Straight-Through and Cross-Over Cables- What are they and When to use them? What does cooling fans do?

WHEN TO USE STRAIGHT-THROUGH CABLE and WHEN TO USE CROSSOVER CABLE:

To connect two similar devices, we use Crossover cable.

To connect two dissimilar devices, we use Straight- through Cables

If we want to connect a host to console port on a router/ switch, then we use Rollover Cables.

A straight- through cable is needed to connect Hosts and Hubs since they are different devices. If same devices are connected, then, we must use a Crossover Cable

The below diagram provides an easy way to know what type of cable to use where:

MDI and MDIX:

The standard wiring for end stations is known as “MDI” (Media Dependent Interface), and the standard wiring for hubs and switches is known as “MDIX” (Media Dependent Interface with Crossover).

AUTO-MDIX:

Some devices support something called as Auto-MDIX wherein it doesn't matter whether you use straight-through or crossover cables to connect your devices. This is called as Auto-MDIX and what it does is it detects the type of cable used and sends signals accordingly. On these devices, it is possible for hardware to automatically correct errors in cable selection, making the distinction between a “straight through” cable and a “crossover” cable unimportant. This capability is known as Auto-MDI/MDIX.

WHAT DO PHYSICAL TOPOLOGY DIAGRAMS MEAN:

A network topology is the pattern in which nodes (i.e., computers, printers, routers or other devices) are connected to a local area network (LAN) or other network via links (e.g., twisted pair copper wire cable or optical fiber cable).

There are four principal topologies used in LANs: bus, ring, star and mesh.

The most widely used of these is bus, because it is employed by Ethernet, which is the dominant LAN architecture.

The several basic network topologies can be combined in various ways to form hybrid topologies, such as a ring-star network or a tree network.

Why we need cooling fans and how they work?

Ideally, all processors should have at least two fans: one fan to intakes cool air, while the other fan expels heat by blowing the hot air out. The specification of the heat sinks and cooling fans depends on its compatibility with the processor, and on how much they are expected to perform. The fan is attached to this fin-like structure and improves the transfer of hot air by pulling the hot air from the electrical heat generated by the components and pushing in cooler air between the aluminum fins, thus keeping the processor cool.

There are two types of switches- F and R.

• R= Rear . here, the hot air comes out of the rear
• F= Front. The hot air comes out from front

This helps in datacenter design requirements