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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: that 4byte ASN you were considering...
> > - 'Canonical representation of 4-byte AS numbers ' > > http://www.ietf.org/internet-drafts/draft-michaelson-4byte-as-representation-01.txt > > and what is good or bad about this representation? seems simple to me. > and having one notation seems reasonable. what am i missing? It breaks any applications which recognize IP address-like objects by seeing a dot in an otherwise numeric token. For the purposes of parsing a string into internal representation, an application can treat IP addresses, netmasks and inverse masks identically. We all know that the Internet is awash in homegrown scripts written in PERL or TCL or bash or Ruby or Python. It is likely that many authors have, in the past 15 years, written scripts which contain regular expressions like "[0123456789.]*" to match a string containing only digits and the period. Those scripts will be confused by this AS number notation. Also, any script which "recognizes" IP address-like objects when it hits the first period in a numeric string. The real question is what does the notation 1.0 add that the notation 65536 does not provide? All I can see is that it adds the risk of broken scripts and the confusion of AS numbers that look like decimal numbers. If the IETF had really wanted to create a universal notation then they should have recommended that AS numbers be represented in the form AS65536 which is completely unambiguous. When IP addresses were created, it was important to indicate the boundaries between the network number and the host address. Originally, the periods represented this boundary for the three classes of IP address, class A, class B and class C. Long ago, we removed this classfulness attribute, but the notation remains because lots of applications expect this notation. So why on earth are we changing AS number notation today? --Michael Dillon
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