Network Service

Overview

ZStack Cloud provides VM instances with multiple network resources, including VPC firewall, security group, virtual IP address (VIP), elastic IP address (EIP), port forwarding, IPsec tunnel, load balancing, and flow monitoring.

ZStack Cloud supports the following three network models:

Flat network
vRouter network
VPC

Network Service Module

Network Service Module provides a group of network services. Note that this module has been hidden on the UI.

Network Service Module has the following four types:

Virtual Router Network Service Module (Not recommended)
Provides various network services: DNS, SNAT, load balancing, port forwarding, EIP, and DHCP.
Flat Network Service Module (Flat Network Service Provider)
Provides the following network services:
- User Data: Customizes some parameters, such as ssh-key injection. By running cloud-init, these parameters will be loaded and injected into your VM instance when the VM instance is started.
- EIP: Is realized by distributed EIP to access private networks through public networks.
- DHCP: Is realized by distributed DHCP to dynamically obtain an IP address.
  Note: The DHCP service includes the DNS feature.
- VIP QoS: Adjusts the upstream bandwidth and downstream bandwidth, and can only be applied to EIPs.
vRouter Network Service Module
Provides the following network services:
- IPsec: Achieves VPN connections.
- vRouter route table: Manages custom routes.
- Centralized DNS: Is provided when the DHCP service is enabled.
- VIP QoS: Adjusts the upstream bandwidth and downstream bandwidth.
- DNS: Uses vRouters to provide the DNS service.
- SNAT: Enables VM instances to access directly the Internet.
- Load balancing: Distributes inbound traffics from a VIP to a group of backend VM instances. Then, unavailable VM instances will be detected and isolated automatically.
- Port forwarding: Forwards port traffics of specified public IP addresses to the ports of corresponding VM instances according to specified protocols.
- EIP: Uses vRouters to access private networks of VM instances through public networks.
- DHCP: Provides the centralized DHCP service.
Security Group Network Service Module
Provides the following network service:
- Security group: Manipulates securities of VM instance firewalls by using iptables.

Flat Network Practice

In your production environments, we recommend that you use the following combination of network services:

Flat Network Service Module
- User Data: Customizes some parameters, such as ssh-key injection. By running cloud-init, these parameters will be loaded and injected into your VM instance when the VM instance is started.
- EIP: Is realized by distributed EIP can access private networks through public networks.
- DHCP: Is realized by distributed DHCP to dynamically obtain an IP address.
  Note: The DHCP service includes the DNS feature.
Security Group Network Service Module
- Security group: Manipulates securities of VM instance firewalls by using iptables.

vRouter Network Practice

In your production environments, we recommend that you use the following combination of network services:

Flat Network Service Module
- User Data: Customizes some parameters, such as ssh-key injection. By running cloud-init, these parameters will be loaded and injected into your VM instance when the VM instance is started.
- DHCP: DHCP allows you to dynamically obtain an IP address.
vRouter Network Service Module
- DNS: Uses vRouters to provide the DNS service.
- SNAT: Allows VM instances to access directly the Internet.
- vRouter route table: Manages custom routes.
- EIP: Uses vRouters to access private networks of VM instances through public networks.
- Port forwarding: Forwards port traffics of specified public IP addresses to the ports of corresponding VM instances according to specified protocols.
- Load balancing: Distributes inbound traffics from a VIP to a set of backend VM instances. Then, unavailable VM instances will be detected and isolated automatically.
- IPsec: Achieves VPN connections.
Security Group Network Service Module
- Security group: Manipulates securities of VM instance firewalls by using iptables.

VPC Network Practice

In your production environments, we recommend that you use the following combination of network services:

Flat Network Service Module
- User Data: Customizes some parameters, such as ssh-key injection. By running cloud-init, these parameters will be loaded and injected into your VM instance when the VM instance is started.
- DHCP: Is realized by distributed DHCP to dynamically obtain an IP address.
vRouter Network Service Module
- DNS: Uses VPC vRouters to provide DNS services.
- SNAT: Allows VM instances to access directly the Internet.
- vRouter route table: Manages custom routes.
- EIP: Uses VPC vRouters to access private networks of VM instances through public networks.
- Port forwarding: Forwards port traffics of specified public IP addresses to the ports of corresponding VM instances according to specified protocols.
- Load balancing: Distributes inbound traffics from a VIP to a set of backend VM instances, and unavailable VM instances will be detected and isolated automatically.
- IPsec: Achieves VPN connections.
Security Group Network Service Module
- Security group: Manipulates securities of VM instance firewalls by using iptables.

