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Removing features
At 08:09 AM 10/10/2003, Margaret.Wasserman@nokia.com wrote:
Removing a feature from a specification doesn't even prevent people from
using it
I'm changing the thread subject. While this is relevant to the subject of
Tony's appeal, it is also a general debate orthogonal to Tony's appeal. It
is a side note that may prove relevant. While your assertion may generally
be true, this particular change does prevent people from using it, and I'm
not sure the assertion is true as worded.
The site-local proposal says that there is an assurance that a particular
block of addresses is available to a network administration to use in
whatever way it chooses within the confines of its own network, on the
proviso that it neither advertise those addresses outside its network in
routing nor trust announcements of the block by others, and presumably also
ingress filters for the address prefix. Removing the concept removes that
capability. YMMV as to whether you want the capability, but you cannot
accurately say that the capability still exists once it has been removed.
Your assertion is also dangerous in protocols. If a capability is
deprecated (remains defined but its implementation/use is discouraged, as
for example true of TOS routing in OSPF, cf RFCs 1583, 2178, and 2328),
then an implementation that contains the capability can accurately say it
is using a superset of the specification. If the capability is simply
removed, one has to presume that at some time in the future the bits will
be reused with different semantics, making the implementation that
yesterday was using a superset of the specification an active hazard today,
and causing operational networks that were using the capability to have to
make some potentially hard choices.
So in the general case I don't see a problem with deprecating things under
the right circumstances, but I do have a problem with removing them
outright. Deprecation doesn't prevent people from using them, but outright
removal can be dangerous. And in this case, the assertion that one can
still use the address prefix in a local manner is simply incorrect; it can
be assigned at the whim of IANA, and network administrations need to plan
accordingly.