A method is disclosed for providing interoperation of a first execution
image of a first version and a second execution image of a second
version. A compatibility matrix specifies whether the versions are
compatible, base-level compatible, or incompatible. In one embodiment,
the compatibility matrix may comprise a sparse table that stores a
compatibility indicator for all permutations of a plurality of versions
of a network operating system. As part of initialization of a system that
includes the first execution image and second execution image, version
information for the execution images is determined. An entry in the
compatibility matrix corresponding to the versions is identified. The
execution images are operated in a fully synchronized state when the
identified entry of the compatibility matrix specifies that the versions
are either compatible or base-level compatible. Individual components of
the execution images interoperate according to the results of individual
session negotiations. If the versions are incompatible, an alternative
redundancy operation mode may be used. Embodiments provide for
negotiation of compatible message versions and capabilities among peer
components or clients of the execution images as source information to
generate the compatibility matrix.