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Episode 2 – What is a Network, Anyway?

A network is defined by its address space. If you’re the integrator stuck with assigning and maintaining IP addresses, you are going to NEED to understand what a network is so you can understand subnetting and masking. Having a strong grounding in IT concepts and vocabulary will enable you to have a stronger and more productive relationship to your IT-focused colleagues. AV/IT teams that work well together produce the best results for their end users, and ultimately their employers.

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Tim Albright

Episode guest

Tim Albright
CMO, Conference Technologies

Tim Albright is the founder of AVNation and is the driving force behind the AVNation network. His career has taken him from broadcasting to designing and programming AV. Albright has spent his life continually learning and helping others.

Episode transcript

Justin Kennington (00:36):

Hello, and welcome to SDVoE LIVE! I’m your host, Justin Kennington, and this is TV for pro AV.

Today we’re going to bring you an interesting question. It seems like a simple question. It seems like a question we almost know the answer to, but as Matt Dodd is going to explore later in our education segment, there are some subtleties to it, and different ways to look at the answer. That question is, “What is a network, anyway?”. Matt’s going to break down the OSI Model at layers two and three, and help us understand different ways to look at a network, and understand how networks fit together with one another.

Before we jump into education, we’ve got some exciting news that we’re going to cover. A couple of interesting articles popped up our radar screen this week, related to this topic of networking inside and outside of a facility.

We also have a new segment on the show we’ll get to in just a moment: it’s a quiz section. So as I leave in a moment to go find Matt in the newsroom, you’re going to be presented with a question on the screen, and you can answer that question in the chat below, or on Twitter at hashtag #sdvoelive. That’s also where you’re going to be able to interact with us in our aftershow. When the 30-minute program is over, I want you to stick around, stay right where you are, watch those credits roll for a minute, and then you’ll find Matt and me in a more relaxed environment, ready to interact with you directly. We’ll answer your questions about the show and collect your feedback for what we should do next. We’re really excited to hear from you, so we want this to be interactive; stay right where you are for the aftershow.

With the agenda items out of the way, it’s time to head over to the newsroom. While I go find Matt, I want you all to have a look at this quiz question, and anybody who gets both questions right will be eligible to win some exciting prizes at the end of the show. Thanks for watching, everybody. I’m off to the newsroom.

Matt Dodd (02:30):

Oh, hello, Justin, how are you?

Justin Kennington (02:54):

Good, good to see you.

Matt Dodd (04:06):

What’s this, I see? Plants and chairs? What’s this all about?

Justin Kennington (04:14):

We explained last week that we blew our budget on these great giant TVs and the set itself, and asked for your feedback on what furniture to get. We were underwhelmed by some of the responses, but we want to give a special thanks to Leah McCann, who gave us the fantastic idea that fit the budget, for this blue inflatable chair. Matt, do you want to tell them about this plant? It’s a sort of your baby.

Matt Dodd (04:41):

It’s a Swiss cheese plant and it hails from Mexico. They like the warm, humid climate so the studio is going to be absolutely perfect for it. It has a Latin name, which I can’t pronounce very well so I’m just going to throw that up on the display here. There’s the Latin name. Maybe you guys can go and check that out and Google it, find out what that means.

Matt Dodd (05:35):

So there’s the furniture. Any more furniture that anybody wants us to pull in? Please, just get your suggestions in.

Matt Dodd (08:47):

Should we do some news?

Justin Kennington (09:01):

I think we should. Tell us about the first piece. What do we have?

Matt Dodd (09:04):

5G is a big thing, it’s the new buzzword. What we’re seeing now, is that 5G is breaking records with eight gigabits per second, which is incredible speed. This is quite exciting, JK, because this is leading us towards maybe, SDVoE wirelessly?

What about you, JK? What do you take away from this?

Justin Kennington (12:30):

Eight gigs, it’s not enough, right? We need more, we need faster. No, I think that was a really cool test that they did. And it really speaks to where we’re headed in the future. Today, every time I hear this “10-gig, one-gig” debate; and somebody says, “Oh, one gig is what’s important. One gig is what we’re using now”, okay, maybe that’s true, but here we’re talking about wireless technologies doing eight gig! Bandwidth is cheap. Bandwidth gets cheaper. That’s what happens.

So I was really happy to see this. I would love to see a world of IoT-connected AV-over-IP endpoints that all just talk to the cloud. They don’t need to worry about building infrastructure at all. That would be, let’s call it a roadmap, not something we’re delivering in the next six months.

Matt Dodd (13:17):

So this next piece is about the IT departments.  What do IT people know about AV and vice versa? What was your takeaway from that?

Justin Kennington (13:45):

I heard you talking about the knowledge difference, which is something that we try to help within our SDVoE Academy, that you guys are all in now. After this show is over, check out all the other courseware we have.

