Remote Network Monitoring (RMON) *

1. Remote Network Monitoring (RMON)* *Mani Subramanian “Network Management: Principles and practice”, Addison-Wesley, 2000.

2. Basic Concepts RMON Goals Control of Remote Monitors Multiple Managers Table Management Statistics group History group Host and hostTopN groups Matrix group Alarm group Filter and packet Capture group Outline

3. Extends the SNMP functionality without changing the protocol Allows the monitoring of remote networks (inter-network management) MAC-layer (layer 2 in OSI) monitoring Defines a Remote MONitoring (RMON) MIB that supplements MIB-II with MIB-II, the manager can obtain information on individual devices only with RMON MIB, the manager can obtain information on the LAN as a whole Basic Concepts

4. called network monitors, analyzers or probes A monitor generally can produce summary information on error statistics, e.g., counts # of collisions on a LAN Performance statistics: #packets delivered per second, packet size distribution, etc. A monitor also can store packets for later analysis A Monitor may also filter data to limit the # packets counted or captured filter based on packet type or characteristics (e.g., packets with certain source address, erroneous packets) Basic Concepts

5. A Monitor is required per subnetwork A monitor could either be a standalone device whose only job is monitoring and traffic analysis or it could also be a device with other functionalities (e.g., router, server) A monitor usually communicates with one (or more) central MS RMON essentially is a definition of a MIB Standard monitoring functions and interfaces for communication between SNMP consoles and remote monitors Basic Concepts

6. Monitoring subnetwork-wide behavior while reducing the burden on agents and managers Monitors and analyzes locally and relays data Continuous off-line monitoring in the presence of failures RMON should collect fault, performance, and configuration information continuously even when it is not being polled  save communication cost This information may be retrieved later by a manager Proactive monitoring Continuously runs diagnostics and store network performance even in the absence of failures Upon a failure, notify the manager and provide him with useful info to be able to diagnose the fault RMON Goals

7. Provide value-added data Perform analysis on collected data, thus relieving the MS from this responsibility Support multiple managers Multiple managers improves reliability, provides diversity in network management, etc. A monitor should be configured to deal with more than a manager simultaneously RMON Goals

8. Management console with RMON probe Ethernet Central Site Router Router Local management console with RMON probe Router Router Ethernet PC with RMON probe FDDI backbone Bridge Router with RMON probe Ethernet Token Ring LAN PC with RMON probe Network with RMONs

9. RMON is configured for data collection: RMON MIB contains a number of functional groups Each group may contain one or more “control tables” and one or more “data tables” Control tables (read-write) contain parameters describing data in data tables (read-only) Control of RMON- Configuration • A NMS sets appropriate control parameters to configure RMON to collect the desired data: • The parameters are set by adding a new row to the “control table” or by modifying an existing row • As information is collected, data is stored in rows of the corresponding “data table”

10. Functions performed by a monitor are defined and implemented in terms of table rows Control table may contain objects that specify the “source of data” to be collected, the “type of data”, the “collection timing”, etc. Associated with a single control row are one ore more rows in one or more data tables Control of RMON- Configuration • To modify a particular data collection function: • it is necessary first to invalidate the control row • this causes the deletion of that row and the deletion of all associated rows in data tables • NMS can create a new control row with the modified parameters • NOTE: when a row of a control table is deleted, associated rows in data tables are also deleted.

11. RMON probe may be subject to management from multiple MSs Potential conflict and unwanted results Simultaneous requests for resources could exceed the capability of the monitor Monitor resources could be captured by a MS for a long time, preventing other MSs from accessing desired information Resources could be assigned to a MS that crashes without releasing resources Avoidance and resolution features are required Ownership label:identifies the owner of a particular row of the control table and associated function Multiple Managers

12. RMON suggests that ownership label contains one or more of: IP address, management station name, network manager’s name, location or phone number The ownership label can be used in the following ways A MS may recognize resources it owns and no longer needs A network operator can identify the MS that owns a particular resource and negotiate its release A network operator may have the authority unilaterally to free resources A MS after experiencing failure or re-initialization can recognize resources it had reserved in the past and free those it no longer needs NOTE: A row in a control table should only then be altered by its owner and read by other MSs. Multiple Managers

13. Resource sharing to improve efficiency If a certain management function has been defined by some MS, another MS can share its usage by observing the associated “read-only” data rows (see EntryStatus definition) However, the MS that owns this control row may modify or delete the row at any time (and hence the associated data rows) Monitor’s default functions These are monitoring functions owned by the monitor itself By convention, such ownership labels start with “monitor” A MS can make use of such resources in a read-only fashion Multiple Managers

