ACP-Cloud1 ACP Cloud Computing Certification Questions and Answers

Alibaba Cloud OSS (Object Storage Service) provides extremely high data reliability, typically around 99.99999999%, due to its multi-replica and distributed architecture, ensuring data durability and resilience against single points of failure (SPOF). OSS is designed to store massive amounts of data with high redundancy, making it a preferred choice for businesses that require high reliability and fault tolerance in cloud storage.

When using Alibaba Cloud SLB to forward layer 7 (HTTP) service requests, SLB will replace the IP address in the HTTP header file to forward requests. Therefore, the source IP address that can be seen on the backend ECS instance is the IP address of SLB instead of the client’s real IP address. However, SLB also provides a feature called  X-Forwarded-For  (XFF) that can help you obtain the real IP address of the client. XFF is a standard HTTP header field that records the original IP address of the client and the proxy servers that the request passes through. You can enable XFF on the SLB console or by using the API, and then configure your backend ECS instance to parse the XFF header field and get the real IP address of the client.  References:   1  - SLB overview - Alibaba Cloud Document Center - Layer 7 listeners - X-Forwarded-For

 According to the Alibaba Cloud SLB documentation 1 , SLB provides a health check feature that monitors the availability and performance of the backend servers. If a backend server fails the health check, SLB stops routing requests to it and redirects the traffic to other healthy servers. This way, SLB can improve the system’s availability by eliminating single points of failure (SPOFs). Therefore, option A is a correct statement about SLB.

According to the same documentation 1 , SLB instances are assigned with public IP addresses or private IP addresses based on the network type. If you delete an SLB instance and create a new one, a new IP address will be allocated to the new instance. You cannot specify or reserve an IP address for an SLB instance. Therefore, option B is also a correct statement about SLB.

Option C is incorrect, because SLB does not require you to install or configure any SLB agent on the backend servers. You only need to add the backend servers to the SLB instance and configure the listener and the server group.  SLB will automatically distribute the traffic to the backend servers based on the load balancing algorithm and the health check status 2 .

Option D is also incorrect, because SLB does not provide a function to automatically synchronize data among backend servers. SLB only handles the network traffic distribution and does not interfere with the data on the backend servers.  You need to use other methods or tools to synchronize data among backend servers, such as rsync, lsyncd, or Alibaba Cloud Data Transmission Service (DTS) 3 .

References :  Server Load Balancer:SLB overview ,  Add backend servers , and  Data Transmission Service .

A low CDN cache hit rate can be due to low website traffic, poor cache configurations (such as a short Cache Expiry Time), or the presence of dynamic resources that require frequent retrieval from the origin. Proper configuration of " Cache-Control " and " Expires " headers is necessary to ensure caching.

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Changing directory permissions of the system root directory in Linux can have a significant impact on system functionality and services. Modifying these permissions can lead to restricted access for essential system services, potentially causing service disruptions. Proper care is necessary when altering permissions on critical directories.

ECS instance monitoring provides a process monitoring feature that allows you to check the status of specific processes, such as a Python process, and set alerts for automatic notifications if the process terminates unexpectedly. This method is quicker and more efficient than writing a custom script or manually logging in to the console.

Alibaba Cloud ECS allows users to set an auto-release time for Pay-As-You-Go instances, giving flexibility in handling temporary workloads without manually releasing instances. Notably, the auto-release time can be adjusted multiple times even after the instance has been created, allowing for modifications as business needs change. This feature provides a convenient way to manage costs by automatically releasing instances when they are no longer needed. However, once the auto-release time is set, it must be adjusted or canceled if changes are required.

To improve access speeds for U.S. users, Company G can enable OSS with CDN in the West US (Silicon Valley) region. By deploying CDN in a region close to the target audience, the static content stored in OSS can be cached and delivered more efficiently. CDN caches the content at edge locations, reducing latency for users in different geographical areas. This approach is ideal for expanding the application to international markets while maintaining fast access times.

