1. Overview
   1. Cloud Load Balancing distributes load-balanced compute resources in single or multiple regions
   2. It meets high availability requirements by putting resources behind a single anycast IP, scaling resources up or down with intelligent autoscaling
   3. Cloud Load Balancing is integrated with Cloud CDN for cached content delivery
   4. Cloud Load Balancing can serve content as close as possible to users on a system that can respond to over one million queries per second
   5. Cloud Load Balancing is a fully distributed, software-defined managed service
   6. It is not instance-based or device-based, so users do not need to manage a physical load balancing infrastructure
2. Traffic type
   1. HTTP and HTTPS traffic can be handled by external HTTP(S) Load Balancing or Internal HTTP(S) Load Balancing
   2. TCP traffic can be handled by TCP Proxy Load Balancing, Network Load Balancing, or Internal TCP/UDP Load Balancing
   3. UDP traffic can be handled by Network Load Balancing or Internal TCP/UDP Load Balancing
3. Underlying technology
   1. Google Front Ends (GFEs) are software-defined, distributed systems that are located in Google points of presence (PoPs)
   2. GEFs perform global load balancing in conjunction with other systems and control planes
   3. Andromeda is Google Cloud's software-defined network virtualization stack
   4. Maglev is a distributed system for Network Load Balancing
   5. Envoy proxy is an open source edge and service proxy, designed for cloud-native applications
4. Global versus regional load balancing
   1. Use global load balancing when backends are distributed across multiple regions.
   2. It is useful were users need access to the same applications and content
   3. It provides access via a single anycast IP address
   4. Global load balancing can provide IPv6 termination
   5. Use regional load balancing when backends are in one region, and only IPv4 termination is required
5. External HTTP(S) Load Balancing
   1. HTTP(S) Load Balancing is implemented on GFEs
   2. GFEs are distributed globally and operate together using Google's global network and control plane.
   3. In Premium Tier, GFEs offer cross-regional load balancing, directing traffic to the closest healthy backend that has capacity
   4. It erminates HTTP(S) traffic as close as possible to users
6. SSL Proxy Load Balancing
   1. SSL Proxy Load Balancing is implemented on GFEs that are distributed globally
   2. With the Premium Tier, SSL proxy load balancer is global
   3. With the premium tier, users can deploy backends in multiple regions
   4. The load balancer automatically directs user traffic to the closest region that has capacity
   5. With the Standard Tier, an SSL proxy load balancer can only direct traffic among backends in a single region
7. TCP Proxy Load Balancing
   1. TCP Proxy Load Balancing is implemented on GFEs that are distributed globally
   2. With the Premium Tier, a TCP proxy load balancer is global
   3. In Premium Tier, users can deploy backends in multiple regions, and the load balancer automatically directs user traffic to the closest region that has capacity
   4. With Standard Tier, a TCP proxy load balancer can only direct traffic among backends in a single region
8. External TCP/UDP Network Load Balancing
   1. Network Load Balancing is built on Maglev
   2. This load balancer enables users to load balance traffic on systems based on incoming IP protocol data, including address, port, and protocol type
   3. It is a regional, non-proxied load balancing system
   4. Use Network Load Balancing for UDP traffic, and for TCP and SSL traffic on ports that are not supported by the SSL proxy load balancer and TCP proxy load balancer
   5. A network load balancer is a pass-through load balancer that does not proxy connections from clients
9. External versus internal load balancing
   1. External load balancers distribute traffic from the internet to Virtual Private Cloud (VPC) networks
   2. Global load balancing requires the use of Premium Tier
   3. For regional load balancing, use Standard Tier
   4. Internal load balancers distribute traffic to instances within Google Cloud
10. Internal HTTP(S) Load Balancing
    1. Internal HTTP(S) Load Balancing is built on the Andromeda network virtualization stack and is a managed service based on the open source Envoy proxy
    2. It provides proxy-based load balancing of Layer 7 application data
    3. Users specify how traffic is routed with URL maps
    4. The load balancer uses a private IP address that acts as the frontend to backend instances
11. Internal TCP/UDP Load Balancing
    1. Internal TCP/UDP Load Balancing is built on the Andromeda network virtualization stack
    2. Internal TCP/UDP Load Balancing enables users to load balance TCP/UDP traffic behind a private load balancing IP address that is accessible to internal virtual machine (VM) instances
    3. By using Internal TCP/UDP Load Balancing, an internal load balancing IP address is configured to act as the frontend to private backend instances
    4. Only internal IP addresses are used for load balanced service
    5. Internal TCP/UDP Load Balancing supports regional managed instance groups for auto scaling across a region, protecting services from zonal failures