14. The RMON specification includes a set of textual conventions and procedural rules for row addition and deletion Textual conventions: 2 new data types OwnerString ::= DisplayString EntryStatus ::=INTEGER { valid (1), createRequest (2), underCreation (3), invalid (4) } Indicates the owner of a row in control table Indicates the status of the row Table Management

15. Control Table

16. Data Table

17. rm1ControlTable rmlControlIndex rmlControlParameter rmlControlOwner rmlControlStatus 1 5 monitor valid (1) 2 26 manager alpha valid (1) 3 19 manager beta valid (1) rm1DataTable rmlDataControlIndex rmlDataIndex rmlDataValue 1 1 46 2 1 96 2 2 85 2 3 77 2 4 27 2 5 92 3 1 86 3 2 26 Control and Data Table- Example

18. A MS uses SNMP messages to add a row into an RMON table SetRequest-PDU message will contain a list of object identifiers for all columns in the table When a monitor receives a request it must check whether there are any restrictions defined in the RMON MIB (object is not currently supported by the MIB) or any implementation specific restrictions (e.g., lack of resources) If row addition is not possible GetResponse-PDU with badValue error is returned Row Addition and deletion • Multiple managers attempt for row addition • multiple requests to create a row with same parameters, including index parameters  conflict • Conflict arbitration is required • Only the first request is awarded • Row Deletion • is achieved by (the owner) setting the status object for that row to “invalid” • Row Modification • is achieved by first invalidating the row and then adding the row with new object instance values

19. rmon (mib-2 16) statistics (1) agent a agent b agent c history (2) alarm (3) Subnetwork X host (4) Interface 1 hostTopN (5) RMON probe matrix (6) Interface 2 filter (7) Subnetwork Y capture (8) event (9) agent e agent d tokenRing (10) RMON MIB 10 groups • Each group is used to store data and statistics derived from data collected by the monitor • A monitor may have more than one physical interface and hence may be connected to more than one sub-network

20. agent a agent b agent c Subnetwork X Interface 1 RMON probe Interface 2 Subnetwork Y agent e agent d Statistics Group • Basic statistics for each monitored subnetwork • A “single” table with one entry for each interface • Variety of counts for each subnetwork, such as: bytes, packets, errors, frame sizes, etc. • Provides useful information about the load on a subnetwork and its health (counts collisions, etc..)

21. History Group • Sampling function for one or more of the interfaces of the monitor • historyControlTable: specifies the interface and details of the sampling function • etherHistoryTable: records data • historyControlTabledefines a set of samples at a particular sampling interval for a particular interface • historyControlIndex identifies a row in the control table • historyControlDataSource identifies interface or subnetwork that is source of data • historyControlBucketsRequestedrequested # sampling intervals over which data is saved in the data table (default value = 50) • historyControlBucketsGranted actual # sampling intervals over which data will be saved • historyControlInterval interval in seconds over which data is sampled (default value = 1800 seconds (30 minutes))

22. histroyControlTable historyControl- DataSource historyControl- BucketsGranted historyControl- Index historyControl- Interval B1 I1 1 D1 B2 2 D2 I2 DK BK K IK History Group etherHistoryIndex etherHistorySampleIndex 1 x+1 1 x+2 1 x+3 1 x+B1 2 y+1 2 y+2 y+B2 2 etherHistoryTable

23. (1) (2) T Pkts(96+64) + (Octets8)  =   T History Group • etherHistoryTable • etherHistoryIndex: the history of which this entry is part (index) • etherHistorySampleIndex: identifies the particular sample among all samples associated with the same row in control table • Table contains also some useful counters • etherStatsOctets: # of received octets of data • etherStatsPkts: # of received packets, etc… • Subnetwork utilization: • : medium data rate (bps) • T: sampling interval (seconds) • Pkts = [ etherStatsPkts ]2 - [ etherStatsPkts ]1 • Octets = [etherStatsOctets]2 - [ etherStatsOctets ]1 •  = utilization NOTE: 64-bit preamble, and 96-bit IFG

24. History Group • For a given subnetwork, historyControlDataSource, more than one sampling process is allowed at different sampling period historyControlInterval • Sampling over short period (e.g. 30s) enables the monitor to detect sudden changes in traffic pattern • Sampling over long periods (e.g., 30 minutes) enables a monitor to observe the steady state behavior of certain interface • After each sampling interval, the monitor adds a new row to the etherHistoryTable with the same etherHistoryIndex • When the # rows of a history becomes equal to historyControlBucketsGranted, as each new row is added, the oldest row associated with this history is deleted. “circular buffer”

