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Network Management Concepts: Models and Languages *. * Mani Subramanian “Network Management: Principles and practice” , Addison-Wesley, 2000. Network Management Concepts: Models and Languages. Network Management Systems Origin of Network Management OSI Management Models Organization
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Network Management Concepts: Models and Languages* *Mani Subramanian “Network Management: Principles and practice”, Addison-Wesley, 2000.
Network Management Concepts: Models and Languages • Network Management Systems • Origin of Network Management • OSI Management Models • Organization • Information • Communication • Functional • Abstract Syntax Notation 1 (ASN.1) • Basic Encoding Rules, BER
Server (agent) NMA Appl NME NME Appl Comm Comm OS OS Router (agent) NME Comm Appl NME OS Comm OS Network Management Systems (NMS) Network control host (Manager) • A NMS is an integrated collection of tools for network monitoring and control • Network management is concerned with system resources (e.g., hubs, bridges, routers, etc.) and the connectivity among them • NME and NMA: collection of software devoted for NM task Workstation (agent)
Elements of NMS • Network Management Entity (NME) • Collect statistics on communication and related activities • Store statistics locally • Responds to commands from the network control center (e.g. report its object status, etc.) • Generate messages to the network control center when local conditions change (e.g., port failure) • Network Management Application (NMA) • Interface allowing authorized users to manage the network • Display mgnt information and issue control commands to NME • To maintain high availability, two or more network control hosts (managers) are used!
NMS Network Network Agent Agent Network Network Objects Objects Network Management Components • Network Agent monitors its respective objects either in response to a query from the NMS or triggered by a local alarm • The agent communicates the relevant data to the NMS
NMS Network Network Agent Agent Network Network Objects Objects Network Management Components • A NMS manages all the components connected to a network which may be coming from different vendors • This might require installing multiple NMS or a single NMS capable of managing multiple vendor components (Interoperability). • Therefore, standards are required (2 major standards emerged: the Internet and OSI)
Management related applications e.g., fault and configuration management) Application Services Objects Objects Management Vendor A Vendor B Protocol Objects Objects Transport Case of two service providers: each managed independently. Some mgnt information can be shared Protocols Interoperability
Server (agent) NMA Appl NME NME Appl Comm Comm OS OS Router (agent) NME Comm Appl NME OS Comm OS Distributed Network Management Manager Centralized management • central control (makes sense when key resources reside in a central site and services are provided to remote users). • Enables managers to maintain control over the entire configuration, balancing resources against needs, and optimizing the overall resource utilization Drawbacks • traffic overhead, scalability and “single point of failure” Workstation (agent)
Distributed Network Management Advantages: • Traffic overhead is minimized: much of the traffic is confined to the local environment • Greater scalability: more workstations can be deployed to provide additional management • Eliminate the single “point of failure” by using multiple networked management stations Distributed management • replaces the single network control with interoperable workstations located on distributed LANs. • local control for managers over their own segments. • Hierarchical architecture is typically used where a central workstation (with backup) has global access rights and the ability to manage all network resources
Each may have access to one or more mgnt servers Devices with different management protocols Devices to be managed Distributed Network Management Management clients (PCs, workstations) Network Management server Management server Management application Management application MIB MIB Network Proxy Proxy Network resources with management agents (servers, routers, etc.)
Proxies • Ideally, all network components that are to be managed should include a network management entity (NME) with common network management software across all managers and agents. • This may actually not be practical or possible: • Proprietary management systems • Some components (e.g., modems) may not support additional software • It is common to have agents acting as proxies: • A proxy acts on behalf of other nodes • A manager communicates with a proxy to get information for a specific node
Proxies Proprietary management interface Management application Proxy manager Server proxy stub Client proxy stub Client stub Server stub Protocol stack Protocol stack Protocol stack Protocol stack Standard operations and event reports Proprietary operations and event reports
MANAGER Polling Event Reporting AGENTS MIB Polling and Event Reporting • Information that is useful for monitoring is collected and stored by agents and is made available to one or more manager systems. • Polling and event reporting are two techniques used for this purpose by both network managers and agents.
