Network Switches

A network switch is a device that connects nodes and can be configured to intelligently pass information and direct network traffic.

Overview

Switches are what make Internet Protocol (IP) networks possible, acting as intermediary devices that connect nodes to each other and intelligently manage the flow of data by forwarding received packets to their intended destinations.

Switches have a varying number of network ports, allowing multiple nodes to be plugged in at once. These ports may have different connectivity speeds and capabilities. Not all ports on a switch may be able to be used interchangeably.

As with all hardware, switches and connected Network Wiring can wear out over time. Switches and attached cabling should be evaluated for replacement every decade, or sooner if elements of the network are commonly moved or reconfigured.

Managed switches are typically more reliable than unmanaged switches, but also more expensive. Install switches are a type of managed switch designed to be the core of larger or more complex systems, and are often recommended for entertainment control networks.

Switches with more features and robustness may be more expensive, but provide the value of a reliable network for no-fail lighting traffic transmission. When selecting network equipment, including wiring and switches, balancing avoiding unplanned downtime (including potentially during a live event) with cost will vary by use-case.

Switch Management

Network switches generally fall into one of two categories, managed or unmanaged.

Switches in a network should all be similarly managed or unmanaged: any switches added to a managed system must also be managed, and unmanaged switches should not be used in a managed network. Mixing the two types could cause data to be passed indiscriminately, which can affect the network's real-time performance.

Managed

For the purposes of this document, a managed switch is defined as a switch that allows the user to configure individual settings for features (such as IGMP, VLAN, Spanning Tree, and so on). It is recommended that you use managed switches for ETC lighting networks as they can be configured based on the requirements outlined in Eos Network Requirements.

Managed switches offer advanced features generally required for the efficient transmission of Multicast data, particularly Internet Group Management Protocol (IGMP). Networks requiring Logical VLAN Isolation must use a managed switch with VLAN capabilities.

Switches sold by ETC are managed switches preconfigured based on the system into which they are being installed. Managed switches should otherwise be configured by qualified individuals during the wiring and setup of the network. As a misconfigured switch can affect every aspect of network traffic and communication, ETC does not recommend altering switch configurations in the field once a network is up and running unless the network is being altered or the usage of the network is shifting from its original design.

Unmanaged

For the purposes of this document, an unmanaged switch is defined as a switch with no interface from which to configure settings for advanced features.

Unmanaged switches require no configuration and offer very basic features, forwarding frames to specific ports and maintaining multicast and MAC address lists.

Unmanaged switches should only be used in smaller-scale temporary networks utilizing a limited quantity of networked devices, such as a festival or film shoot where all networked devices are connected to the same network switch and no third-party integration is required. Even then a managed switch is still preferred.

Some consumer switches branded as unmanaged will have managed features enabled that may not be directly exposed to the user. Consult the documentation of any switch candidates thoroughly to determine whether it is appropriate for use in your system.

Switch Bandwidth

As switches are responsible for the communication between many or all of the devices in a network, they should be robust enough to handle more traffic than necessary. Switch throughput affects how quickly a switch can parse data, and should be evaluated for the needs of the network in which the switch will be utilized. This is important for switches on the edges of a Star Topology, but can become even more crucial for core switches at the center of a network.

Switch bandwidth in Eos network systems must be no less than 60% of the capacity of the total possible bandwidth of all ports. To calculate switch bandwidth:

1. Add the bandwidths of all individual ports (for example, a switch with 24x 1 Gbps ports and 4x 10 Gbps ports would add up to 64 Gbps).
2. Multiply by 2 for two-way traffic (64 Gbps x 2 = 128 Gbps). This speed represents a full-bandwidth switch.
3. Multiply by 0.6 for the acceptable maximum saturation bandwidth (60% of 128 Gbps = 76.8 Gbps).
4. Ensure the switch's documented Gbps bandwidth is higher than the calculated bandwidth needed.

Many switches document bandwidth in Packets Per Second (PPS) or Millions of Packets Per Second (MPPS). To convert from these units:

1. Multiply MPPS by 1,000,000 for PPS (for example, 156.25 MPPS x 1,000,000 = 156,250,000 PPS).
2. Multiply PPS by the packet size in bytes for the transfer rate in bytes per second (156,250,000 PPS x 64 byte packet = 10,000,000,000 bps).
   1. Typical packet size is 64 bytes, but may differ between switches. Consult your switch documentation for the appropriate packet size.
3. Divide the transfer rate by the number of bytes in a gigabit, 125,000,000, for the bandwidth in Gbps (10,000,000,000 bps / 125,000,000 = 80 Gbps).

Latency

Latency refers to the delays in network communication introduced by the various components of a network. Everything, from the switches to endpoint devices to the Network Wiring, contributes some amount of latency. In a larger network, it is often necessary to calculate total latency in order to ensure the transmission speeds necessary for real-time entertainment control.

Latency in switches is closely related to their bandwidth capacity and how much of that throughput is being used at any given time. Ensuring network traffic does not exceed the calculated bandwidth of a switch and its ports will help minimize latency in a system.

Switch Features

Many managed and unmanaged switches include various hardware and software network configuration and management features. Not all of these features are recommended for entertainment control networks; see Eos Network Requirements for switch configuration specifics.

Power Over Ethernet (PoE)

Many network switches, both managed and unmanaged, have the ability to power small connected devices via a feature called Power over Ethernet (PoE). PoE sends voltage directly to a node over the data wiring, providing power along with network connectivity and eliminating the need for a separate node power supply.

Smaller, portable switches that offer PoE generally have a limited number of ports that can be used to power devices, while rackmount install switches generally offer PoE on all ports.

PoE ports have power limits that vary between switch models. Consult any third-party documentation to determine these limits, as well as the power requirements of any devices powered via PoE, to ensure that the port can handle the devices connected to it. Usage of PoE should be also factored in when estimating the total power consumption of the switch to ensure the switch is able to handle all ports in use at full capacity.

Additional power output can also lead to increased fan volume from the switch, which may be undesirable in noise-sensitive areas. Smaller, convection-cooled switches may work better in these spaces.

Quality of Service (QoS)

Quality of Service (QoS) allows switches to monitor network traffic and prioritize transmission of certain types of data over others. Incoming packets are sorted into classes and organized into a queue to be sent out in a specific order.

QoS should be disabled in Eos networks.

Flow Control

Flow control allows switches to manage traffic by temporarily stopping the transmission of data when a speed mismatch exists between two nodes, or during periods of network congestion.

Flow control should be disabled in Eos networks.

Broadcast Storm Protection

Broadcast storm protection allows switches to cease forwarding traffic in the event of too much broadcast data on the network. Switches can misidentify Multicast traffic as broadcast, potentially resulting in some or all entertainment control data being blocked by the switch.

Broadcast storm protection should be disabled in Eos networks.

Energy Efficient Ethernet

Energy-efficient Ethernet allows switches to reduce power consumption to some or all ports during periods of low network activity. Even small port delays can affect the overall latency and real-time operation of an entertainment control network. Some network protocols and features are incompatible with ports in a low-power state, interpreting the energy-efficient mode as a disconnection which may not automatically reconnect when the port power is restored.

Energy-efficient ethernet should be disabled in Eos networks.