9.1 What InfiniBand Is
The native RDMA fabric — designed from scratch in 1999, lossless via credit-based flow control, sub-microsecond latency, ~99% NVIDIA. The fabric inside DGX SuperPOD and most pre-2022 large GPU clusters.
9.2 Under the Hood
How InfiniBand actually works — credit-based flow control, the Subnet Manager as a centralized control plane, LID and GID addressing, the wire format, and the speed-grade history from SDR to XDR.