1. www.infotech.monash.edu Models of Network Administration Burgess (2 nd Ed) Chapter 6

2. www.infotech.monash.edu 2 Understanding the system as a whole Requires ability to see relationships and dependencies between distinct parts The idea of a “causal web” Complex system may have multiple operating modes – adaptive behaviour

3. www.infotech.monash.edu 3 Models for Management IETF (SNMP RFC1155) and ISO (TMN) have defined models for management of systems These don’t always scale well –Focus on managing devices –Require a Human controller –Micro-manage the system Best model are those which automate functions and regulate interactions of components

4. www.infotech.monash.edu Management metaData

5. www.infotech.monash.edu 5 Information Models Represent the data used by an organisation eg database of Personnel, Assets and Services Uses a Directory service (eg X.500) –Structured: hierarchical, object-oriented –Common schema: allows interoperability –Access Control: per record –Optimised for read-only use. Not updated during use Specific vs General search –“White pages” vs “Yellow pages”

6. www.infotech.monash.edu 6 Network Directory X.500 ISO 9594 (1988) Uses ASN.1 to define format of protocols Access method (DAP) defined in ISO terms LDAPv3 (RFC 2251–2256) Now replacing or being integrating into vendor solutions eg NDS and MS ActiveDirectory

7. www.infotech.monash.edu 7 Lightweight Directory Access Protocol (LDAP) Contains Name-Value(s) pairs (“attributes”) Attributes have rules (sub-attributes) controlling –Method of value matching during search –Order of value matching during search –Whether attribute is mandatory or optional Attributes identified by Distinguished Name (DN) or Relative Distinguished Name (RDN) RDN is a Name-Value pair eg cn=“Chris Freeman” DN is a concatenation of RDNs in hierarchy

8. www.infotech.monash.edu 8 Hierarchical Directory Services Well suited to distributed environment; Allows delegation of parts to separate hosts Directory tree may be partitioned into sub-trees with no overlap Cooperating groups with can then manage their own data locally and share with others May allow Availability and Redundancy through replication of data and service

9. www.infotech.monash.edu 9 Hierarchical Directory Services

10. www.infotech.monash.edu 10 Querying Directory Services Usually built-in to application software –Unix system call: GetHostByName( ) –Uses “nsswitch” to select one of several directory services –See also “Pluggable Authentication Modules” (PAM) Original UNIX methods based on /etc files Later used NIS (aka “YellowPages” or yp) –Non-hierarchical, lacked security –Replaces by NIS+

11. www.infotech.monash.edu 11 Other Directory Services OpenLDAP –Versatile, common platform –Difficult syntax and sensitive to network LoS Novell Directory Service (NDS) –Consistent distributed physical organisation of devices and software objects –Directly implements the information model Microsoft Active Directory –Replaced NT4 Domain model –Compatible with simplified version of LDAP

12. www.infotech.monash.edu Managing Network Infrastructure

13. www.infotech.monash.edu 13 System Infrastructure A network is a “community of cooperating and competing” components… Administrator selects components and assigns roles depending on tasks required This may involve machines and users (staff) –Computing machinery: functional infrastructure –Staff: build and maintain infrastructure

14. www.infotech.monash.edu 14 System Infrastructure Identify purpose of computer system Choose hardware and software –Appropriate to task Set policies and procedures

15. www.infotech.monash.edu 15 Aspects of System Infrastructure Homogeneity –All systems identical or Configure for purpose? Load Balancing –One service per host or multi-service hosts? –Separate data storage and data processing can double network traffic Human limitations on group size: max150 objects Mobile and AdHoc networks Peer-to-Peer: Scaled approach to management

16. www.infotech.monash.edu 16 Network Administration Models Central management – “star” model

17. www.infotech.monash.edu 17 Network Administration Models Centralised policy and enforcement JobRate controller =Rate 1 +Rate 2 +…Rate n If sum of Requests exceeds maxCapacity/n then work will queue at the controller Disadvantage of centralised control: bottleneck in communications with controller

18. www.infotech.monash.edu 18 Other Network Administration Models Star with intermittently connected hosts Mesh: centralised policy & local enforcement –Each host gets own copy of common policy. Does not need constant connection to controller –Each host updates itself according to policy –But: Is policy up-to-date? Has policy been applied? Mesh: partial host autonomy & local enforcement Mesh: partial autonomy and peer policy exchange

19. www.infotech.monash.edu Network management Technologies SNMP, OSI TMS, WBEM, etc…

20. www.infotech.monash.edu 20 Network Management Technologies SNMP OSI TMN and Others Java Management Extensions (JMX) Jini and UPnP: management-free networks WMI and WBEM

21. www.infotech.monash.edu 21 Building an Infrastructure What is the correct way to build a complex networked application ? 1.NIC drivers 2.Local host config: Host name, SysLog 3.IP configuration (DHCP) 4.Domain Name configuration (Resolver, dDNS) 5.Middleware services (NIS, Kerberos, RADIUS) 6.Application services (MySQL, httpd, java, …) 7.Client applications (Browser, java, client APIs)

22. www.infotech.monash.edu 22 Aspects of Infrastructure Creating uniformity through Automation Revision control: HostFactory, RCS Software distribution & synchronisation –Push model:rdist –Pull model:cfengine, rsync Reliability through parallelism

23. www.infotech.monash.edu 23 System Maintenance models Reboot –return to original (if it still exists!) Manual administration –not scalable, relies on knowledgable user Central control –HP Openview, Tivoli, Sun Solstice –star model problems Immunology (self-maintenance) –Eg. Windows automatic restore

24. www.infotech.monash.edu 24 Multiple Operating Systems in a LAN Real situations are rarely “Green Field” systems. Management involves compromise between: Convenience vs Differentiation Simple file transfer vs Open file sharing? Software compatibility between systems Problems: –Different object naming schemes –File System sharing: different Naming & ACLs –Different User ID and password schemes –User Authentication

25. www.infotech.monash.edu End…