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Load balancing is process of balancing incoming requests to multiple machines, processes or services. In this video we will explain two types of load balancers, layer 4 and layer 7.

Chapters
0:00 Intro
6:00 L4 Load balancer
9:10 L4 Load Balancer Pros and Cons
16:18 Example L4 Load Balancer with HAPROXY
22:30 L7 Load Balancer
27:00 L7 Pros and Cons
31:00 Example L7 Load Balancer with HAPROXY
37:00 Summary



Layer 4 (4/3)
Take content forwards it based on basic rules, it knows ip and port and perhaps latency of the target service.

Layer 4 - haproxy, NLB
Pros
- great for simple packet-level load balancing
- Fast and efficient doesn’t look at the data
- More secure as it cant really look at your packets. So if it was compromised no one can look
- Uses NAT
- One connection between client and server NATed
Cons
- Cant do smart load balancing based on the content, such as switch request based on requested media type
- Cant do microservices with this type
- Has to be sticky as it is a stateful protocol (all segments)



Layer 7 (Nginx , haproxy)

This type of proxy actually looks at the content and have more context, it knows you are visiting the /users resources so it may forward it to a different server. Essential and Great for microservices , it knows the content is video:image etc..


it can also cache.. we cant really do caching on layer 4 because we have no clue whats in the packets.

But expensive because it has to decrypt and look and compute


Layer 4 - haproxy, nlb
- great for simple packet-level load balancing
- fast and efficient doesn’t look at the data
- More secure as it cant really look at your packets. So id it was compromised no one can look
- Uses NAT
- One connection between client and server NATed
Layer 7 - examples nginx
- Smart routing based on the url (microservices) flexible
- Provide caching
- Expensive need to decrypt
- Secuirty, you have to share your certificate with the load balancers. Id compromised attacker has access to all your data.
- Proxy creates multiple connection (client to proxy/proxy to server)




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Hussein

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