tion. The authentica- tion server (AS), ticket-granting server (TGS), and the real or data server that provides services to others are the different servers involved in Kerberos. The authentication server (AS) is the key distribution center in Kerberos protocol. Each user that registers with the AS is provided with a user identity and password. These identities and passwords are stored in the AS database. After verifying the user, AS issues a session key to be used between the sender and TGS and then sends a ticket for TGS. The ticket-granting server (TGS) issues a ticket for the real server and a session key between the sender and receiver. User verification is separate from ticket issuing SO that the sender can contact TGS several times for obtaining tickets for different real servers, although the sender ID is verified just one time with AS. The real or data server provides services to other users. Global distribution of ASs and TGSs are allowed by Kerberos where each system is called a realm. The user gets a ticket for the local server. The user can ask local TGS to issue a ticket that is accepted by a distant TGS, and the ticket is sent provided that the distant TGS is registered with the local TGS. The user can then use the distant TGS in order to access the distant real server. Fundamentals of EMS, NMS and OSS/BSS Needham-Schroeder protocol: This key management protocol uses multiple challenge response interactions between parties SO as to achieve a flawless protocol. 31.6 Security Protocols The internet engineering task force (IETF) developed a collection of protocols to provide security for a packet at the IP level called IPSec (Internet protocol security). Selection of encryption, authentication, and hashing methods are left to the user. IPSec simply provides the framework and mechanism. A logical unidirectional (simplex) connection can be established between the source and the destination by an IPSec signaling protocol called security association (SA). Two SA connections are required for a bidirectiona