Fault Management

1. Fault Management IACT 918 July 2004 Gene Awyzio SITACS University of Wollongong

2. Overview • Fault Management is the process of locating and correcting network problems or faults • Comprehensive fault management is probably the most important task in Network Management

3. Benefits of Fault Management Process • Increased network reliability • Provides tools allowing engineer to quickly • Detect problems • Initiate recovery procedures • Need to maintain the illusion of complete and continuous connectivity • Also provides tools to extract information about the networks current state

4. Accomplishing Fault Management • Can be considered as a three (3) step process • Identify the fault • Isolate the cause of the fault • Correct the fault if possible

5. Identifying the fault • Gathering Information to identify a problem • To learn that a problem exists we need to gather data about the current state of the network • Two approaches • Log critical network events • Poll network devices

6. Identifying the fault • Critical network events • Examples • Failure of a link • Lack of response from host • Transmitted by network device when fault conditions occur • Reactive method • If device fails it cannot send an event

7. Identifying the fault • Occasional Polling • Can help find faults in a timely manner • Tradeoff • Degree of timeliness vs bandwidth consumption • Other factors • Number of devices to poll • Bandwidth of links • Example • Assume each query and response is 100 bytes long (including data and header information) • For a network of 30 devices • (100 + 100) * 30 = 6000bytes/polling interval = 48,000 bits/polling interval • Polling every minute • 800 bits/second • (48,000 bits/polling interval * 60 secs * 60 polls) = 172,800,000 = 173 Megabits/hour • Polling every 10 minutes • 17.3 Megabits/hour • May not know about event for 10 minutes

8. Deciding Which Faults to Manage • Need to decide which faults to mange • Need to prioritise faults • If number of faults reports is high network may not handle volume • Limiting event traffic can reduce redundant transmissions and storage • Factors to consider • Scope of control over network • Size of network

9. Fault Management of a Network Management System • Simplest system • Reports existence of fault but NOT location • More complex tool • Uses capability of hosts and network devices to • Send critical network events • Facilitate isolation of fault cause • Advanced tool • Correction of fault

10. Impact of a Fault on the Network • A fault management tool MUST be capable of analysing how a fault can affect other areas of the network • Need to know • What services the fault • STOPS • IMPACTS • Not only that a fault has occurred but also how that fault affects other network communication • Data can come from performance management tools

11. Form of Reporting Faults • Common forms of fault reporting • Text • Graphical • Auditory signals • Text • Will work on any type of terminal • Graphical • Considered to be very effective • Can use flashing images to gain attention • Colour can be used to indicate device status • Auditory signals • Will quickly call attention to the occurrence of a fault