ACA-Cloud1 ACA Cloud Computing Associate Questions and Answers

Alibaba Cloud Server Load Balancer (SLB) is a service that distributes network traffic across multiple ECS instances to improve the service capabilities of applications. SLB supports the following protocols for the listener configuration:

• HTTP: Hypertext Transfer Protocol, a stateless application-layer protocol that is used to transfer web pages and other resources over the internet.
• HTTPS: Hypertext Transfer Protocol Secure, an extension of HTTP that uses SSL/TLS encryption to provide secure communication between the client and the server.
• TCP: Transmission Control Protocol, a reliable, connection-oriented transport-layer protocol that provides reliable data delivery and error recovery.
• UDP: User Datagram Protocol, a connectionless transport-layer protocol that provides fast and efficient data transmission without guaranteeing reliability or order.

SLB does not support the following protocols:

• MPLS: Multiprotocol Label Switching, a data-carrying technique that uses labels to forward packets across a network.
• MQTT: Message Queuing Telemetry Transport, a lightweight publish/subscribe messaging protocol that is designed for constrained devices and low-bandwidth networks.

References:

• Alibaba Cloud Server Load Balancer
• ACA Cloud Computing Certification Exam Preparation Course
• Alibaba Cloud Computing Exam Question 2022

SLB and Auto Scaling are two Alibaba Cloud services that can work together to provide high availability, scalability, and performance for your applications. SLB is a load balancing service that distributes incoming traffic across multiple ECS instances. Auto Scaling is a service that automatically adjusts the number of ECS instances based on your business needs. When you use SLB and Auto Scaling together, you need to follow some best practices and precautions to ensure the optimal performance and reliability of your system. One of the precautions is that SLB instances must have Health Check enabled, or they cannot be used together with Auto Scaling1. Health Check is a feature of SLB that monitors the health status of the backend ECS instances. If an ECS instance becomes unhealthy or fails, SLB automatically stops sending traffic to that instance and redirects the traffic to other healthy instances. This ensures that your application can continue to serve user requests without interruption. Health Check is also essential for Auto Scaling, because Auto Scaling relies on the health status reported by SLB to decide whether to add or remove ECS instances. If an ECS instance is unhealthy, Auto Scaling will automatically replace it with a new one. If the traffic increases and the average health status of the ECS instances decreases, Auto Scaling will automatically add more instances. If the traffic decreases and the average health status of the ECS instances increases, Auto Scaling will automatically remove some instances. Therefore, Health Check is a prerequisite for using SLB and Auto Scaling together. If you disable Health Check, SLB and Auto Scaling will not be able to communicate with each other and coordinate their actions. This may result in performance degradation, service interruption, or resource waste. The other options are incorrect, because they are not necessary or relevant for using SLB and Auto Scaling together. The backend ECS instances under the same SLB instance can have different operating systems, configurations, and scaling groups, as long as they can provide the same service and respond to the same requests. SLB and Auto Scaling do not impose any restrictions on these aspects of the ECS instances. References: Associate SLB instances with or disassociate SLB instances from a scaling group

Server Load Balancer (SLB) is a service that distributes network traffic across multiple ECS instances to improve the service capabilities of applications. By using SLB, you can increase the availability and fault tolerance of your applications. You can also use SLB with Auto Scaling to dynamically adjust the number of ECS instances based on the traffic load. Multiple lower-configuration I/O-optimized ECS instances can be used with SLB to deliver a high-availability architecture that can handle traffic spikes and reduce costs.

References:

• Alibaba Cloud Server Load Balancer
• Alibaba Cloud Elastic Compute Service
• ACA Cloud Computing Certification Exam Preparation Course

 Cloud disks are reliable because they use a distributed file management system with 3 redundant copies to provide block-level data storage for ECS instances, ensuring 99.9999999% data reliability. This means that the data stored on cloud disks is automatically replicated across three different physical servers in the same zone. If one server fails, the data can still be accessed from the other two servers. Cloud disks also support snapshot backup and recovery, which can help users restore data to a previous point in time in case of accidental deletion or corruption. References: Elastic Compute Service (ECS) - Alibaba Cloud Academy, Cloud Disk - Alibaba Cloud Documentation Center

An ECS disk can be used jointly or separately to meet the requirements of different application scenarios. ECS disks are categorized into ephemeral SSD disks and cloud disks. Compared with ephemeral SSD disks, cloud disks are more reliable as they use a triplicate distributed system to provide block-level data storage for ECS instances, ensuring 99.9999999% data reliability.

