MRTG training course description A hands on course focusing on the installation, configuration and use of the MRTG network monitoring and graphing tools. What will you learn Install MRTG. Configure MRTG. Use MRTG to monitor networks. MRTG training course details Who will benefit: Anyone working with MRTG. Prerequisites: Total SNMP for engineers Duration 2 days MRTG training course contents What is MRTG? Network monitoring, review of SNMP. What MRTG does do, what MRTG doesn't do, MRTG architecture, MRTG components. Hands on configuring SNMP support on network devices, configuring extended SNMP support on Windows. Installing MRTG Configuring MRTG tasks, .cfg files, index.html files, running MRTG tasks, instances. Hands on Configuring and running MRTG tasks. MRTG tasks Configuring MRTG tasks, .cfg files, index.html files, running MRTG tasks, instances. Hands on Configuring and running MRTG tasks. MRTG graphs Daily, weekly, monthly, yearly, MRTG database support, RRDTOOL. Hands on MRTG graphs. Using MRTG MRTG examples, custom SNMP OIDs, using the MRTG configuration reference. Hands on MRTG examples. RRDTOOL Installing RRD database support, MRTG instances with the RRD database, RRD database structure, resizing and extending the database. Exporting database records into plain text and XML formats, on demand MRTG graphs using the database. Hands on Using MRTG with RRD database support. Alternatives to MRTG MRTG strengths and weaknesses, scalability, cricket, cacti, other SNMP tools.
Data centre infrastructure course description This course provides a foundation in data centre infrastructure technologies. It begins with a tour of virtualisation and the impact of this on the network before moving on to the spine and leaf design, how it works and how to scale. Layer 2 technologies enabling this architecture are studied in terms of the impact on the data centre. The course then progresses onto how Layer 3 technologies such as BGP, EVPN and VXLAN are used in data centre networks. The course then studies interconnecting data centres finishing with a section on automation and orchestration of both underlay and overlay networks. What will you learn Explain the spine and leaf architecture Recognise the impact of virtualisation, containers and orchestration on the network Describe how the following technologies are used in data centres: Multi port aggregation Overlay networks MBGP, VRFs, EVPN VXLAN COOP Data centre infrastructure course details Who will benefit: Staff involved with Data centres. Prerequisites: Network fundamentals for engineers Duration 2 days Data centre infrastructure course contents What is Ethernet? Data centres versus enterprise networks. Servers, Blades, Racks, Clusters, Storage, Virtual Machines, Hosts, guests, containers, orchestration. Virtual switches. Distributed switches. Live migrations (e.g. vMotion). IP addressing and VM traffic. Data centre network architecture Spine leaf design. North south traffic, East West traffic, Scaling: Ports, bandwidth. N+1 redundancy, ratio East West optimisation, oversubscription. 2 tier versus 3 tier Leaf/Spine. Pods. Underlay, Overlay L2 technologies STP vs link aggregation vs multi link aggregation. LACP, LLDP, CDP. Scalability. VLANs and VLAN pruning. L2 design recommendations. Disabling STP on edge ports. L3 technologies Underlay, Overlay, VXLAN, VTEP, VXLAN overlay forwarding, EVPN, IS-IS, COOP, MP BGP, VRFs, EBGP, IBGP, AS numbers, route reflectors. Anycast gateways. MTU considerations-for data and control planes. BUM traffic. Data centre interconnects Pods, fabrics, multi pods, multi fabric, multi site. VXLAN with BGP/EVPN Data center interconnect. Cloud integration, Inter Site Networks. Automation Automation and orchestration, Zero touch provisioning, Devops, Netops, telemetry automated configuration for underlay and overlay, SDN.
