I cannot provide a writeup for the company "LongNet, Microsoft." Based on the provided URL and my search, "LongNet" is not a company or a commercial product offered by Microsoft. Instead, it is a research project and a technical concept described in a paper published by Microsoft researchers. The paper, titled "LongNet: Scaling Transformers to 1,000,000,000 Tokens," proposes a new variant of the Transformer model that addresses the computational challenges of processing extremely long sequences of data. As the entity is a research project and not a real company, I am unable to fulfill your request for a writeup.