Often times nodes need to communicate with each other what their implementation is, looking for specific features that are only in select implementations, the desired feature is a question of node implementation.
A concept of Unspecified protocol extensions has been
proposed, they are unspecified as they are not part
of the BOLT specifications, each extension must have a set of random
type bigger than a certain number. Using the concept of
current extension, any extensions that are unidentified by a node will not be
recognized, while if the node’s implementation identifies this unspecified
extension, both nodes can continue communications knowing that they have the
same set of extra features.