RADIUS training course description A fast paced hands-on introduction to RADIUS. Moves from installation and configuration through to packet analysis and accounting. Practical exercises are spread throughout the course to maintain student interest. What will you learn Configure PPP and PAP/CHAP. Install and configure RADIUS servers. Describe how RADIUS works. Setup RADIUS accounting. Analyse RADIUS packets. Troubleshoot RADIUS installations. RADIUS training course details Who will benefit: Network Administrators. Support personnel. Anyone who will be working with RADIUS. Prerequisites: Knowledge of the TCP/IP protocols would be advantageous. Duration 2 days RADIUS training course contents What is RADIUS? AAA services, Authentication, Authorisation, Accounting, local AAA services, remote AAA services, What is RADIUS? RADIUS as a protocol, RADIUS as an architecture, RADIUS as a standard. Installing RADIUS RADIUS platforms, RADIUS servers, client server communications, services, daemons. Hands on Installing RADIUS and testing with NTRadPing. Server configuration Configuring clients on the server, shared secrets, usernames and passwords. IP address pools. Hands on Configuring a server and testing with NTRadPing. Client configuration Example clients, client configuration steps, enabling RADIUS, pointing clients to the server, shared secrets, example Cisco authentication, example Cisco authorization. Hands on Configuring clients for RADIUS. How RADIUS works RADIUS architecture, RADIUS and authentication, PPP, PAP, CHAP, RADIUS SUCCESS, RADIUS FAILURE, the RADIUS protocol stack, the RADIUS protocol, the RADIUS header, RADIUS codes, RADIUS attributes, ACCESS-REQUEST example, ACCESS-ACCECPT example, CHAP example, proprietary attributes, using unassigned type codes, RADIUS attribute 26, Cisco specific attributes. Hands on Analysing RADIUS packets, configuring PPP CHAP to work with RADIUS. RADIUS accounting Simplified operation, Accounting codes, Accounting attributes, client and server configuration for accounting. Hands on Configuring RADIUS accounting. RADIUS architectures Traditional architecture, multiple RADIUS servers for resilience, Proxy RADIUS servers, Realms, RADIUS in VPNs, RADIUS with 802.1x. Hands on Using multiple RADIUS servers, Proxies. Troubleshooting RADIUS General problem solving, basic tools, RADIUS troubleshooting, Common configuration errors, log files, RADIUS design and performance. Hands on Fixing RADIUS problems.
Essential EVPN training course description Ethernet VPN (E-VPN) and Provider Backbone Bridging E-VPN (PBB-EVPN) are emerging technologies providing Ethernet services over MPLS. This course studies the technologies in E-VPN/PBB-EVPN providing multi-homing, multi pathing, auto discovery, multicast, forwarding and fast convergence. What will you learn Differentiate between E-VPN and PBB-EVPN. Explain how E-VPN operates. Explain how PBB-EVPN operates. Explain how E-VPN provides: Multi homing Multi pathing Auto discovery. Essential EVPN training course details Who will benefit: Network engineers. Staff working for carriers. Prerequisites: Definitive Ethernet switching for engineers Concise MPLS for engineers Duration 2 days Essential EVPN training course contents Introduction to EVPN Network virtualization What Is network virtualization? types of virtual networks, network tunnelling, the consequences of tunnelling, packet load balancing, network interface card behaviour. maximum transmission unit, lack of visibility, VXLAN, protocols to implement the control plane, support for network virtualization technologies, merchant silicon Software, standards. The building blocks of Ethernet VPN A brief history of EVPN, architecture and protocols for traditional EVPN deployment, EVPN in the data center BGP constructs for Virtual networks, address family indicator/subsequent address family indicator, route distinguisher, route target, RD, RT, and BGP processing, route types, modifications to support EVPN over eBGP, keeping the NEXT HOP unmodified, retaining route targets, FRR support for EVPN, automatic propagation of NEXT HOP, RT/RD derivation, what Is not supported in FRR. Bridging with Ethernet VPN An overview of traditional bridging, overview of bridging with EVPN, what Ifs, why does NVE L3 get an advertisement for MACA? handling BUM packets, handling MAC moves, support for dual-attached hosts, the host-switch Interconnect, VXLAN model for dual-attached hosts, switch peering solutions, handling Link failures, duplicate multi-destination frames, ARP/ND suppression. Routing with Ethernet VPN The case for routing in EVPN, routing use cases in the data center, routing models, where is the routing performed? centralized routing, distributed routing, how routing works in EVPN, asymmetric routing, symmetric routing, VRFs in EVPN routing, summarized route announcements, BGP support for EVPN routing, comparing asymmetric and symmetric models, vendor support for EVPN routing. Configuring and administering Ethernet VPN The sample topology, configuration cases, configuring the MTU, the end first: complete FRR configurations, the Invariants: configuration for the spines, firewall, and servers, centralized routing, asymmetric distributed routing, symmetric routing, dissecting the configuration, configuring the underlay, configuring the overlay: FRR configuring the overlay: interfaces, examining an EVPN network, show running configuration, show BGP summary, show EVPN VNIs and VTEPs, identify which VTEP advertised a MAC address, comparing FRR and Cisco EVPN configurations, considerations for deploying EVPN in large networks.
