Example
As an example, assume the case of Wake-on-LAN. Traditionally, the OS controls Wake-on-LAN and must call third-party device drivers to enable support on a network card. With the HECI bus, the host is able to assert its request line (REQ#), the ME will assert its grant line (GNT#), and the host can send its message using its serial transmit signal. Upon receipt of the Wake-on-LAN enable message on HECI, the ME directly enables Wake-on-LAN in the integrated (or externally supported) network device. Without HECI drivers in the OS, Wake-on-LAN functionality is lost even if standard network drivers would be able to enable it. This is a major problem in large-scale enterprise deployments with standard software images.
When the magic wake packet is received by the LAN device, the encapsulated data is passed to the ME, which has its own TCP/IP stack and can decapsulate the packet. The ME then asserts its request line (REQ#), the host acknowledges by asserting grant (GNT#), and the message is passed to the host to initiate a wake event.
With this technology, the magic packet may be encapsulated in TCP packets thus allowing the packet to traverse network infrastructures via routers and thereby increasing the attack surface, something which traditional Wake-on-LAN does not enable. An advantage in Intel-centric deployments is that the solution does not require non-Intel drivers. If no host/ME interaction is needed, HECI and other ME technologies are OS independent.
Read more about this topic: Host Embedded Controller Interface
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