The MIHF is the central entity of the IEEE 802.21 standard, defined as a logical entity whose purpose is to facilitate handover decisions to the network selector entity. Its purpose is achieved by providing the inputs to higher layers through abstract services and communicating with the lower layers of the mobility-management protocol stack through technology-specific interfaces. By other words, the MIHF provides mechanisms that enable the upper layers to manage and control the handover procedure in a media independent way.

The MIH-User specifies a media independent interface between the MIHF and upper layers of the mobility management protocol stack. The upper layers need to register with the MIHF as users to receive MIHF-generated events and link-layer events which are originated at lower layers. MIH-Users directly send commands to the local MIHF using the service primitives available in the 802.21 standard.

The MIIS Server provides details about the characteristics and services provided by the serving and neighbor networks. The information enables effective system access and effective handover decisions.

The DNS-User enables the discovery of PoS entities in a given domain using the DNS services (according to the guidelines depicted in the RFC5679).

The DHCP-User enables the discovery of PoS entities by using the DHCP procedures (according to the guidelines depicted in the RFC5678).

The Link SAP specifies an abstract media dependent interface between the MIHF and the lower layers media-specific protocol stacks of technologies such as IEEE 802.3, IEEE 802.11, IEEE 802.16, 3GPP and 3GPP2.

The ICMP Link SAP allows the attachment detection of another node using the ICMP protocol.

The client is a simple application that lets you send any message to a particular destination. In this way, it is possible to send a specific message to a choosen destination in order to test is behaviour easily and quickly.

The dummyserver is a simple application that, as the name implies, works like a dummy server. It is always listening (at port 4000) for incoming messages and it outputs them in the console.

The NL80211 SAP is a Linux implementation of a basic Link SAP. It supports the most important events and commands for 802.11 devices. It is based on the nl80211 generic protocol, and depends on the netlink library version 3.

The sap_80211 Link SAP is a Windows implementation of a Link SAP for 802.11 interfaces. It supports the most important events and commands for 802.11 devices. It is based on the XXX.

The 802.3 SAP is a Linux implementation of a basic Link SAP. It supports the most important events and commands for 802.3 devices. It is based on the route netlink protocol, and depends on the netlink library version 3.