 RDS for MySQL is a Platform as a Service (PaaS) product that provides a complete database solution on Alibaba Cloud. It is fully compatible with MySQL and supports various MySQL features, such as transactions, views, triggers, stored procedures, and functions. RDS for MySQL frees users from the tasks of managing the underlying operating system, runtime environment, and software packages. Users only need to focus on their business logic and data. Alibaba Cloud takes care of the database installation, configuration, backup, recovery, monitoring, scaling, and security. References: MySQL Database Concepts and Operations - Alibaba Cloud Academy, Alibaba RDS Course | Cloud Academy, ACA Cloud Computing Certification - Alibaba Cloud Academy

The main purpose of DDoS attack is to make the target server unable to provide service normally, which is one of the network attacks that are most difficult to defend. Comprehensive and Detailed Explanation: A Distributed Denial-of-Service (DDoS) attack is a malicious attempt to disrupt the normal operation of a target server, service, or network by overwhelming it with a flood of internet traffic from multiple sources1. The main purpose of a DDoS attack is to make the target server unable to provide service normally, which is one of the network attacks that are most difficult to defend. A DDoS attack can cause serious damage to the availability, performance, and reputation of the target server, service, or network, and result in significant financial losses and customer dissatisfaction2.

The other options are not accurate descriptions of a DDoS attack. The main target for a DDoS attack is not the database, but the server, service, or network that hosts the database or other applications. A DDoS attack will not try to crack the password through a large number of attempts, but rather try to exhaust the resources of the target server, service, or network. The purpose of a DDoS attack is not to steal confidential information, but rather to disrupt the normal operation of the target server, service, or network. References: 1: What is a DDoS Attack?1 2: Anti-DDoS: Intelligent DDoS Protection Service - Alibaba Cloud2

 According to the Alibaba Cloud Academy, Alibaba Cloud provides powerful security services that are the same level of security services used to support Alibaba Group’s Double 11 Shopping Festival. However, you do not have to pay first before using any of the security services. Alibaba Cloud offers some security services for free, such as Anti-DDoS Basic, Server Guard, and Security Center Basic Edition. Other security services, such as Anti-DDoS Pro, WAF, and Security Center Enterprise Edition, are charged based on different billing methods, such as subscription, pay-as-you-go, or traffic-based. Therefore, the statement is false. References: Alibaba Cloud Security Services - Alibaba Cloud Security Course - Cloud Academy, Alibaba Cloud Security Pricing - Alibaba Cloud

An ICP license is a permit issued by the Chinese Ministry of Industry and Information Technology (MIIT) that allows websites to operate in China. An ICP license is required for any website that is hosted on a mainland China server, or that wants to use a China-based CDN service to accelerate its access in China. Therefore, you would need to apply an ICP license in the following cases:

• Accelerate your Overseas Website in China: If you have a website that is hosted outside of China, but you want to use Alibaba Cloud’s CDN service to improve its performance and user experience in China, you would need to apply an ICP license for your domain name. This is because Alibaba Cloud’s CDN nodes are located in mainland China, and any website that uses them must comply with the Chinese regulations.
• Launch your website in China: If you want to host your website on an Alibaba Cloud ECS instance or OSS bucket that is located in mainland China, you would need to apply an ICP license for your domain name. This is because any website that is hosted on a mainland China server must have an ICP license to be accessible and legal in China.
• Launch your online shop in China: If you want to run an e-commerce website that sells goods or services to customers in China, you would need to apply an ICP license for your domain name. This is because any website that engages in commercial activities in China must have an ICP license to operate legally and securely in China.

