Video Transcript
Quantum Networking (Part 1)
9m 13s
00:08
Welcome to “Q-SYS Networking I”, which is part of our Q-SYS Quantum Training,
00:13
an advanced service and troubleshooting curriculum.
00:15
My name is Nathan Makaryk and I’ll be giving you a look at some best practices
00:19
in regard to IP addresses and subnet configuration within a Q-SYS system.
00:24
A good way to understand Ethernet networking is to think of it in terms of street addresses
00:30
and the roadways that connect them. We find a place by using a distinct street address.
00:36
Hopefully you don't have two of the same street addresses in the same city, or you're going to have problems.
00:41
But the same street address could exist in different cities.
00:46
That marks the difference between a physical address
00:49
which in the real world might be represented by something like exact GPS coordinates,
00:53
and a logical address, which is what humans use to direct ourselves.
00:58
Theoretically, every city might have this 9466 Oak Street address,
01:04
but that's okay because they are all in physically different places, with have with different zip codes, etc.
01:10
To navigate from address to address, we build an infrastructure.
01:14
In the physical world we have surface streets which would be analogous to an Ethernet switch.
01:20
And then we have what we call the information superhighway, or the internet,
01:24
or a wide area network that would create larger pathways connected through a router.
01:30
That's essentially how we connect our different cities together, right?
01:35
So, looking at a similar network diagram, our “city” would be our local area network of different devices connected via switches,
01:44
and then we use a router to connect to the cloud, out to the internet at large.
01:49
Network appliances typically have two types of addresses: There’s a Media Access Controller or MAC address.
01:58
This would be like the absolute GPS coordinates of a place. It is globally unique.
02:04
This address is programmed into the device when it is manufactured, and it's not configurable from that point forward.
02:12
The Internet Protocol or IP address of a device however, IS configurable.
02:19
It’s a logical address like the street address of our houses here on Oak Street.
02:24
We could rename Oak Street to Elm Street, but the global coordinates of each house are still the same.
02:31
The MAC address of a device is formatted as 6 8-bit binary “words” expressed in hexadecimal,
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because we love hexadecimal.
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Each octet ranges from 0 to 255.
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The first three parts of the MAC address is what we call the ‘Organizationally Unique Identifier’
02:53
or OUI, and that tells us who made it.
02:58
Common OUIs we might see on a typical Q-SYS network would be of course QSC (which has 00-60-74),
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Audinate (which is 00-1D-C1) or maybe Attero Tech (which is 00-1C-E2).
03:16
The OUI combined with the last three possible octets
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allows each manufacturer to make about 16.7 million devices
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before they need to go back and apply for another OUI.
03:29
Very large manufacturers like HP and Cisco - they have several OUIs.
03:35
Note that you won’t always see 00-60-74 as the OUI of every Q-SYS device and peripheral.
03:43
Q-SYS cores can sometimes appear as INTEL devices as that’s the underlying topology of the Q-SYS platform.
03:50
In addition to the MAC address, we have the IP address that we more typically encounter and work with.
03:56
In IPV4, 4 8-bit binary words are separated by dots to show the address.
04:04
It’s expressed in number format from 0 to 255. Just like those street addresses,
04:10
I don't want to use the same IP address on two devices,
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because we’re going to get confused about where we’re going from that point forward.
04:16
Note that Q-SYS does not support IPV6 at this point,
04:21
this will not be covered in an effort to keep it simple and practical.
04:25
So far we’ve discussed the two major ways devices are addressed.
04:29
We know their global and logical addresses,
04:32
but this knowledge alone doesn’t explain how we get data from one device to another without … a pileup.
04:40
If I’m an Ethernet packet, who is my navigator? How do I find my way?
04:45
Lucky for us, there’s a governing model of how Ethernet-based technologies work.
04:51
That model gives rise to network protocols with the appropriate functions to make networks work.
04:57
We now know where we’re starting and we know where we’re going.
05:02
So the roads are already paved, we just need to get our driver’s license essentially.
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This governing model that I mentioned is known as the Open Systems Interconnect, or OSI model.
05:13
It's nerdy but it works!
05:15
The OSI model is made of seven layers.
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The lowest layers concern themselves with the basic means of connectivity we’ve been discussing.
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These are known as the media layers. Of these, layer 1 represents the actual physical connections.
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Layer two, the data link layer, defines the framework for communication between devices.
05:38
Layer three, builds up to the routable, far-reaching ability to transmit a packet virtually anywhere.
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And then the host layers (which are layers 4-7) of the OSI model concern themselves with how machines deal
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with multiple services and applications, and how they’re organized and interpreted.
05:55
Now that we’ve covered a little background on the framework,
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let’s begin to think about how the media layers work together to make traffic flow.
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This involves a very important part of the network – the Ethernet switch.
06:09
In order to understand, we need to think the way that it does.
06:13
The first role of the switch is to provide Layer 1 connectivity.
06:17
We need to have electrical connections, right, to get the job done.
06:21
The layer 2 function of the switch is to keep track of what MAC addresses are attached to each port.
06:28
The switch will build a table to keep track of those addresses.
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The job of the switch from that point forward is to make sure that
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only packets destined for those devices get to the corresponding ports.
06:40
The switch will inspect packets and look for destination MAC addresses in order to make the right decisions.
06:46
When it comes to the use of IP addresses on the local area network,
06:51
that’s really a function of the devices themselves.
06:54
We know that the switch is concerned with MAC addresses, not IP addresses.
06:58
But the devices on the network, they like to think in terms of IP addresses.
07:03
So, the Address Resolution Protocol (or ARP) helps the devices correlate IP addresses to hardware addresses.
07:11
Once that’s known, the device will include the destination MAC and IP
07:16
in the message so the switch knows what to do.
07:19
To illustrate how the Address Resolution Protocol works, let’s look at an example.
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The computer to the right needs to talk to the IP address 192.168.1.101, but it doesn’t know that device’s MAC.
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The computer sends a broadcast query to ask that device to respond.
07:39
A broadcast message will go to every port on the switch to make sure it finds the correct device.
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The device then responds, giving its MAC to the sender of the query.
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Once it receives the response, the querier adds that IP and MAC to its ARP table.
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It will use this table to construct packets with the correct IP and MAC from then on.
08:02
So, by now you must be thinking
08:04
‘that’s dumb! Why do machines think in terms of IPs and switches in terms of MACs?’
08:11
‘why don’t we just manage everything by MAC address instead?’
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The answer is we used to and it wasn’t a lot of fun.
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MAC addresses, first of all, they are not terribly easy to remember.
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And since your network devices may be made by multiple manufacturers, they're going to be completely different.
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So there’s no consistent model for logical groupings of your devices.
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It’s also much more convenient for routers to do their jobs
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if they don’t have to memorize all the MAC addresses of everything they might converse with.
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So while there’s some underlying complication,
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the use of IP addresses makes it easier for humans to interact with computers and for routers to do their jobs.
08:51
We can use the same IP schemes for many internal networks for instance,
08:56
and also create logical groups of machines that can share information.
09:00
Let’s take a break here, and when we come back we’ll talk about how we can use subnets
09:06
to make even smaller groups of machines within your network.
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Quantum Networking (Part 1)
9m 13s