pplication layer for management. Some of the messages are: Message Explanation Request Used to invoke a remote method Reply This is the response to a "Request" message LocateRequest Used to check if a particular address is supported or request on the address of the remote object Application objects TCP/IP Figure 6.2 Layered view showing where IIOP fits in. Management Protocols LocateReply This is a response to the "LocateRequest" and contains the address of the object, in case the remote object has moved CancelRequest Used to cancel a request that was send previously MessageError Used to report an error in message CloseConnection Used to end a session between distributed objects Messages can also be split into fragments for communication. HTTP, which is widely used for internet communication, was not suited for remote method invoca- tion (RMI) based on CORBA. Hence, the use of IIOP on CORBA can be used as an alternative to HTTP for Internet communication. IIOP is based on the client- server model. Advantages of IIOP: Neutral architecture for communication Transparency in communication Scalability and code reuse Robust firewall navigation Disadvantages of IIOP Complex standard The disadvantages of CORBA and RMI are combined in IIOP 6.10 Conclusion This chapter only gives an overview on some of the popular management protocols. There are many other application layer protocols that are used for telecom manage- ment. For example, it is a common practice to have FTP (file transfer protocol) used to support performance management. This involves the element to be man- aged, writing performance records to files on the element. The manager collects the performance records generated by the element at regular intervals using FTP protocol and parses the records to collect performance data. Here the interaction between the element and the manager to get performance data is based on the FTP. Application layer protocols for connection like TELNET (TELecommunication NETwork) and SSH (Secure SHell) can be used to have a console f