Adding a UDP Listener¶
Scenarios¶
UDP listeners are suitable for scenarios that focus more on timeliness than reliability, such as video chat, gaming, and real-time quotation in the financial market.
Constraints¶
UDP listeners do not support fragmentation.
The port of UDP listeners cannot be 4789.
UDP packets can have any size less than 1,500 bytes. The packets will be discarded if they are too big. You need to modify the configuration files of the applications based on the maximum transmission unit (MTU) value.
Dedicated load balancers: The backend protocol can be UDP or QUIC if the listener protocol is UDP.
Shared load balancers: If the listener protocol is UDP, the protocol of the backend server group is UDP by default and cannot be changed.
If you only select application load balancing (HTTP/HTTPS) for your dedicated load balancer, you cannot add a UDP listener to this load balancer.
Adding a UDP Listener to a Dedicated Load Balancer¶
Log in to the management console.
In the upper left corner of the page, click
and select the desired region and project.Click
in the upper left corner to display Service List and choose Network > Elastic Load Balancing.Locate the load balancer and click its name.
Under Listeners, click Add Listener. Configure the parameters based on Table 1.
Table 1 Parameters for configuring a listener¶ Parameter
Description
Example Value
Name
Specifies the listener name.
listener
Frontend Protocol
Specifies the protocol that will be used by the load balancer to receive requests from clients.
UDP
Frontend Port
Specifies the port that will be used by the load balancer to receive requests from clients.
The port number ranges from 1 to 65535.
80
Access Control
Specifies how access to the listener is controlled. The following options are available (for details, see Access Control):
All IP addresses
Blacklist
Whitelist
Blacklist
IP Address Group
Specifies the IP address group associated with a whitelist or blacklist. If there is no IP address group, create one first. For more information, see Creating an IP Address Group.
ipGroup
Transfer Client IP Address
Specifies whether to transmit IP addresses of the clients to backend servers.
This function is enabled for dedicated load balancers by default and cannot be disabled.
N/A
Advanced Settings
Idle Timeout
Specifies the length of time for a connection to keep alive, in seconds. If no request is received within this period, the load balancer closes the connection and establishes a new one with the client when the next request arrives.
The idle timeout duration ranges from 10 to 4000.
300
Tag
Adds tags to the listener. Each tag is a key-value pair, and the tag key is unique.
-Description
Provides supplementary information about the listener.
You can enter a maximum of 255 characters.
N/A
Click Next: Configure Request Routing Policy to configure the backend server group. Table 2 describes the parameters for configuring a backend server group.
Table 2 Parameters for configuring a backend server group¶ Parameter
Description
Example Value
Backend Server Group
Specifies a group of servers with the same features to receive requests from the load balancer. Two options are available:
Create new
Use existing
Note
To associate an existing backend server group, ensure that it is not in use. Select the backend server group with the correct protocol. For example, if the frontend protocol is TCP, the backend protocol must be TCP.
Create new
Backend Server Group Name
Specifies the name of the backend server group.
server_group
Backend Protocol
Specifies the protocol that will be used by backend servers to receive requests.
The backend protocol can be UDP or QUIC.
UDP
Load Balancing Algorithm
Specifies the algorithm that will be used by the load balancer to distribute traffic. The following options are available:
Weighted round robin: Requests are routed to different servers based on their weights, which indicate server processing performance. Backend servers with higher weights receive proportionately more requests, whereas equal-weighted servers receive the same number of requests.
Weighted least connections: In addition to the number of active connections established with each backend server, each server is assigned a weight based on their processing capability. Requests are routed to the server with the lowest connections-to-weight ratio.
Source IP hash: The source IP address of each request is calculated using the consistent hashing algorithm to obtain a unique hash key, and all backend servers are numbered. The generated key is used to allocate the client to a particular server. This allows requests from different clients to be routed based on source IP addresses and ensures that a client is directed to the same server that it was using previously.
Note
Choose an appropriate algorithm based on your requirements for better traffic distribution.
For Weighted round robin or Weighted least connections, no requests will be routed to a server with a weight of 0.
Weighted round robin
Sticky Session
Specifies whether to enable sticky sessions. If you enable sticky sessions, all requests from a client during one session are sent to the same backend server.
This parameter is optional and can be enabled only if you have selected Weighted round robin for Load Balancing Algorithm.
N/A
Sticky Session Type
Specifies the type of sticky sessions. Source IP address is the only choice available when TCP or UDP is used as the frontend protocol.
Source IP address: The source IP address of each request is calculated using the consistent hashing algorithm to obtain a unique hashing key, and all backend servers are numbered. The system allocates the client to a particular server based on the generated key. This allows requests from the same IP address to be forwarded to the same backend server.
Source IP address
Stickiness Duration (min)
Specifies the minutes that sticky sessions are maintained. You can enable sticky sessions only if you select Weighted round robin for Load Balancing Algorithm.
Stickiness duration at Layer 4: 1 to 60
Stickiness duration at Layer 7: 1 to 1440
20
Description
Provides supplementary information about the backend server group.
You can enter a maximum of 255 characters.
N/A
Click Next: Add Backend Server. Add backend servers and configure health check for the backend server group. For details about how to add backend servers, see Overview. For the parameters required for configuring a health check, see Table 3.
Table 3 Parameters for configuring a health check¶ Parameter
Description
Example Value
Health Check
Specifies whether to enable health checks.
If the health check is enabled, click
next to Advanced Settings to set health check parameters.N/A
Advanced Settings
Health Check Protocol
Specifies the protocol that will be used by the load balancer to check the health of backend servers. The health check protocol is UDP by default and cannot be changed.
UDP
Health Check Port
Specifies the port that will be used by the load balancer to check the health of backend servers. The port number ranges from 1 to 65535.
