCP. Though IPv6 enabled hosts do not require any
DHCPv6 Server to acquire IP address as they can be auto-configured.
Neither do they need DHCPv6 to locate DNS server because DNS can be
discovered and configured via ICMPv6 Neighbor Discovery Protocol. Yet
DHCPv6 Server can be used to provide these information.
DNS: There has been no new version of DNS but it is now
equipped with extensions to provide support for querying IPv6 addresses.
A new AAAA (quad-A) record has been added to reply IPv6 query
messages. Now DNS can reply with both IP versions (4 & 6) without
any change in query format.
Summary
IPv4 since 1982, has been an undisputed leader of Internet. With
IPv4’s address space exhaustion IPv6 is now taking over the control of
Internet, which is called Internet2.
IPv4 is widely deployed and migration to IPv6 would not be easy. So
far IPv6 could penetrate IPv4’s address space by less than 1%.
The world has celebrated ‘World IPv6 Day’ on June 08, 2011 with a
purpose to test IPv6 address over Internet in full. On June 06, 2012
the Internet community officially launched IPv6. This day all ISPs who
were offering IPv6 were to enable it on public domain and were to keep
it enable. All the device manufacturer also participated to offer IPv6
by-default enabled on devices.
This was a step towards encouraging Internet community to migrate to IPv6.
Organizations are provided plenty of ways to migrate from IPv4 to
IPv6. Also organization, willing to test IPv6 before migrating
completely can run both IPv4 and IPv6 simultaneously. Networks of
different IP versions can communicate and user data can be tunneled to
walk to the other side.
Future of IPv6
IPv6 enabled Internet version 2 will replace todays IPv4 enabled
Internet. When Internet was launched with IPv4, developed countries
like US and Europe took the larger space of IPv4 for deployment of
Internet in their respective countries keeping future need in mind. But
Internet exploded everywhere reaching and connecting every country of
the world increasing the requirement of IPv4 address space. As a
result, till this day US and Europe have many IPv4 address space left
with them and countries like India and China are bound to address their
IP space requirement by means of deployment of IPv6.
Most of the IPv6 deployment is being done outside US, Europe. India
and China are moving forward to change their entire space to IPv6.
China has announced a five year deployment plan named China Next
Generation Internet.
After June 06, 2012 all major ISPs were shifted to IPv6 and rest of them are still moving.
IPv6 provides ample of address space and is designed to expand
today’s Internet services. Feature-rich IPv6 enabled Internet version 2
may deliver more than expected.
The successor of IPv4 is not designed to be backward compatible.
Trying to keep the basic functionalities of IP addressing, IPv6 is
redesigned entirely. It offers the following features:
Larger Address Space:
In contrast to IPv4, IPv6 uses 4 times more bits to address a device on
the Internet. This much of extra bits can provide approximately
3.4×1038 different combinations of addresses. This address can
accumulate the aggressive requirement of address allotment for almost
everything in this world. According to an estimate, 1564 addresses can
be allocated to every square meter of this earth.
Simplified Header:
IPv6’s header has been simplified by moving all unnecessary information
and options (which are present in IPv4 header) to the end of the IPv6
header. IPv6 header is only twice as bigger than IPv4 providing the
fact the IPv6 address is four times longer.
End-to-end Connectivity:
Every system now has unique IP address and can traverse through the
internet without using NAT or other translating components. After IPv6
is fully implemented, every host can directly reach other host on the
Internet, with some limitations involved like Firewall, Organization’s
policies, etc.
Auto-configuration:
IPv6 supports both stateful and stateless auto configuration mode of its
host devices. This way absence of a DHCP server does not put halt on
inter segment communication.
Faster Forwarding/Routing:
Simplified header puts all unnecessary information at the end of the
header. All information in first part of the header are adequate for a
Router to take routing decision thus making routing decision as quickly
as looking at the mandatory header.
IPSec:
Initially it was decided for IPv6 to must have IPSec security, making it
more secure than IPv4. This feature has now been made optional.