25. B2 2 D2 I2 A new interface or subnetwork 1 x+3 A new sample added 2 y+1 2 y+2 y+B2 2 History Group histroyControlTable historyControl- DataSource historyControl- BucketsGranted historyControl- Index historyControl- Interval B1 I1 1 D1 etherHistoryTable etherHistoryIndex etherHistorySampleIndex 1 x+1 1 x+2

26. B2 2 D2 I2 A new interface or subnetwork 1 x+3 A new sample added 2 y+2 2 y+3 y+B2+1 2 History Group histroyControlTable historyControl- DataSource historyControl- BucketsGranted historyControl- Index historyControl- Interval B1 I1 1 D1 etherHistoryTable etherHistoryIndex etherHistorySampleIndex 1 x+1 1 x+2 Oldest entry (sample) is deleted

27. host and hostTopN Groups • host Group • Gather statistics about specific hosts on the LAN • hostInPkts, hostOutPkts, etc.. • By observing s-d MAC addresses in monitored packets, a monitor can discover new attached hosts on the LAN • hostTopN Group • To maintain statistics about the set of hosts on one subnetwork that top a list based on some parameter • List of the 10 hosts that transmitted the most data during a particular day • List of nodes ordered according to errors they’ve sent in the last hour

28. Matrix Group • matrixControlTable: • matrixControlIndex integer uniquely identifies a row. • matrixControlDataSourceInterface that is source of traffic • matrixControlTableSize # of rows in data table (matrixSDTable) associated with this row • matrixSDTable: • store statistics on traffic from a source to multiple destinations • matrixSDSourceAddress: MAC address of source • matrixSDDestAddress: MAC address of destination • matrixSDPckts: # packets transmitted from s- to d- • matrixSDOctets: # octets in packets transmitted from s- to d- • Record information about traffic between pairs of hosts on a subnetwork • error and utilization, e.g. traffic amount, number of errors • Information is stored in the form of a matrix • so the operator can retrieve information for any pair of network addresses, e.g., to find which devices are making the most use of a server

29. alarm Group • Measuring network performance consists of identifying abnormal conditions by the monitor and issuing alarms accordingly: • e.g., if there are more than 200 CRC errors (the threshold) in any 5-minute period (the sampling interval), an alarm is generated and sent to the central console. • Alarm group contains a single table alarmTable, each entry: • a variable to be monitored (alarmVariable) • INTEGER, counter, gauge, TimeTicks • A sampling interval (alarmInterval) • most recent sampled value (alarmValue) • Threshold parameters • alarmRisingThreshold, andalarmFallingThreshold • alarmStartupAlarm • alarm is generated when a row becomes active and 1st sampled value  risingThreshold, or  fallingThreshold or both

30. Fluctuations not counted! Avoid generating excessive alarms alarm Group Mode of operation: • Rising threshold (RT) and Falling threshold (FT) are defined • RT is crossed when current sampled value is greater than RT and value of last sampling interval was less than threshold • FT is crossed when current sampled value is less than FT and value of last sampling interval was greater than threshold • absoluteValue and deltaValue (difference of 2 successive intervals). Counter  use deltaValue Sampled Object value Rising threshold Falling threshold Time

31. filter Group • Observing only “selected packets” on a particular interface • Data filter • Screen observed packets based on a bit pattern that a portion of the packet matches (or fails to match) • Status filter • Screen observed packets based on their status (e.g., valid, CRC errors, etc.) • Example: screen those packets on some interface with certain source MAC address! • The monitor may capture packets that pass the filter or simply record statistics based on such packets • Both filters can be combined to form a complex test to be applied to incoming packets • filter test example: we wish to accept all Ethernet packets with destination address 0xA5 and that do not have a source address of 0xBB! capture Group

32. event Group • eventTable: • eventDescritpion: textual description of the event • eventType: none(1), log(2), snmp-trap (3) log-and-trap(4) • log: an entry is added to the logTable for this event • snmp-trap: an SNMP trap is sent to a MS • eventCommunity: identifies the communities of MSs to receive the SNMP trap, etc. • logTable: • logTime: value of sysUpTime when this log entry was created • logDescription: description of the event that activated this entry (implementation-dependent) • logEventIndex: the event that generated this log entry • Supports definition of events (problems, symptoms of problems) • An event is triggered by a condition located elsewhere in the MIB • E.g., monitoring a variable that crossed a rising threshold would cause an event to be generated • Controls the generation and notification of events • An event may cause an SNMP trap message to be issued by the monitor

33. Remote FDDI LAN Routerwith RMON FDDI Probe FDDI Backbone Network Router Bridge Local LAN Router NMS Ethernet Remote Token Ring LAN Probe Token Ring Probe RMON2 • Enable probes to look beyond LAN segments • Analyze traffic passing through the router to determine the ultimate source and destination • Monitor application level traffic (e-mails, file transfer, WWW, etc.)