I have a question about the snd-base/hot-spot of flexpage mapping feature. in many l4 documents, there are a lot of words about the snd-base/hot-spot concept, it seem that are a complex mechanism to calculate the send base when the sender's flexpage have different size compares to receiver's flexpage, I have read a lot of documents(l4 user manual/l4 reference manual etc.) about this mechanism, but I can not figure out it... Could you tell why l4 needs this mechanism, and what situation that this mechanism adapt to? 

And I have another question to Dresden University guys: what is the l4 version of Fiasco.OC based?

Thank for your help!

Naus