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Network components
Switches
Switches are Multi-Input Multi-Output (MIMO) devices that enable packets to travel from one node to another. Switches connect hosts that belong to the same layer-2 network. Switches enable forwarding of the packet received on one port (input) to another port (output) so that they reach the desired destination node. Switches operate at layer-2 in the networking model. They forward the traffic based on the destination Ethernet address in the packet header.
Routers
Routers are special devices that enable packets to travel from one layer-3 network to another. Routers enable communication between two nodes on different layer-3 networks that are not directly connected to each other. Routers operate at layer-3 in the networking model. They route the traffic based on the destination IP address in the packet header.
Firewalls
Firewalls are used to regulate traffic to and from a host or a
network. A firewall can be either a specialized device connecting two
networks or a software-based filtering mechanism implemented on an
operating system. Firewalls are used to restrict traffic to a host based
on the rules defined on the host. They can filter packets based on
several criteria such as source IP address, destination IP address, port
numbers, connection state, and so on. It is primarily used to protect
the hosts from unauthorized access and malicious attacks. Linux-based
operating systems implement firewalls through iptables.
Load balancers
Load balancers can be software-based or hardware-based devices that allow traffic to evenly be distributed across several servers. By distributing the traffic across multiple servers, it avoids overload of a single server thereby preventing a single point of failure in the product. This further improves the performance, network throughput, and response time of the servers. Load balancers are typically used in a 3-tier architecture. In this model, a load balancer receives a request from the front-end web server, which then forwards the request to one of the available back-end database servers for processing. The response from the database server is passed back to the web server for further processing.