1299 Courses in Coventry

CWISA training course description This CWISA course covers wireless technologies with reference to IoT. It examines from an IoT perspective how wireless works, and is an excellent introduction to IoT for the wireless engineer. Topics range from wireless technologies, RF, to mobile networks, IoT, and security. What will you learn Describe wireless networking and IoT technologies. Explain basic RF communications. Plan wireless solutions. Describe how to implement wireless solutions. Use best practices in implementing wireless solutions. CWISA training course details Who will benefit: Anyone working with IoT technologies. Prerequisites: RF fundamentals. Duration 4 days CWISA training course contents Introduction to wireless technologies History of wireless, radio waves and frequencies, wireless technologies and related components, common components of wireless solutions, LAN networking requirements, Network security, Implementing wireless solutions, staging, documentation, security updates, Industry organizations, IEEE, compatibility and certification groups. Wireless network use cases Wireless BANs, Wireless PANs, Wireless LANs, Wireless MANs, Wireless WANs, Wireless sensor networks, New network driver-Internet of Things, IoT for industry (IIoT), IoT for connected vehicles, Residential environments, Retail, Education (K12), Higher education, Agriculture, Smart cities / Public access, Health care, Office buildings, Hospitality, Industry, Stadiums, arenas, and large public venues. Planning wireless solutions Identifying use cases and applications, common wireless requirements and constraints, performing a wireless system design, selecting and evaluating design parameters. RF communications RF wave characteristics, RF propagation behaviours, RF signal metrics, fundamentals of wireless modulation. other wireless carriers, common frequency bands. Radio frequency hardware Hardware levels, basic RF hardware components (circuit board level), RF link types (use category). RF device types. Mobile communications networks Mobile networks, LTE, 5G, Use cases. Short-range, low-rate, and low-power networks RF and speed, RF and range, RF and power, 802.11, 802.15.4, Bluetooth, LoRa (Long range) / LoRaWAN, ZigBee, 6LoWPAN, NB-IoT and LTE-M. Wireless sensor networks What is a Wireless Sensor Network (WSN)? WSN applications, Sensors and actuators, WSN architectures, Planning a WSN. Internet of Things (IoT) Internet of Things (IoT) defined, IoT history and its definition revisited, one more comment on the definition of IoT, IoT verticals, Oil & Gas, IoT structure/ architecture basics, IoT connected objects. Securing wireless networks Confidentiality, integrity and availability, Privacy, non-repudiation, authenticity & safety, Importance of authentication in wireless networks, Key cryptographic technologies & concepts, Authentication methods, Authorisation, OAuth 2.0 authorisation framework, monitoring. Troubleshooting wireless solutions Proper solutions design, designing and implementing wireless solutions, basic installation procedures, general configuration considerations, troubleshooting and remediation, troubleshoot common problems in wireless solutions. Programming, scripting and automation What is an API? categories of APIs, common API communication methods, choosing a language, why are we integrating systems? Application & integration architectures. Data structures & types, XML, YAML, API types.

Complete Python training course description Python is an agile, robust, expressive, fully objectoriented, extensible, and scalable programming language. It combines the power of compiled languages with the simplicity and rapid development of scripting languages. This course covers Python from the very basics of 'hello world!' through to object oriented programming and advanced topics such as multi threading. Hands on follows all the major sections in order to reinforce the theory. What will you learn Read Python programs. Write Python programs. Debug Python programs. Use Python's objects and memory model as well as its OOP features. Complete Python programming training course details Who will benefit: Anyone wishing to learn Python. Prerequisites: None. Duration 5 days Complete Python programming training course contents Welcome to Python: What is Python? Origins, features. Downloading and installing Python, Python manuals, comparing Python, other implementations. Getting started: Program output, the print statement, "hello world!", Program input, raw_input(), comments, operators, variables and assignment, numbers, strings, lists and tuples, dictionaries, indentation, if statement, while Loop, for loop. range(), list comprehensions. Files, open() and file() built-in functions. Errors and exceptions. Functions, Classes, Modules, useful functions. Python basics: Statements and syntax, variable assignment, identifiers, basic style guidelines, memory management, First Python programs, Related modules/developer tools. Python Objects: Other built-in types, Internal Types, Standard type