 You do not need to activate and purchase Alibaba Cloud CloudMonitor service to monitor the status of the ECS instance via Alibaba Cloud console. CloudMonitor is a service that monitors Alibaba Cloud resources and Internet applications.  CloudMonitor provides a one-stop, out-of-the-box, and enterprise-class monitoring solution 1 .  CloudMonitor collects monitor metrics of Alibaba Cloud resources and custom metrics and enables you to view and understand the usage of the cloud resources, and the health of your business 2 .  CloudMonitor allows you to monitor the metrics of Alibaba Cloud services, detect the availability of websites hosted on ECS instances or carrier servers, and configure alert rules for specified metrics 3 . However, CloudMonitor is not a prerequisite for monitoring the status of the ECS instance via Alibaba Cloud console. You can monitor the status of the ECS instance via Alibaba Cloud console without activating and purchasing CloudMonitor service. You can view the basic information, configuration, security group, and tags of the ECS instance in the console. You can also view the CPU, memory, disk, and network usage of the ECS instance in the console.  You can also use the Cloud Assistant feature to run commands on the ECS instance remotely 4 . 

In Alibaba Cloud’s VPC architecture, a VRouter (Virtual Router) is used to connect multiple VSwitches within a VPC. The VRouter routes traffic between VSwitches, and each VSwitch in a VPC is associated with a route table managed by the VRouter. This setup enables efficient communication between subnets and applies to the entire VPC.

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Once a VPC is created in Alibaba Cloud, its CIDR Block cannot be modified. This design ensures stability and network consistency within the VPC. To change the network range, a new VPC would need to be created with the desired CIDR Block.

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Alibaba Cloud Express Connect is a service that enables high-bandwidth, reliable, secure, and private connections between different networks, such as VPC networks across regions, Alibaba Cloud accounts, and on-premise data centers 1 .  It supports different connection methods, such as physical connections, virtual border routers, and Express Cloud Connect 1 .

Scenario A: Intranet communication between VPCs and Smart Access Gateway in customers different branch offices.  This scenario can be achieved by using Express Cloud Connect, which is based on the hardware capacities of Smart Access Gateway and provides SD-WAN capabilities 1 .  Express Cloud Connect allows you to connect your branch offices to Alibaba Cloud through a dedicated partner backbone network, and access VPC networks in all regions 1 .

Scenario B: Intranet communication between a VPC and servers in an external IDC.  This scenario can be achieved by using physical connections, which are dedicated network connections between on-premise data centers and VPC networks 1 .  You can lease a line from your ISP or work with an Alibaba Cloud partner to establish a physical connection to Alibaba Cloud 1 .  This way, you can access VPC networks in all regions with high bandwidth and low latency 1 .

Scenario C: Intranet communication between two VPCs in different accounts and different CIDR Blocks.  This scenario can be achieved by using peering connections, which are logical connections that enable communication between VPC networks 2 .  Peering connections support cross-region and cross-account scenarios, and allow you to connect VPC networks with different CIDR blocks 2 .  However, peering connections are not part of Alibaba Cloud Express Connect, but a separate service called Cloud Enterprise Network 2 .

Scenario D: Intranet communication between two VPCs under the same account in the same region.  This scenario can also be achieved by using peering connections, which are logical connections that enable communication between VPC networks 2 .  Peering connections support intra-region and same-account scenarios, and allow you to connect VPC networks with different CIDR blocks 2 .  However, peering connections are not part of Alibaba Cloud Express Connect, but a separate service called Cloud Enterprise Network 2 .  References :  1 :  Express Connect - Alibaba Cloud   2 :  Introduction to Cloud Enterprise Network - Alibaba Cloud Document Center

A route table is a set of rules that determine how network traffic is routed within a VPC or between different network instances 1 .  A VRouter is a hub that connects all VSwitches in the same VPC and enables communication between them 2 .  When you create a VPC, a VRouter and a default route table are automatically created for the VPC 1 .  The default route table contains system routes that are automatically generated by the system based on the network topology 1 .  The system routes cannot be modified or deleted 1 .

