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Electronic Theatre Controls Inc

Network Definitions

This article provides basic definitions to words, phrases, or concepts used in networking.  As with most support articles, the definitions listed will be added or modified over time.

This article does not go into full details about every word, phrase, or concept.  If you would like to learn more about networking definitions in general, the Internet has lots of in-depth network support articles and we encourage you to use your search engine of choice to explore these topics.  If you would like to learn more about a specific word, phase, or concept and how it specifically relates to an ETC control system, please feel free to reach out to ETC Applications Engineering or ETC Technical Support.

10/100/1000 - coming soon

2.4Ghz - coming soon (wifi)

5.0Ghz - coming soon (wifi)

Access Control Entry - coming soon

Access Control List - coming soon

Anycast - Used to describe the transmission of data over a network.  Read the definition for Multicast first to better understand the concept of Anycast.  First, there are no ETC products that support Anycast at this time.  Anycast is when a network device (receiver for multicast network traffic) sources it's multicast network traffic from the closest logical source on the network when multiple sources are present.  A good analogy would be to think of Internet video streaming services.  If the streaming service has let's say 5 locations around the country that all host a video that you want to watch, Anycast would tell the network switches (network infrastructure) that your receiver (home PC or smart TV or phone) would stream the video from the closest logical host (source).  The video would be streamed over multicast (only those who ask to get that information will get it).  Once again, this is not supported by ETC hardware.  In a lighting network, if more than one source of sACN exists, the receivers, DMX gateways for example, would want to receive all sACN sources and decide for itself which one "wins" using HTP (Highest Takes Precedence) and sACN Priority values.  Hence, lighting receivers want to listen to all multicast sources.

arp -a - This is a Command Prompt command.  The purpose of arp -a is to return or print a list of IP Addresses and MAC Addresses that this computer has communicated with.  This is an excellent way to gather a list of MAC Addresses for the ETC networked hardware on a site.  The easiest way for your computer to interact with networked hardware is to run Concert or other product specific software such as LightDesigner or EchoAccess.  The simplest way is to simply ping IP Address and arp -a will return the MAC Address.  In the screenshot below, the PC has an IP Address of 10.101.19.20 and launched LightDesigner.  The returned list shows a PCCS at 10.101.10.10 and the remaining are all PACPs.

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BACnet - coming soon

BACnet/IP  - coming soon

BBMD coming soon (BACnet)

BPDU coming soon (Spanning Tree)

Bridge Priority coming soon (Spanning Tree)

Broadcast - Used to describe the transmission of data over a network.  Broadcast is when network information from the source (transmitter) is sent to all devices on the network.  Think of this like a flyer in the mail that gets sent to every home.  This forces all devices to receive the broadcast information and do one of two things; either act on it (do an action) or ignore it (throw it in the invisible trash can).  Broadcast storms often refer to instances when all the data on the network is being broadcast and forcing devices to spend all their time throwing away messages rather than doing their normal computing tasks.  In the mail example with the flyers, its like spending all of your time throwing away flyers you are not interested in.  This can result in slower response from devices or even device reboots.

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Cat5 - coming soon

Cat5e - coming soon

Cat6 - coming soon

Cat6a - coming soon

Command PromptThis is a command line interface available on Windows computers.  An equivalent is available on Apple computers called Terminal.  The commands mentioned in this article are referencing those on a Windows PC.  Apple syntax will likely vary.  The Command Prompt allows the user to enter commands written in specific syntax in order to return information about your computer or the network the computer is connected to.  Command Prompt examples such as arp -a and ping are also defined in this article.  To access the Command Prompt, press the Windows button and go to Run (Windows button + R shortcut).  Next type in cmd and press enter.  This will launch a new window with a black background and a blinking cursor.

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Console Port - coming soon

Core Switch - coming soon

Daisy Chain Topology - coming soon (Network Topology)

DHCP - coming soon

DNS - coming soon

Edge Port - This is a feature in Cisco network switches related to Spanning Tree.  Edge Port is what the feature is called in the Cisco Web Interface for network switches.  In the switch configuration file or when using CLI (command line interface) this feature is called PortFast.  There are three settings the can be applied on a port by port basis; Enable, Auto, and Disable.  If Enabled, the port is set to a Forwarding State.  This means that all traffic is allowed through this port in relationship to the Spanning Tree.  This also means that BPDU exchange between switches will not force this port to change state to Blocking, Listening, or Learning.  Those other states are what keeps a Loop/Ring topology from sending traffic indefinitely ultimately resulting in a Broadcast Storm / Network Storm that could cause undesired behavior (lag, reboot, etc.) in network switches and edge devices (gateways, controllers, consoles).