operators, Standard type built-in functions, Categorizing standard types, Unsupported types. Numbers: Integers, Double precision floating point numbers, Complex numbers, Operators, Built-in and factory functions, Other numeric types. Sequences: strings, lists, and tuples: Sequences, Strings, Strings and operators, String-only operators, Built-in functions, String built-in methods, Special features of strings, Unicode, Summary of string highlights, Lists, Operators, Built-in functions, List type built-in methods, Special features of lists, Tuples, Tuple operators and built-in functions, Tuples special features, Copying Python objects and shallow and deep copies. Mapping and set types: Mapping Type: dictionaries and operators, Mapping type built-in and factory functions, Mapping type built-in methods, Dictionary keys, Set types, Set type operators, Built-in functions, Set type built-in methods. Conditionals and loops: If, else and elif statements, Conditional expressions, while, for, break, continue and pass statements, else statement . . . take two, Iterators and iter(), List comprehensions, Generator expressions. Files and input/output: File objects, File built-in functions [open() and file()], File built-in methods and attributes, Standard files, Command-line arguments, File system, File execution, Persistent storage modules. Errors and exceptions: What are exceptions? Detecting and handling exceptions, Context management, Exceptions as strings, Raising exceptions, Assertions, Standard exceptions, Creating Exceptions, Why exceptions, Exceptions and the sys module. Functions: Calling, creating and passing functions, formal arguments, variable-length arguments, functional programming, Variable scope, recursion, generators. Modules: Modules and files, Namespaces, Importing modules, Module import features, Module built-in functions, Packages, Other features of modules. Object-Oriented Programming (OOP): Classes, Class attributes, Instances, Instance attributes, Binding and method invocation, Static methods and class methods, Composition, Sub-classing and derivation, Inheritance, Built-in functions for classes, and other objects, Customizing classes with special methods, Privacy, Delegation, Advanced features of new-style classes (Python 2.2+), Related modules and documentation. Execution environment: Callable and code Objects, Executable object statements and built-in functions, Executing other programs. 'Restricted' and 'Terminating' execution, operating system interface. Regular expressions: Special symbols and characters, REs and Python, Regular expressions example. Network programming: Sockets: communication endpoints, Network programming in Python, SocketServer module, Twisted framework introduction. Internet client programming: What are internet clients? Transferring files, Network news, E-mail. Multithreaded Programming: Threads and processes Python, threads, and the global interpreter lock, The thread and threading Modules. GUI programming: Tkinter and Python programming, Tkinter Examples, Brief tour of other GUIs. Web programming: Web surfing with Python: creating simple web clients, Advanced Web clients, CGI: helping web servers process client data, Building CGI applications, Using Unicode with CGI, Advanced CGI, Web (HTTP) Servers. Database programming: Python database application programmer's interface (DB-API), ORMs. Miscellaneous Extending Python by writing extensions, Web Services, programming MS Office with Win32 COM, Python and Java programming with Jython.

WiMax training course description Broadband wireless access is an emerging technology area. This course looks at WiMAX, where it can be used, how it works and the alternative technologies. What will you learn Describe WiMAX. Explain how WiMAX works. Compare and contrast WiMAX with alternative broadband wireless access technologies. WiMax training course details Who will benefit: Anyone wishing to know more about WiMAX. Prerequisites: None. Duration 2 days WiMax training course contents Introduction What is WiMAX? WiMAX applications, The Internet, Internet access choices, wireless broadband access, WiMAX benefits. WiMAX overview Spectrums, LOS vs. non-LOS, bit rates, modulation, mobility, channel bandwidth, cell radius. WiMAX standards The WiMAX forum, IEEE, ETSI, HIPERACCESS, HIPERMAN, 802.16, 802.16-2004, 802.16a, 802.16e, 802.16f. WiMAX architecture Subscriber Stations (SS), Indoors, outdoors, antennas, Radio Base Stations (BS), LOS, Non LOS BackHaul, Point to multipoint, mesh support. Physical layer 10 - 66GHz, TDMA, TDD, FDD, 2 -11 GHz, SC2, OFDM, OFDMA, QPSK, QAM, Radio Link Control (RLC), uplink, downlink. MAC layer Traffic types (continuous, bursty), QoS, service types. MAC operations, connection oriented, frame structure, addressing. Convergence sublayers, service specific, common part, profiles (IP, ATM). Bandwidth request-grant, ARQ, Management messages. Security MAC privacy sublayer, network access authentication, AAA, 802.1x, key exchange and privacy. WiMAX alternatives WiMAX vs. 3G, WiMAX vs. 802.20.

