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Management Architecture and Standards

Management Architecture and Standards. IACT 418 IACT 918 Corporate Network Planning Gene Awyzio Spring 2001. Objectives. Recognise the protocols used in management of a telecommunications network with reference to the OSI stack, in particular SNMP ASN 1 MIB

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Management Architecture and Standards

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  1. Management Architecture and Standards IACT 418 IACT 918Corporate Network Planning Gene Awyzio Spring 2001

  2. Objectives • Recognise the protocols used in management of a telecommunications network with reference to the OSI stack, in particular • SNMP • ASN 1 • MIB • Identify databases and their use to manage the telecommunications network

  3. Objectives • Understand what is involved in change control, configuration management and configuring a network • Demonstrate appropriate practical and problem solving skills

  4. The OSI Stack • Proposed by the International Organisation for Standardisation (ISO) and other standards bodies • Its a layered approach to network protocols involving encapsulation of packets at each level of the stack and the sub-layers

  5. The OSI Stack • Each layer has its own functionality • All layers are likely present at the end user’s host machine or Front End processor (FEP) or customers equipment, but …

  6. The OSI Stack • Inside the network you may have only the first two or three layers • A router mostly has up to the network layer • A bridge uses the data link layer (sublayers LLC [Logical Link Control] and MAC [Medium Access Control]) • The network management protocols operate at the APPLICATION layer, like TELNET and FTP

  7. The OSI Stack Application 7 Presentation 6 Session 5 Transport 4 Network 3 Data Link 2 Physical 1

  8. The OSI Stack

  9. Network Management Software Architecture • A network management system consists of incremental hardware and software additions (scalable) implemented among existing network elements • The software used to accomplish the network management tasks resides in the host computers and communications processors: • Front End Processors (FEP) • terminal cluster controllers • Bridges • Routers

  10. Network Management Software Architecture • A network management system allows viewing of the entire network as a unified architecture: • With addresses and labels assigned to each network element • With specific attributes of each network element and its connectivity known to the system • The active elements of the network provide regular feedback of status information to the network control centre

  11. Network Management Software Architecture • A generic network management structure might be as given in the following figure:

  12. NMA NME Appl Comm NMA NME Comm NME NME Appl Appl OS Comm Comm NMA NMA Network Management Software Architecture

  13. Network Management Software Architecture • Each node contains a collection of software devoted to an appropriate network management task • Referred to as the network management entity ( NME)

  14. Network Management Software Architecture • At least one (and probably more ) host in the network is designated the network control host or manager • As well as the software for a NME, these hosts include extra software called the network management application (NMA)

  15. Distributed Network Management • Centralised network management systems aredevolving into distributed network management systems • Due to the same factors are involved that have lead to the distributed networks • Low cost of hardware / PC’s • High powered PC’s • Proliferation of LAN’s

  16. Distributed Network Management • A distributed management system replaces the single network control centre with interoperable workstations located on LANs distributed throughout the organisation • This gives departmental (local) level managers the tools they need to maintain responsive networks, systems and applications for their local end users

  17. Distributed Network Management • But… how do we avoid anarchy?

  18. Management server Management server MIB MIB Management Application Management Application Element Manager Distributed Network Management Management clients (PCs, workstations) Network Network Network Network Element Manager Network Resources (servers, routers, hosts) with management agents

  19. Distributed Network Management • The distributed system has the following benefits: • Network management traffic is minimised • Distributed management offers greater scalability • adding capability only involves adding another workstation in the appropriate location • The use of multiple networked stations eliminates the single point of failure represented by having only one central manager

  20. Proxies • Proxies may be required when: • Older network elements exist in the network that do not use the protocols implemented by the management servers • Small systems that would be unduly burdened (too many management packets would flow on the system) to support a full blown NME (agent) • Modems and multiplexers which do not support additional software / agents

  21. The term Simple Network Management Protocol (SNMP) actually refers to a collection of specifications that include: the protocol itself the definition of data structures associated concepts (eg proxies) We will now look at a brief overview of the SNMP setup, the most prolific method of network management today SNMP

  22. The History • SNMP’s development follows a similar pattern to the development of TCP/IP • ARPANET evolved during 1970’s, into a set of protocols approved by the internet architecture board (IAB) {www.iab.Org}

  23. The History • Standards were issued as RFC’s (Request for comment) and were adopted by the military in the United States in their procurement policies, forming the core of the TCP/IP protocol suite, which was adopted by vendors for non military activities, and grew dramatically during the 1980’s

  24. The History • Many still predict that OSI standards will replace TCP/IP, but this has not occurred at this time. Why? Possible reasons are: • TCP/IP suite is mature, and adapts to interoperability issues via the IAB / IETF • TCP/IP provides a high level of functionality - from the majority of users points of view • The international standards have been slowly developed (OSI), while providing a richer functionality they will also require more effort in implementation and conformance testing

  25. The History • As TCP/IP developed little thought was given to network management, especially in the early days where many programmers and protocol designers would modify the network as required • Through the late 1970’s there were still no network management protocols, but the one tool used for management that was available was the Internet Control Message Protocol (ICMP)

