tion links left the down state and transitioned into some other state (but not into the notPresent state) . This other state is indicated by the included value of ifOperStatus.</descriptor> </event> <!- End of xml generated from MIB: IF-MIB 32.6 Conclusion The intent of this chapter is to introduce the reader to the basic concepts of imple- menting NETCONF. The chapter started with a basic overview of NETCONF. Then the layers that are relevant for NETCONF application development were discussed. The chapter concludes with an implementation example for converting MIB file to XML with libsmi library. Implementing communication between cli- ent and server using a management protocol is the base framework over which busi- ness logic of operation support solution is added. The basic operations remain the same when using another management protocol. For example NETCONF <get- config> is similar to SNMP "GET" and SNMP "SET" is similar to NETCONF <set-config> operation. Additional Reading 1. Alexander Clemm, Marshall Wilensky, and Scott Bradner. Network Management Fundamentals. Indianapolis, IN: Cisco Press, 2006. 2. Robert L. Townsend. SNMP Application Developer's Guide. New York: Wiley, 1995. 3. Larry Walsh. SNMP MIB Handbook. England: Wyndham Press, 2008. 4. Douglas Mauro and Kevin Schmidt. Essential SNMP. 2nd ed. California: O'Reilly Media, Inc., 2005. Chapter 33 OSS Design Patterns This chapter is about design patterns that are commonly used in programming management applications. There are several design patterns that can be applied in the development of specific modules in management application. The discussion in this chapter is limited to a few of the common design patterns used in management application development. 33.1 Introduction This chapter details the following design patterns in the context of developing man- agement applications: The Singleton Design Pattern The Chain of Responsibility Design Pattern The Observer Design Pattern The Factory Design Pattern The Adapter Design Pattern The Iterator Design Pat