Essential IMS training course description The IP Multimedia Core Network Subsystem (IMS) is defined by 3GPP as a new mobile infrastructure. This course studies the discreet elements in the IMS. What will you learn Describe the IMS. Describe the IMS architecture. Explain how charging, security and QoS is handled in the IMS. Explain how the IMS supports service enablers such as Push to talk and Presence. Essential IMS training course details Who will benefit: Telecommunications staff. Prerequisites: Mobile communications overview Duration 2 days Essential IMS training course contents Mobile communications review The role of IP in telecommunications. GSM to IMS. Enhanced multimedia services, Push To, convergence, conferencing, roaming. What is IMS? What it is, why IMS, standard bodies: 3GPP, IETF, OMA, IMS services. MMD comparison. IMS architecture blocks Overview, IMS functions, IMS interfaces, IMS protocols, IMS elements, IMS reference points. Access network, IMS in GSM, CDMA, WiFi & PSTN networks. Core network. Application, Control and Call planes. HSS - User database Identification. The user database, role of HSS, SLF and multiple HSSs. 'Normal' identities, IMPI, IMPU. IMS signalling: SIP What is SIP? SIP URI, contact address, UAs, Proxies, basic SIP call flow, SIP sessions. IMS other protocols Megaco, Diameter, XML, XCAP, COPS, RTP/RTCP, SDP, H.324M, IM and MSRP. Call/Session Control Call Session Control Functions (CSCF). Domains. Home networks, visited networks. CSCF and SIP. P-CSCF, P-CSCF discovery, P-CSCF functions. I-CSCF, DNS and I-CSCF. S-CSCF, S-CSCF functions, ENUM lookups. QoS. Example call flows. IMS services Open service platform, Application Servers, profiles, AS interface with S-CSCF. 'Normal' services (Caller ID, Call waiting, transfer…) Push to talk Over Cellular (PoC), IMS conferencing, Group management, IMS Presence, IMS Messaging. Other possible applications. Media servers. (MRFC, MRFP). Gateways IMS PSTN procedures, BGCF, PSTN interface. SGW, MGCF, MGW Charging Architecture, Offline, online and flow based charging, charging reference points, CCF, DIAMETER, ICID, IOI. IMS security IMS security architecture, identities, AAA, public and private user ID, service filters, Cx interface, RADIUS, Diameter protocol, 3GPP AKA, integrity, privacy, NDS, IPSEC, trust, assertion.

D-Link switches training course description A hands on course covering the product specifics of D-Link switches. Installation, configuration, maintenance and troubleshooting are all covered in a practical oriented way. What will you learn Install D-Link switches. Use the command line interface and the web based interface to manage D-Link switches. Configure and troubleshoot D-Link switches. Perform software upgrades and maintain configurations using TFTP. D-Link switches training course details Who will benefit: Anyone working with D-Link switches. Particularly aimed at engineers and technicians supporting D-Link switches. Prerequisites: None. Duration 2 days D-Link switches training course content Introduction How Ethernet works with hubs, How Ethernet works with switches. Installing D-link switches. Hands on Building a network with a hub, building a network with a D-Link switch. Basic troubleshooting The D-Link switch range, LEDs, cabling issues, factory resets, default settings. Hands on Building a network with multiple D-link switches. Configuration methods Managed vs. unmanaged switches, Console port access, telnet, web based access, SNMP, saving configurations, NVRAM, switch stacks. Hands on Accessing the switch using the CLI, IP address configuration, telnet. Command line interface Users, privileges, the CLI, online help. Hands on Basic commands, user accounts, displaying the switch configuration. Web based interface Getting started, basic format. Hands on Configuring the switch using the web interface. Port configuration Common port configuration tasks, link aggregation. Hands on Configuring ports. STP configuration What is STP? 802.1D vs. 802.1W (RSTP), configuring STP. Hands on Enabling and disabling STP, changing STP versions, configuring STP. VLAN configuration What are VLANS? 802.1Q, tagged/untagged, creating VLANS, applying VLANS. Hands on Setting up VLANS, setting up 802.1Q, Inter VLAN traffic. Housekeeping TFTP, upload download, updating firmware, updating configuration files, BOOTP/DHCP for IP addresses. Hands on Using TFTP to configure a D-Link switch. SNMP Switch configuration, D-View, other NMS's. Hands on Using SNMP to manage a D-link switch putting it all together: troubleshooting.

