## 5 BSI Secure Networking Guide  
The BSI, founded in 1991, is a German federal office responsible for solving security issues and giving recommendations on the secure use of information technology. One of their biggest assets is the \"IT-Grundschutz-Katalog\" (basic IT protection catalog). The catalog is about 4000 pages long and provides recommendations for enterprises to keep their IT secure. Moreover, it is possible for companies to achieve a \"BSI Grundschutz\" certificate if an enterprise implements the necessary controls and measures. The catalog is divided into three main sections. The first, \"Bausteine\" (building blocks), describes all elements of IT which might exist within an enterprise. The second, \"Gefahrdungskataloge\" (risks catalogs), contains a list of various security risks for IT and describes the problems that can occur. The last catalog, \"Massahmenkatalog\" (measure catalog), lists measures that have to be taken in order to prevent or avoid security risks. Each one of the IT building blocks is associated with one or more security risks, and these again are associated with appropriate measures to avoid them.  
The last version of the IT-Grundschutz-Katalog was released in 2008. It gets updated with smaller additional parts if necessary. The latest version, however, does not cover IPv6 yet. IPv6 is named, if at all, only as a side note and considered as not relevant enough at that point of time. The only recommendation regarding IPv6 is that new network devices should be checked for IPv6 compliance and that IPv6 addresses are four times as long as IPv4. However, other documents for secure use of IPv6 have been published by the BSI. Among them is the guide for a secure deployment of IPv6.  
The BSI published this updated secure networking guide \"Sichere Anbindung von lokalen Netzen an das Internet (ISi-LANA)\" in July 2012 [65]. Before this, there existed an older version of the same guide that did not cover IPv6 at all. There was another small addition for IPv6 which only covered basic information. The new guide version two incorporates IPv6 from the beginning to end [65]. It is labeled as \"Studie\" (study) and provides a comprehensive overview of networking technology and protocols. The general structure of the BSI guide is the following.  
First, it introduces computer networks with basic networking protocols and components, which are needed to set up a Local Area Network (LAN). Second, it provides a complete chapter introducing IPv6 basics (new in this version). This chapter covers basically all relevant technologies of IPv6 without going into much detail. The guide continues with introducing ways to connect to the Internet and explains basic security technologies, such as packet filters and concepts such as Demilitarized Zone DMZ. The next chapter covers a basic infrastructure for requirements that the BSI calls \"normaler Schutzbedarf\" (common protection requirements). This chapter recommends an architecture for network segmentation, address planning, and a structure for the implementation of a security gateway to connect to the Internet and use and deliver Internet services. Chapter 6 describes by what criteria security components should be selected, the standards according to which they should be configured, and how they can be securely operated. The last chapter, which accounts for one third of the document, covers potential security hazards and provides recommendations to mitigate them, or at least to reduce the probability of network outages. It does not only feature solutions for the common protection requirements, but also for higher protection requirements. Also worth mentioning is the appendix where several variations of the basic infrastructure are shown and a recommendation for an addressing concept with IPv6 is given.