  • If Edge Port is set to Enabled; BPDU's are ignored and traffic will flow around the Loop/Ring indefinitely.
    • Use this setting for all ports with Edge Devices connected (gateways, controllers, consoles, anything that is not another network switch).
    • CLI Syntax:  spanning-tree portfast
  • If Edge Port is set to Auto, The link will become active (Forwarding State) after 3 seconds of no BPDU's on the port, thus giving the port time for STP to resolve loops.
    • CLI Syntax:  spanning-tree portfast auto
  • If Edge Port is set to Disabled, BPDU's are respected and STP issues are resolved.
    • Use this setting for all ports connected to other network switches.
    • CLI Syntax:  no spanning-tree portfast

Ether Channel - coming soon

Fiber Optic Cable - coming soon

Fiber (Short Haul) - coming soon

Fiber (Long Haul) - coming soon

GBIC - coming soon

HTP - coming soon

HTTP - coming soon

HTTPS - coming soon

Hops - coming soon

IGMP Querier - When enabled, a network switch will act as a querier for multicast traffic such as sACN lighting levels.  It's job is to send out a "query" at a pre-determined interval like 30 seconds or 2 minutes to ask all network devices if they are interested in multicast traffic such as sACN universes.  A DMX Gateway for example will respond to a query with a simple Membership Report packet, instructing the querier that it is interested in a universe, say universe 1.  The Querier then forwards that universe from the network port hosting the source, like a console, to the DMX gateway port.  This is done to help with network bandwidth and minimize traffic.  Think of the switch like a post office that is sending mail to the ports who asked for it, like a magazine subscription.  If no one asks for it, we enter the world of Unregistered Multicast.

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IGMP Querier Election - Only one IGMP Querier can be present on a network (or VLAN).  The Querier is a feature that can be enabled and disabled on managed switches (mileage may vary depending on make/model).  In a multiple network switch system, if Querier is only enabled on one switch, that switch will be the Querier.  If Querier is enabled on all switches (recommended incase of failure), the switch with the lowest IP Address will be elected the Querier.  This is the case with ETC provided Cisco switches (mileage may vary with other manufacturers).  All other switches with Querier enabled will yield to the one with the lowest address and not output Querier messages.  In the event the Querier is no longer seen on the network, the next lowest IP Address will take over as Querier and so on. 

If the lowest IP Addressed switch is not the desired Querier, it is recommended to change the IP Address of the desired switch so that it is the lowest.  In the default ETC network scheme, 10.101.1.1 is the lowest IP address but it is recommended to leave this reserved if a router is needed in the future.  10.101.1.2 would be the next lowest IP address.

It is recommended to make the core switch or the switch closest to the center of the network (fewest hops to all other switches) be the IGMP Querier.  This switch should also be easily accessible in the event of failure.

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IGMP Snooping - coming soon

IP Address - coming soon

IP Gateway - coming soon

ipconfig -all - coming soon (Command Prompt)

IPv4 - coming soon

IPv6 - coming soon

LAG - coming soon

LAN - coming soon

LTP - coming soon

MAC Address - coming soon

Managed Switch - coming soon

Mesh - coming soon (Network Topology)

MFA - coming soon (Multi-Factor Authentication)

Multicast - Used to describe the transmission of data over a network.  Multicast is when a transmitter wants to send information to multiple receivers at the same time, but does not want the information to be "broadcast".  A real-world example is a lighting controller (console or arch controller) that is transmitting (outputting) sACN lighting levels on Universe 1.  Only those DMX Gateways programmed to output Universe 1 will receive those levels.  DMX Gateways outputting Universe 2 would not receive those levels (unless it is a multiple-port gateway outputting both universes).  In network speak, the receiver (DMX Gateway in this example) would tell an IGMP Querier that it wants to be a member of the multicast group that corresponds with sACN Universe 1 (239.255.0.1).  The IGMP Querier would add that receivers network port (physical port its plugged into) to an internal "table" inside the network switch.  As the network switch (Querier) gets information from a source of the multicast data, the switch then forwards that information to only those network ports listed in the "table".  For those devices not interesting in the multicast group, they simply do not get the message.  This is much more efficient than Broadcast.

It is possible to have more than one source of multicast information on a network such as sACN data.  Using that example, there could be two controllers such as a lighting console and an architectural controller both feeding information (level data) to a single DMX Gateway.  A typical ETC network utilizes multiple variations of multicast simultaneously.

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Network Diameter - coming soon

Network Storm / Broadcast Storm - coming soon

NIC - coming soon

NTP - coming soon (Time Service)

OSC coming soon

PIM coming soon (Protocol Independent Multicast)

PIM Dense Mode coming soon

PIM Spare Mode coming soon

Ping - coming soon

Ping -t - coming soon

PortFast - (See Edge Port) - This is the Cisco CLI (command line interface) command for using the Edge Port feature.  Edge Port is what it is called on the Web Interface of a network switch.

