IP address fee??

Fri Sep 6 16:33:09 UTC 2002

At 10:00 AM 9/6/02 -0400, Joe Abley postulated:

>On Thu, Sep 05, 2002 at 01:13:27PM -0500, Stephen Sprunk wrote:
> > Because "Cee" is easier to pronounce than "slash twenty-four".  Ease of use
> > trumps open standards yet again :)
>
>Nobody was talking. "/24" is easier to type than "class C". No
>trumps!  Everybody loses!
>
>How many people learn about networks from certification courses or
>in school, anyway? It was always my impression that people learnt
>mainly by listening to other people.
>
>If networking on the front lines is an informal oral tradition more
>than it is a taught science, then perhaps it's natural for obsolete
>terminology to continue to be "taught" long after it stopped having
>any relevance.
>
>
>Joe

    The class of an address is determined by the bit-pattern of the first 
octet of the address.  10.0.0.0 will always be a Class A 
address.  172.16.0.0 will always be a Class B address, and 192.168.0.0 will 
always be Class C address.  I'm not aware of any RFC that rescinded the 
definition of the Class of an address.

    Masks, when associated with an address, enable one to determine  (a), 
what network I'm on (if I'm an IP host) or (b) how many addresses exist 
within a given range of addresses (if I'm a routing table).

    Subnetting (robbing mask host bits (0's) to make network bits (1's) 
allowed one to more effectively use the decreasing amounts of networks that 
required less than the default number of addresses (65,536 in the case of a 
Class B) by more effeciently using the space one had been allocated.  With 
subnetting, I can take one Classful network and make many (sub)networks 
from it.  There was no way prior to 1993, however, to effectively represent 
the range of addresses in more than one Classful network.

    CIDR, simply stated, says that one can use any address with any mask, 
regardless of the original class of the address, to represent a range of 
addresses (i.e. rob network bits to make host bits).  It allows the 
properties of IP to be more effectively used for IP host addressing (only 
need a /23 to support 400 IP hosts (a very effecient  78% use of the 
allocated space), as well as (one of the original, primary reasons for 
CIDR) aggregate ("Supernet") "X" traditional Class C's into one routing 
statement (who today would advertise delivery to the range of 4,096 
addresses from, for example, 192.168.192.0 through 192.168.207.255 with 16 
individual traditional Class C statements?).

    Since NANOG is "the front line", then perhaps that is where the oral 
tradition should be teaching the history of IP addressing, from Classful 
addressing (default masks) to Subnetting (other than default) to 
Supernetting (ranges of addresses regardless of original - or legacy if you 
will - class (Classless)).

    The prefix, of course, does not refer to the class of the address, but 
the number of contiguous ones in the mask.  As far as pronounciation goes, 
I prefer "slash 24" to "two fifty five dot two fifty five dot two fifty 
five dot zero" :)

$.02

Ted Fischer

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