No Broadcast:
Though Ethernet/Token Ring are considered as broadcast network because
they support Broadcasting, IPv6 does not have any Broadcast support
anymore left with it. It uses multicast to communicate with multiple
hosts.
Anycast Support:
This is another characteristic of IPv6. IPv6 has introduced Anycast
mode of packet routing. In this mode, multiple interfaces over the
Internet are assigned same Anycast IP address. Routers, while routing,
sends the packet to the nearest destination.
Mobility:
IPv6 was designed keeping mobility feature in mind. This feature
enables hosts (such as mobile phone) to roam around in different
geographical area and remain connected with same IP address. IPv6
mobility feature takes advantage of auto IP configuration and Extension
headers.
Enhanced Priority support:
Where IPv4 used 6 bits DSCP (Differential Service Code Point) and 2 bits
ECN (Explicit Congestion Notification) to provide Quality of Service
but it could only be used if the end-to-end devices support it, that is,
the source and destination device and underlying network must support
it.
In IPv6, Traffic class and Flow label are used to tell underlying routers how to efficiently process the packet and route it.
Smooth Transition:
Large IP address scheme in IPv6 enables to allocate devices with
globally unique IP addresses. This assures that mechanism to save IP
addresses such as NAT is not required. So devices can send/receive data
between each other, for example VoIP and/or any streaming media can be
used much efficiently.
Other fact is, the header is less loaded so routers can make forwarding decision and forward them as quickly as they arrive.
Extensibility:
One of the major advantage of IPv6 header is that it is extensible to
add more information in the option part. IPv4 provides only 40-bytes
for options whereas options in IPv6 can be as much as the size of IPv6
packet itself
Internet Protocol version 6, is a new addressing protocol designed to
incorporate whole sort of requirement of future internet known to us as
Internet version 2. This protocol as its predecessor IPv4, works on
Network Layer (Layer-3). Along with its offering of enormous amount of
logical address space, this protocol has ample of features which
addresses today’s shortcoming of IPv4.
Why new IP version?
So far, IPv4 has proven itself as a robust routable addressing
protocol and has served human being for decades on its
best-effort-delivery mechanism. It was designed in early 80’s and did
not get any major change afterward. At the time of its birth, Internet
was limited only to a few Universities for their research and to
Department of Defense. IPv4 is 32 bits long which offers around
4,294,967,296 (232) addresses. This address space was
considered more than enough that time. Given below are major points
which played key role in birth of IPv6:
Internet has grown exponentially and the address space allowed by
IPv4 is saturating. There is a requirement of protocol which can
satisfy the need of future Internet addresses which are expected to grow
in an unexpected manner.
Using features such as NAT, has made the Internet discontiguous
i.e. one part which belongs to intranet, primarily uses private IP
addresses; which has to go through number of mechanism to reach the
other part, the Internet, which is on public IP addresses.
IPv4 on its own does not provide any security feature which is
vulnerable as data on Internet, which is a public domain, is never safe.
Data has to be encrypted with some other security application before
being sent on Internet.
Data prioritization in IPv4 is not up to date. Though IPv4 has
few bits reserved for Type of Service or Quality of Service, but they do
not provide much functionality.
IPv4 enabled clients can be configured manually or they need some
address configuration mechanism. There exists no technique which can
configure a device to have globally unique IP address.
Why not IPv5?
Till date, Internet Protocol has been recognized has IPv4 only.
Version 0 to 3 were used while the protocol was itself under development
and experimental process. So, we can assume lots of background
activities remain active before putting a protocol into production.
Similarly, protocol version 5 was used while experimenting with stream
protocol for internet. It is known to us as Internet Stream Protocol
which used Internet Protocol number 5 to encapsulate its datagram.
Though it was never brought into public use, but it was already used.
