System support & Management Protocols

1. System support & Management Protocols Lesson 13 NETS2150/2850 School of Information Technologies

2. Lecture Outline • Simple Network Management Protocol- SNMP • Domain Name System- DNS • Dynamic Host Configuration Protocol- DHCP

3. Network Management - SNMP • Simple Network Management Protocol • Networks are becoming indispensable • More complexity makes failure more likely • Require automatic network management tools • Standards required to allow multi-vendor networks • Covering: • Services • Protocols • Management information base (MIB)

4. Network Management Systems • Collection of tools for network management • Single operator interface • Powerful, user friendly command set • Performing most or all management tasks • Minimal amount of separate equipment • i.e. use existing equipment • View entire network as unified architecture • Active elements provide regular feedback

5. Key Elements • Management station or manager • Agent • Management information base • Network management protocol

6. Management Station • Stand alone system or part of shared system • Interface for human network manager • Set of management applications • Data analysis • Fault recovery • Interface to monitor and control network • Translate manager’s requirements into monitoring and control of remote elements • Data base of network management information extracted from managed entities

7. Management Agent • Hosts, bridges, hubs, routers equipped with agent software • Allow them to be managed from management station • Respond to requests for information • Respond to requests for action • Asynchronously supply unsolicited information

8. Management Information Base • MIB • Representation of network resources as objects • Each object a variable representing one aspect of managed object • MIB is collection of access points at agent for management of station • Objects standardized across class of system • Bridge, router etc.

9. Network Management Protocol • Link between management station and agent • TCP/IP uses SNMP • OSI uses Common Management Information Protocol (CMIP)

10. Protocol Capabilities • Get • Set • Notify

11. Management Layout • May be centralized in simple network • May be distributed in large, complex network • Multiple management servers • Each manages pool of agents • Management may be delegated to intermediate manager

12. Example of Distributed Network Management Configuration

13. Network Management Protocol Architecture • Application-level protocol • Part of TCP/IP protocol suite • Runs over UDP • From management station, three types of SNMP messages issued • GetRequest, GetNextRequest, and SetRequest • Port 161 • Agent replies with GetResponse • Agent may issue trap message in response to event that affects MIB and underlying managed • Port 162

14. SNMP v3: The latest version • Addresses security issues of SNMP v1/2 • RFC 2570-2575 • Proposed standard January 1998 • Defines overall architecture and security capability • To be used with SNMP v2

15. SNMP v3 Services • Authentication • Part of User-Based Security (UBS) • Assures that message: • Came from identified source • Has not been altered • Has not been delayed or replayed • Privacy • Encrypted messages using DES • Access control • Can configure agents to provide a number of levels of access to MIB • Access to information • Limit operations

16. Domain Name System – DNS • Name Space • Flat • Hierarchical

17. Domain Name Space • Was designed in order to have a • hierarchical name space • Label • Domain Name

18. Domain name space

19. Domain names and labels

20. Domain Names: FQDN and PQDN

21. Domains

22. Distribution of Name Spaces • Hierarchy of Name Servers • Zone • Root Server • Primary and Secondary Servers

23. Hierarchy of name servers

24. Zones and domains Note A primary server loads all information from the disk file; the secondary server loads all information from the primary server.

25. DNS In The Internet • Generic Domain • Country Domain • Inverse Domain

26. DNS in the Internet

27. Generic domains

28. New generic domain labels

29. Country domains

30. Inverse domain

31. Resolution • Resolver • Mapping Names to Addresses • Mapping Addresses to Names • Recursive Resolution • Iterative Resolution • Caching

32. Recursive resolution

33. Query and response messages

34. Note: DNS can use the services of UDP or TCP, using the well-known port 53.

35. Dynamic Address Configuration • Each computer attached to the Internet must have: • Its own IP address • Its subnet mask • The IP address of a Router • The IP address of a name server • Usually stored in a config file • Used at bootup

36. Dynamic Address Configuration… • How about first-time bootup? • Diskless terminal? • Or, the movement of a computer from one subnet to another? • Protocols needed for on-demand config (dynamically) • Example: DHCP

37. DHCP • Client-server program • DHCP server: two databases • First one: Statically binds physical addresses to IP addresses (Static db) • Second one: makes DHCP dynamic (Dynamic db) • Temporary IP addresses are assigned consulting available (unused) address pool • Valid for a negotiated time period only (leased) • Must renew or stop using after the lease expires • Renewal may or may not be granted by the server

38. DHCP: Client Transition States

39. Recommended Reading: • Stallings 22.3 (SNMP), • Forouzan 25 (DNS) & 19.2 (DHCP)