# Host Controller Interface ## Identification [[IEEE 802.1Q|802.1Q]] tags Ethernet frames for VLAN segmentation. In Bluetooth, [[Host Controller Interface|HCI]] connects host software to the controller, [[Logical Link Control and Adaptation Protocol|L2CAP]] multiplexes higher protocols, [[Synchronous Connection-Oriented link|SCO]] carries synchronous audio, and [[Bluetooth Network Encapsulation Protocol|BNEP]] emulates Ethernet networking. [[XFRM|XFRM]] is Linux’s IPsec transformation framework. [[PCI Express Hot Plug|PCIe hot-plug]] and [[Input-output memory management unit|IOMMU]] concern hardware attachment, isolation, and DMA address translation. ## Notebook evidence - [[Scanned_20260730-1719#PDF page 24 — VLAN, Bluetooth protocol layers, hot-plug, and IOMMU|PDF page 24: VLAN, Bluetooth protocol layers, hot-plug, and IOMMU]] — The sequence likely comes from a Linux kernel boot log. It describes a machine bringing up segmentation, radio networking, packet transformation, hot-pluggable PCIe, and DMA isolation—precisely the substrate needed for secure virtualization and flexible networking. ## Relationships and overlays The source places this note in a shared evidence cluster with [[Bluetooth Network Encapsulation Protocol|Bluetooth Network Encapsulation Protocol]] · [[IEEE 802.1Q|IEEE 802.1Q]] · [[Input-output memory management unit|Input-output memory management unit]] · [[Logical Link Control and Adaptation Protocol|Logical Link Control and Adaptation Protocol]] · [[PCI Express Hot Plug|PCI Express Hot Plug]] · [[Scanned_20260730-1706|Scanned_20260730-1706]] · [[Synchronous Connection-Oriented link|Synchronous Connection-Oriented link]] · [[XFRM|XFRM]]. Within the larger collection, this evidence extends [[Vendor-Agnostic Recovery|vendor-agnostic recovery]] and [[Continuity Architecture|continuity architecture]] by showing how software, hardware, identity, and pre-OS control depend on recoverable interfaces. ## Evidentiary status and open leads Record IOMMU group topology, interrupt-remapping state, kernel parameters, and device assignment. “RF Bluetooth protocol” may be a paraphrase of an initialization message. ## Source - [[Scanned_20260730-1719|Scanned_20260730-1719]]