[ppml] Policy Proposal 2005-9: 4-Byte AS Number

Owen DeLong owen at delong.com
Tue Dec 20 18:28:36 EST 2005


> This is an entirely separate question from the question
> of introducing a special notation in the first place.
> It's not a simple binary partition of positions and 
> I don't believe the discussion demonstrated any significant
> support for any of the positions discussed. The discussion
> raised serious questions:
> 
>    Should there be a special notation for AS numbers
>    greater than 65535?
> 
No.  However, once we start using 32 bit AS numbers, having a divided
notation for them is desirable as an adjunct to human readability.
Thus, I favor the future notation of existing AS numbers as 0.ASN
and AS numbers in excess of 65535 as A.B where A=int(ASN/65536)
and B=ASN mod 65536.

>    Should a dot be preferred to a colon in such a 
>    special notation?
> 
Absolutely.  Colons are ambiguous with current use of community notation.

> However, the discussion did not decide the answers to
> these questions.
> 
OK, well... I guess there will be more discussion on this.  You now have
my votes on these two questions.

>> > Is the number 0.63535 a valid AS number?
>> 
>> yes
> 
> How can you tell?
> 
What do you mean?

0.63535 is the 32 bit representation of what is currently 63535.
There is no difference between 0.63535 and 63535.

>> > What about 0.65553?
>> 
>> I would say that it is equally valid to 0.0.0.384 as an IP address.
> 
> Huh? Everyone knows that is not a valid IP address 
> because each segment is an 8 bit number which cannot
> be greater than 255.
> 
Exactly.

>> Technically, I suppose, an argument could be made that it is valid, but,
>> I doubt most parsers would treat it the way you would expect.
> 
> The point is that big numbers, such as the maximum unsigned
> representation of 16 bits, are not terribly intuitive, not
> as easy for people to remember and understand as 256, and not
> as easy to figure out when the question is put to you about the 
> validity of a number. People can understand 256 possibilities 
> because you can almost visualize them and millions of people 
> have seen illustrations of tables of 256 eight-bit character
> codes. The same cannot be said for 16 bit codes. In addition,
> millions of people know that the maximum 16 bit integer is 
> 32,767 but that is not the same as the maximum 16 bit positive
> number used in the definition of an AS number.
> 
I'm betting most of the people who know that 32767 is the maximum
16 bit integer are well aware that 65535 is the maximum unsigned
16 bit integer.

>> However, there's three dots and only one boundary for any given
>> address.  I don't know whether you'll accept this or not, but,
>> I do believe that a portion of the thinking of using dotted quads
>> was to make IP addresses more human-readable and reduce human
>> audio transmission/reception errors.
> 
> That was at a time before the existence of text messages
> and email and IM and ...
> 
What's your point?  As someone who works in an actual NOC, I can
guarantee you that IP addresses and ASNs are still exchanged
in telephone conversations on a regular basis today.

>> I'll also point out that dotted quad did not go away with the
>> advent of CIDR
> 
> That's not the point. The point is that it CAME IN for
> a good reason related to the structure of IP addresses 
> and there use in subnet and host addressing. There is
> no structural and usage related reason to INTRODUCE a
> new AS number notation superceding the old one.
> 
I guess we'll have to agree to disagree on this.  I think that
the readability issue is a good reason.

>> IP addresses today are simple integers as well.
> 
> Not so. That's why we have slash notation. There is
> still an important distinction between network and
> host addresses even though CIDR allows for more variation
> in network sizes.
> 
Please explain the purpose of the dots in IP addresses as
it relates to this?  Please explain the purpose of the :s
separating 16 bit chunks in IPv6 addresses as it relates
to this.  It just doesn't fit.

>>  Either way, the position of the dots
>> in IP addresses is no longer related to that structure, but, the dots 
> have
>> not moved or been abandoned.
> 
> Exactly! When IPv4 subnetting was changed by CIDR, we
> stayed with the convention of representing IPv4 address 
> as they always had been. That's why I believe we should
> also STICK WITH THE CONVENTION of representing AS numbers
> as simple decimal integers with optional prefixes like
> AS or ASN.
> 
> There is no need to change things at all.
> 
I suppose that when the US went from phone numbers like BR549 to
NPA-NXX-SUFX, you would have preferred to continue representing
those phone numbers as two letters followed by a larger string of
numbers.  

> There is no need to write AS number 65536 as AS 65536 and AS 1.0
> There is no need to explain to people that 1.324 is not actually
> a real number but it is a 32 bit integer.
> 
Need is an interesting term.  However, I would argue that there is
also no need to make people look at ASNs like AS129391243 and that
it is much better to, instead, represent that as AS1974.23179.

Just as I prefer +1.408.555.1212 to 14085551212 and prefer
95121-1520 to 951211520 and 123-45-6789 to 123456789[1].  Sure,
there is some structural significance in each of these cases,
but, said structure is not important to most common usages of
those data.  Instead, it is primarily there to improve
readability.

Owen

[1] These numbers are, respectively, NANP (North America) Telephon Number,
united States Postal code, United States Social Security Number.

--
If it wasn't crypto-signed, it probably didn't come from me.
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