How to Choose the Right Switch for Your Data Center?

If you plan to set up a 10G network, what do you need? The answer is 10G switch, 10G transceiver and optical cable. In addition, the option of switch is the most basic and important step to start the network deployment. How to choose the right switch for your data center? This article will introduce the three-tiered network model which can help you make a right choice.

Basic Knowledge of Switch

Before we come to the three-tiered network model, let’s learn about some basic knowledge of switch. All switches maintain a media access control (MAC) address-to-port table which is used to intelligently forward frames out the right ports to the intended destinations. Besides, all switches use standards-based protocols to segment traffic using the concept of virtual local area networks, 802.1q trunks and 802.3ad port aggregation. They also prevent network loops using one of the many variants of the 802.1d spanning-tree protocol.

Three-Tiered Network Model

We know that different types of switches have their own characteristics. And we have to compare them before making the decision. Here is an easy way to look at these differences that we can break them up into traditional three-tiered network model. The three tiers are core tier, distribution tier and access tier. Core switches interconnect with other core switches and down to the distribution tier. The distribution tier sits in between the core and the access tier. The access tier connects the entire structure to end devices like computers, printers and servers. To better understand this, here is a figure for you.

The Three-Tiered Network Model

Core Switch

The most striking feature of core switch is speed. The task of a core switch is routing at Layer 3 (the network layer) and switching at Layer 2 (the data link layer). In addition, core switch is high-throughput, high-performance packet and frame mover, which simply moves packets and frames from one core switch to another core switch, and eventually down to the next tier of switches—the distribution tier.

Distribution Switch

The function of distribution switch is connecting the core and access tier together on the network. Since there are many interconnections in a network, and distribution switch has higher port density than core switch, distribution switch also interconnects all access tier switches. What’s more, distribution switch enforces all forms of network policies.

Access Switch

Access switch directly interacts with end-user devices and it connects the majority of devices to the network. For this reason, the access tier typically has the highest port density of all switch types. Also, access switch usually provides the lowest throughput-per-port of all switches. It commonly supports Power over Ethernet, which can power many endpoint devices, including wireless access points and security cameras. Additionally, access switch is better able to interact with endpoints from a security perspective.

Conclusion

Tasks and workloads can be distinct for switches in different tiers. While all switches share universal functions like MAC tables, spanning-tree and trunking, they also have exclusive capabilities performed only within that network tier. Therefore, you have to figure out what type of switch you need. Then, you can buy compatible optical module and cable.

Originally published at: http://www.fiber-optical-networking.com/choose-right-switch-data-center.html

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Practical Knowledge About Optical Module

With the rapid development of fiber optical technology, various optical communication products are available on the market. Optical module is a small size but important optical component in telecommunication and data communication applications. Being able to realize the photoelectric conversion, it is popular among network users and vendors. To avoid unnecessary loss when using optical modules, it is necessary to master the skill of selecting patch cable for an optical module as well as installing or removing an optical module. This passage is going to guide you how to select patch cable for optical module and install or remove optical module.

Overview of Optical Modules and Patch Cables

Before we come to the practical content, let’s learn something basic about optical modules and patch cable. Optical module is a self-contained component that can both transmit and receive signals. Usually, it is inserted in devices such as switches, routers or network interface cards which provide one or more transceiver module slot. There are many optical module types (shown in the figure below), such as SFP, X2, XENPAK, XFP, SFP+, QSFP+, CFP and so on.

Optical Modules

A patch cable is a electric or optical cable terminated with connectors on both ends. It is used to connect one electronic or optical device to another for signal routing. Optical patch cables are now widely used in data centers for data transmission. They have different connector types (shown in the figure below), like LC, SC, ST and FC, etc. They also have different fiber types, like single-mode patch cable, multimode patch cable, simplex patch cable, duplex patch cable and so on.

Optical Connectors

Selecting Patch Cable for Optical Module

There are three basic aspects that you have to consider when selecting patch cable for optical module—transmission media, transmission distance and rate as well as module interface. Transmission media can be optical fiber or copper; transmission rate will decrease as the transmission distance increases in the fiber optic cables; duplex SC and LC interfaces are usually employed, and some optical modules often use MPO/MTP interfaces. Let’s take Cisco GLC-LH-SM Compatible 1000BASE-LX/LH SFP Transceiver for example, and its detailed information is shown in the table below. From the table, we can easily find that this GLC-LH-SM 1000BASE-LX/LH SFP Transceiver can transmit and receiver data signals over SMF with LC duplex connector and operating at 1310nm wavelength. So when connecting two transceivers of this type, we are supposed to use a single-mode patch cable with LC-LC connector.

Detailed Information of Cisco GLC-LH-SM Compatible 1000BASE-LX/LH SFP Transceiver

Installing or Removing Optical Module

After knowing how to select patch cable for your optical module, let’s move on to how to install or remove optical module effectively. First, there are several warming tips about installing or removing optical module:

  • To prevent the cables, connectors and the optical interfaces from damages, you must disconnect all cables before installing or removing an optical module.
  • Remember to protect the optical modules by inserting clean dust plugs into them after the cables are removed. Avoid getting dust and other contaminants into the optical ports of your optical modules.
  • Frequently remove and install an optical module can shorten its useful life. Thus, you should remove or insert it unless it is necessary.
  • Optical modules are sensitive to static, so be sure to use an ESD wrist strap or comparable grounding device during both installation and removal.
Installing Procedure

Step 1. Attach an ESD (electric-static discharge) preventive wrist strap to your wrist and to the ESD ground connector or a bare metal surface on your chassis.
Step 2. Remove the optical module from its protective packaging.
Step 3. Check the label on the module body to verify that you have the correct module for your network.
Step 4. Align the optical module in front of the socket opening.
Step 5. Insert the optical module into the socket until the module makes contact with the socket connector.

Removing Procedure

Step 1. Attach an ESD-preventive wrist strap to your wrist and to the ESD ground connector or a bare metal surface on your chassis.
Step 2. Disconnect and remove interface cable from optical module.
Step 3. Immediately install the dust plug into the module’s optical bore.
Step 4. Slide the optical module out of the socket connector.
Step 5. Place the removed optical module into an antistatic bag.

In fact, different types of optical modules have different structures, so remember to follow the instruction when inserting them into the socket or removing then out of the socket connector.

Conclusion

Optical module, essentially completing the conversion of data signals between different media, can realize the connection between two switches or other devices. It has become the key component in today’s transmission network. Therefore, it is helpful to learn how to select patch cable for an optical module as well as install and remove an optical module, even though you are not a professional telecom engineer. I hope this passage can help you during the operation.