To communicate not only with home electric appliances, but also between "objects" connecting to the network, IP addresses are required. In the conventional Client/Server model, DNS is used for name resolution. In the m2m-x model, descriptive definition is additionally expanded in the framework of SIP (session initiation protocol) which is a signaling protocol for End-to-End communication, thereby realizing a name resolution function.

Figure 3 shows the outline of the m2m-x framework. The devices for End-to-End communication are generically called User Agent (UA).

[Figure 3] (Click to enlarge)

All the UAs on the network register SIP-URI in advance (in the form of "sip:video@m2m-x.com", for example) which is the user's name and the user's IP address in association in the m2m-x server. (This is called the REGISTER message in (1).)

In this register sequence, an encrypted communication channel is formed between the m2m-x server and the UA.

In registering in the m2m-x server, authentication of a registered user is conducted. The information assigned by ISP at entry into the service is used for authentication. The user needs to set the information in the terminal device. (In some cases, the information has been preset in the device or is automatically set.) Normally, the IP address of the user terminal is automatically obtained by the terminal device. Therefore, the user doesn't need to set the IP address.

Next, when starting the actual End-to-End communication, the UA negotiates the session start by designating the SIP-URI of the other UA. (This is called the INVITE message in (2).) This INVITE message is transmitted to the m2m-x server. Even if the UA doesn't know the IP address of the other UA, the m2m-x server relays the message responsibly.

At this time, the m2m-x server relays the message after judging it as an INVITE message from an authorized user. If the m2m-x server receives an INVITE request from an unauthorized user, the m2m-x server returns it as a user-unknown message and conceals the existence.

Through the exchange of these INVITE messages, UAs share various information such as IP addresses, ports and key data for encryption, and reach an agreement on protocol to be used for End-to-End connections.

After that, End-to-End direct communications will become available without the m2m-x server (P2P Communication in (3)).
Then, the UA controls the FW so that the packet of the other communicating party can be passed to the FW of the user's LAN. (After the end of communication or a certain lapse of time, the FW will be automatically closed.)

The communication channel for conducting (1) and (2) is called the "Signaling Channel" (dashed line), and the communication channel for (3) is called the "Data Channel" (full line).