References: What is an ICP License? - Alibaba Cloud Academy, ICP License Application - Alibaba Cloud Documentation Center

Alibaba Cloud provides anti-DDoS products of different levels to protect your applications and data from DDoS attacks. Among them, Anti-DDoS Service Pro is the most suitable product for ensuring high service availability under DDoS attacks. Anti-DDoS Service Pro is a proxy-based mitigation service that diverts network traffic to the Alibaba Cloud global anti-DDoS network through DNS resolution, mitigates volumetric DDoS attacks and resource exhaustion DDoS attacks, and ensures the stability and availability of your origin servers1. Anti-DDoS Service Pro provides the following features and benefits2:

• Over 10 Tbit/s mitigation capacity: Anti-DDoS Service Pro can defend against large-scale DDoS attacks at the Tbit/s level and ensure high service availability.
• AI-enabled for mitigating sophisticated attacks: Anti-DDoS Service Pro can automatically detect and mitigate sophisticated DDoS attacks, such as HTTP flood, HTTPS flood, and DNS flood, and quickly adjust protection policies based on the attack characteristics.
• Hiding origin server IPs: Anti-DDoS Service Pro can hide the IP addresses of your origin servers and prevent attackers from bypassing the proxy and directly attacking your origin servers.
• Multiple protection modes: Anti-DDoS Service Pro supports normal protection mode, emergency protection mode, and always-on protection mode, which can be switched based on your business needs and risk levels.
• Comprehensive security reports: Anti-DDoS Service Pro provides comprehensive security reports that display the attack details, protection status, and traffic statistics of your protected domains. References: 1: Anti-DDoS: Intelligent DDoS Protection Service - Alibaba Cloud2: Anti-DDoS Pro and Anti-DDoS Premium features - Anti-DDoS Pro and Anti-DDoS Premium - Alibaba Cloud Documentation Center.

According to the Alibaba Cloud Academy, Auto Scaling is a service that automatically creates and releases ECS instances based on pre-defined rules in order to scale services to match demand. Furthermore, it can configure server load balancer and relational database service white lists, without any manual intervention. Therefore, when ECS is used with Auto Scaling, the number of ECS instances is automatically adjusted based on traffic. References: Introduction to Alibaba Auto Scaling - Cloud Academy, ACA Cloud Computing Exam Preparation Course - Alibaba Cloud, Module 4: Cloud Computing Elasticity, Lesson 1: Auto Scaling, Slide 2.

 Server Load Balancer (SLB) can help protect from distributed denial-of-service (DDoS) attacks by distributing network traffic across groups of backend servers to improve the service capability and application availability. SLB also supports built-in Anti-DDoS services to ensure business security. Anti-DDoS services can mitigate DDoS attacks at the Tbit/s level and provide multiple defense methods, such as blackhole filtering, traffic scrubbing, and access control1. In addition, you can integrate Application Load Balancer (ALB) with Web Application Firewall (WAF) in the console to ensure security at the application layer and prevent attacks such as SQL injection2. References: 1: Server Load Balancer(SLB) - Alibaba Cloud2: Associate an EIP protected by Anti-DDoS Pro/Premium with an ALB instance - Server Load Balancer - Alibaba Cloud Documentation Center.

Alibaba Cloud Auto Scaling service allows you to automatically adjust the number of ECS instances in a scaling group based on your business needs and scaling policies. You can set the minimum and maximum number of instances in a scaling group to limit the range of scaling actions1. When you create a scaling rule, you can specify the number of instances to be added or removed, or the expected number of instances after the scaling action2. You can also create a scheduled task to execute a scaling rule at a specified time or periodically3.

In this question, the customer sets the minimum number of instances to 6 and the maximum number of instances to 8 in the scaling group. This means that the scaling group will always have at least 6 instances and at most 8 instances. The customer also adds a scaling rule to remove 5 instances, and creates a scheduled task based on this rule. However, this scaling rule will not be executed if it violates the minimum and maximum limits of the scaling group. Therefore, when the scheduled task is activated once, the scaling group will only remove 2 instances, which is the difference between the current number of instances (8) and the minimum number of instances (6). The remaining number of instances in the scaling group will be 6, which is the correct answer. References: 1: Create a scaling group - Auto Scaling - Alibaba Cloud Documentation Center2: Create a scaling rule - Auto Scaling - Alibaba Cloud Documentation Center3: Create a scheduled task - Auto Scaling - Alibaba Cloud Documentation Center.

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Explanation

Alibaba Cloud Server Load Balancer (SLB) is a service that distributes network traffic across multiple ECS instances to improve the service capabilities of applications. SLB supports the following protocols for the listener configuration:

• HTTP: Hypertext Transfer Protocol, a stateless application-layer protocol that is used to transfer web pages and other resources over the internet.
• HTTPS: Hypertext Transfer Protocol Secure, an extension of HTTP that uses SSL/TLS encryption to provide secure communication between the client and the server.
• TCP: Transmission Control Protocol, a reliable, connection-oriented transport-layer protocol that provides reliable data delivery and error recovery.
• UDP: User Datagram Protocol, a connectionless transport-layer protocol that provides fast and efficient data transmission without guaranteeing reliability or order.

