IPv6 Header vs IPv4 Packet Header Differences

IPv6 Header vs IPv4 Packet Header Differences

This article will explain the function of the main header fields i.e IPv6 Header vs IPv4 Packet Header  and the differences between them.

What is IPV6?

In the early 1990s, problems with IPv4 worried the Internet Engineering Task Force (IETF) which, as a result, began looking for a replacement. This resulted in the development of IP version 6 (IPv6). IPv6 overcomes the limitations of IPv4 and represents the following important improvements:

• Increased address space : IPv6 addresses are based on 128-bit hierarchical addressing.
• Better packet handling : The number of IPv6 header fields was reduced to make it simpler.
• Eliminates the need for NAT : By having such a large number of public IPv6 addresses, the NAT between private and public IPv4 addresses is no longer necessary.

IPV6 PACKET HEADER

One of the most important design improvements of IPv6 with respect to IPv4 is the simplified IPv6 header.The most important fields in the IPv6 header are the following:

1. Version = 4-bit binary value set as 0110 for IPv6.
2. Traffic class = 8-bit field is the equivalent to the IPv4 DS field.
3. Flow tag = 20-bit field suggests that all packets of the same flow receive the same handling.
4. Content Length = It is equal to the total IPv6 packet length.
5. Next header = 8-bit field equivalent to the IPv4 protocol .
6. Hop Limit = 8-bit field replaces the IPL4 TTL field.
7. Source IPv6 Address : 128-bit field that identifies the IPv6 address of the sending host.
8. Destination IPv6 Address : 128-bit field that identifies the IPv6 address of the receiving host.

Image ref: cisco.com

IPV4 PACKET HEADER

The IPv4 packet header consists of fields that contain important information about the packet. These fields have binary numbers that identify various configuration parameters of the IP packet. The protocol header diagrams, which are read from left to right and top to bottom, provide a visual representation of the query when analyzing the protocol fields.

The most important fields in the IPv4 header are the following:

1. Version : Contains a 4-bit binary value: 0100 set for IPv4.
2. Differentiated services or DiffServ (DS): formerly known as “type of service” (ToS), is an 8-bit field that is used to determine the priority of each packet. The first six bits are the differentiated services code point (DSCP), and the last two bits are the explicit congestion notification (ECN).
3. TTL : Contains an 8-bit binary value that is used to delimit the lifetime of a packet. If the TTL field reaches zero, the router discards the packet and sends a timeout message from the Internet Control Message Protocol (ICMP) to the source IP address.
4. Protocol : Identifies the upper layer protocol, such as TCP (6), UDP (17)
5. Source IP address: packet origin (IPv4 address), a 32-bit binary value.
6. Destination IP address: packet destination (IPv4 address), a 32-bit binary value

Further:

1. Internet header length (IHL), total length and checksum header : Used to identify and validate the package.
2. Identification, flags and fragment displacement : It is used to reorder a fragmented package.

IPV4 LIMITATIONS

IPv4 still has three big problems:

1. IP address depletion : IPv4 has a limited number of unique public IPv4 addresses available. (approx. 4000 million IPv4 addresses)
2. Internet routing table expansion : Routers use routing tables to determine the best routes. As the number of servers connected to the Internet increases, the number of network routes also increases.
3. Lack of complete connectivity : One of the most implemented technologies in IPv4 networks is the translation of network addresses. NAT provides a way for multiple devices to share a single public IPv4 address. However, since the public IPv4 address is shared, the IPv4 address of a host on the internal network is hidden. This can be a problem for technologies that need full connectivity.