However, you can also create custom route tables for your VPC and add custom routes to them 1 .  Custom routes are manually configured by users to route traffic to specific destinations, such as other VPCs, VBRs, VPN Gateways, or NAT Gateways 1 .  Custom routes can be modified or deleted as needed 1 .  You can also associate VSwitches with different route tables to implement fine-grained routing control 1 .

Therefore, the statement that the routing entries of the route table can not be modified manually is not correct, as it only applies to system routes, not custom routes.  The other statements are correct, as each VRouter may have multiple route tables, one default and several custom 1 ; when a VPC is deleted, the corresponding route table is also deleted 3 ; and the default route table cannot be deleted 1 .  References:   Route table overview - Virtual Private Cloud - Alibaba Cloud Documentation Center ,  VRouter overview - Virtual Private Cloud - Alibaba Cloud Documentation Center ,  Delete a VPC - Virtual Private Cloud - Alibaba Cloud Documentation Center

For Layer-4 SLB using TCP, the health check determines ECS instance availability based on the successful completion of a TCP 3-way handshake. This ensures that the backend server is reachable and can accept connections, which is critical for reliable TCP-based load balancing.

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To isolate ECS instances within different VSwitches in a VPC while allowing them to access the internet and other intranet resources, each VSwitch ' s instances should be in separate Security Groups. By configuring each group to allow all VPC CIDR blocks first and then restricting access to other VSwitch CIDR blocks with a higher priority rule, instances in each VSwitch are isolated without affecting the VPC ' s external connections. This approach follows Alibaba Cloud ' s Security Group best practices and CIDR-based access control within VPC environments.

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Auto Scaling in Alibaba Cloud supports both Pay-As-You-Go and monthly subscription ECS instances within a scaling group. Pay-As-You-Go instances provide flexibility during traffic surges, while idle monthly subscription instances can be added manually to optimize costs and resource usage.

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Alibaba Cloud ECS (Elastic Compute Service) is an Infrastructure as a Service (IaaS) offering, providing users with virtualized computing resources like virtual machines. IaaS services offer fundamental cloud infrastructure such as compute, storage, and networking resources.

Option B is correct because using Server Load Balancer (SLB) and adding additional ECS instances can help to distribute the traffic among multiple servers and improve the availability and scalability of the platform.  SLB can also provide health checks and fault tolerance for the ECS instances 1

Option D is correct because replacing the self-built MySQL database with ApsaraDB for RDS can provide better database performance, security, and reliability. ApsaraDB for RDS is a fully managed cloud database service that supports MySQL, SQL Server, PostgreSQL, and other engines. It can automatically handle tasks such as backup, recovery, monitoring, and patching.  Using RDS read-only instances can also handle read-only requests and reduce the load on the primary database 2

Option A is incorrect because importing database data into Object Storage Service (OSS) will not share the storage pressure on the platform. OSS is a cloud storage service that provides high durability, availability, and scalability for storing unstructured data such as images, videos, and documents. It is not suitable for storing structured data such as database tables.  Moreover, importing data into OSS will incur additional costs and latency 3

Option C is incorrect because using Content Delivery Network (CDN) will not enhance the content loading speed of the platform. CDN is a distributed network that delivers content to users based on their geographic locations, the origin of the content, and the content delivery server. It is mainly used to accelerate the delivery of static content such as images, videos, and scripts.  It is not effective for dynamic content such as database queries and transactions 4

References :

1 :  Server Load Balancer - Alibaba Cloud

2 :  ApsaraDB for RDS - Alibaba Cloud

3 :  Object Storage Service - Alibaba Cloud

4 :  Content Delivery Network - Alibaba Cloud

Alibaba Cloud RDS automatically deploys instances in master-slave mode (high availability) without additional configuration or charges. This ensures data redundancy and disaster recovery by maintaining synchronous data replication from the master to the slave instance.

