RFC 4443 simply introduces and describes and defines ICMPv6 for IPv6. In the very first couple of sentences (Introduction) it states:
"Other documents may also introduce additional ICMPv6 message types, such as Neighbor Discovery messages [IPv6-DISC], subject to the general rules for ICMPv6 messages given in Section 2 of this document." That's what RFC 4861 is doing. Acting as that "other document" that introduces a useful application of ICMPv6.
To recap, RFC 4443 defines ICMPv6. RFC 4861 describes how ICMPv6 is leveraged to perform neighbor discovery.
i want to asking you another question i think it`s very easy or stupid
what is the difference between the word "digit " and "Number" in English language ?
i networking field is there any difference ?
Dear Mohamed--I'm not going to write much about your original question, except to say that Steven answered it quite clearly, I think. (And also, I know that Steven "enjoys" reading the RFCs more than anyone else I know!)
I might have written this to you or someone else a while back.... the RFCs are written in a very formal English style that is much more typically used in the legal profession when writing to the court. As a retired lawyer, and native English speaker, I can tell you that even I have some trouble understanding them sometimes! So hang in there, and don't give up!
If something is described as an "industry standard" (versus something that is "proprietary") then it means that it has been submitted to some reviewing body (in the case of RFCs it's the IETF). The reviewing body has approved the technology and published a description of the technology. (In this case, the RFCs are the IETF's description of technology it has approved of.) That means, if there is ever a question on how a standard technology works, the published standard describing it is the best source of information.
But as we both found out, however, they might not be the easiest things in the world to read! So, the next step is what you are doing... consulting other sources such as textbooks, white papers, and our peers!
ok now i understand
but what is the difference between "digit" and "decimal"and "binary"?
ok i will draw you what make me confused :-
we have 3 types of counting systems:-
1-hexa-decimal counting system (hexa-decimal digit)
2- binary counting system
can we say about this counting system is "binary digit " ? or "binary number"
in other words , why we don`t say "binary digit" like we say "hexa decimal digit" ? why we remove keyword "digit "after"binary"?
3- decimal counting system
same thing , can we say "decimal digit" like what we do in "hexa-decimal digit" ? or we must say "decimal" without keyword "digit" ?
does "digit"keyword in "hexa-decimal digit" only added beside "hexa-decimal" ? or we can add it beside "binary"and "decimal"
iam sorry for this long question, but i need to let you understand question inside my brain
According to merriam-webster.com a digit is not limited to decimal. It can apply to binary (base 2), and hexadecimal (base 16). I don't know why we say hexadecimal. I just say hex. So basically there are eight binary digits in decimal number 255 (which has three digits). 255 is also FF (a two digit hexadecimal value).
Hexadecimal-- hexa is Greek (I think?) for six and deci is ten. So hexadecimal means 6 + 10. 16. Hex for short.
A digit is the sub-unit that makes up a number. So in the different counting systems:
- 27 is the number. 2 and 7 are the digits. (Decimal digits are 0-9.)
- 11011 is the number. 0 and 1 are the digits. (Binary digits are 0 and 1.)
- 1B is the number. 1 and B are the digits. (Hexadecimal digits are 0-9 and A-F.)
why we don`t say "binary digit" like we say "hexa decimal digit" ? why we remove keyword "digit "after"binary"?
We don't use the keyword digit after the word describing the counting system because referring to the digit means we are talking about the sub-units not the whole number, we rarely talk about the digits themselves. Generally what is important is not the individual digits, but the value of the number that the digits make up. However, if you were having a discussion about the digits, it would be correct (and probably more clear) to use the word digit. If you were having a discussion about the difference of digits among the various counting systems, you would use both words.... binary digits are cooler than hexadecimal digits, for example.
On the other hand, we will often talk about the "binary number" or the "hex number" or the sometimes, "the number". Here we refer to the value of the whole unit. In the example I gave above, all of the numbers I gave represent the same value. So if we were having a conversation about at number, and the counting system didn't matter, it would be OK to refer to it as "the number." But if it were important to make the distinction between the counting systems, it would be correct and more clear to say, "the binary number... the hex number... the decimal number." (Or better, "the number in ... [counting system]".)
Does this make better sense? MM