Survey of modern fault diagnosis methods in networks <s> A. Information gathering <s> Network-aware applications, i.e., applications that adapt to network conditions in an application-specific way, need both static and dynamic information about the network to be able to adapt intelligently to network conditions. The CMU Remos interface gives applications access to a wide range of information in a network-independent fashion. Remos uses a logical topology to capture the network information that is relevant to applications in a concise way. However, collecting this information efficiently is challenging for several reasons: networks use diverse technologies and can be very large (Internet); applications need diverse information; and network managers might have concerns about leaking confidential information. In this paper we present an architecture for a hierarchical collector of network information. The decentralized architecture relies on data collectors that collect information on individual subnets; data collectors can collect information in manner that is appropriate for that subnet and can control the distribution of the information. For application queries that involve multiple subnets, we use a set of master collectors to partition requests and distribute subrequests to individual data collectors and to combine the results. Collectors cache recent network information to improve efficiency and responsiveness. This paper presents and justifies the collector architecture, describes a prototype implementation, and presents preliminary measurements characterizing its operation. <s> BIB001 </s> Survey of modern fault diagnosis methods in networks <s> A. Information gathering <s> In order to maintain the topological consistency during updating,an incremental updating method of spatial database based on the topological linkage is proposed in this paper.In this method,for each kinds of entity,the basic topological linkages are analysed,if necessary they will be subdivided until the state of each entity involved and their topological relationship can be determined.A set of rules used to determine the change type of each entity should be concluded based on the entity's semantic,topological consistency rules,and the topological relations between the involved entities before and after the change.Then the changes of each involved entity will be inferred according to these rules.A set of updating operators mapping the spatial changes of entities to the corresponding objects' state changes are designed and implemented.The incremental updating of cadastral database is used as an example to illustrate this method,cadastral spatial changes are divided to five basic types: union,split,modification of common border,reallocation and node moving.Union,split,modification of common border are subdivided to 17 cases.The spatial change determination rules of cadastral entities are presented.The approach was implemented using VC++ in Oracle9i Spatial and MapX platform,the algorithms are checked by real and simulation data. <s> BIB002
There are four central protocols for managing in network fault diagnosis: the Internet Engineering Task Force Internet (IETF) defines the Simple Network Management Protocol (SNMP) [4]; International Organization for Standardization (ISO) defines the Common Management Information Protocol (CMIP) [5]; Transaction Language 1 (TL1) is widely used to manage optical network (SONET) and broadband access infrastructure in North America  . SNMP gains dominant market share and becomes the real industrial standard because of the support of CISCO and other main network equipment manufacturers. Information gathering can be divided into three kinds: active, passive, active-passive method BIB001  . Most active methods of gathering information depend on SNMP. In SNMP polling model, agents running on the aim network element and a central controller running on a computer are necessary. Central controller sends request for aim status to the agents periodically. Some network management systems use this method, like the Open View system of HP Company, the Net View system of IBM Company and the Net Management system of SUN Company. For sending request to agents and agents echoing timely, networks cost mu bandwidth and time on transferring and computing. Passive gathering SNMP Trap makes the controller monitor the SNMP Trap, without sending anything. So this method is real-time. However, Trap is carried by the User Data gram Protocol (UDP), which cannot ensure the quality of transmission. So passive gathering SNMP Trap is easy to lose something important. For the equipment which does not support the SNMP, topology linkage query BIB002 , ICMP message parsing  , syslog analyzing can be used. Some commercial software adapts these methods, such as the SPECTRUM system of the Cabletron Company, and the New Web NMS system of the Advent Company.