Event Reporting the agent initiates, and the manager acts as a listener waiting for incoming information A “reporting period” may be defined and configured by the manager When a significant (unusual) event occurs (e.g., a fault), the agent reports to the manager Reporting is more efficient than polling, especially for monitoring objects whose values change only infrequently Polling and Event Reporting Polling • A “request-response” interaction between a manager and agent. • A query is made by a manager to an authorized agent to request values for various information elements • The agent responds with information from its MIB • The request may take any shape: • asking for some specific values or could be about the structure used for the MIB
Polling and Event Reporting • A network monitoring system employs both polling and reporting schemes • Traditional TMN relies on event reporting whereas SNMP relies on polling and OSI falls in between • The choice of either depends on number of factors: • Amount of traffic generated • Robustness in critical situations • Delays in notifying • Amount of processing in managed devices • Reliable vs. unreliable transport • Network monitoring applications supported • Robustness of notification devices
Network Management Concepts: Models and Languages • Network Management Systems • Origin of Network Management • OSI Management Models • Organization • Information • Communication • Functional • Abstract Syntax Notation 1 (ASN.1) • Basic Encoding Rules, BER
ICMP: Internet Control Message Protocol • used by hosts & routers to communicate network-level information • error reporting: unreachable host, network, port, protocol • echo request/reply (used by PING) • network-layer “above” IP: • ICMP msgs carried in IP datagrams • ICMP message: type, code plus first 8 bytes of IP datagram causing error TypeCodedescription 0 0 echo reply (ping) 3 0 dest. network unreachable 3 1 dest host unreachable 3 2 dest protocol unreachable 3 3 dest port unreachable 3 6 dest network unknown 3 7 dest host unknown 4 0 source quench (congestion control - not used) 8 0 echo request (ping) 9 0 route advertisement 10 0 router discovery 11 0 TTL expired 12 0 bad IP header
When ICMP message arrives, source calculates RTT Traceroute does this 3 times Stopping criterion UDP segment eventually arrives at destination host Destination returns ICMP “host unreachable” packet (type 3, code 3) When source gets this ICMP, stops. Traceroute and ICMP • Source sends series of UDP segments (probes) to dest • First has TTL =1 • Second has TTL=2, etc. • Provide also unlikely port number • When nth datagram arrives to nth router: • Router discards datagram • And sends to source an ICMP message (type 11, code 0) • Message includes name of router& IP address
Ping, ”Sends ICMP ECHO_REQUEST packets to network hosts”, used to: Test destination reachability, compute round trip time count the # of hops to destination may provide record route option Ping failure does not guarantee un-reachability Firewalls may filter pings PING and ICMP • PING (Packet Internet Groper) is a simple management tool that depends on ICMP protocol • Measure round trip delays, packet loss, etc. • Isolates points of failure and areas of congestion
Standardized protocols with more functionalities than PING and yet as simple! SNMP (Simple Network Management Protocol) and CMIP (Common Management Information protocol) over TCP/IP have emerged and were approved by the IAB Origin of NM • Internet currently • growth in the number of attached hosts, • number of distinct administrative domains, • multi-vendor equipment, etc. • PING capability was not satisfactory! need for automated capabilities
Standard Salient Points OSI / CMIP International standard (ISO / OSI) Management of data communications network - LAN and WAN Deals with all 7 layers Most complete Object oriented Well structured and layered Consumes large resource in implementation Industry standard (IETF) SNMP/Internet Originally intended for management of Internet components, currently adopted for WAN and telecommunication systems Easy to implement Most widely implemented TMN International standard (ITU-T) Management of telecommunications network Based on OSI network management framework Addresses both network and administrative aspects of management IEEE IEEE standards adopted internationally Addresses LAN and MAN management Adopts OSI standards significantly Deals with first two layers of OSI Web-based Web-Based Enterprise Management (WBEM) Management Java Management Application Program Interface (JMAPI) NM Standards
NM Standards OSI (Open System Interconnection) NM • Adopted by the ISO (International Standards Organization) • Its management protocol is the CMIP (Common Management Information Protocol) • Very comprehensive and addresses the 7 layers of OSI • Managed objects are based on object classes and inheritance rules • Management of data communications network - LAN and WAN • Complex and consumes large resource in implementation • designed 1980’s: too slowly standardized
NM Standards Simple Network Management protocol (SNMP) • Industry standard (IETF) • Managed objects are defined as scalars with few characteristics such as data types, read-only, read-write attributes • Originally intended for management of Internet components, currently adopted for WAN and telecommunication systems • Easy to implement • Most widely implemented NM: most vendor equipment supports SNMP
IEEE Adopted Internationally Addresses LAN/MAN management Based on OSI Network Management Deals with first two layers of OSI (physical and data link layers) NM Standards Telecommunication Management Network (TMN) • International Standard (ITU) • Based on OSI Network Management • Management of telecommunications networks • Addresses both network and administrative aspects of management
