Seeking Alternatives to LinkedIn for Professionals

there are no global players like linkedin, though there is Xing, but it's active in some certain countries.

I doubt that there are any alternatives when it comes to social networks that are a good fit for different professions. However, there are many niche communities where engagement is much higher precisely because they focus on a specific audience. For example, when I was involved in academic research, I used ResearchGate and Academia.edu. There are also some great communities for women entrepreneurs like "Dreaders & Doers," and good communities for founders such as "Foundernetwork," and so on. If you specify the sphere you are interested in, it will be easier to provide an answer :)