LTE Airside training course description This course provides a concise insight into the LTE airside. Key parts of the course are detailed looks at the air interface protocol stack, cell acquisition, transmission and reception of data and of he layer 1 procedures along with layer 2 procedures. What will you learn Explain the RF optimisation flowchart. Describe the importance of Reference Signal Received Power (RSRP). List many of the 3GPP recommended KPIs. Describe the concept of APN AMBR and UE AMBR within LTE. Describe the use of planning and optimisation computer tools. LTE Airside training course details Who will benefit: Anyone working with LTE. Prerequisites: Essential LTE Duration 2 days LTE Airside training course contents Introduction and review of LTE This section describes the requirements of LTE and key technical features, and reviews the system architecture. LTE Architecture, UE, E-UTRAN and EPC. Specifications. OFDMA, SC-FDMA and MIMO antennas This section describes the techniques used in the LTE air interface, notably orthogonal frequency division multiple access (OFDMA) and multiple input multiple output (MIMO) antennas. Communication techniques for fading multipath channels. OFDMA, FFT processing and cyclic prefix insertion. SC-FDMA in the LTE uplink. Multiple antenna techniques including transmit & receive diversity and spatial multiplexing. Introduction to the air interface This section covers the operation of the air interface, the channels that it uses, and the mapping to the time and frequency domains of OFDMA and SC-FDMA. Air interface protocol stack. Logical, transport and physical channels. Frame and slot structure, the resource grid. Resource element mapping of the physical channels and physical signals. LTE spectrum allocation. Cell acquisition This is the first of three sections covering the air interface physical layer. Here, we cover mobile procedures to start low-level communications with the cell, and base station transmission of the corresponding information. Primary/secondary synchronisation signals. Downlink reference signals. The master information block. Physical control format indicator channel. Organisation and transmission of the system information. Data transmission and reception In this section, we cover procedures used for data transmission and reception on the shared channels, and describe in detail the individual steps. Data transmission and reception on the uplink and downlink. Scheduling commands and grants on the PDCCH. DL-SCH and UL-SCH. Physical channel processing of the PDSCH and PUSCH. Hybrid ARQ indicators on the PHICH. Uplink control information on the PUCCH. Uplink demodulation and sounding reference signals. Additional physical layer procedure This section concludes our discussion of the air interface physical layer, by discussing a number of procedures that support its operation. Transmission of the physical random access channel. Contention and non-contention based random access procedures. Discontinuous transmission in idle and connected modes. Uplink power control and timing advance. Air interface layer 2 This section describes the architecture and operation of layer 2 of the air interface protocol stack. MAC protocol, interactions with the physical layer, use for scheduling. RLC protocol, transparent, unacknowledged and acknowledged modes. PDCP, including header compression, security functions and recovery from handover.