NM Standards Web-based Management • Based on Web technology (web servers and browsers) • Still an evolving technology • Web-Based Enterprise Management (WBEM) • Desktop Management Task Force (DMTF) is actively developing specs for WBEM • DMTF had chosen Microsoft OO management model • Java Management Extensions (JMX) • Based on JAVA applets developed by Sun Microsystems
Network Management Concepts: Models and Languages • Network Management Systems • Origin of Network Management • OSI Management Models • Organization • Information • Communication • Functional • Abstract Syntax Notation 1 (ASN.1) • Basic Encoding Rules, BER
Network Management Organization Information Communication Functional Model Model Model Model Network Management Models Organization Model • the components of a NM system, their functions, and relationships (it defines manager, agent, object) Information Model • Structure of Management Information (SMI: Syntax and semantics) • Management Information Base (MIB: Organization of management information)
Network Management Organization Information Communication Functional Model Model Model Model Network Management Models Communication Model • Transfer syntax with bi-directional messages; Transfer structure (PDU) Functional Model • Application functions • Configure components • Monitor components • Measure performance • Secure information • Usage accounting
Manager MDB Managed objects Unmanaged objects MDB Management Database Agent process Two-Tier Network Management Organization Model Organization Model Managed object • A network element that is managed (e.g., routers, bridges, hubs, etc.) • Houses SNMP management agent • Objects are classified into managed/unmanaged • Managed object has a running management agent
Manager MDB Managed objects Unmanaged objects MDB Management Database Agent process Two-Tier Network Management Organization Model Organization Model Management Station (Manager) • Interface for network managers to monitor and control the network • Contains management applications (data analysis, fault recovery, etc.) • Translation capabilities from manager’s requirements into actual monitoring and control of remote elements • Contains DB of information extracted from MIBs of all the managed entities in the Network
Manager MDB Managed objects Unmanaged objects MDB Management Database Agent process Two-Tier Network Management Organization Model Organization Model Management Agent • Gathers information from objects • Configures parameters of objects (e.g., enable/disable a router port, shut down a port on a hub, etc.) • Responds to requests for information and actions from managers • Generates alarms and sends them to managers
Manager MDB Agent / Manager MDB Managed objects MDB Management Database Agent process Three-Tier Network Management Organization Model Organization Model • Middle layer plays the dual role • Agent to the top-level manager • Manager to the managed objects • collects, processes and stores data locally • Performs statistical operation on the data and passes it to top level manager • The intermediate system could be at a local site and passes info. to a remote site. • Example of middle level: Remote monitoring agent (RMON)
MoM Manager of Managers MoM NMS Network Management System MDB Agent Agent Agent NMS Agent NMS MDB MDB Manager Manager Managed objects Managed objects Organization Model Different network domains, each managed locally • Agent NMS manages the domain • MoM presents integrated view of domains • Domain may be geographical, administrative, vendor-specific products, etc.
SNMP MIB MANAGER AGENT Communication Model • Resources are represented as objects (or data variables) • Collection of objects is a MIB (more later) • A manager performs monitoring by retrieving the value of MIB objects • A manager causes an action to take place or changes the configuration settings by modifying values of specific variables
SNMP MIB MANAGER AGENT Communication Model • Management stations and agents are linked by a network management protocol • SNMP is used for the management of TCP/IP networks • Get: manager or management station can retrieve the value of objects at the agent • Set: set the values of objects at the agent • Trap: agent notifies manager on significant events
Protocol Architecture -SNMP uses UDP port 161 - connection-less (e.g., Ethernet, X.25, ATM) Interprets SNMP messages and controls the agent’s MIB
Operations / Requests Manager Responses Agent Notifications / Network Elements Applications Traps Managed Objects Management Message Communication Model Communication Model • Management data is communicated between agent and manager as well as between managers • Three aspects: • Transport medium of message exchange (transport protocol) • Message format (application protocol) • Actual message (commands and responses)
Application manages object Central MIB GetRequest GetNextRequest SetRequest GetResponse Trap GetRequest GetNextRequest SetRequest GetResponse Trap SNMP Manager SNMP Agent SNMP Messages UDP UDP IP IP Network Layer 1 & 2 Layer 1 & 2 Communication Model SNMP managedobjects Managementapplication
data agent managing entity data data agent data agent data agent Trap-Directed Polling • SNMP encourages the manager to use trap-directed polling • A manager may be responsible for a large number agents, each maintains a large number of managed objects • It is impractical to regularly poll all agents for all their readable objects (management overhead on the network may be very excessive!) managing entity managed device network management protocol managed device managed device managed device
data agent managing entity data data agent data agent data agent Trap-Directed Polling • Initially a manager may poll all the agents for some key information • e.g., interface characteristics (# pckts in/out, etc..) • Then, each agent is responsible for notifying (through trap messages) the manager of any unusual event • e.g., high pckt drop rate at some interface managing entity managed device network management protocol managed device managed device managed device • Substantial savings in network capacity and agent processing (use network resources for the right reason!)
