Thursday, June 9, 2011

IPV6 - Chapter 1 - Introduction

Total of 3.403×10^38 tottal address in IPV6.

IPV6 is a new version of the internet protocol, designed as a successor to ipv4.
The changes from IPV4 to IPV6 are predominantly in the following areas:
  1. Addressing
  2. Header Format
  3. Flow
  4. Extensions and Options
  5. Authentication and Privacy

1. The most significant change in the upgrade from IPV4 to IPV6 is the increase in addressing space from 32 bits to 128 bits. This new addressing capability can cope with the accelerating usage of the internet. IPV6 changes the addressing types by introducing any-cast addressing and discarding the broadcast address employed by IPV4

2. IPV4 headers contain at least 12 fields, which can vary in length from 20 to 60 bytes.
IPV6 has simplified the header formatting structure by using a fixed length of 40byts. The reduction in the number of fields that needs to be processed allows for more effective networking routing. IPV6 changes the packet fragmentation principle by enabling fragmentation to be conducted by source node only. This also reduces the number of fields required in the packet header. The format of the packet header is simplified in IPV6 by the removal of the check-sum field. IPV6 focuses on routing packets, and the check-sums are implemented in higher level protocols, such as UDP and TCP

3. IPV4 processes each packet individually at intermediate routers. These routers do not record packet details for future handling of similar packets. IPV6 introduces the concept if packets in a flow. A flow is series of packets in a stream of data that require special handling. An example of a flow is a  stream of real-time video data.IPV6 routers can monitor flows and log consistent information for the effective handling of flow packets.

4. IPV4 adds options to the end if the IP header , whereas IPV6 adds options to separate extension headers. This means that, in IPV6, the option header is processes only when a packet contains options.The use of extension headers to contain options obviates the need for all routers to examine certain options.For example, in IPV6, only the source node can fragment a packet, therefore the only nodes that need to examine the fragmentation extension header are the source and destination nodes.

5. The two security extensions employed by IPV6 are
  • authentication header
Packet authentication is implemented through message-digest functions. The sender calculates a  message digest or hash on the packet being sent. The results of this calculation are contained in the authentication header. The packet recipient performs a hash on the received packet and compares the  result against the value in the authentication header. Matching values confirm that the packet traveled from source to destination without violation. Differing values indicate that the packet was modified during transition.

  • encapsulating security payload (ESP) header
The ESP header can encrypt the payload field in an IPV6 packet or the entire packet, ensuring data integrity as it is forwarded across the network. Encrypting the entire packet ensures that packet data, such as the source and destination addresses, are not intercepted during transmission. Encrypted packets are transported within another IPV6 packet that functions as a security gateway.

Header Structure of IPV4 & IPV6

The IPV4 packet header has a 32 bit or 4 byte boundary.
It contains
  • Ten fields
Contains: Version, Header Length, Type of Service, Total length, Identifier, Flags, Fragment Offset, Time to Live, Protocol, Header Check-sum
  • Two addresses
Source Address and Destination Address
  • Options
Options + Padding

The IPV6 packets header expands on the IPV4 header by providing 64 bit, or 8byt, boundary. All IPV6 headers are 40 bytes in total. It contains a simpler header format of
  • Six Fields
Version, Traffic Class, Flow Label, Payload Length, Next Header & Hop Limit
  • Two Addresses
Source Address and Destination Address

Extension Headers
IPV4 implements a complex method for the inclusion of options in the routing of packets. The IPV4 packet structure can vary in size from 20-60 bytes, and IPV4 options are included as extra data. As a result, options may be forwarded without being processed or be processed at each router. Such inefficient routing can lead developers to avoid the use of options.
IPV6 implements a new variety of extension headers to improve the routing of packets with options.Instead of incorporating options into the IPV6 header, the options are placed in separate extension headers appended to the IPV6 header and identified by the Next Header field.
Extension headers - with the exception of hop-by-hop options header - are not processed until they reach the destination address. Each extension header is a multiple of 8 octets in length, preserving the 64-bit alignment for subsequent headers.


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