HOW DANCING CAN IMPROVE YOUR MENTAL AND PHYSICAL HEALTH Move your body to your favourite tunes – it’s the ultimate feel-good exercise and has some surprising effects on both the body and mind Music and dance have been fundamental parts of the human experience for thousands of years. No matter what your favourite tune may be, music can have a huge effect on your wellbeing – Charles Darwin even thought that our ability to make and understand rhythmic beats worked as an early form of communication. Whether or not we still share messages through music, we all know that it can change our mood and studies have shown that we share a natural sense of rhythm (no matter how much you might protest). Dance is therefore a natural outlet, and one which can do a lot to make us feel good. Club Azucar offers corporate dance packages for the workplace in order for your organisation (Companies, Institutions & Schools) not only function at its best, but to be happy and healthy in life. These are the expected benefits for the individual employee which have been also confirmed by the participants: Physical Health: Salsa/Zumba or any Latin Dance Classes improves mobility, coordination / motor skills and fitness level.while being a low-impact exercise which includes people of all ages, abilities and fitness levels Mental Health: Dancing requires full concentration so for one hour away from their desk ,participants will experience reduced stress levels, , feel refreshed and more alert and able to concentrate better following the lesson Music in combination with physical exercise has an uplifting effect through the release of endorphins and dopamine in the body & brain Learning a new skill is proven to train your brain, contribute to prevention of dementia and give the confidence to face new tasks and challenges in other areas of work and life The patience and encouragement of the teachers has furthered this new confidence and sense of achievement and contributed to participants’ belief in themselves and their ability to take themselves out of their “comfort zones” and take on new challenges Getting to know each other in a social rather than work context and learning a new skill together, dancing and laughing together, gives participants a sense of belonging and furthers team buildingDo you want more proof? Get involved and hire us!!! Booking Terms & Conditions 1. The above prices are only for Greater London 2. Fees are non refundable 3. Courses are subject to availability from both parties 4. Train, plane. petrol, or any sort of transport fares are to be refunded. 5. Cancellation must be before 24 hours every class
Get to grips with what drives large-scale occupiers Who Could Benefit? Corporate occupiers can be much more powerful than the landlords or investors they deal with. As long as they have a Corporate Real Estate department fighting their corner and coordinating and controlling the estate of space they occupy, whether leased or owned. Corporate Real Estate Managers keep an eye on productivity and performance of the entire ‘estate’. Business plans take in short term tactical allocations and long-term structural plans. Corporate Real Estate Managers are essential in enabling a large corporate or governmental occupier to get the most out of the space they occupy. This on-line course gives a solid grounding to those who work in Corporate Real Estate departments for occupiers and service / data / software providers, as well as those who work for investors and want to understand the considerations from the occupiers’ point of view (as occupiers are in fact their tenant, and their main source of income). Modules Understanding Corporate Real Estate The course “Understanding Corporate Real Estate” offers a foundation knowledge course. Perfect for those working in the real estate departments of large corporate and government-related occupiers, or those working with/for Corporate Real Estate occupiers. We explain the main drivers in the property market seen from an occupier perspective. Have you always been keen to understand better what a Corporate Property Managers does? How does this fit into the bigger picture? What factors are most important in deciding whether to Lease or Buy? Where to locate and for how long? What factors ought to drive disposal decisions, and what drives it in reality? Are you curious to understand what the main lease considerations are for a corporate occupier? How do various processes work, how do you factor in strategic and tactical objectives, changes to the business plan, the economy and the business environment? Along the way we explain lots and lots of jargon and how it all fits together. Taught by Cléo Folkes, CEO of Property Overview. See contentNext Date Available: Enquire for a date | Location: UK, abroad or in-line Pricing Find the best price. Property Overview offers competitively priced training courses with unique practitioner-led content, which means we can tailor our in-house courses around your requirements. Applied, relevant content leads to greater impact and value-for-money. Pricing below is shown for on-line public courses for individual bookings (left), and for on-line in-house courses (right). For bookings of 4 or more staff an on-line in-house course is recommended, also as the content can be tailored around your needs and your products or services. To book one or two individual places please fill in our booking form, otherwise please email kaushik@propertyoverview.co.uk Understanding Corporate Real Estate £3,025/day in-house – incl. 6 attendees • 1-day training course, can be split over 2 half days• 6 hours of CPD in total• UK VAT @ 20% applies• In-house course includes up to 6 attendees(£60pp + VAT surcharge applies thereafter)
