Classic Elastic Load Balancer is a Combination Application Load Balancer & Network Load Balancer (old version)
Classic Load Balancer is a combination layer 4 (Network / IP level) and layer 7 (application level HTTP etc.) load balancer. This load balancer will not keep up with the newer ELB product in terms of feature set. It is still available but use of the new ELB is strongly suggested.
Use Proxy Protocol to get the source IP passed thru to the target server. If proxy protocol is not used the load balancer IP address will not be fed to the target level 4 server.
Transparently implements very high availability
Elastic Load Balancer (new version)
The newer version of ELB is actually broken into two products. ALB Application Load Balancer and NLB Network Load Balancer – for layer 7 and layer 4 respectively.
AWS – ALB / Application Load Balancer a layer 7 load balancer (new ELB)
Support for Host based routing
Support for Content based routing
Support for URL path based routing
Support for HTTP & HTTPS X-Forwarded-For (XFF) to pass thru the IP Client info to the application servers
Supports container based applications – multiple ports – one per container – with port based routing and port based health checks
Supports HTTP/2
Supports Websockets
Different API than the Classic / Old – not compatible – must migrate – or re-implement if upgrading from Classic to ALB
Transparently implements very high availability and provides low latency
AWS – NLB / Network Load Balancer a layer 4 load balancer (new ELB)
Network Load Balancer preserves the source IP of the client by default and passes thru.
Support only TCP (Layer 4) listeners
Uses Amazon Route 53 health checking and DNS failover features to enhance the availability of the applications running behind Network Load Balancers (zonal failover)
Different API than the Classic / Old – not compatible – must migrate – or re-implement if upgrading from Classic to NLB
Transparently implements very high availability and provides low latency
More from LonzoDB on AWS
References:
https://aws.amazon.com/elasticloadbalancing/faqs/