  26. Internet Control Message Protocol: • ICMP • Provides a means for transferring control messages from routers and other hosts to a host to provide feedback about problems in the networking environment • Most useful message is the echo / echo reply message pair - provides a mechanism to test if communication is possible between two network elements / entities on the TCP/IP network • Also provides a mechanism for measuring delay across the connection using time stamp and time stamp reply

  27. Internet Control Message Protocol: • The ICMP messages can be used with IP header options such as source routing and record route ( a trace route feature) to develop simple but powerful management tools • The most useful example of this is the widely used PING (Packet INternet Groper)

  28. Internet Control Message Protocol: • PING can perform a variety of functions • Determine if a particular network element can be addressed • Verifying that a network can be addressed • Observe variations in round trip times • Observe datagram loss rates, which can help isolate points of congestion and high error rates / points of failure

  29. Internet Control Message Protocol: • This was satisfactory up until the late 1980’s when exponential growth in the internet required more powerful network management capability • In November 1987, the Simple Gateway Monitoring Protocol (SGMP) was issued, providing a way to monitor gateways on the internet

  30. Internet Control Message Protocol: • At this time three approaches were proposed or emerged: • High Level Entity Management System (HEMS) • Simple Network Management Protocol (SNMP) • CMIP (Common Management Information Protocol from OSI) over TCP /IP (CMOT

  31. Internet Control Message Protocol: • In 1988 the IAB reviewed these proposals and approved SNMP for a short term solution and CMOT as the long range solution • Both SNMP and CMOT were to use the same database of managed objects • There would be only a single • Structure of Management Information (SMI - the basic format conventions for objects) • Management Information Base (MIB - the actual structure or schema of the database)

  32. Internet Control Message Protocol: • In 1989, after it was found impractical to have the same set of managed objects, the IAB relaxed its condition of common SMI / MIB and allowed the two protocols to develop independently • Freedom from OSI constraints led to rapid SNMP development

  33. SNMP Related Standards • Three foundation specifications of SNMP are: • Structure and Identification of Management Information for TCP/IP-based networks(RFC 1155) • Management Information Base for Network Management of TCP/IP-based Internets: MIB-II (RFC 1213) • Simple Network Management Protocol (RFC 1157)

  34. The SNMP Network Management Architecture • The model used for network management of TCP/IP includes the key elements: • Management station • Management agent • Management Information Base • Network management protocol

  35.  Management Station • Typically a stand-alone network element, but may be a capability on a shared system (eg mainframe) • Serves as the network interface for the human network manager into the network management system

  36.  Management Station •  As a minimum the network management station will have: • A set of management applications • An interface • The capability of translating the network manager's requirements into the actual monitoring and control of remote elements in the network • A database of information extracted from the MIBs of all the managed entities in the network •  SNMP standards only cover points 3 and 4

  37. Management agent • The management agent • Responds to requests for information and actions from the management station • May asynchronously provide the management station with important but unsolicited information

  38. Managed objects •  Resources in the network may be managed by representing these resources as objects • Each object is a data variable that represents one aspect of the managed agent • The collection of objects is referred to as a Management Information Base (MIB) • The MIB functions as a collection of access points at the agent for the management station

  39. Management Information Base • The objects are standardized across systems of a particular class • For example, a common set of objects is used for the management of various bridges •  A management station performs the monitoring function by retrieving the value of MIB objects

  40. Management Information Base • A management station can • Cause an action to take place at an agent • change the configuration settings at an agent by modifying the value of specific variables • The management station and agents are linked by a network management protocol

  41. SNMP - the Management Protocol Used for TCP/IP •  SNMP includes the following key capabilities: • Get • Set • Trap • The standards do not specify • The number of management stations • The ratio of management stations to agents

  42. SNMP - the Management Protocol Used for TCP/IP • In general, it is prudent to have at least two systems capable of performing the management station functions • As SNMP is simple it can handle many agents • SNMP is designed to be an application-level protocol that is part of the TCP/IP protocol suite which operates over the user datagram protocol (UDP)

  43. SNMP - the Management Protocol Used for TCP/IP

  44. SNMP - the Management Protocol Used for TCP/IP

  45. SNMP - the Management Protocol Used for TCP/IP • From a management station, three types of SNMP messages are issued on behalf of a management application: • GetRequest • GetNextRequest • SetRequest

  46. SNMP - the Management Protocol Used for TCP/IP • The first two are two variations of the get function • All three messages are acknowledged by the agent in the form of a GetResponse message, which is passed up to the management application

  47. SNMP - the Management Protocol Used for TCP/IP • An agent may issue a trap message in response to an event that affects the MIB and the underlying managed resources - this is received by the manager • SNMP relies on UDP, which is connectionless so SNMP is itself connectionless ie each exchange is a separate transaction between a management station and an agent

  48. Trap - Directed Polling • Preferred strategy is: • A management station can poll all of the agents it knows for some key information • Once the baseline is established, the management station refrains from polling • Each agent is responsible for notifying the management station of any unusual event

  49. Trap - Directed Polling • These events are communicated in SNMP messages known as traps • Once a management station is alerted to an exception condition, it chooses to take the appropriate action

  50. Trap - Directed Polling • Trap-directed polling can result in substantial savings of • Network capacity • Agent processing time • Reduces unnecessary polling of agents by managers thus reducing management induced network traffic

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