Re: The IESG Approved the Expansion of the AS Number Registry

On 29-Nov-2006, at 08:30, Henk Uijterwaal wrote:

> Michael.Dillon@btradianz.com wrote:
>
>> On the NANOG list it has already been pointed out that a lot
>> of network management software cannot handle such notation and
>> in some cases, 1.0 could be interpreted as the IP address 1.0.0.0.  
>> It has been confirmed that one widely used PERL library interprets  
>> x.y as IP address x.0.0.y.
>
> I think this is a bug.

If it is, it's a very long-standing one. For example, see INET(3)  
which I think is of 4.2BSD vintage, and which appears to have similar  
semantics to the mentioned perl library:

INTERNET ADDRESSES
      Values specified using the `.' notation take one of the  
following forms:

            a.b.c.d
            a.b.c
            a.b
            a

      When four parts are specified, each is interpreted as a byte of  
data and
      assigned, from left to right, to the four bytes of an Internet  
address.
      Note that when an Internet address is viewed as a 32-bit  
integer quantity
      on the VAX the bytes referred to above appear as ``d.c.b.a''.   
That is,
      VAX bytes are ordered from right to left.

      When a three part address is specified, the last part is  
interpreted as a
      16-bit quantity and placed in the right-most two bytes of the  
network
      address.  This makes the three part address format convenient  
for speci-
      fying Class B network addresses as ``128.net.host''.

      When a two part address is supplied, the last part is  
interpreted as a
      24-bit quantity and placed in the right most three bytes of the  
network
      address.  This makes the two part address format convenient for  
specify-
      ing Class A network addresses as ``net.host''.

      When only one part is given, the value is stored directly in  
the network
      address without any byte rearrangement.

>> Because of this I think it would be useful for the IETF
>> to publish a draft defining the notation for AS numbers
>> so that we can either keep it simple or, if a new notation
>> is to be used, then publicly state the issues of software which  
>> needs to be changed. Such a draft should really come
>> from the WG which extended the AS number in the first place.
>
> There is:
>
>   Canonical Textual Representation of 4-byte AS Numbers
>   draft-michaelson-4byte-as-representation-02
>
> describing the format of ASN32 and

The draft above received significant operator criticism.

The consensus I saw on NANOGm, for example, was that there was (a) no  
useful reason to be able to distinguish between a 16-bit AS number  
and a 32-bit AS number less than 65536, (b) no good reason to use  
punctuation to separate the most- and least-significant 16 bits of  
the 32-bit ASN, and (c) every reason to think that the most sensible  
representation was just "bigger decimal numbers".

Joe

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