About this Training Course Liquefied Natural Gas (LNG) has provided intercontinental mobility to natural gas, which now provides about 25% of the global primary energy. Being the cleanest fossil fuel, natural gas/LNG consumption is forecasted to grow in all future scenarios. With the entry of various players, including Trading companies, the LNG value chain is becoming increasingly complex, and a solid understanding of its economics and management of its interfaces have become crucial to identify and assess investment opportunities and risks. Recent market disturbances caused by COVID-19, Oil & Gas price instabilities - coupled with the political (Ukraine/Russia) challenges - make a deep understanding of LNG Value Chain Logistics and Economics even more essential to ensure the security of energy supplies sustainably and profitably. This intermediate level 3 full-day course starts with a concise introduction to the LNG business. Thereafter, the elements of the LNG value chain are described, and their individual economics analysed. A Business Activity Model along the value chain will be developed and discussed in depth, covering the following key processes: 'Buy Gas - Transport Gas - Liquefy Gas - Sell LNG/Products - Ship LNG - Regasify LNG' The integrated chain economics will then be developed and quantified. A hands-on group workshop/exercise developing the economic case of a full-sized Liquefaction project will be carried out, considering the forecasted cash flows throughout the project life, the location of the plant, its markets, project sensitivities and profitability assessment. Participants will be provided with Excel based tools/models (LNG Liquefaction project development Net Present Value (NPV) analyses, Shipping Freight Calculations and Economics) to work through the exercises and also for their future personal use. Training Objectives After the completion of this course, participants will be able to: Understand how the LNG Value Chain operates, bound by the relevant Contracts and Agreements. Learn the basic economic parameters (operating, capital costs, financing, profitability) of each major element of the value chain. Appreciate the complexity of the value chain, and the associated opportunities and risks. Develop quantitative project evaluation skills. Explore options to maximise profitability in a given LNG value chain. Discuss best practices on how to manage, steer and govern these activities. Target Audience Technical, Operational, Shipping, Commercial, Project and Governance professionals who are already active in a specific section of the LNG Value Chain will directly benefit in developing a wider and deeper perspective on how the LNG Value Chain operations and can be optimised. Managers (Technical, Financial, Legal and Governance) less familiar with the specifics of the LNG Industry will also benefit from attending this VILT course, as they will obtain the required background to be able to set sharper targets, suitable performance indicators, and governance and performance assessment guidelines for units engaged in the chain. The course is most relevant for professionals engaged in the LNG industry at: National and International Oil & Gas/Energy Companies LNG Importers/Exporters/Traders/Shippers Government & Regulatory Agencies Finance Institutions It will also apply to the following audience: Business Development Managers Corporate Planning Professionals Project Developers Supply Planners & Scheduling Professionals Regulators Tax & Finance Advisors Compliance Officers Equity Analyst and Bankers Joint Venture Representatives, Board Directors Negotiators and Contracting Staff Trading Professionals Course Level Intermediate Trainer Your expert course leader is an Oil & Gas/LNG professional with more than 35 years of international experience, majority of which was gained at Shell International Joint Ventures engaged in Oil Refining, Supply / Trading, Gas Supply and LNG Businesses in the Netherlands, France, Thailand, Dominican Republic and Nigeria. Since 2004, he has had several roles in the management of the LNG Value Chain including the Commercial Operational Management of Nigeria LNG (NLNG). He played an active role in the start-up and integration of LNG trains 4, 5 and 6 with NLNG becoming the 3rd largest LNG producer in the world in 2007. Commercial operations spanned 4 Gas Supply, 11 LNG Sales & Purchase Agreements, ad-hoc LPG and Condensate Sales and LNG Ship Chartering contracts. Under his supervision, more than 2,000 LNG cargoes were exported. He was part of the organizational transformation of the company from a Project-based set-up to a Production / Commercial based structure and implemented an 'Integrated Planning and Scheduling Department' in which he optimized the value chain (Buy-Gas - Liquify Gas to LNG - Sell - Ship LNG). Staff competence management was one of his focus areas during this period. He was also the NLNG representative on JV Technical, Commercial, Shipping Committees where he interfaced with Government & Regulatory authorities. In 2014, he was appointed as Shell Shareholder representative to NLNG and became a Non-Executive Board member to NLNG companies, including Bonny Gas Transport (BGT) managing 24 LNG Ships. During this period, he was involved in the Economic and Technical steering of the Shipping Fleet and Liquefaction Plant Rejuvenation projects and a further capacity expansion of liquefaction plant which resulted in the achievement of NLNG train 7 project FID in 2019. Since 2016, he has been active as an independent consultant. He co-authored 2 patents and more than 30 