Ch6: Models of network and system administration

Introduction to Network and System Administration

• System Interaction:

  • Systems consist of interacting components that have mutual dependencies.

  • Ignoring these dependencies results in management errors and false assumptions.

  • Systems operate as complex cause-and-effect relationships, comparable to ecological webs.

• Adaptability:

  • An adaptable system is defined by its ability to cope with unexpected changes.

  • If original assumptions about a system fail, they can be modified in an adaptable system.

  • Adaptability enhances predictability during changes and facilitates recovery from failures.

• The Role of System Management:

  • The primary role of management is to secure the conditions required for system components to perform their specific functions.

  • Management should avoid controlling every minor detail; the focus must remain on securing necessary conditions.

  • Systems are first designed to function, and then management discusses attributes based on three key themes:

    1. Resource Management: Managing consumables and reusables.

    2. Scheduling: Managing time and queues.

    3. Strategy.

6.1 Information Models and Directory Services

• Definition and Function:

  • A directory service is a software application designed to manage information regarding network resources.

  • It acts as a centralized database to organize and store data about computers, users, printers, and various network devices.

  • Access is restricted to authorized applications and users.

• Utility in Enterprise Networks:

  • Widely utilized for authentication, authorization, and general resource management.

  • Enables Single Sign-On (SSO) capabilities, allowing users to log in once and access resources across multiple systems without repeated authentication.

  • Named Examples:

    • Active Directory (Microsoft)

    • OpenLDAP (The OpenLDAP Project)

    • Novell eDirectory (Micro Focus)

• Usage Models:

  • White Pages: A lookup performed when the user starts with a specific key for a specific resource (e.g., looking up a specific number in a telephone book).

  • Yellow Pages: A browsing-based service used when the exact resource is unknown, requiring a list of categories to match services or users.

• Technical Infrastructure:

  • Maps network resources to their respective physical network addresses.

  • Provides a shared infrastructure for organizing and administering resources such as volumes, files, folders, groups, users, devices, and telephone numbers.

  • In a directory server (or name server), every network resource is treated as an object.

  • Information about resources is stored as a collection of attributes associated with that object.

• Namespace and Identification:

  • Directory services define a network namespace and assign a unique identifier (name) to every object.

  • Namespace rules ensure names are unique and unambiguous.

  • Allows users to locate resources by name instead of physical address.

  • Access control provisions may limit information availability to authorized users.

X.500 Standards and Protocols

• Overview:

  • X.500 refers to a set of ITU-T standards defining protocols for global directory services.

  • It uses a hierarchical directory structure for organizing network resource information.

  • While widely used in enterprises for auth/auth and resource management, it has largely been superseded by the simpler Lightweight Directory Access Protocol (LDAP).

• Protocol Suite:

  1. Directory Access Protocol (DAP)

  2. Lightweight Directory Access Protocol (LDAP) (Note: DAP and LDAP constitute Group 1; they differ in description and complexity)

  3. Directory System Protocol (DSP)

  4. Directory Information Shadowing Protocol (DISP): Used as a replication protocol.

  5. Directory Operational Bindings Management Protocol (DOP)

  6. Certificate Authority Subscription Protocol (CASP)

  7. Authorization Validation Management Protocol (AVMP)

  8. Trust Broker Protocol (TBP)

• Object Classes:

  • Abstract: Located at the upper levels of the hierarchy. Entries are only populated if inherited by a structural class. Examples include ‘top’, ‘Country’, ‘Device’, ‘Organizational-Person’, and ‘Security-Object’.

  • Structural: The primary content or ‘meat’ of an object class used for actual entries. Examples include ‘person’ and ‘organization’. The attribute ‘objectClass’ declares the entry type (e.g., ‘Computer’ or ‘Configuration’).

  • Auxiliary: Defines special-case attributes added to specific entries as hints. For instance, both a person and an organization might need a telephone number or web page, even if it is not a requirement of their structural class.

• Distributed Directory Partitioning:

  • As shown in Figure 6.1, a distributed directory can be partitioned into distinct areas, each handled by a separate server (indicated by dotted areas in the visualization).

6.2 System Infrastructure Organization

• Economic Balance: Administrators must find the equilibrium between spending money effectively and saving money where appropriate.

• Team Work and Communication:

  • Bi-directional communication is essential in several forms:

    • Computer programs and their data.

    • Computers and devices.

    • Collaborating humans in teams.

    • Clients and servers.

    • Users and systems.

    • Policy decision-makers and policy enforcers.

    • Computers and the environment (indicated by physical hazards like spilled coffee).

• Communication Noise and Errors:

  • Environmental noise can interfere with communication in two ways:

    1. Faulty Communication/External Interference: Information is distorted, omitted, or inserted.

    2. Incorrect Interpretation: Symbols are incorrectly identified due to external interference or imprecision.

• System Administration as a Meta-Program:

  • System administration is viewed as a meta-program executed by both machines and humans to manage system evolution. It involves:

    • Configuring systems within policy.

    • Maintaining machine operation within policy.

    • Managing user activity within policy.

• The Development Loop (Figure 6.2):

  • Visualizes system development over time based on a set of rules.

  • Components: Rule, Message, Noise, Computer, and Users.

  • Users influence the system by altering rules, changing the conditions for rules, or directly touching/configuring the computer.

Homogeneity and Delegation

• 6.2.2 Homogeneity (Uniformity):

  • Refers to making all hosts identical or similar in software and hardware configuration.

  • Advantages: Increased system predictability, easier management for administrators, and the ability to reuse hardware during emergencies.

  • Disadvantages: Specialized hardware may offer superior performance for specific applications (e.g., high-availability servers requiring multiple processors, high memory, and high bandwidth) that homogeneous systems lack.

• Delegation II:

  • Assigns responsibilities to local administrators who understand local host usage patterns.

  • Minimizes the distance between the administrative center and the zone of responsibility.

  • Types of Delegation:

    1. Administrative: Assigning specific tasks to a subordinate.

    2. Project: Responsibility for a specific project/set of tasks.

    3. Resource: Access to budget or equipment.

    4. Authority: Delegating the power to make decisions on behalf of a superior.

    5. Policy: Responsibility for creating, implementing, and enforcing policies.

    6. Functional: Delegating specific functions (e.g., HR or marketing).

6.2.4 Mobile and Ad Hoc Networks

• Definition: An Ad Hoc Network (AHN) is a collection of mobile objects capable of transmitting information.

• Characteristics:

  • Forms an arbitrary graph that evolves over time.

  • Nodes (humans and devices) move randomly, leading to rapid and unpredictable changes in network topology.

  • Important for intermittent connectivity and describing high-level associations (who is in contact with whom; information flow paths).

• Study Importance:

  • Flexibility: Adapts to changing topologies; ideal for military operations, emergency response, or remote locations.

  • Resource Efficiency: No need for pre-existing infrastructure; cost-effective and quick to deploy.

  • Scalability: Can scale from small personal networks to large industrial ones.

  • Research & Development: A fresh field leading to new technological advancements.

6.2.5 Peer-to-Peer (P2P) Services

• Definition: Applications where each node chooses whether to participate in or abstain from data exchange with others over a common channel.

• Key Concepts:

  • Platforms connect parties directly without a third-party intermediary.

  • Technology is used to overcome traditional transaction costs related to trust, enforcement, and information asymmetries.

  • Services provided include payment processing, quality assurance, and information about buyers/sellers.

• Examples:

  • Open-source Software.

  • Filesharing.

  • Online Marketplaces.

  • Cryptocurrency and Blockchain.