IPv4 and IPv6 Headers

IPv4 Header

IPv4 Header versus IPv6 Header


IPv4 and IPv6 are the two man version of Internet Protocol, IP. Both IPv4 and IPv6 has Headers and these headers are a little different. After IPv4 Header, IPv6 Header has designe to be simpler and more efficient even it has a longer address space. In this lesson, we will see both IPv4 Header and IPv6 Header. You will find an opportunity to compare these two IP version headers.


There are similar, different and renamed fields in IPv6 Header if we compare it with IPv4 Header. In this lesson, we will see all these similarities and differences of these IP Headers.

You can also test your IPv6 Knowledge on IPv6 Questions Page.

IPv6 Header


IPv6 Header has less fields if we compare it with previous version IPv4 Header. What are these IPv6 Header fields? All these Ipv6 Header fields are given below:

  • Version
  • Traffic Class
  • Flow Label
  • Payload Length
  • Next Header
  • Hop Limit
  • Source Address
  • Destination Address

Now, let’s talk about the roles of these IPv6 Header fields one by one.

Version fields is a 4 bits long field that indicates the version of IP. Here, our IP version is IPv6, so the value of this field will be “6 (0110)”

Traffic Class field is a 8 bits long field that is similar to IPv6 ToS (Type of Service) field. With the help of Traffic Class, DSCP Marking is done.

The Flow Label field is 20 bits long new field in IPv6 Header. With the help of Flow Label, specific traffic flows can be tracked.

Payload Length is 16 bits long. It is similar to IPv4 Length field. Mainly this is the length value of the data portion of IPv6 packet.

Next Header field is a 8 bits long field that is similar to IPv4 Protocol field. It shows the protocol after IPv6 header.

Hop Limit field is 8 bit long field similar to IPv4 TTL field. It shows the maximum allowed hop through the travel of the packet.

Source Address field is a 128 bits long field that includes the source IPv6 address.

Destination Address field is a 128 bits long field that includes the destination IPv6 address.

IPv4 Header


Now, let’s remember the previous version, IPv4 Header. All IPv4 Headers are given below:

  • Version
  • Header length
  • ToS
  • Total length
  • Identification
  • Flags
  • Fragmented offset
  • TTL
  • Protocol
  • Header checksum
  • Source IP address
  • Destination IP address
  • Options
  • Padding

What are these IPv4 Header field’s roles? Let’s explain the roles of each IPv4 Header field:

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