BGP training course description A detailed study of BGP, from the basics of how it works through to advanced issues such as route reflectors, policy, filtering, route selection and routing registries. The course culminates with a study of an industrial strength BGP template illustrating important issues such as bogon filtering. Practical hands on with routers follow the major sessions to reinforce the theory. A multiple choice exam, leading to the LAIT III certification, is available after the course. The exam consists of 60 questions and lasts 2 hours. What will you learn Connect enterprises to the Internet, and ISPs to each other. Describe how BGP works. List, describe and configure the main BGP attributes. Implement and troubleshoot BGP. Work with route aggregation and calculate CIDR prefixes in seconds. Influence traffic paths with BGP. BGP training course details Who will benefit: Anyone who will be working with BGP. Prerequisites: TCP/IP Foundation for engineers Definitive IP routing for engineers. Duration 5 days BGP training course contents Basic BGP IGPs, EGPs, What's BGP? BGP RIB, in/out process, tables peers, adding routes. Hands on Simple configuration and troubleshooting. The Internet and peering ASs, AS numbers, Internet structure, ISP types, ISP network design, IXs, peering vs. transit, public/ private peering, bi/multi-lateral peering. Hands on AS information gathering. How BGP works Incremental updates, Path vector protocols, BGP protocol stack, the BGP header, message types, NLRI, withdrawn routes, route refresh, route dampening. Hands on More troubleshooting, packet analysis. MBGP and IPv6 Multiprotocol routing, AFI, SAFI, MBGP and multicasts, IPv6, MPLS VPNs. Hands on IPv6 BGPv4 aggregation CIDR, benefits, techniques, shortcuts, configuring BGP aggregation, leaking routes. Hands on Reducing routing table size. BGP path selection BGP attributes, attribute types, route selection order, Local preference, AS prepend, MEDs. Hands on Influencing traffic with BGP. BGP routing policies What is policy? Examples, route filtering, AS filtering, REs, applying preference selectively, peer groups. Hands on Sophisticated policies. RIPE and routing registries RIRs, Allocations, assignments, PI vs. PA. Objects, RPSL, routing registry, Hands on The RIPE database. Automating BGP configuration Automation tools, whois, IRRToolSet, Bogon lists, tracking bogon lists, HTTP, Peering, routing registries, DNS. Communities What is a community? Community names, communities for: peer types and geography. RFC 1998, default communities. Hands on Setting local preference on other routers. Route servers What are route servers? LINX route servers, route server policy control, What are route collectors, Looking glasses. Hands on Setting up and working with a route server. Peer relationships IBGP, EBGP, next hop self, advertising routes into/out of BGP, synchronisation. Hands on IBGP, troubleshooting a large BGP network. Route reflectors and confederations Full mesh IBGP, Route reflectors, RR configuration and design, confederations, migration issues. Hands on RR configuration. BGP architectures Stub vs. transit AS, when to use BGP, multihoming strategies and issues, default routes. Multihop EBGP, load balancing. Hands on Multihoming. BGP security RFC 7454, security steps, BGP TTL security, filters, RPKI, ROAs, rsync, rrdp, validators. A secure BGP template. Hands on RPKI prefix validation.

