Page 381 - Handbook of Modern Telecommunications

3-172 CRC Handbook of Modern Telecommunications, Second Edition

3.7.2.1.4 Time Services
In distributed systems and network environments, where processes and applications are running on dif-
ferent machines, time differences may occur between systems. Such time differences become critical when
correct time stamps determine sequencing of events, job scheduling, measurement timing, and reporting
intervals. Consistent use of time services is imperative when dealing with global networks, which span
multiple time zones. Time service general requirements can be summarized as follows (MORR00):
• Use of an absolute, universal, coordinated time reference source
• Consistent synchronization services across hardware and software components
• Translation of universal time to local time for networks spanning multiple time zones
• Automatic resynchronization of manager and agent platforms after service interruptions
• Ability to operate in a heterogeneous computer and network environment
• Ability to keep the service running in case of major network instabilities
• Ability to provide both clock corrections and time source synchronization
In most cases, the Internet Network Time Protocol (NTP) is used. Its primary reference time source
is the absolute Universal Time Clock (UTC) or sources directly derived from the UTC.

3.7.2.1.5 Software Distribution
In complex environments, management systems are usually distributed. These systems consist of serv-
ers, clients, and the communication paths between them. In order to ensure that they remain in synch,
software versions or releases running on servers and clients must be compatible with each other. Manual
software distribution is too slow and not sufficiently reliable. Electronic software distribution offers two
popular alternatives: push and pull. Distributing software by “push” allows easier scheduling and better
automation and does not require the physical presence of administrators. However, receiver servers and
clients should be prepared for the distribution. Distributing by “pull” offers better control by admin-
istrators and changes during distribution at the price of low automation. Scheduling is flexible and
depends solely on human decisions. At present, pull is the usual choice in Web environments.

3.7.2.1.6 Security Services
Open distributed network environments consist of an increasing number of interconnected computing
resources, networks, and users. Networks are no longer closed networks but mixtures of private and
public networks. These networks include heterogeneous components, which has a bearing on security
services as well. The security of a network depends on the security of adjacent networks and other trusted
partners. Frequent changes, such as adding new resources and new users, lead to additional concerns
regarding security. Security can be seen as the security management functional feature built into certain
management applications, namely security management applications. Since management frameworks
control resources, security becomes an issue, as other framework services must operate securely if the sys-
tem as a whole is to be secure. Security is often embedded in framework services such as communications,
database management, and object manipulation services, which perform management operations.
Basic security requirements include (MORR00):
• Support for basic security features such as authentication, access control, and data integrity
• Ability to protect the system against potential intrusions
• Security features in the entire software development life cycle
• Distinctions in user security access profiles according to their role in the network
• Ability to group resources and users and apply common security policies to them
• Need to test security features and services against possible violations
• Protection of passwords and encryption keys by storing them in protected, encrypted files
• Mechanism to provide automatic clearing of disabled user accounts, user IDs, and passwords
• Capacity to communicate security data in a secured fashion