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Removing features

2003-10-10 11:44:07
At 08:09 AM 10/10/2003, Margaret(_dot_)Wasserman(_at_)nokia(_dot_)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.



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