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Saturday, 11 June 2011

Brief explanation about IPv6 and Comparison IPv4 vs. IPv6

Internet Protocol Version 6 (IPv6) or IP next generation (IPng)
IPv6 or IPng
IPv6 stands for Internet Protocol version 6 also known as IPng (IP next generation) is the second version of the Internet Protocol to be used generally across the virtual world. The first version was IPv4. IPv6 was designed to take an evolutionary step from IPv4. It was not a design goal to take a radical step away from IPv4. Functions which work in IPv4 were kept in IPv6. Functions which didn’t work were removed. IPv6 was developed by the Internet Engineering Task Force (IETF) to deal with the long-anticipated IPv4 address exhaustion, and is described in Internet standard document RFC 2460, published in December 1998. Like IPv4, IPv6 is an Internet Layer protocol for packet-switched internetworking and provides end-to-end datagram transmission across multiple IP networks. While IPv4 allows 32 bits for an Internet Protocol address, and can therefore support 2^32 (4,294,967,296) addresses, IPv6 uses 128-bit addresses, so the new address space supports 2^128 (approximately 340 undecillion or 3.4×1038) addresses. This expansion allows for many more devices and users on the internet as well as extra flexibility in allocating addresses and efficiency for routing traffic. It also eliminates the primary need for network address translation (NAT), which gained widespread deployment as an effort to alleviate IPv4 address exhaustion.

The changes from IPv4 to IPv6 fall primarily into the following categories :-

1) Expanded Routing and Addressing Capabilities

2) IPv6 increases the IP address size from 32 bits to 128 bits, to support more levels of addressing hierarchy and a much greater number of addressable nodes, and simpler auto-configuration of addresses.

3) The scalability of multicast routing is improved by adding a “scope” field to multicast addresses.

4) A new type of address called a “anycast address” is defined, to identify sets of nodes where a packet sent to an anycast address is delivered to one of the nodes. The use of anycast addresses in the IPv6 source route allows nodes to control the path which their traffic flows.

5) Header Format Simplification

6) Some IPv4 header fields have been dropped or made optional, to reduce the common-case processing cost of packet handling and to keep the bandwidth cost of the IPv6 header as low as possible despite the increased size of the addresses. Even though the IPv6 addresses are four time longer than the IPv4 addresses, the IPv6 header is only twice the size of the IPv4 header.

7) Improved Support for Options

8) Changes in the way IP header options are encoded allows for more efficient forwarding, less stringent limits on the length of options, and greater flexibility for introducing new options in the future.

9) Quality-of-Service Capabilities

10) A new capability is added to enable the labeling of packets belonging to particular traffic “flows” for which the sender requests special handling, such as non-default quality of service or “real- time” service.

11) Authentication and Privacy Capabilities

12) IPv6 includes the definition of extensions which provide support for authentication, data integrity, and confidentiality. This is included as a basic element of IPv6 and will be included in all implementations.

13) The IPv6 protocol consists of two parts, the basic IPv6 header and IPv6 extension headers.

IPv6 Header (IPv6 Packet Format) :-
IPv6 Header (IPv6 Packet Fromat)

IPv6 header contains the following things :-

1) Version - This field contains the version of the IP used in the packet. It is of 4-bit in IP version 6.

2) Traffic class - This is an 8-bits field determining the packet priority. Priority values subdivide into ranges: traffic where the source provides congestion control and non-congestion control traffic.

3) Flow label - This 20 bits specifies the QoS management. Originally created for giving real-time applications special service, but currently unused.

4) Payload length - This 16 bits determines the payload length in bytes. When cleared to zero, the option is a "Jumbo payload" (hop-by-hop).The payload can have a size of up to 64KB in standard mode, or larger with a "jumbo payload" option.

5) Next header - This 8-bits field specifies the next encapsulated protocol. The values are compatible with those specified for the IPv4 protocol field.

6) Hop limit - This is an 8-bits field newly introduced in IPv6. It replaces the time to live field of IPv4.

7) Source Address - This 128 bits field determines the logical address of the host that is sending the packet.

8) Destination Address - This 128 bits field determines the logical address of the host that is receiving the packet.

Addressing in IPv6 :-

The most important feature of IPv6 is a much larger address space than in IPv4. IPv6 addresses are 128 bits long, compared to only 32 bits previously. While the IPv4 address space contains only about 4.3×10^9 (4.3 billion) addresses, IPv6 supports approximately 3.4×10^38 (340 undecillion) unique addresses, deemed enough for the foreseeable future.

IPv6 addresses are written in eight groups of four hexadecimal digits separated by colons, for example, 2001:0db8:85a3:0000:0000:8a2e:0370:7334. IPv6 addresses are logically divided into two parts: a 64-bit (sub-)network prefix, and a 64-bit interface identifier.

IPv6 addresses are classified by three types of networking methodologies:
Unicast address : It identify each network interface
Anycast addresses : It identify a group of interfaces, usually at different locations of which the nearest one is automatically selected
Multicast addresses : They are used to deliver one packet to many interfaces.

IPv6 in the Domain Name System:
In the Domain Name System, hostnames are mapped to IPv6 addresses by AAAA resource records, so-called quad-A records. For reverse resolution, the IETF reserved the domain, where the name space is hierarchically divided by the 1-digit hexadecimal representation of nibble units (4 bits) of the IPv6 address. This scheme is defined in RFC 3596.

Address Format:
IPv6 addresses have two logical parts: a 64-bit network prefix, and a 64-bit host address part. (The host address is often automatically generated from the interface MAC address.) An IPv6 address is represented by 8 groups of 16-bit hexadecimal values separated by colons (:) shown as follows:

A typical example of an IPv6 address is

The hexadecimal digits are case-insensitive.