Advanced Network Services

Dynamic routing: Uses the Open Shortest Path First (OSPF) routing protocol to distribute routing information within a single autonomous system. This service applies to VPC network scenarios.
Multicast routing: Forwards the multicast information sent by the multicast source to VM instances, achieving one-to-multi-point communication in the transmission side and receiving side. This service applies to VPC network scenarios.
VPC firewall: Filters the south-north traffic on the VPC vRouter ports, effectively protecting the VPC communication security and VPC vRouter security. This service applies to VPC network scenarios.
Port mirroring: Copies and sends network traffics of VM NICs from a port to another port, and analyzes the business packets on the ports, better monitoring and managing the network data. This service applies to flat network, vRouter network, and VPC network scenarios.
Netflow: Monitors and analyzes the inbound and outbound traffics of the VPC vRouter NICs. Currently, the following two types of data-flow output formats are supported: Netflow V5 and Netflow V9. This service applies to VPC network scenarios.

VPC Firewall

A firewall is an access control policy that monitors ingress and egress traffic of VPC vRouters and decides whether to allow or block specific traffic based on the associated rule sets and rules.

Concepts

Firewall rule set: A firewall rule set is a set of rules that a firewall uses to defend against network attacks. You need to associate a rule set with the egress or ingress flow direction of VPC vRouter NICs to make the rule set take effect.
- You can associate a rule set with the egress or ingress flow direction of VPC vRouter NICs:
  - Ingress: applies to the traffic that flows into the specified VPC vRouter via a network.
  - Egress: applies to the traffic that flows out of the specified VPC vRouter via a network.
Firewall rule: A firewall rule is an access control entry associated with the egress or ingress flow direction of VPC vRouter NICs to defend against network attacks. A firewall rule includes rule priority, match condition, and behavior.
- You can associate a rule with the egress or ingress flow direction of VPC vRouter NICs:
  - Ingress: applies to the traffic that flows into the specified VPC vRouter via a network.
  - Egress: applies to the traffic that flows out of the specified VPC vRouter via a network.
- Firewall rules can be categorized into custom rules and system rules:
  - Custom rules: rules that you customize. You can select the ingress or egress direction that the rules take effect and configure the rule priorities, match conditions, and behaviors.
    - Rule priority: the priority of a rule to be matched and take effect when compared with other firewall rules. Valid values: 1001 to 2999.
      - Generally, a rule with a higher priority is primarily matched when compared to a rule with a lower priority. Priorities are represented by using numbers. A smaller number indicates a higher priority.
      - Generally, the more specific the match condition that you configure for a rule is, the higher priority you shall configure for the rule.
    - Match condition: the condition based on which traffic flowing into or out of a VPC network is matched. It includes source IP address, destination IP address, source port, destination port, packet status, and protocol.
      - You can specify one or more source and destination IP addresses. These IP addresses can be static IP addresses, IP ranges, CIDR blocks, or a mix of the three.
      - If you specify multiple entries, which include one or more CIDR blocks, the netmask of the CIDR block must be 24. If you specify only one CIDR block, the netmask of the CIDR block is not limited.
      - You can enter a maximum of ten entries, with each entry separated by a comma (,).
    - Behavior: the action to be applied to traffic that meets the match condition. Valid values: accept, drop, and reject.
      - Accept: accepts the traffic that flows in or out of the specified VPC vRouter.
      - Drop: drops the traffic that flows in or out of the specified VPC vRouter and does not respond to the client.
      - Reject: rejects the traffic that flows in or out of the specified VPC vRouter and responds to the client.
  - System rules: rules predefined to support system services. The system predefines the direction that the rules take effect, and the priority, match condition, and behavior of the rules.
    - The priority of system rules ranges from 1 to 1000 or from 4000 to 9999.
    - ZStack Cloud has predefined the following system rules:
      - Firewall rules that take effect on the ingress direction of VPC vRouter NICs:
        
        Rule 1: The priority is 4000, and the behavior and match condition combination determines to allow established or related data packets from any IP address/port, with any protocol, or to any IP address/port, to flow into the specified VPC vRouter via a network.
        
        Rule 2: The priority is 9999, and the behavior and match condition combination determines to allow new data packets from any IP address/port, with any protocol, or to any IP address/port, to flow into the specified VPC vRouter via a network.
        