MPLS training course description A hands-on introduction to MPLS covering the basics of what MPLS is and how to configure it, through to more advanced concepts such as MPLS VPNs and traffic engineering with MPLS. What will you learn Describe MPLS Explain how MPLS works Describe the interaction between OSPF/IS-IS/BGP and MPLS Describe MPLS traffic engineering MPLS training course details Who will benefit: Anyone working with MPLS. Prerequisites: IP Routing BGP Duration 3 days MPLS training course contents What is MPLS? What does MPLS stand for? What is MPLS? Core MPLS, MPLS and the 7 layer model, MPLS is a protocol, MPLS is a standard, MPLS runs on routers, MPLS history, Why MPLS? For service providers, For enterprises. MPLS Architecture Label Switch Routers, two types of LSR, PE and P router roles, FEC, swapping labels, MPLS packet format, Loops, TTL control. Hands on: Building the base network. Enabling MPLS. Simple testing and troubleshooting of MPLS. Label distribution Label review, label switch path, label distribution methods, piggybacking, Label distribution Protocols, LDP, LDP operation, LDP packets, discovery messages, session messages, advertisement messages, notification message, Label Information Base, routing tables, the LFIB, MPLS forwarding, penultimate hop popping, handling labels, LSP control modes, when to distribute labels, how long to keep labels, aggregation, label merging. Hands on: LDP traffic analysis. MPLS TE and QoS What is MPLS TE? Why TE? TE versus shorted path, how MPLS TE works, CR-LDP, OSPF-TE, IS-IS-TE, TE with BGP, RSVP-TE, MPLS Fast reroute, MPLS QoS. Hands on: Enabling MPLS-TE. BFD BFD, hello the BFD protocol. MPLS VPN What is a VPN? MPLS VPN types, MPLS VPN comparison, MPLS L3 VPN, VRFs, MBGP, MPLS VPN architecture, VRF RD, VRF RT, the label stack, L2 VPNs, VPWS, AToM, VPLS. Hands on: MPLS L3 VPN setup, troubleshooting.

Ethernet LANS training course description This course has been replaced as part of our continuous curriculum development. Please see our Definitive Ethernet switching course What will you learn Describe what Ethernet is and how it works. Install Ethernet networks Troubleshoot Ethernet networks Analyse Ethernet packets Design Ethernet networks Recognise the uses of Hubs, Bridges, switches and routers. Ethernet LANS training course details Who will benefit: Those wishing to find out more about how their LAN works. Prerequisites: Intro to Data comms & networking. Duration 3 days Ethernet LANS training course contents What is Ethernet? LANS, What is Ethernet?, history, standards, the OSI reference model, how Ethernet works, CSMA/CD. Ethernet Cabling UTP, cat 3,4,5, Cat 5e, Cat 6, Cat 7, fibre optic cable, MMF, SMF. Hands on Making a cable. 802.3 physical specifications Distance limitations, hubs and repeaters, 5-4-3-2-1 rule, 10BaseT, 10BaseF, 100BaseTX, 100BaseFX, 1000BaseSX, 1000BaseT, 10gbe. Hands on Working with hubs. Ethernet layer 2 Overview, NICS, device drivers, MAC addresses, broadcasts, multicasts, frame formats, Ether II, 802.3, 802.2, SNAP, compatibility, Ethernet type numbers, Ethernet multicast addresses, Ethernet vendor codes. Hands on Installing Ethernet components, analysing MAC headers. IP and Ethernet ARP Hands on Analysing ARP packets. Ethernet extensions Full/half duplex, auto negotiation, flow control methods, 802.3ad, 802.3af, 802.3ah. Hands on Configuration of full/half duplex. Ethernet speed enhancements Encoding, Carrier extension, packet bursting, jumbo frames. Prioritisation 802.1P, 802.1Q, TOS, WRR, QOS, VLANs. Hands on 802.1p testing Interconnecting LANS Broadcast domains, Collision domains, What are bridges, transparent bridging, What are switches? STP, VLANS, What are routers? Layer 3 switches, Connecting Ethernet to the WAN. Hands on STP, Analysing Ethernet frames in a routed architecture. Troubleshooting and maintaining Ethernet Utilisation, performance, TDR and other testers, bottlenecks, statistics, RMON. Hands on Monitoring performance, troubleshooting tools.