The 128-bit IPv6 address can be abbreviated with the following rules:
* Rule one: Leading zeroes within a 16-bit value may be omitted. For example, the address fe80:0000:0000:0000:0202:b3ff:fe1e:8329 may be written as fe80:0:0:0:202:b3ff:fe1e:8329
* Rule two: A single occurrence of consecutive groups of zeroes within an address may be replaced by a double colon. For example, fe80:0:0:0:202:b3ff:fe1e:8329 becomes fe80::202:b3ff:fe1e:8329

Special Addressing in IPv6:
* ::/96 :- The zero prefix denotes addresses that are compatible with the previously used IPv4 protocol.

* ::/128 :- An IPv6 address with all zeroes in it is referred to as an unspecified address and is used for addressing purposes within a software.

* ff00::/8 :- This prefix is offered by IPv6 to denote the multicast addresses. Any address carrying this prefix is automatically understood to be a multicast address.

* fe80::/10 :- This is a link-local prefix offered by IPv6. This address prefix signifies that the address is valid only in the local physical link.

IPv6 Security (IPSec) :-

IPSec, is a framework of open standards (from IETF) that define policies for secure communication in a network.

Some security services offered by IPSec are:
* access control,
* connectionless integrity,
* data origin authentication,
* protection against replays (a form of partial sequence integrity),
* confidentiality (encryption),
* limited traffic flow confidentiality.

IPSec supports:
* Data Encryption Standard (DES) 56-bit and Triple DES (3DES) 168-bit symmetric key encryption algorithms in IPSec client software.
* Certificate authorities and Internet Key Exchange (IKE) negotiation. IKE is defined in RFC 2409.
* Encryption that can be deployed in standalone environments between clients, routers, and firewalls.

Advantages of IPv6 over IPv4 :-

1) Adress Space :
* IPv4 : 2^32 Addresses.
* IPv6 : 2^128 Addresses.
* Advantage of IPv6 : 79 Octillion times the IPv4 address space.

2) Configuration :
* IPv4 : Manual or use DHCP.
* IPv6 : Universal Plug and Play (UPnP) with or without DHCP.
* Advantage of IPv6 : Lower Operation Expenses and reduce error.

3) Broadcast/Multicast :
* IPv4 : Uses both.
* IPv6 : No broadcast and has different forms of multicast.
* Advantage of IPv6 : Better bandwidth efficiency.

4) Anycast Support :
* IPv4 : Not part of the original protocol.
* IPv6 : Explicit support of anycast.
* Advantage of IPv6 : Allows new applications in mobility and data center.

5) Network Configuration :
* IPv4 : Mostly manual and labor intensive.
* IPv6 : Facilitate the re-numbering of hosts and routers.
* Advantage of IPv6 : Lower operation expenses and facilitate migration.

6) QoS Support :
* IPv4 : ToS using DIFFServ.
* IPv6 : Flow classes and flow labels.
* Advantage of IPv6 : More Granular control of QoS.

7) Security :
* IPv4 : Uses IPsec for Data packet protection.
* IPv6 : IPsec becomes the key technology to protect data and control packets.
* Advantage of IPv6 : Unified framework for security and more secure computing environment.

8) Mobilty :
* IPv4 : Uses Mobile IPv4.
* IPv6 : Mobile IPv6 provides fast handover, better router optimization and hierarchical mobility.
* Advantage of IPv6 : Better efficiency and scalability; Work with latest 3G mobile technologies and beyond.

Comparison IPv4 vs. IPv6 / Difference Between IPv4 and IPv6 :-

IPv4 :-
* Source and destination addresses are 32 bits (4 bytes) in length.
* IPSec support is optional.
* IPv4 header does not identify packet flow for QoS handling by routers.
* Both routers and the sending host fragment packets.
* Header includes a checksum.
* Header includes options.
* Address Resolution Protocol (ARP) uses broadcast ARP Request frames to resolve an IP address to a link-layer address.
* Internet Group Management Protocol (IGMP) manages membership in local subnet groups.
* ICMP Router Discovery is used to determine the IPv4 address of the best default gateway, and it is optional.
* Broadcast addresses are used to send traffic to all nodes on a subnet.
* Must be configured either manually or through DHCP.
* Uses host address (A) resource records in Domain Name System (DNS) to map host names to IPv4 addresses.
* Uses pointer (PTR) resource records in the IN-ADDR.ARPA DNS domain to map IPv4 addresses to host names.
* Must support a 576-byte packet size (possibly fragmented).

IPv6 :-
* Source and destination addresses are 128 bits (16 bytes) in length.
* IPSec support is required.
* IPv6 header contains Flow Label field, which identifies packet flow for QoS handling by router.
* Only the sending host fragments packets; routers do not.
* Header does not include a checksum.
* All optional data is moved to IPv6 extension headers.
* Multicast Neighbor Solicitation messages resolve IP addresses to link-layer addresses.
* Multicast Listener Discovery (MLD) messages manage membership in local subnet groups.
* ICMPv6 Router Solicitation and Router Advertisement messages are used to determine the IP address of the best default gateway, and they are required.
* IPv6 uses a link-local scope all-nodes multicast address.
* Does not require manual configuration or DHCP.
* Uses host address (AAAA) resource records in DNS to map host names to IPv6 addresses.
* Uses pointer (PTR) resource records in the IP6.ARPA DNS domain to map IPv6 addresses to host names.
* Must support a 1280-byte packet size (without fragmentation).

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