Professional Installer’s Guide to IP Networking Ethernet Switches
In the previous three installments of this series, we discussed the basic components of an IP network, the functions of those components, and then took a closer look at routers. In this issue we will focus on Ethernet switches—the backbone of your local network. When selecting a switch or a combination of switches for your network, there are several issues to consider:
Fast Ethernet or Gigabit?
The decision of whether to use Fast Ethernet (10/100Mbps) or Gigabit (1000Mbps) is really a matter of economics, practicality and where the switch resides within the network. A network is only as good as its weakest link, so it stands to reason that using Gigabit (which delivers 10x the performance of Fast Ethernet) is typically the safe and recommended choice to ensure network performance and longevity. This is especially true for any core switch within the network.
At the same time, Fast Ethernet is relatively inexpensive and 100Mbps is more than sufficient for many applications. That being the case, Fast Ethernet may be a reliable and cost-effective option for connecting non-critical devices at the edge of the network.
The Switch Fabric or Backplane determines how much bandwidth the switch really offers. All switches are not created equal, and it’s important to understand the switching capacity before making a buying decision. For optimal network performance, be sure to choose a switch with a Non-Blocking (Full Duplex) architecture. What this means is that the switch can send and receive data simultaneously at full data rates.
For example, a Gigabit (1000Mbps) connection based on a Full Duplex architecture provides a download rate of 1000Mbps as well as an upload rate of 1000Mbps—essentially making the true throughput of each port 2000Mbps.
On the other hand, a Half Duplex switch architecture does not allow for simultaneous data transfers. Rather, it uses one channel for both send and receive data, creating a bottleneck and dramatically reducing network performance.
A Non-Blocking/Full Duplex switch fabric essentially doubles the amount of bandwidth available. So, if buying a 24-port Gigabit switch, look for one that has a 48 Gigabit (48000Mbps) Switch Fabric/Backplane Bandwidth. Making sure your switch choice is capable of non-blocking performance will provide an optimal local network backbone and improve user experience tremendously.
Managed or Unmanaged?
Ethernet switches can be either Unmanaged plug-and-play devices with no user definable settings; or Managed, allowing for optimization and prioritization of certain ports and applications. When should you use a managed switch? Here are a few cases where a managed switch will help you deliver the best possible solution to your customer:
• Whenever using VoIP, streaming media or other critical applications. Most managed switches support Quality of Service (QoS) functionality, which allows you to set priorities for these applications and ensure optimal performance.
• If you need to set up a secure guest network or otherwise isolate network traffic of certain applications, a managed switch can be used to configure a Virtual Local Area Network (VLAN).
• Any applications that call for specific protocol support, such as IGMP (Internet Group Management Protocol) or STP-RSTP-MSTP (Spanning Tree Protocols) will require a managed switch.
• The number of devices on the network may determine whether or not to use a managed switch. With more devices, you have more switches. Anytime you have a network with three or more switches, a central managed switch is recommended for optimal control and configuration.
• Another practical benefit of a managed switch is the ability to gather data. With Port Statistics, SNMP (Simple Network Management Protocol), and Syslog support, there are many different ways to see what is going on and even be notified when you are off-site (through a supported SNMP Management Suite).
The choice of managed or unmanaged depends on the circumstances, and is typically even a mix of both when using multiple switches. The primary consideration really comes down to understanding how many and what types of devices will be on the network, as well as any extra support that may be required by the devices or applications.