Not all upload methods in Alibaba Cloud OSS support resuming from a breakpoint. Only specific methods, such as multipart upload, support this feature. Small files can be uploaded using a single PUT request, while APPEND is useful for continuously updated log files. For large files, multipart uploading is recommended to handle potential interruptions.

 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 regions 1 .  For subscription instances, you will be charged for the entire subscription period regardless of whether the instance is running or stopped 2 .  References:

1 : Billing FAQ - Elastic Compute Service - Alibaba Cloud Documentation Center 1

2 : Billing overview - Elastic Compute Service - Alibaba Cloud Documentation Center 2

In Alibaba Cloud VPCs, only custom route tables can be created and deleted by users. The default route table associated with each VPC cannot be deleted, although custom routing entries within it can be modified. This limitation ensures the integrity of essential VPC networking components.

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In cloud environments, Alibaba Cloud emphasizes that security responsibilities, data ownership (data attribution), and security standards remain with the user. However, O & M (Operations and Maintenance) methods often change due to the distinct management tools, automated processes, and distributed nature of cloud infrastructure. Cloud environments typically use different O & M approaches, so option D is not aligned with Alibaba Cloud ' s security principles.

Applications deployed on ECS instances that are managed by Auto Scaling should be stateless and horizontally scalable. Stateless applications do not store session data or any critical information on a single instance, allowing them to be replicated or terminated without affecting the application ' s overall functionality. Horizontal scalability ensures that more instances can handle additional traffic as demand increases. This setup allows Auto Scaling to add or remove instances seamlessly without requiring reconfiguration.

To handle high download traffic efficiently, Company F can use Object Storage Service (OSS) to store the installation package and Content Delivery Network (CDN) to distribute it. OSS provides scalable, low-cost storage, while CDN caches content at edge nodes, reducing the load on the ECS instance and improving download speeds for users. This combination helps control bandwidth costs on ECS and provides faster download speeds by serving content closer to end-users.

 Cloud Firewall is a service that provides centralized protection for your cloud assets and prevents unauthorized access to your servers. Cloud Firewall can monitor and control the inbound and outbound traffic of your servers, and block malicious requests and attacks. Cloud Firewall can also detect and prevent brute force password cracking attempts by using intelligent algorithms and threat intelligence. Therefore, option A is the correct answer.  References :  What is Cloud Firewall? ,  Protect servers from brute force attacks

Data Transmission Service (DTS) is a real-time data streaming service that supports data transmission between data sources such as relational databases, NoSQL, and Big Data (OLAP). DTS supports data migration, data synchronization, and change data subscription scenarios. DTS can migrate your data to and from most of the widely used commercial and open source databases. It supports homogeneous migrations such as MySQL to MySQL, as well as heterogeneous migrations between different database platforms, such as Oracle to MySQL. Migrations can be from on-premises databases to RDS or ECS, databases running on ECS to RDS, or vice versa, as well as from one RDS database to another RDS database. DTS also supports database schema replication between instances, which means that DTS can automatically create the same schema as the source database in the target database. DTS also supports warning when source and destination has some unresolved conflict found, such as data type mismatch, primary key conflict, or foreign key constraint violation. DTS can help you resolve these conflicts by providing suggestions or allowing you to modify the data mapping rules. Therefore, the correct answer is C. Supports all of the above functions.  References :

