## 5 Discussion  
The security research applied to LoWPAN networks is considered by the industry and by the research community a very hot topic. Several security mechanisms were proposed, some of them to address some particular scenarios, application and protocols. Besides protecting the network from some well-known threats, it is important that security mechanisms can withstand to attacks that have not been identified before. Therefore, the challenge is on how can the attackers explore vulnerabilities that have not been yet identified. The control of which nodes can take part of the network and their security compliance can help to reduce several vulnerabilities, making the network more manageable, while increasing its reliability and extending its lifetime. The proposed security framework proposal can be used to achieve these objectives, in particular to make the network more resilient to internal attacks. First, network assessment control restricts the network access only to authorized nodes. Second, node security compliance is enforced before node can access to the network. Finally, beyond to security compliance assessment, the software image can also be checked in order to guarantee that node is able to realize the expected functions. Therefore, only authorized nodes that fulfill security and functions requirements are accepted. This is particularly relevant if multi-hop networks are used. Node authorization depends on:  
* Administrator authorization: a manual authorization was considered because it is very hard to define rules that can be applied to all network security requirements. For example, in a monitoring network installed in a nuclear power plant, if a new node tries to access the network, it will be most probably a malicious node since the network infrastructure remains unchanged for long time periods. Therefore, the administrator can approve the new nodes based on: hardware type, layer-two address and location. This approval method also protects the framework against DoS attacks, because only approved nodes will be evaluated. All nodes are identified by a cryptographic generated address, according to LSEND protocol. * Security check compliance: several conditions can be considered as inputs to the agent used to assess the security compliance such as, for example, the installed software image and the security protocols in use. Note that multiple agents might be required if different operating systems or hardware platforms are used in the same network. The decision on which agent should be used on each device node is a challenge. * Hardware and software image compliance: providing plug-and-play mechanism is not enough to guarantee that node is able to realize the desired functions. For example, a sensor node is unable to monitor the temperature if the module used to retrieve the temperature is missing. The same occurs with the hardware. Software image compliance also helps to protect against malicious code injection. The proposed framework also improves the network manageability, since remote software installation is supported. The implementation success of the proposed security framework depends on the ability to integrate the above described mechanisms and protocols in order to take advantage of synergies between them. In fact, the following modifications are required in order to maximize the integration benefits. LSEND requires the addition of a secure mechanism to inform nodes that a neighbor must be removed from its neighbor cache in order to avoid communications between authorized nodes and malicious nodes. It is also necessary to define a data structure to share the ECC key pairwise generated by the LSEND protocol with the RPL routing protocol and remote image installation mechanism. Note that the ECC key pairwise can also be used to protect the application layer data exchange, in order to guarantee data authentication and authenticity.