## 3 Our Next Generation Internet Architecture  
In this section, a brief overview of the HiiMap architecture is given. We only discuss the aspects which are relevant for the security extension introduced and evaluated in this article. For a more detailed introduction, please refer to [1]. In today's Internet architecture, the IP address has two semantic meanings. First, it serves as the address stating _who_ I want to communicate with and, second, _where_ I can find that person or node. Figure 1: Simplified geometric representation of [PERSON]’s Secret Sharing. Contrary to the IP addressing scheme, any protocol following the locator/identifier-split principle, provides two separate addresses--namely an identifier and a locator. One advantage of the locator/identifier-split idea is the built-in support for mobility. Applications communicate based on identifiers which are not changing even if a node is roaming. By changing its connection point towards the network only the locator reflects the new topological location of the node. An intelligent entity within the network is responsible to map the identifier to the current valid locator. The mapping system stores the current valid \(\langle identifier,locator\rangle\)-tuple. Whenever a node roams and its locator changes, it needs to inform the mapping system of the updated locator. Storing multiple locators for a single identifier is also possible. In addition to the locator, a timestamp is stored with each mapping entry. This timestamp indicates the last update of the locator. The HiiMap architecture is based on the locator/identifier-split and provides a two-tier hierarchical mapping system. The 128 bit identifier in HiiMap is a flat randomized address and once assigned it never changes other than the user requests a new identifier for his node. In HiiMap, the identifier can also be used to address persons or content, but for simplification we only consider end nodes from here on. The mapping system in HiiMap is split into administrative domains, so called regions. Each region holds the mapping for the nodes it is responsible for. Even if a node roams (temporarily residing within another region) the mapping for that node is still resolved at its responsible region. To identify the responsible region of a node, an 8 bit regional prefix is provided for each identifier. Contrary to the identifier, this prefix is allowed to change whenever a node relocates to another region--this means, switching to another provider which is associated with another region for example. Figure 2 illustrates the identifier--regional prefix set. The regional prefix for any identifier can be learned in various ways. It can be provided along with the identifier from either a link on a web page or a domain name system entry. It also can be queried at the global authority which holds the identifier to responsible region mapping for each id. To lessen the burden of the global authority, the regional prefix can be cached as it is expected to change quite rarely. Figure 3 shows the topology of the HiiMap mapping system and an example of the lookup process. In this case, node A wants to establish a connection to a server S. In case node A did not learn the identifier from a domain name system or link--and, therefore, did not learn the regional prefix--it first needs to contact the global authority (1). The global authority returns the regional prefix corresponding to the server's identifier. In a next step--and all succeeding connections--user A directly contacts the region of the server S to resolve the mapping for the locator (2). The mapping system of the region returns the current valid locator and node A is able to send packets addressed to the locator of server S (3). In case node A wants to communicate with another mobile node, the connection setup process remains the same. If the second node, however, roams during the connection, it informs node A directly about its new locator. Figure 2: Identifier with regional prefix (RP).