Here is a table of IP version and their use:
Brief History
After IPv4’s development in early 80s, the available IPv4 address
pool begun to shrink rapidly as the demand of addresses exponentially
increased with Internet. Taking pre-cognizance of situation that might
arise IETF, in 1994, initiated the development of an addressing protocol
to replace IPv4. The progress of IPv6 can be tracked by means of RFC
published:
1998 – RFC 2460 – Basic Protocol
2003 – RFC 2553 – Basic Socket API
2003 – RFC 3315 – DHCPv6
2004 – RFC 3775 – Mobile IPv6
2004 – RFC 3697 – Flow Label Specification
2006 – RFC 4291 – Address architecture (revision)
2006 – RFC 4294 – Node requirement
June 06, 2012 some of Internet giants chose to put their Servers on
IPv6. Presently they are using Dual Stack mechanism to implement IPv6
parallel with IPv4. http://ipv4-ipv6.blogspot.com/2014/07/ipv6-overview.html
One problem in transition from IPv4 to IPv6 completely is that IPv6
is not backward compatible. This results in a situation where either a
site is on IPv6 or it is not. Unlike an implementation of new
technology where the newer one is backward compatible so the older
system can still work with the newer without any additional changes.
To overcome this short-coming, there exist few technologies which can be used in slow and smooth transition from IPv4 to IPv6:
Dual Stack Routers
A router can be installed with both IPv4 and IPv6 addresses
configured on its interfaces pointing to the network of relevant IP
scheme. [Image: Dual Stack Router]In above diagram, a Server which is having IPv4 as well as IPv6
address configured for it now can speak with all hosts on IPv4 network
and IPv6 network with help of Dual Stack Router. Dual Stack Router, can
communicate with both networks and provides a medium for hosts to
access Server without changing their respective IP version.
Tunneling
In a scenario where different IP versions exist on intermediate path
or transit network, tunneling provides a better solution where user’s
data can pass through a non-supported IP version. [Image: Tunneling]The above diagram depicts how two remote IPv4 networks can
communicate via Tunnel, where the transit network was on IPv6. Vice
versa is also possible where transit network is on IPv6 and remote sites
which intends to communicate, are on IPv4.
NAT Protocol Translation
This is another important method of transition to IPv6 by means of a
NAT-PT (Network Address Translation – Protocol Translation) enabled
device. With help of NAT-PT device, actual conversion happens between
IPv4 and IPv6 packets and vice versa. See the diagram below: [Image: NAT - Protocol Translation]
A host with IPv4 address sends a request to IPv6 enabled Server on
Internet which does not understand IPv4 address. In this scenario,
NAT-PT device can help them communicate. When IPv4 host sends a request
packet to IPv6 Server, NAT-PT device/router, strips down the IPv4
packet, removes IPv4 header and adds IPv6 header and passes it through
the Internet. When a response from IPv6 Server comes for IPv4 host, the
router does vice versa. http://ipv4-ipv6.blogspot.com/2014/07/one-problem-in-transition-from-ipv4-to.html
What is IPv4 and IPv6. ?
Are you confused between IPv4 and IPv6 .Here I have listed the Differences between them.
IPv4 :- 1) All the addresses of IPv4 are 32 bit length 2)The support of IPsec is only Optional 3)The Senders and Forwarding Routers will do the Fragmentation 4) Broadcasts Messages are available too 5)Static of IP addresses or Dynamic configuration is required to Configure IP address 6)No Packet Flow identification 7) Internet group Management Protocol ( IGMP ) is used for the Multicast Group Membership.
IPv6:- 1) All the addresses of IPv4 are 128 bit length 2) Inbuilt IPsec Support 3) Only Sender will do the Fragmentation 4)) Broadcasts Messages are not available.Instead a Link local scope all nodes multi cast address is used for Broadcast 5)Auto configuration of Addresses is Available 6)Packet Flow identification is available within the IPv6 header Using the Flow Label Field 7) IGMP is replaced with the Neighbour Discovery Protocol.
Author: Vicky singh
