Figure 2 shows the IP stack of a device with optional elements that are only required for a router. Basically, the IP stack provides access to the TCP or UDP protocols for applications running on the device. Usually, applications will implement further application-level protocols on top of TCP, for example, the Hypertext Transfer Protocol (HTTP) in the case of a Web browser. A device will transmit the IP data on a given network interface. Depending on the number of network interfaces of a device, the IP stack contains a complex routing table, which decides over which interface an IP packet is transmitted.
Figure 2: IP-related Protocols and Services
To support dynamic addressing in an IP system, e.g., for the user’s mobile devices, the router implements a server for the Dynamic Host Configuration Protocol (DHCP), which provides IP addresses and other IP-related settings to devices in the system. MOST devices, however, are assigned with static IP addresses to allow for a faster start-up of the system. Network Address Translation (NAT) converts the IP address received from a service provider into local addresses. For the resolution of textual addresses (Universal Resource Locator, URL) into IP addresses, the HU also implements a forwarding mechanism for the Domain Name System (DNS).
As a security mechanism, an Internet Protocol Security (IPSec) client is used to establish an encrypted connection with a Daimler backend system. All traffic to and from applications on the infotainment system is routed through this backend, where suitable security mechanisms can be implemented and managed in one place. Firewall mechanisms prevent any other traffic to and from these applications. Only defined exceptions are allowed to bypass the secure tunnel to