Stefan,
... Not sure I agree on this one. One mandatory to implement algorithm does not ensure interoperability if other algorithms are allowed.
We should probably clarify this by noting that "mandatory to implement" algorithms MUST be supported by both servers and clients. However, the choice of which of these algorithm to USE in a given context is a local matter, and this means that a server may choose to restrict the algs that it supports, and thus interoperability may be impaired.
Steve
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