What are the differences between Network and HTTP(s) load balancer in GCP

Question

GCP provides two load balancers namely Network and HTTP(s) where the former works on layer 4 and the later works on layer 7 .

There is also a documentation which states that even HTTP traffic can be load balanced by a network load balancer. This slightly confuses which load balancer to choose for a web app in GCP. It is better to understand the differences before selecting one for the project.

What are the differences between them based on the workflow , setup , region/zone based, options for session affinity , and other settings?

Answer 1

Network load balancer Vs HTTP(s) Load Balancer

+---------------------+------------------------------------------+------------------------------------------------------+
|       Category      |       Network Load Balancing (NLB)       |             HTTP(S) Load Balancing (HLB)             |
+---------------------+------------------------------------------+------------------------------------------------------+
|     1. Region /     | NLB supports only within a region.       | HLB supports both within cross-region                |
|     Cross-Region    | Does not support cross-region            | load balancing.                                      |
|                     | load balancing                           |                                                      |
+---------------------+------------------------------------------+------------------------------------------------------+
|  2. Load balancing  | NLB is based on IP address, port         | HLB is based only on HTTP and HTTPS                  |
|       based on      | and protocol type. Any TCP/UDP           | protocols.                                           |
|                     | traffic, even SMTP can be                |                                                      |
|                     | load balanced.                           |                                                      |
+---------------------+------------------------------------------+------------------------------------------------------+
|      3. Packet      | Packet inspection is possible and        | HLB cannot inspect packets.                          |
|      inspection     | load balance based on packets            |                                                      |
+---------------------+------------------------------------------+------------------------------------------------------+
|     4. Instance     | No need of creating instance group.      | Managed / UnManaged Instance group                   |
|         Group       | Target pools need to be created.         | is necessary for creating HTTP / HTTPS               |
|                     | Instance can be just tagged to the pool. | load balancer.                                       |
|                     | Ideal for unmanaged instance group       |                                                      |
|                     | where instances are non homogeneous.     |                                                      |
+---------------------+------------------------------------------+------------------------------------------------------+
|     5. Workflow     | Forwarding rules is the starting point.  | This is quite complex in HTTP(s) load balancer.      |
|                     | It directs the request to the            | Global forwarding rulesroutes direct the request     |
|                     | target pools from which compute          | to target HTTP proxy, which in turn checks the       |
|                     | engines will pick the request.           | URL map to determine appropriate backend             |
|                     |                                          | services.  These services in turn direct the request |
|                     | Forwarding rules -> target pool          | to the instance group.                               |
|                     |  -> instances                            |                                                      |
|                     |                                          |                                                      |
|                     |                                          | Global forwarding rules -> Target HTTP proxy ->      |
|                     |                                          | URL map -> Backend Sevices -> instance group         |
+---------------------+------------------------------------------+------------------------------------------------------+
|     6. Types of     | Basic network load balancer which        | 1. Cross-region load balancer uses only one          |
|    load balancer    | directs the request based on IP address, | global IP address and routes the request             |
|                     | port and the protocol within the region. | to the nearest region.                               |
|                     |                                          |                                                      |
|                     |                                          | 2. Content-based load balancer is based              |
|                     |                                          | on the URL path. Different path rules need           |
|                     |                                          | different backend services. for eg: /video           |
|                     |                                          | and /static require two separate backend services.   |
+---------------------+------------------------------------------+------------------------------------------------------+
| 7. Session affinity | Session affinity can be set, but only    | 1. Client IP Affinity: This directs the same         |
|                     | during the creation of target pool.      | client ip to same backend instance by                |
|                     | Once it is set, the value                | computing hash of the IP.                            |
|                     | cannot be changed.                       | 2. Generated Cookie Affinity: Load balancer stores   |
|                     |                                          | cookie in clients and directs the same client to     |
|                     |                                          | same instance with the help of retrieved cookie.     |
+---------------------+------------------------------------------+------------------------------------------------------+
|   8. Health check   | Health check is optional, but network    | Health can be verified by either using HTTP          |
|                     | load balancing relies on HTTP Health     | heath check or HTTPS health check.                   |
|                     | checks for determining instance health.  |                                                      |
+---------------------+------------------------------------------+------------------------------------------------------+

The above table is based on my perspective. If anything is incorrect or If I had missed something, please feel free to comment and I will add it to the table.

Here is the link for instructions on setting up an HTTP load balancer in GCP.

Answer 2

In general below is the difference between Network and Http load balancers.

Network Load balancer (layer 4): This is the distribution of traffic based on network variables, such as IP address and destination ports. It is layer 4 (TCP) and below and is not designed to take into consideration anything at the application layer such as content type, cookie data, custom headers, user location, or the application behavior. It is context-less, caring only about the network-layer information contained within the packets it is directing this way and that.

Application load balancer (Layer 7) This is the distribution of requests based on multiple variables, from the network layer to the application layer. It is context-aware and can direct requests based on any single variable as easily as it can a combination of variables. Applications are load balanced based on their peculiar behavior and not solely on server (operating system or virtualization layer) information.Provides the ability to route HTTP and HTTPS traffic based upon rules, host based or path based. Like an NLB, each Target can be on different ports.

The other difference between the two is important because network load balancing cannot assure availability of the application. This is because it bases its decisions solely on network and TCP-layer variables and has no awareness of the application at all. Generally a network load balancer will determine “availability” based on the ability of a server to respond to ICMP ping, or to correctly complete the three-way TCP handshake. An application load balancer goes much deeper, and is capable of determining availability based on not only a successful HTTP GET of a particular page but also the verification that the content is as was expected based on the input parameters.

Ref : https://medium.com/awesome-cloud/aws-difference-between-application-load-balancer-and-network-load-balancer-cb8b6cd296a4

Answer 3

In addition, I would like to mention there are 3 main aspects to consider in choosing the correct Load Balancer (LB) in GCP:

1) Global versus regional
2) External versus internal
3) Traffic type

Please find more information on this chart as well.