LINX 3 training course description A detailed study of BGP, from the basics of how it works through to advanced issues such as route reflectors, policy, filtering, route selection and routing registries. The course culminates with a study of an industrial strength BGP template illustrating important issues such as bogon filtering. Practical hands on with routers follow the major sessions to reinforce the theory. A multiple choice exam, leading to the LAIT III certification, is available after the course. The exam consists of 60 questions and lasts 2 hours. What will you learn Connect enterprises to the Internet, and ISPs to each other. Describe how BGP works. List, describe and configure the main BGP attributes. Implement and troubleshoot BGP. Work with route aggregation and calculate CIDR prefixes in seconds. Influence traffic paths with BGP. LINX 3 training course details Who will benefit: Network engineers. Prerequisites: LAIT I and II OR CCNP and take LAIT I and LAIT II exams whilst on this course. Duration 5 days LINX 3 training course contents Basic BGP IGPs, EGPs, What's BGP? BGP RIB, in/out process, tables peers, adding routes. Hands on Simple configuration and troubleshooting. The Internet and peering ASs, AS numbers, Internet structure, ISP types, ISP network design, IXs, peering vs. transit, public/ private peering, bi/multi-lateral peering. Hands on AS information gathering. How BGP works Incremental updates, Path vector protocols, BGP protocol stack, the BGP header, message types, NLRI, withdrawn routes, route refresh, route dampening. Hands on More troubleshooting, packet analysis. MBGP and IPv6 Multiprotocol routing, AFI, SAFI, MBGP and multicasts, IPv6, MPLS VPNs. Hands on IPv6 BGPv4 aggregation CIDR, benefits, techniques, shortcuts, configuring BGP aggregation, leaking routes. Hands on Reducing routing table size. BGP path selection BGP attributes, attribute types, route selection order, Local preference, AS prepend, MEDs. Hands on Influencing traffic with BGP. BGP routing policies What is policy? Examples, route filtering, AS filtering, REs, applying preference selectively, peer groups. Hands on Sophisticated policies. RIPE and routing registries RIRs, Allocations, assignments, PI vs. PA. Objects, RPSL, routing registry, Hands on The RIPE database. Automating BGP configuration Automation tools, whois, IRRToolSet, Bogon lists, tracking bogon lists, HTTP, Peering, routing registries, DNS. Communities What is a community? Community names, communities for: peer types and geography. RFC 1998, default communities. Hands on Setting local preference on other routers. Route servers What are route servers? LINX route servers, route server policy control, What are route collectors, Looking glasses. Hands on Setting up and working with a route server. Peer relationships IBGP, EBGP, next hop self, advertising routes into/out of BGP, synchronisation. Hands on IBGP, troubleshooting a large BGP network. Route reflectors and confederations Full mesh IBGP, Route reflectors, RR configuration and design, confederations, migration issues. Hands on RR configuration. BGP architectures Stub vs. transit AS, when to use BGP, multihoming strategies and issues, default routes. Multihop EBGP, load balancing. Hands on Multihoming. BGP security RFC 7454, security steps, BGP TTL security, filters, RPKI, ROAs, rsync, rrdp, validators. A secure BGP template. Hands on RPKI prefix validation.

Concise Cisco routers course description A fast paced practical hands on introduction to Cisco routers concentrating on basic product knowledge needed for the real world. Starts with the basics of routing through configuring static routes, RIP, OSPF, and EIGRP ending with access lists. Hands on sessions follow all the major chapters with a major practical at the end to reinforce all that was learnt in the course. What will you learn Use the Cisco setup script. Use the Cisco command line. Perform basic troubleshooting. Configure - Interfaces - RIP, IGRP - OSPF, EIGRP Concise Cisco routers course details Who will benefit: Anyone who will be working with Cisco routers. In particular: Network Administrators, Field engineers, Network support personnel Prerequisites: None, although a knowledge of the TCP/IP protocols would be advantageous. Duration 3 days Concise Cisco routers course content Basics of routing What are routers? Network protocols, Routing protocols. The Cisco routers Router models, The IOS, DRAM, SRAM, NVRAM, Flash, ROM and boot flash. Getting started Accessing the router, installing a Cisco, using the setup script. The command line interface User and privilege modes, online help show, debug, basic troubleshooting Configuring Ciscos The configuration editor, Global, major and sub commands, enable, secret and other passwords, telnet. Miscellaneous exercises Buffered logging, web access, CDP… Subnetting IP addressing rules. The need for subnetting, subnet masks, Calculating network numbers. Configuring Interfaces Basics, Ethernet, Serial lines, PPP, DCE, loopback interfaces. Static routes Why use static routes? Configuring static routes, default routes. Configuring RIP and IGRP How they work, configuration, troubleshooting. OSPF Configuration and troubleshooting. EIGRP Configuration and troubleshooting. Housekeeping Configuration management, offline editing and TFTP usage. Cisco boot sequence, IOS upgrades. Bypassing Cisco passwords. Access lists What are access lists? General rules, basic and extended IP access lists. Putting it all together A series of exercises based around, installs, adds, moves, changes, upgrades and troubleshootin