What Are the Relationships Between Load Balancing Algorithms and Sticky Session Types?

Sticky sessions ensure that requests from the same client are forwarded to the same backend server. ELB supports three types of sticky sessions. Table 3 lists the relationships between load balancing algorithms and sticky session types of classic load balancers. Table 1 lists the relationships between load balancing algorithms and sticky session types of shared load balancers, and Table 2 lists the relationships between load balancing algorithms and sticky session types of dedicated load balancers.

Classic load balancers can no longer be created on the management console. Use shared load balancers or dedicated load balancers instead.

Table 1 Sticky sessions supported by shared load balancers

Load Balancing Algorithm

Sticky Session Type

Layer 4 (TCP/UDP)

Layer 7 (HTTP/HTTPS)

Weighted round robin

Source IP address

Supported

Not supported

Load balancer cookie

N/A

Supported

Application cookie

N/A

Supported

Weighted least connections

Source IP address

Not supported

Not supported

Load balancer cookie

N/A

Not supported

Application cookie

N/A

Not supported

Source IP hash

Source IP address

N/A

Not supported

Load balancer cookie

N/A

Not supported

Application cookie

N/A

Not supported

Table 2 Sticky sessions supported by dedicated load balancers

Load Balancing Algorithm

Sticky Session Type

Layer 4 (TCP/UDP)

Layer 7 (HTTP/HTTPS)

Weighted round robin

Source IP address

Supported

Not supported

Load balancer cookie

N/A

Supported

Application cookie

N/A

Not supported

Weighted least connections

Source IP address

Not supported

Not supported

Load balancer cookie

N/A

Not supported

Application cookie

N/A

Not supported

Source IP hash

Source IP address

N/A

Not supported

Load balancer cookie

N/A

Not supported

Application cookie

N/A

Not supported

Table 3 Session stickiness of classic load balancers

Load Balancing Algorithm

Sticky Session Type

Layer 4 (TCP/UDP)

Layer 7 (HTTP/HTTPS)

Round robin

Source IP address

Supported

Not supported

Load balancer cookie

N/A

Supported

Application cookie

N/A

Not supported

Least connections

Source IP address

Supported

Not supported

Load balancer cookie

N/A

Not supported

Application cookie

N/A

Not supported

Source IP hash

Source IP address

N/A

Not supported

Load balancer cookie

N/A

Not supported

Application cookie

N/A

Not supported

Generally, the weighted round robin algorithm is recommended. Sticky sessions at Layer 4 use source IP addresses to main sessions, and sticky sessions at Layer 7 use load balancer cookies.

Parent topic: Listener