ACP-Cloud1 Practice Test

B.   The main purpose of a DDoS attack is to prevent the target server from providing normal services. Currently, the DDoS attack is one of the strongest and most indefensible website attacks.

Explanation: A DDoS attack is a type of cyberattack that aims to exhaust the resources of a target server or network, such as bandwidth, CPU, memory, or disk space, by sending a large amount of malicious traffic or requests. This can cause the server or network to slow down, crash, or become unavailable to legitimate users. A DDoS attack is not intended to steal confidential information, crack passwords, or target databases, although these may be secondary objectives or consequences of some attacks. A DDoS attack is one of the most common and powerful threats to website security, as it can be launched from multiple sources, use various attack methods, and evade traditional defense mechanisms. According to the DDoS Attack Statistics and Trend Report by Alibaba Cloud, the proportion of volumetric attacks at 50Gbps and above has doubled, and the resources exhaustion attack reached a peak value of 3 million QPS in 2020-2021. References: DDoS Attacks: Sources, Strategies and Practices - Alibaba Cloud, DDoS Attack Statistics and Trend Report by Alibaba Cloud, Use Alibaba Cloud Anti-DDoS Service to Defend DoS Attack, Anti-DDoS Basic - Alibaba Cloud

B.   False

Explanation: You can change the private IP address of an ECS instance after it is created, but you need to stop the instance first. The private IP address must be within the CIDR block of the VPC and the VSwitch that the instance belongs to. You can modify the private IP address of an instance by using the console or the API. References: 3, ACP Cloud Computing Certification - Alibaba Cloud Academy After stopping an Alibaba Cloud Elastic Compute Service (ECS) instance, you will still be charged for some resources related to that ECS instance, such as disks, snapshots, and public IP addresses, until you release them. The charging policy depends on the billing method and network type of the ECS instance. For pay-as-you-go instances, you can choose whether to enable the No fees for stopped instances feature, which allows you to stop paying for vCPUs and memory when the instance is stopped. However, this feature is only available for VPC-connected instances in some regions1. For subscription instances, you will be charged for the entire subscription period regardless of whether the instance is running or stopped2. References: 1: Billing FAQ - Elastic Compute Service - Alibaba Cloud Documentation Center1 2: Billing overview - Elastic Compute Service - Alibaba Cloud Documentation Center2

D.   Tomcat: 4 cores: 4G, Memcache: 2 cores: 16G

Explanation: According to the Alibaba Cloud ECS documentation1, the recommended instance type for Tomcat is ecs.c5.xlarge, which has 4 vCPUs and 4 GiB of memory. This instance type is suitable for web applications that require high performance and low latency. The recommended instance type for Memcache is ecs.r5.large, which has 2 vCPUs and 16 GiB of memory. This instance type is optimized for memory-intensive applications that require high memory bandwidth and low latency. Therefore, option D is the most recommended configuration for deploying Tomcat and Memcache on two ECS instances. References: Instance type families and Alibaba Cloud Elastic Compute Service Product Introduction

A.   Elastic Compute Service (ECS) image achieve efficient and convenient deployment.

C.   Utilizing Server Load Balancer (SLB) and ECS instances can improve data reliability.

E.   Reasonable selection of Regions/Zones meets the location needs of application deployment as well as the demands for redundantly backup critical business applications and data.

Explanation: A. Elastic Compute Service (ECS) image achieve efficient and convenient deployment. This is correct because ECS images are pre-configured operating system environments that can be used to create and launch ECS instances quickly and easily. ECS images can reduce the cost and time of deploying applications on Alibaba Cloud1. B. Utilizing Content Delivery Network (CDN) can meet the demands for redundant backup. This is incorrect because CDN is not a backup service, but a service that accelerates the delivery of content to end users by caching it at edge nodes. CDN can improve the performance and availability of applications, but it does not provide data redundancy or backup2. C. Utilizing Server Load Balancer (SLB) and ECS instances can improve data reliability. This is correct because SLB is a service that distributes traffic among multiple ECS instances based on predefined rules. SLB can improve the availability and reliability of applications by eliminating single points of failure and ensuring that requests are routed to healthy instances3. D. Elastic Compute Service (ECS) snapshot satisfies the needs of rapid recovery of applications and data. This is incorrect because ECS snapshot is a feature that allows users to create point-in-time backups of ECS disks. ECS snapshots can be used to restore data or create new disks, but they do not satisfy the needs of rapid recovery of applications and data. Snapshots are stored in Object Storage Service (OSS), which is a low-cost and durable storage service, but it has higher latency and lower performance than disks4. E. Reasonable selection of Regions/Zones meets the location needs of application deployment as well as the demands for redundantly backup critical business applications and data. This is correct because regions and zones are the physical locations of Alibaba Cloud data centers. Regions are geographically isolated from each other, and zones are physically independent within the same region. Users can choose the regions and zones that best suit their application deployment needs, such as proximity to customers, compliance with local regulations, and availability of services. Users can also use multiple regions and zones to achieve redundancy and backup for their critical business applications and data. References: 1: ECS Images 2: CDN Overview 3: SLB Overview 4: ECS Snapshots : Regions and Zones

D.   X-Forwarded-For

Explanation: The X-Forwarded-For field in HTTP header is used to identify the originating IP address of a client connecting to a web server through an HTTP proxy or a load balancer. When the “Obtain the Visitor’s Real IP Address” function is enabled in Alibaba Cloud SLB, the SLB instance adds the X-Forwarded-For field to the HTTP header of each request and forwards the request to the backend server. The backend server can then obtain the real IP address of the visitor from the X-Forwarded-For field1. The format of the X-Forwarded-For field is as follows:
X-Forwarded-For: client, proxy1, proxy2
where the value is a comma+space separated list of IP addresses, the left-most being the original client, and each successive proxy that passed the request adding the IP address where it received the request from. In this example, the request passed through proxy1, proxy2, and then the SLB instance (proxy3).2 References: Obtain client IP addresses - Server Load Balancer - Alibaba Cloud, XForwarded- For - MDN Web Docs