1 : Data Transmission Service - Alibaba Cloud

2 : What is Data Transmission Service? - Alibaba Cloud

3 : Database Migration - AlibabaCloud

4 : Cloud Migration without Stopping Services: Alibaba Cloud DTS

When creating an ECS instance in your Alibaba Cloud VPC, you must specify a VSwitch for that instance at the same time. Otherwise, you will not be able to create this ECS instance.  This is true according to the Alibaba Cloud documentation on ECS 1 .  A VSwitch is a basic network device of a VPC and is used to connect different cloud product instances deployed in a VPC 2 .  A VSwitch defines a network segment within a VPC and allows you to specify the IP address range, network mask, and gateway for the network segment 2 .  When you create an ECS instance, you must select a VSwitch that belongs to the same zone as the ECS instance 3 .  If you do not specify a VSwitch, the ECS instance will not be able to communicate with other cloud product instances in the VPC or access the Internet.  References:   1 :  Create an instance by using the provided wizard - Elastic Compute Service - Alibaba Cloud Documentation Center   2 :  What is a VSwitch? - Virtual Private Cloud - Alibaba Cloud Documentation Center   3 :  Create an instance by using the advanced wizard - Elastic Compute Service - Alibaba Cloud Documentation Center  : [VPC FAQ - Virtual Private Cloud - Alibaba Cloud Documentation Center]

When changing the specifications of an RDS instance, service interruptions can occur during some upgrade and downgrade operations, depending on the RDS instance type and the complexity of the change. While upgrades are generally supported, certain modifications may result in brief downtime as the system reconfigures resources. This is contrary to option B. Additionally, database version downgrades are restricted, and MySQL 5.1 can indeed be upgraded directly to MySQL 5.6 in Alibaba Cloud RDS.

CDN is most effective for scenarios with high repetitive access, where content is frequently requested and can be cached, such as static websites, video delivery, and application download sites. In contrast, a personal netdisk service typically involves unique, private files with low repeat access rates, making CDN less effective since the content is unlikely to be accessed by multiple users frequently, thus reducing the benefit of caching.

Zones in the same region support low-latency intranet communication, ideal for high- availability deployments with inter-Zone fault isolation. Placement of ECS instances in the same or different Zones depends on the disaster recovery and latency needs of the application.

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 The statement A is not correct, because self-built databases do not support quick deployment and elastic scaling. On the contrary, self-built databases require hardware procurement, data center hosting, and machine deployment, which can be time consuming and costly. Moreover, self-built databases have low resource utilization, as they have to accommodate peak traffic requirements, while RDS can scale elastically according to the actual demand.  References : =  ApsaraDB for RDS vs. Self-built Databases - Alibaba Cloud

Alibaba Cloud SLB’s " Rewrite Cookie " mode allows selective session persistence for specific subdomains by setting and rewriting cookies as specified. For example, you can enable session persistence on vip.a.com while leaving img.a.com without it. SLB uses the rewritten cookie to direct subsequent requests to the previously assigned backend server.

Before data communication is set up, the security groups match the security group rules one by one to query whether to allow access requests. If the protocol type, port range, authorization type, and authorization object of two security group rules are the same, the following rules apply:

If the two rules have the same priority, the rule of the denial policy takes effect first, and the rule of the allowed policy does not take effect. This is because the security group rules follow the principle of minimum permission, which means that the most restrictive rule is applied when there is a conflict.

If the two rules have different priorities, the rule with a smaller priority number takes effect. This is because the security group rules follow the principle of priority, which means that the rule with a higher priority (lower number) is applied when there is a conflict.  References:   ECS Security Groups - Alibaba Fundamentals - Cloud Academy ,  Security group rules - Elastic Compute Service - Alibaba Cloud Documentation Center

Weighted Round Robin (WRR) is a load balancing mode that assigns requests to backend ECS instances based on their weights. The higher the weight of the backend ECS instance, the higher the chance that the instance will receive requests. This mode can exploit the different service capacities of backend ECS instances by setting higher weights to ECS instances with higher capacities. For example, if there are two ECS instances in the backend server pool, one with a weight of 10 and the other with a weight of 20, the ECS instance with a weight of 20 will receive twice as many requests as the ECS instance with a weight of 10.