Note
This parameter is optional. If you do not specify a health check port, a port of the backend server will be used for health checks by default. If you specify a port, it will be used for health checks.
80
Interval (s)
Specifies the maximum time between two consecutive health checks, in seconds.
The interval ranges from 1 to 50.
5
Timeout (s)
Specifies the maximum time required for waiting for a response from the health check, in seconds. The timeout duration ranges from 1 to 50.
3
Maximum Retries
Specifies the maximum number of health check retries. The value ranges from 1 to 10.
3
Click Next: Confirm.
Confirm the configuration and click Submit.
Adding a UDP Listener to a Shared Load Balancer¶
Log in to the management console.
In the upper left corner of the page, click
and select the desired region and project.Click
in the upper left corner to display Service List and choose Network > Elastic Load Balancing.Locate the load balancer and click its name.
Under Listeners, click Add Listener. Configure the parameters based on Table 4.
Table 4 Parameters for configuring a listener for a shared load balancer¶ Parameter
Description
Example Value
Name
Specifies the listener name.
listener
Frontend Protocol
Specifies the protocol that will be used by the load balancer to receive requests from clients.
UDP
Frontend Port
Specifies the port that will be used by the load balancer to receive requests from clients.
The port number ranges from 1 to 65535.
80
Access Control
Specifies how access to the listener is controlled. The following options are available (for details, see Access Control):
All IP addresses
Blacklist
Whitelist
Whitelist
IP Address Group
Specifies the IP address group associated with a whitelist or blacklist. If there is no IP address group, create one first. For more information, see Creating an IP Address Group.
ipGroup
Transfer Client IP Address
Specifies whether to transmit IP addresses of the clients to backend servers.
N/A
Advanced Settings
Tag
Adds tags to the listener. Each tag is a key-value pair, and the tag key is unique.
-Description
Provides supplementary information about the listener.
You can enter a maximum of 255 characters.
N/A
Click Next: Configure Request Routing Policy. Table 5 describes the parameters for configuring a backend server group.
Table 5 Parameters for adding a backend server group¶ Parameter
Description
Example Value
Backend Server Group
Specifies a group of servers with the same features to receive requests from the load balancer. Two options are available:
Create new
Use existing
Note
To associate an existing backend server group, ensure that it is not in use. Select the backend server group with the correct protocol. For example, if the frontend protocol is TCP, the backend protocol must be TCP.
Create new
Backend Server Group Name
Specifies the name of the backend server group.
server_group
Backend Protocol
Specifies the protocol that will be used by backend servers to receive requests.
The backend protocol is UDP by default and cannot be changed.
UDP
Load Balancing Algorithm
Specifies the algorithm used by the load balancer to distribute traffic. The following options are available:
Weighted round robin: Requests are routed to different servers based on their weights, which indicate server processing performance. Backend servers with higher weights receive proportionately more requests, whereas equal-weighted servers receive the same number of requests.
Weighted least connections: In addition to the number of active connections established with each backend server, each server is assigned a weight based on their processing capability. Requests are routed to the server with the lowest connections-to-weight ratio.
Source IP hash: The source IP address of each request is calculated using the consistent hashing algorithm to obtain a unique hash key, and all backend servers are numbered. The generated key is used to allocate the client to a particular server. This allows requests from different clients to be routed based on source IP addresses and ensures that a client is directed to the same server that it was using previously.
Note
Choose an appropriate algorithm based on your requirements for better traffic distribution.
For Weighted round robin or Weighted least connections, no requests will be routed to a server with a weight of 0.
Weighted round robin
Sticky Session
Specifies whether to enable sticky sessions. If you enable sticky sessions, all requests from a client during one session are sent to the same backend server.
Note
You can enable sticky sessions only if you have selected Weighted round robin for Load Balancing Algorithm.
N/A
Sticky Session Type
Specifies the type of sticky sessions. Source IP address is the only choice available when TCP or UDP is used as the frontend protocol.
Source IP address: The source IP address of each request is calculated using the consistent hashing algorithm to obtain a unique hashing key, and all backend servers are numbered. The system allocates the client to a particular server based on the generated key. This allows requests from the same IP address to be forwarded to the same backend server.
Source IP address
Stickiness Duration (min)
Specifies the minutes that sticky sessions are maintained. You can enable sticky sessions only if you select Weighted round robin for Load Balancing Algorithm.
Stickiness duration at Layer 4: 1 to 60
Stickiness duration at Layer 7: 1 to 1440
20
Description
Provides supplementary information about the backend server group.
You can enter a maximum of 255 characters.
N/A
Click Next: Add Backend Server. Add backend servers and configure health check for the backend server group. For details about how to add backend servers, see Overview. For details about how to configure health check parameters, see Table 6.
Table 6 Parameters for configuring a health check¶ Parameter
Description
Example Value
Health Check
Specifies whether to enable health checks.
N/A
Advanced Settings
Health Check Protocol
Specifies the protocol that will be used by the load balancer to check the health of backend servers. The health check protocol is UDP by default and cannot be changed.
UDP
Health Check Port
Specifies the port that will be used by the load balancer to check the health of backend servers. The port number ranges from 1 to 65535.
Note
This parameter is optional. If you do not specify a health check port, a port of the backend server will be used for health checks by default. If you specify a port, it will be used for health checks.
80
Interval (s)
Specifies the maximum time between two consecutive health checks, in seconds.
The interval ranges from 1 to 50.
5
Timeout (s)
Specifies the maximum time required for waiting for a response from the health check, in seconds. The timeout duration ranges from 1 to 50.
3
Maximum Retries
Specifies the maximum number of health check retries. The value ranges from 1 to 10.
3
Click Next: Confirm.
Confirm the configuration and click Submit.