        Rule 3: the default rule with a priority of 10000. The behavior and match condition combination determines to reject data packets from any IP address/port, with any protocol, in any status, or to any IP address/port, from flowing into the specified VPC vRouter via a network. You can modify the behavior of the rule. Valid values: accept, drop, and reject.
      - Firewall rules that take effect on the egress direction of VPC vRouter NICs:
        
        Rule 1: the default rule with a priority of 10000. The behavior and match condition combination determines to reject data packets from any IP address/port, with any protocol, in any status, or to any IP address/port, from flowing into the specified VPC vRouter via a network. You can modify the behavior of the rule. Valid values: accept, drop, and reject.
      - System rules cannot be modified, except the behavior of the default rule.
      - System rules cannot be created or deleted.
Rule template: A rule template is a template that you can select when you add rules to a rule set or a firewall.
IP/Port set: An IP or port set is a set of IP addresses or ports that you can select when you add rules to a rule set or a firewall.

Fundamentals

ZStack Cloud allows you to associate rule sets and rules with the ingress and egress direction of VPC vRouter NICs. Then traffics that flow in or out of the VPC vRouter NICs are filtered based on the rule priority, match condition, behavior, and the effect direction. This ensures the security of data communications across VPC networks, of VPC vRouters, and of user business operations.

Assume that a server and two VM instances are deployed in a VPC network to run significant business applications. To ensure business security, firewall rule sets and rules are associated with the ingress or egress direction of VPC vRouters, so that only trustful traffics from the public network are allowed to access VM data in the VPC network and that the server in the VPC network can access the server data in the public network.

When VM-1 attempts to access VM-3: The traffic from VM-1 will match the inbound rule set of the public NIC on the VPC vRouter. If malicious traffics are detected, the access is denied.
When VM-2 attempts to access VM-4: The traffic from VM-2 will match the inbound rule of the public NIC on the VPC vRouter, and then will match the outbound rule set of the private NIC on the VPC vRouter. If trusted traffics are detected, the access is allowed.
When Server-2 attempts to access Server-1: The traffic from Sever-2 will match the inbound rule set of the private NIC on the VPC vRouter, and then will match the outbound rule set of the public NIC on the VPC vRouter. If trusted traffics are detected, the access is allowed.

Firewall vs Security

A firewall manages the south-north traffic of VPC networks. A security group manages the east-west traffic of VPC networks and is applied to VM NICs. The two services complement with each other. The following table compares the two services from three aspects.

Item	Security Group	Firewall
Application scope	VM NIC	The entire VPC network
Deployment mode	Distributed	Centralized
Deployment location	VM instance	VPC vRouter
Configuration policy	Supports only Allow policies	Allows you to customize Accept, Drop, or Reject policies as needed
Priority	Takes effect based on the predefined rule sequence	Allows you to customize priorities
Match condition	Source IP address, source port, and protocol	Source IP address, source port, destination IP address, destination port, protocol, and packet status

Security Group

A security group provides security control services for VM instances on the L3 network. It filters the ingress or egress TCP, UDP, and ICMP packets of specified VM instances in specified networks based on the specified security rules.

Characteristics

A security group rule can be categorized into the following two types based on the packet flow direction:
- Ingress: indicates data packets that flow into a VM instance.
- Egress: indicates data packets that are sent from a VM instance.
Security group rules support the following communication protocols:
- ALL: indicates all types of protocols. If you select ALL, you cannot specify a port.
- TCP: allows you to specify a port that ranges from 1 to 65535.
- UDP: allows you to specify a port that ranges from 1 to 65535.
- ICMP: start port and end port defaulted to -1. This protocol indicates all ICMP messages are supported.
You can specify data sources in a security group rule to limit data access:
- If you specify a CIDR block, only the ingress data from the CIDR block or egress data to the CIDR block is allowed.
- If you specify a security group, only the ingress data from the security group or egress data to the security group is allowed.
Note: If you specify both a CIDR block and a security group, only the ingress data from the intersection of the security group and CIDR block or egress data to the intersection of the security group and CIDR block is allowed.

Considerations

You can assign a security group to one or more VM instances. These VM instances share the same security group rules.
You can associate a security group with one or more L3 networks. These L3 networks share the same security group rules.
Security groups apply the allowlist mechanism. Only the traffic that follows the created rules is allowed to reach the specified ports.
When you create a security group, the system automatically configures two rules (an ingress rule and an egress rule whose protocol types are both ALL) for communications of VM instances in the security group. You can delete these two default rules to cancel the intra-group communication.
When you create a security group, if you do not set a rule, ingress traffic is not allowed to access VM instances in the security group. However, egress traffic from VM instances in the security group is allowed.
If you use a security group along with other network services, such as load balancing and vRouter table, make sure that the security group rules required by these network services are added to the security group.
Public networks, flat networks, and VPC networks support the security group service. It is provided by the security group network service module, which uses iptables to implement security control.
A security group is a distributed firewall. Each security rule change, NIC association or disassociation will cause the security group rule to be updated on all associated VM instances.