References :

1 : SLB overview - Server Load Balancer - Alibaba Cloud Documentation Center

4 : Server Load Balancer - Alibaba Cloud

5 : Alibaba Server Load Balancer (SLB) Course - Cloud Academy

For optimal use of SLB with Auto Scaling, enabling Health Check is essential to determine which instances are healthy and ready to handle traffic. SLB doesn’t require all backend servers to have the same OS, be in the same scaling group, or have identical configurations, as it can manage heterogeneous server setups within the same load-balancing group.

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Modifying the MAC address of an ECS instance’s NIC can cause network disconnection issues because Alibaba Cloud ' s VPC network infrastructure relies on consistent NIC configuration. Changing the MAC address may prevent the instance from being identified correctly on the network.

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Security Center is a centralized security management system that dynamically identifies and analyzes security threats, and generates alerts when threats are detected.  Security Center provides multiple features to ensure the security of cloud resources and servers in data centers 1 . Security Center can help the company to quickly resolve its security problems by providing the following benefits:

Unified security management: Security Center automatically collects various log data from the company’s services on the cloud, and implements control over found security threats.  Security Center can also manage assets, attacks, vulnerabilities, and threats in the Security Center console 2 .

Proactive defense: Security Center supports the proactive detection and termination of mainstream ransomware, mining programs, backdoor programs, worms, malicious programs, DDoS trojans, and trojan programs. Security Center also prevents websites from being maliciously implanted with the acts that involve terrorism, politics, dark chains, trojans, and backdoors.  This ensures the normal operation of web page information 2 .

Automated security operations: Security Center automatically traces the sources and causes of attacks. This helps the company understand the ins and outs of intrusion threats and make quick responses.  Security Center also supports custom alerts and third-party data migration to the cloud in a secure manner 2 .  References:   Security Center - Alibaba Cloud ,  Cloud Security- Alibaba Cloud ,  Introduction to Security Center - Alibaba Cloud Document Center

Elastic Computing on Alibaba Cloud ECS includes features that allow users to quickly start or release multiple instances, upgrade bandwidth without downtime, adjust CPU and memory configurations, and perform horizontal scaling in conjunction with Server Load Balancer (SLB). However, option E is incorrect as there is a limit to the number of disks that can be attached to an ECS instance.

Alibaba Cloud provides basic security services for ECS instances, which include protection against unexpected remote logins, DDoS attacks, brute-force password cracking, and alerts for potential sensitive information leakage. Key management services (KMS) are available but are not part of the free security services for ECS.

Alibaba Cloud Content Delivery Network (CDN) is a distributed network that delivers content to users based on their geographic locations. CDN can reduce the latency and improve the user experience of accessing content from the Internet. CDN can also reduce the Internet downstream traffic of OSS by caching the content in the edge nodes of CDN. The Internet traffic cost of CDN is lower than that of OSS, and the back-to-source traffic cost from CDN to OSS is also lower than a user access to OSS directly. Therefore, using CDN can reduce the traffic cost of OSS.  References :  Object Storage Service (OSS) - Alibaba Cloud ,  Storage Services Overview:OSS - Alibaba Cloud ,  Introduction to Object Storage Service - Alibaba Cloud ,  Object Storage Service(OSS): Store Data Safely In The Cloud

Active/standby server groups are a feature of Server Load Balancer (SLB) that allows you to configure a primary ECS instance and a secondary ECS instance for the backend of an SLB instance 1 . When the primary instance is working properly, the traffic is only forwarded to the primary ECS.  When the primary instance is down, traffic is switched to the standby instance 1 .  This feature is supported by TCP and HTTPS listeners, but not by HTTP and UDP listeners 1 .  TCP and HTTPS listeners support session persistence, which ensures that requests from the same client are always forwarded to the same backend server 2 .  HTTP and UDP listeners do not support session persistence, and they use round-robin or weighted round-robin algorithms to distribute traffic among the backend servers 2 .  References :  1 :  Create an active/standby server group   2 : [Configure a listener]