published papers/presentations. He holds a PhD from Delft University of Technology in the Netherlands and a MSc and BSc in Chemical Engineering from the University of Birmingham, UK. POST TRAINING COACHING SUPPORT (OPTIONAL) To further optimise your learning experience from our courses, we also offer individualized 'One to One' coaching support for 2 hours post training. We can help improve your competence in your chosen area of interest, based on your learning needs and available hours. This is a great opportunity to improve your capability and confidence in a particular area of expertise. It will be delivered over a secure video conference call by one of our senior trainers. They will work with you to create a tailor-made coaching program that will help you achieve your goals faster. Request for further information post training support and fees applicable Accreditions And Affliations
IPv6 training course description IPv6 is the next generation Internet Protocol. This hands-on course looks at the benefits and features of the new protocol along with an assessment of the likely impact of the protocol and migration strategies. Practical exercises using PCs and routers follow the major sessions in order to reinforce the theory. What will you learn Configure PCs and routers for IPv6. Troubleshoot IPv6 networks. Analyse IPv6 packets. Plan migration strategies for IPv6. Integrate IPv6 and IPv4 networks. IPv6 training course details Who will benefit: Anyone working in the field of networking. Prerequisites: TCP/IP Foundation for engineers Duration 3 days IPv6 training course contents Introduction Reasons for IPv6, IPv4 weaknesses, what is IPv6? IPv4 solutions for solving address wastage, the origins of IPv6. hands on IPv6 on a PC, IPv6 on a router. IPv6 addressing IPv6 address allocation, address format, Prefixes but no masks, address categories, scope zones, aggregatable global unicast, link local, Unicast, Multicast, Anycast. Prefix delegation. hands on Link local addresses, manual address configuration, name resolution. Plug and play Plug and play addressing, ICMP neighbour discovery, router solicitation, DHCPv6, stateful autoconfiguration and stateless autoconfiguration. hands on Plug and play addresses and default gateways. The IPv6 header The IPv4 header, IPv6 header format, QoS, flow control, priority field, extension headers, hop by hop, destinations header, fragmentation header, security, IPsec, AH, ESP, TCP and UDP, ICMPv6. hands on IPv6 packet analysis. Migrating to IPv6 Overview, migration, dual stack, IPv4 compatible addresses, DNS, IPv6 DNS issues, AAAA records, IPv6 reverse delegation, DNS transport, protocol translators, NAT-PT, NAPT-PT, NAT64, DNS64, tunnelling, tunnel establishment, tunnel brokers, Tunnel types. hands on Dual stack operation, tunnelling, IPv6 name resolution. IPv6 routing IPv6 routing, RIPng packet format, RIPng for IPv6, OSPF for IPv6, MBGP, multiprotocol routing, MBGP and multicasts, MBGP and IPv6. hands on Base router setup for IPv6, IPv6 static routes, RIPng, OSPFv3. MBGP
Windows clustering training course description This course covers high availability and disaster recovery technologies such as live migration, storage migration and Hyper-V Replica, as well as providing indepth coverage of failover clustering including a detailed implementation of failover clustering of Hyper- V using SoFS. The course also covers System Center Virtual Machine Manager and implementing Network Load Balancing (NLB) and load balancing clusters. What will you learn Plan and implement a failover cluster. Describe managing server roles and clustering resources. Implement and manage virtual machines. Use System Center Virtual Machine Manager. Describe cloud-based storage and high availability solutions. Implement a Network Load Balancing (NLB) cluster. Windows clustering training course details Who will benefit: Technical staff working with Microsoft clusters. Prerequisites: Supporting Microsoft Windows server Duration 3 days Windows clustering training course contents High Availability in Windows Server Defining levels of availability, High Availability and disaster recovery solutions with Hyper-V Virtual Machines, High Availability with failover clustering in Windows Server. Hands on Configuring High Availability and Disaster Recovery. Implementing failover clustering Planning a failover cluster, creating a new failover cluster. Hands on Creating and Administering a Cluster. Server roles and clustering resources Configuring highly available applications and services on a failover cluster, managing and maintaining a failover cluster, troubleshooting a failover cluster, implementing site high availability with multisite failover clusters. Hands on Managing server roles and clustering resources. Failover clustering with Hyper-V Overview of integrating Hyper-V with failover clustering, implementing Hyper-V with failover clustering, managing and maintaining Hyper-V Virtual Machines on failover clusters. Hands on Implementing failover clustering by using Hyper-V Storage Infrastructure Management with Virtual Machine Manager Virtual Machine Manager, managing storage infrastructure with Virtual Machine Manager, provisioning failover clustering in Virtual Machine Manager. Hands on Managing storage infrastructure. Cloud-Based storage and High Availability Azure storage solutions and infrastructure, cloud integrated storage with StorSimple, disaster recovery with Azure Site Recovery. Hands on Managing cloud-based storage and high availability Network Load Balancing Clusters Overview of NLB, configuring an NLB cluster, planning NLB. Hands on Implementing a Network Load Balancing Cluster