Both of the publish applications in this article use IBM's SSL support, but other implementations can be used by changing the protocol handler and the securityprovider.
For example an application may support both requester and provider role in different end to end interactions or external security services may support one or more of the functions listed.
An example of this would be a service provider that asks for a particular type of encryption method, for which the service requester doesn't have the security infrastructure to support.