IPv4 Limitations and IPv6 Overview

• IPv6 will eventually replace IPv4.

Limitations of IPv4

• IPv4 is still used today.
• IPv4 address depletion is a major issue.
• IPv4 has a limited number of unique public addresses available.
• There are about 4 billion IPv4 addresses.
• The increasing number of IP enabled devices has increased the need for more addresses.
• Lack of end-to-end connectivity is an IPv4 limitation.
• Network Address Translation (NAT) allows multiple devices to share a public IPv4 address.
• NAT hides the IPv4 address of an internal network host.
• NAT can be problematic for technologies requiring end-to-end connectivity.
• Increased network complexity is an IPv4 limitation.
• NAT creates complexity, latency, and makes troubleshooting difficult.

IPv6 Overview

• The Internet Engineering Task Force (IETF) began looking for an IPv4 replacement in the early 1990s.
• IPv6 overcomes IPv4 limitations and better suits current and foreseeable network demands.
• Improvements provided by IPv6:
• Increased address space.
• Improved packet handling.
• Eliminates the requirement for NAT.
• IPv6 addresses are based on 128-bit hierarchical addressing versus IPv4's 32 bits.
• The IPv6 header has been simplified with fewer fields.
• IPv6 eliminates the need for NAT between private and public IPv4 addresses, avoiding NAT-induced problems.
• The 32-bit IPv4 address space provides approximately 4,294,967,296 unique addresses.
• IPv6 address space provides 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses, also known as 340 undecillion.
• IPv6 address space is roughly equivalent to every grain of sand on Earth.

IPv4 Packet Header Fields in the IPv6 Packet Header

• A major design improvement of IPv6 over IPv4 is the use of a simplified IPv6 header
• The IPv4 header consists of a variable length header of 20 octets and 12 basic header fields along with Options field and Padding field.
• In IPv6, the fields have remained, changed names and positions, and the IPv4 fields are no longer required.
• IPv4 packet header fields that were kept, moved, changed, as well as those that were not kept in the IPv6 packet header.
• The simplified IPv6 header consists of a fixed length header of 40 octets resulting from the IPv6 address lengths.
• The IPv6 simplified header allows for more efficient processing of IPv6 headers.

IPv6 Packet Header

• Consists of 40 fixed length octets.

Important IPv6 Packet Header Fields:

• Version - Contains a 4-bit binary value set to 0110 to identify this as an IP version 6 packet.
• Traffic Class - 8-bit field equivalent to the IPv4 Differentiated Services (DS) field.
• Flow Label - 20-bit field suggests packets with the same flow label receive the same handling by routers.
• Payload Length - 16-bit field indicates the length of the data portion or payload of the IPv6 packet, which excludes the 40-byte IPv6 header.
• Next Header - The 8-bit field, equivalent to the IPv4 Protocol field, indicates the payload type, enabling the network layer to pass data to the appropriate upper-layer protocol.
• Hop Limit - The 8-bit field replaces the IPv4 TTL field and is decremented by 1 by each router, discarding packets if the counter reaches 0 and forwarding an ICMPv6 Time Exceeded message.
• IPv6 does not use an IPv6 Header Checksum so that the checksum does not ned to be recalculated by the router
• Source IPv6 Address - 128-bit field identifies the IPv6 address of the sending host.
• Destination IPv6 Address - 128-bit field identifies the IPv6 address of the receiving host.
• IPv6 Packets may also contain extension headers (EH) providing optional network layer information for security and mobility.
• Routers do not fragment IPv6 packets.

Explore the limitations of IPv4, including address depletion, NAT complexity, and lack of end-to-end connectivity. Discover how IPv6 overcomes these challenges with increased address space and improved network efficiency. Learn why IPv6 is the future of internet protocol.