SLB does not support the following protocols:

• MPLS: Multiprotocol Label Switching, a data-carrying technique that uses labels to forward packets across a network.
• MQTT: Message Queuing Telemetry Transport, a lightweight publish/subscribe messaging protocol that is designed for constrained devices and low-bandwidth networks.

References:

• Alibaba Cloud Server Load Balancer
• ACA Cloud Computing Certification Exam Preparation Course
• Alibaba Cloud Computing Exam Question 2022

Comprehensive protocol support - ICMP, TCP, UDP, HTTP, HTTPS,

 Elastic Compute Service (ECS) is an IaaS offering on Alibaba Cloud that provides high-performance, stable, reliable, and scalable compute capacity in the cloud. ECS eliminates your need to invest in hardware up front. You can create as many or as few instances as you need in response to changes in requirements or popularity of your workloads. With an ever-growing selection of instance types, ECS provides broader and deeper choices to match a wide spectrum of computing needs. References: What is ECS? - Alibaba Cloud

ECS instance filesystem directory operation is not a supported method to create a bucket in OSS. A bucket is a container for objects in OSS, and it is not related to the filesystem of an ECS instance. To create a bucket in OSS, you can use one of the following methods1:

• through OSS API/SDK: You can use the OSS API or SDK to call the PutBucket operation to create a bucket. The OSS API and SDK support various programming languages, such as Java, Python, PHP, C#, and Node.js2.
• through oss cmd tool: You can use the oss cmd tool, which is a command-line tool based on the OSS SDK for Python, to create a bucket by using the ossutil mb command3.
• through cloud console: You can use the Alibaba Cloud console to create a bucket by following the steps in the documentation4. References: 1: Create buckets - Object Storage Service - Alibaba Cloud Documentation Center2: PutBucket - API Reference| Alibaba Cloud Documentation Center3: Create a bucket - OSSUTIL User Guide| Alibaba Cloud Documentation Center4: Create a bucket - Object Storage Service - Alibaba Cloud Documentation Center.

 D is the correct answer because OSS supports 3 internal data copies, no human intervention is required to recover the data when anything goes wrong. OSS provides high data reliability and durability by storing multiple replicas of data on different devices in the same region. OSS automatically detects and repairs data errors or failures, and ensures data consistency across all replicas. OSS also supports cross-region replication (CRR) to back up data to another region for disaster recovery12

A, B, and C are incorrect answers because they do not reflect the actual backup technology and policies of OSS.

• A is incorrect because OSS does not require manual recovery of data, as it automatically handles data errors or failures.
• B is incorrect because OSS provides data protection and backup for customers, and customers do not need to safeguard their own data or use offsite backups.
• C is incorrect because OSS does not use RAID0+1 configuration of its underlying physical hard disks, but rather uses a distributed storage system that stores multiple replicas of data on different devices.

References: 1: OSS Overview 2: OSS Backup

 An ECS image is a copy of data from one or more disks that are attached to an ECS instance. You cannot retrieve data directly from an ECS image and use it right away. You need to create an ECS instance from the image first, and then access the data on the disks of the instance. References: Elastic Compute Service:Image overview

Auto Scaling is a management service that can automatically adjust elastic computing resources based on your business needs and policies. Auto Scaling supports the following features12:

• Elastic Scale-Out: Automatically adds ECS instances to handle increased workloads.
• Elastic Scale-In: Automatically removes ECS instances to reduce costs when workloads decrease.
• Elastic Self-Health: Automatically replaces unhealthy ECS instances to ensure high availability and reliability.
• Scheduled Scaling: Automatically adds or removes ECS instances based on predefined schedules.
• Predictive Scaling: Automatically predicts future workloads and adjusts ECS instances accordingly.

Elastic Self-Diagnostic is not a feature supported by Alibaba Cloud Auto Scaling. It is a fictitious term that does not exist in the Alibaba Cloud documentation or course materials. References: 1: Auto Scaling: Automatically Adjusts Computing Resources - Alibaba Cloud 2: Auto Scaling:What is Auto Scaling? - Alibaba Cloud