According to the Alibaba Cloud Auto Scaling documentation, scheduled mode allows you to configure the scheduled tasks by adding or removing ECS instances for a fixed time. This mode is suitable for scenarios where the service traffic spikes are predictable and periodic. For example, a new media company can use scheduled mode to add or reduce ECS instances dynamically to address service traffic spikes during some busy hours, such as from 07:30 to 09:00 and from 18:30 to 20:00. This mode can help simplify deployment tasks and save costs by avoiding unnecessary scaling activities.  References :  How Auto Scaling works - Auto Scaling - Alibaba Cloud Documentation Center .

Alibaba Cloud RDS allows multiple databases to be created on a single instance. However, each database within the same instance must have a unique name, and resources are shared among instances unless specified otherwise. Additionally, not all RDS editions support High Availability (HA) mode; HA is typically available in certain editions, like RDS for MySQL and RDS for PostgreSQL.

To confirm a previously unhealthy instance is now healthy, Alibaba Cloud SLB requires three consecutive successful health checks. With a health check interval of 2 seconds and a response timeout of 5 seconds, each check cycle takes up to 5 seconds. Therefore, three successive health checks would take a minimum of 5×3=155 \times 3 = 155×3=15 seconds in total. However, because the health checks are conducted at 2-second intervals, there’s overlap, reducing the actual time to at least 11 seconds for the SLB to mark the instance as healthy.

In SLB, a Listener is configured with policies and forwarding rules that define how the load balancer will handle incoming requests, including protocol, port, and health check configurations. It does not represent an SLB instance itself or a collection of ECS instances, but it plays a crucial role in managing traffic routing and session persistence.

Alibaba Cloud provides two main products for Anti-DDoS protection: Anti-DDoS Origin Service, which protects against attacks at the origin server level, and Anti-DDoS Pro Service, which offers advanced DDoS mitigation for applications hosted on Alibaba Cloud. Security Center and Cloud Firewall offer different security functionalities but do not provide direct Anti-DDoS services.

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 PPPoE stands for Point-to-Point Protocol over Ethernet, which is a network protocol that encapsulates PPP frames in Ethernet frames and allows multiple computers to share a single Internet connection. PPPoE is typically used by Internet service providers (ISPs) to provide broadband access to their customers, such as DSL or cable modem. PPPoE is not a protocol that is commonly supported by Open API for cloud computing service providers, because it is not designed for web-based communication and requires a dedicated connection between the client and the server. Open API, on the other hand, is a term that refers to a set of publicly available application programming interfaces (APIs) that allow developers to access the functionality and data of cloud computing service providers. Open API usually follows standard protocols that are widely used on the web, such as HTTP, Restful, and Web Service. HTTP stands for Hypertext Transfer Protocol, which is the foundation of data communication on the web. HTTP defines how messages are formatted and transmitted, and what actions web servers and browsers should take in response to various commands. HTTP is a stateless protocol, which means that each request is independent and does not depend on any previous requests or responses. Restful stands for Representational State Transfer, which is an architectural style for designing web services that are based on the concept of resources. Restful web services use HTTP methods (such as GET, POST, PUT, and DELETE) to perform operations on resources, and use standard formats (such as JSON or XML) to exchange data. Restful web services are stateless, scalable, and cacheable, and aim to provide a uniform interface for interacting with different types of resources. Web Service is a generic term that refers to any software service that is available over the web and uses a standardized format for communication, such as SOAP or REST. Web Service allows different applications to communicate and exchange data across different platforms and languages. Web Service can be described using a specification language, such as WSDL or OpenAPI, which defines the structure, operations, and parameters of the service. Web Service can also be registered and discovered using a directory service, such as UDDI or Swagger.

Alibaba Cloud OSS does not charge for data ingress, meaning there are no traffic charges for uploading files to OSS, whether through the management console or Open API. However, traffic charges may apply for data egress, i.e., downloading files from OSS.