Private IP Address - coming soon

Public IP Address - coming soon

PoE - coming soon

PoE+ - coming soon

Proxy ARP - coming soon

QoS - coming soon

Path Cost - coming soon

Rapid Spanning Tree - coming soon

Ring / Loop Topology - coming soon (Network Topology)

RJ11 - coming soon

RJ45 - coming soon

Root Bridge - In a closed Ring / Loop Topology, Spanning Tree is required to prevent an infinity loop or Network Storm / Broadcast Storm of network traffic.  Read Spanning Tree first to better understand Root Bridge.  Root Bridge is the pre-determined "center" of the switches in a loop.  Essentially a loop has no center switch or core switch so one switch has to be elected from which to reference distance between switches and ultimately shut down the furthest link from it to break the loop and prevent Network Storms from occurring.

In a system where all things are equal between the network switches; (cable type, switch port speed, Bridge Priority, et cetera), the network switch with the lowest MAC Address is elected the Root Bridge.  It is possible to manually configure a switch to be the Root Bridge by altering its Bridge Priority (this will vary by switch and not all switches have the ability to alter this).  Note that physical cable distance or length is not a factor in determining the Root Bridge in most systems.

From the Root Bridge, the Path Cost is determined, and the path to the Root Bridge that has the highest cost will be shut down (the segment between two switches).  The paths to the Root Bridge with the lowest costs will remain open for network traffic.  If traffic has to travel between multiple switches to get to the Root Bridge, the path with the fewest switches to pass through will remain open (every switch passed through adds a cost to the path).

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sACN - coming soon

sACN Priority - coming soon

SNTP - coming soon (Time Service)

Spanning Tree Protcol (STP) - This is a mechanism in network switches that helps to prevent the retransmission of data in a closed Ring / Loop Topology.  In this scenario, we will examine a simple system with 3 network switches connected to one another to for a Ring/Loop.  Without Spanning Tree, data would flow endlessly around the circle and be re-transmitted indefinitely.  Such behavior, also referred to as a Network Storm / Broadcast Storm can easily take down a network (network switches and edge devices such as consoles, controllers, and gateways). 

What Spanning Tree does is to block or close off one of the segments so the network is no longer a closed loop.  The way it does this is by having one switch be the Root Bridge or center / leader of the switches and all other switches determine how far away they are from the center (Root Bridge), this distance is referred to as Path Cost.  Whichever "network segment" has the highest path cost gets blocked and breaks the endless circle.  The lowest cost path is the easiest path for traffic so those are left open.

Note:  For Cisco switches, individual ports on the network switches that connect to other network switches should have Edge Port disabled.  All other ports that host nodes (gateways, controllers, edge devices) should have Edge Port enabled.  See Edge Port definition for more details.

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STP - Learning State - coming soon (Spanning Tree)

STP - Listening State - coming soon (Spanning Tree)

STP - Disregarding State - coming soon (Spanning Tree)

STP - Forwarding State - coming soon (Spanning Tree)

Star Topology - coming soon (Network Topology)

STP -  coming soon (Shielded Twisted Pair)

Subnet Mask - coming soon

Token Ring - coming soon

TTL - coming soon (Time to Live)

TCP coming soon

UDP - coming soon

Unicast - Used to describe the transmission of data over a network.  Unicast is when two devices communicate with each other directly.  Example, a lighting system has two controllers (either consoles or architectural controllers).  In order from them to communicate with one another and sychronize information, they will send unicast messages directly to one another on the network.  This is also commonly used with third party devices that wish to speak to ETC devices over the network.  They will exchange unicast or UDP messages back and forth to perform a simple function like activating a cue or preset.

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Unmanaged Switch - coming soon

Unregistered Multicast - "If no one asks for it, everyone gets it".  If a multicast source like a console is sending out sACN lighting levels or other multicast information and there are no receivers or DMX Gateways asking for that universe, then that universe gets treated like broadcast and those lighting levels get sent to all ports.  In small systems this is not an issue.  On larger systems, that amount of broadcast can result in undesirable behavior.  Example, network products have to discard all packets they receive that don't pertain to them, so a dimmer or relay cabinet has to spent more time discarding packets for universes that it doesn't care about then actually listening to the one or two universes it has patched to itself.  Visible side effects of a "broadcast storm" may include sluggish or laggy response to level changes and even processor reboots.  Using the post office analogy, a broadcast storm is like a mailer or leaflet that just gets sent to everyone, and everyone has to take time to receive the mailer and decide whether to read it (for the coupons) or throw it in the trash/shredder. 

Ideally an IGMP Querier will exist on a network that handles the multicast traffic and eliminates this.  Unregistered multicast is traditionally set to Forwarding by default meaning that all unregistered multicast gets forwarded to all ports as described above.  It is possible to configure network switch ports to instead Filter unregistered multicast.  In a filtered environment, if the network port didn't ask for it, it doesn't get it.  Cisco switches are able to configure Filter/Forwarding settings on a port by port basis.

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UTP coming soon (Unshielded Twisted Pair)

VLAN - coming soon

Wake on LAN - coming soon

WAN - coming soon

Wildcard Mask - coming soon

 

 

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