Information Model • The representation of objects and information relevant to their management • This information is usually communicated between agents and management processes • SMI (Structure of Management Information) defines the syntax and semantics of management information stored in MIB (Management Information Base) ExamplesysDescr: { system 1 }Syntax: OCTET STRINGDefinition: "A textual description of the entity. "Access: read-onlyStatus: mandatory MIB • Contains information about objects • Organized by grouping of related objects • Defines relationship between objects • Agent MIB vs. Manager MIB • MIB Agent: local information • MIB Manager: info. on all network components
Information Model • MDB physical database; e.g.. Oracle • Contains measured or administratively configured values of NEs • MIB virtual database; schema compiled into management software • Info necessary for processes to exchange info. (e.g., #ports/hub) • A NMS can automatically discover (periodic broadcast of PING messages) a managed object, such as a hub, when added to the network • Once detected, its information (e.g., address, number of ports, etc.) is added to MDB • MIB does not need to be updated if another hub from same vendor already exist • The NMS can identify a new added object only after the MIB schema of the new added object is compiled into manager MIB.
Root itu iso iso-itu 0 1 2 Level 1 org Level 2 3 dod Level 3 6 internet Management Information Tree 1 OSI Management Information Tree Management Information Tree • Both Internet and OSI define objects uniquely by a tree structure • Each managed object occupies a node in the tree underneath the root • Designation of objects: iso 1 org 1.3 dod 1.3.6 internet 1.3.6.1 Standard organizations: define management of objects under them Managed Objects
Access: Object Type: Object ID Access and Descriptor privilege circle Status : Implementation requirements Syntax : Definition : model of object Semantics - textual description Internet Perspective Object Type and Instance object ID unique ID and descriptor and name for the object syntax used to model the object access access privilege to a managed object (read-only, etc) status implementation requirements (e.g., optional or mandatory) definition textual description of the semantics of object type
Notifications : Notify changes in attribute values Object Class: Elliptical object Circular Object Class: object Behavior Operations: Push Attributes: : Attributes: ellipse, dimension circle, dimension OSI Perspective Object Type and Instance object class managed object attributes attributes visible at its boundary operations access operations that can be applied to it behavior behavior exhibited by it in response to an operation Notifications notifications emitted by the object
Function Model • Configuration management • set and change network configuration and component parameters • Set up alarm thresholds • Fault management • Detection and isolation of failures in network • Trouble ticket administration • Performance management • Monitor performance of network • Security management • Authentication • Authorization • Encryption • Accounting management • Functional accounting of network usage
Network Management Concepts: Models and Languages • Network Management Systems • Origin of Network Management • OSI Management Models • Organization • Information • Communication • Functional • Abstract Syntax Notation 1 (ASN.1) • Basic Encoding Rules, BER
Abstract and Transfer Syntaxes User is concerned with semantics of data User User The user of data transfer comp. e.g., SNMP, FTP, TELNET for TCP/IP User Presentation Mapping Concerned with syntax of data Application Component Application Component Local Abstract Local Mapping Syntax Mapping LocalStorage LocalStorage Encoding Rules Encoding Rules Data Transfer Component Data Transfer Component Transfer Mechanisms for transfer of data between end systems (e.g., TCP or UDP) Syntax Binary representation of data
Abstract and Transfer Syntaxes • For the application component, information is presented in an abstract syntax that deals with data types and data values • Abstract syntax is the set of rules used to specify data types and structures for storage of information • Abstract syntax is used to exchange info. between application components in systems • Makes application layer protocols independent of lower layer protocols • Abstract syntax must be mapped into some form for presentation to the human user • And to some local format for storage (e.g. of this mapping is in the case of MIB; however, elements within MIB are defined using abstract syntax)