What is a Modem?
A modem is a device that connects a computer or local network to the internet by converting digital signals from a computer and signals that travel over telephone or cable lines.
How it connect network to the internet
- Device send request.
- The request goes to the router.
- The router forward it to the modem via ethernet.
- Encoded the data into isp-specific signals.
- Send it over fiber-cable to the isp.
- Isp routes it to the internet.
- Response comes back the same way.
What is a Router?
A router is a networking device that forwards data packets between different computer network.Router allow multiple devices to share an Internet connection efficiently.
How it directs traffic?
- A router connects different networks
- It receives data packets from devices.
- Each packet has a destination Ip address.
- The router decides the best path to reach that address.
- It forwards the packet to the next network until it reaches to the destination.
Switch vs Hub: how local networks actually work?
.Hub: A hub operates at the Physical Level. It does not distinguish between different devices on the network. When a hub receives a data packet on one port, it broadcasts that data to every other port on the hub.
.Switch: A switch operates at the Data Link Layer. It maintains a table of MAC addresses, remembering which device is connected to which port. When a switch receives data, it identifies the intended recipient and sends the data only to that specific port.
What is a Firewall and why security lives here?
- A firewall is a network security device that monitor and filters incoming and outgoing network traffic based on an organization previously establish security policies.
- Security at the firewall because it acts as the barrier between a trusted internal network and an untrusted external network. It functions as a gatekeeper, inspecting traffic to block malicious data.
What is a Load Balancer and why scalable systems need it?
A Load Balancer is a device that acts as a traffic manager for servers. It sits in front of server farm and routes client requests across all servers capable of fulfilling those requests.
Why Scalable Systems Need It?
- one server might be overwhelmed with traffic while others sit idle.The load balancer ensures traffic is distributed evenly.
- If a server crashes, the load balancer detects the failure and stops sending traffic to that server, redirecting it to active servers. This ensures the application remains online for users.
- It allows you to add more servers to the pool easily. The load balancer simply starts sending traffic to the new servers automatically.
How all these devices work together in a real-world setup?
A user request first sent over the Internet to a CDN for quick delivery of content. If the content is not cached then the request passes through a Firewall for security before reaching to a Load Balancer. The Load Balancer then distributes the request to an available Web Server, which forwards it to an Application Server for processing. The Application Server queries the Database for necessary data and the response follows the path back to the user.
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