what are the two rules of ipv6 compression

Figure 3 - Applying Zero Compression - example 2 Rule 2: Omit Leading zeros Having in mind that we can use only one double colon, we can either replace groups 4 and 5 with :: or group 7, but not both. Note that there are two contiguous strings of zeros - Group 4 and 5, and Group 7. IMPORTANT - The :: can only appear once in an IPv6 address.Įxample 2 illustrates this. There is one very important aspect of this rule - this zero compression with a double colon can be applied only once! Because otherwise, the original IPv6 address cannot be recreated from the shorted representation. The rule says that we can replace them with a single double colon. Note that Groups 4,5,6 and 7 of the IP address are all zeros. Figure 2 - Applying Zero Compression - example 1 Example 1 illustrates the use of this rule. It says that a double colon (::) can replace a single, contiguous string of one or more groups consisting of all 0s.

The first rule that we are going to look at is called Zero Compression. It's important to understand from the very beginning that using these two rules shortens only the representation of the address, the address itself is always 128 bits.

There are two rules, described in RFCs 23, that help engineers to reduce the length of the address representation. That's why there are rules that can significantly shorten the address Shortening IPv6 addresses It is obvious that IPv6 addresses are long and hard to remember and work with. RFC 4291 says that the preferred representation of an IPv6 address is x:x:x:x:x:x:x:x and RFC 5952 recommends that the address is written in lowercase. The eight groups make a total of 32 hexadecimal digits, four bits each, which makes a total of 128 bits. Hexadecimal characters are not case sensitive, therefore an address can be written either in uppercase or lowercase, both are equivalent. Each group is separated from the others by colons (:) as shown in figure 1.

The IPv6 AddressĪn IPv6 address is 128 bits in length and is written as eight groups of four hexadecimal digits. There are rules to shorten down the address and make it easier to work with. In this lesson, we are going to see that working with IPv6 addresses is not that hard. The other distinct difference is that IPv6 includes new address types such as link-local addresses.

It is quite different than the IPv4 one and at first, it seems hard to grasp. When engineers first encounter IPv6, the most obvious and recognizable feature of the protocol is the IP address.

What are the two rules of ipv6 compression