## 3 ICN Architecture
### 3N Architecture  
The Named-Node Network Architecture (3 NA) is an attempt to improve the delay and goodput of ICN for producers and consumers. 3 NA does not have specialized nodes to support mobility, as all nodes have the same structures and capabilities. 3 NA capable nodes differ from a common ICN node in three key ways. First, all nodes handle two additional independent namespaces. Second, there are two new structures to utilize the two new namespaces. Finally, 3 NA creates two sets of new PDUs, mechanism PDUs and data transmission PDUs to leverage the new namespaces [27,28].  
The first independent namespace adds unique labels to nodes belonging to the network. This namespace is called the Node name (3N) namespace. Names from this namespace are called 3N names. The 3N namespace attempts to be a metrizable topological space and consists of a single, complex, multi-level structure into which all 3N names fit. The 3N names follow strict naming instructions and their assignation in the network is highly regulated to maintain the namespace as a metrizable topological space.  
The second independent namespace adds labels to a node's Point of Attachments (PoAs) to the network. This namespace is called the PoA namespace and consists of the names typically used to identify interfaces on a physical transmission medium. Names belonging to this namespace are called PoA names. PoA names must only be unique among the end points of a shared communication medium. The namespace mappings for 3 NA can be seen in Figure 3.  
Figure 3: 3 NA namespaces and mappings.  
The Node Name Signature Table (NNST) is an additional structure to the common ICN architecture. This structure keeps a mapping between 3N names and PoA names. The mapping is used to create direct communication on a physical medium between nodes.  
A second addition to the common ICN architecture is the Node Name Pair Table (NNPT). This structure maintains a 3N name to 3N name mapping. The mapping is used to check whether nodes with a 3N name have been updated due to a change of the nodes' point of attachment to the network. In most cases, this type of reattachment makes the node use a different 3N name to maintain the properties of the names in the 3N namespace.  
Updates to the NNST and NNPT structures are done by signaling. Signaling is made possible by a set of PDUs called mechanism PDUs. Mechanism PDUs are utilized to enroll, dis-enroll, re-enroll nodes into the network and to update this information to the network. The mechanism PDUs for 3 NA are summarized in Table 1. The NNST is signaled whenever a node enrolls into the network via the use of the EN, OEN and AEN PDUs. Whenever a node dis-enrolls from the network, the NNST is signaled via the use of the DEN and ADEN PDUs. All re-enrollments are signaled to the NNST via the use of REN, OEN and AEN PDUs. The NNPT is signaled to update 3N name mappings whenever a node re-enrolls into the network via the use of the INF PDU. A simplified enrollment procedure is summarized in Figure 11. A simplified re-enrollment procedure is summarized in Figure 11. A more detailed explanation of the procedures are explained in [27; 28].  
The common ICN PIT was also modified to aggregate the 3N names of the nodes sending Interest PDUs. This modification allows Data PDUs to be sent directly to nodes by using 3N names. If 3N names are not used in 3 NA, the network performs exactly like the ICN architecture as described in Section 3.