Another thing that Phil mentioned in the piece was the tool set. There are tools built for measuring and understanding AV and there are tools built for measuring and understanding data flows and data networks, but no tools really built for this complicated world of, “What if the AV is moving with the data?”. I thought it was an interesting thing to call out, something that had never explicitly occurred to me. Any of you inventors and startups out there, there’s an idea for you: build some tools for measuring AV on an IT network.

Matt Dodd (14:34):

Or just build some tools. We all need some tools. I think you have a quiz question to announce. I’ve got to shoot off, and get myself ready to do some educating so I should leave you to it.

Justin Kennington (14:44):

That’s right, here comes quiz question number two, and then we’ll catch up with Matt in the classroom.

Matt Dodd (15:14):

Great, here we are. What is a network, anyway?  The video we’re going to see now, it’s using phrases such as “broadcast”, “domain” and “subnets”. You might think that the network layer is layer three of the OSI Model, but actually, it starts at layer two and this video is going to explain why. So rather than me rambling, let’s take a look.

Researching the answer to the question “What is a network?” usually takes you into a very complex and detailed explanation, very quickly. This short course will give you a clear definition of a data network using the OSI Model as a reference, providing you with foundational knowledge, which will make our deeper dive courses into VLANs and subnets far easier to understand.

To begin with, let’s pull up our old friend, the OSI Model. As we learned from the OSI course, the physical layer is the medium we use to send and receive data packets. We can think of the physical layer as the cable or WiFi, which connects hosts to a network. Oh, what is a host?

Audience (18:16):

A device on a network.

Matt Dodd (18:18):

Yes, very good.

During the “Ethernet Explained” course, we learned how this physical layer is connected to the data link layer by a “PHY”. If you’re not sure what we mean by a “PHY”, why not head over to the “Ethernet Explained” course, here on SDVoE Academy, to refresh your memory.

It’s at layer two we can start to answer the question, “What is a network?” Don’t worry about the fact that layer three is called the network layer. We’ll come to that later. The first thing you need to remember is that the network begins at layer two.

We’re going to define the word network from both a layer-two perspective, and a layer-three perspective. Think of layer two as being an actual network of devices or hosts, which are able to communicate with each other. It’s called data link, because at this layer, host devices are linked together to form a single network, often referred to as a local area network, or LAN.

As we learned in the “Ethernet Explained” course, the host addresses used at layer two are the MAC addresses. Because every MAC address is unique, theoretically, every host could communicate on the same LAN.

This is exactly what happens when we connect hosts to a network switch. The switch will use MAC addresses to determine which hosts or group of hosts it needs to send data packets to. This is a network at layer two. In networking, a layer-two network is called a “broadcast domain”. Whenever you hear this term, think of it as a network layer two.

A broadcast is a data packet, which is intended for every host that can be reached via layer-two messaging. The broadcast domain is the set of hosts who will receive it. A broadcast domain is commonly determined by physical connectivity. Any hosts connected to our switches are on a broadcast domain. It is, however, possible to subdivide our physical network into multiple virtual networks, using a technique called VLAN. We’ll take a deeper dive into VLANs very soon here on SDVoE Academy, but for now, let’s keep it simple. Layer two of the OSI Model is where a network is created.

Now, let’s head up to layer three. We can clearly see this is called the network layer and that’s because this is the layer which connects multiple networks together. A simple example would be a home network like this, where a router connects the private network inside the house to the public network outside the house. In the same way we call layer-two networks “broadcast domains”, at layer three we call each network a “subnet”. And at layer three we identify each subnet using a different address, called an “IP address”. You can learn more about IP in the “Layer 3 – So That’s Where IP Lives ” course, here on SDVoE  Academy.

Layer-three subnets, like the layer-two broadcast domains, can also be subdivided to create smaller, more manageable networks using a process called “subnetting”. Now, this process is considerably more complex than VLANs, and would generally be carried out by an IT professional. We’ll take a deeper dive into layer-three subnetting very soon here on SDVoE Academy but for now, let’s revisit the question, “What is a network?” using the OSI Model as a reference.

Networks are created at layer two and we call these networks…

Audience (22:42):

Broadcast domains.

Matt Dodd (22:44):

Very good. Networks are connected together at layer three, and these connecting networks are called…

Audience (22:53):


Matt Dodd (22:55):

Perfect. Stay tuned here on the SDVoE Academy for more courses, which further explain how layer-two and layer-three networks are subdivided and managed for greater network efficiency.

Some really good information in there, right?

Justin Kennington (23:27):

Yeah, I really like thinking in terms of broadcast domains or subnets.

But, you know, I took something new from that video, which I’ve seen a handful of times now. It’s actually one of my favorites in SDVoE Academy.

In the model of the house that you showed, you know, where we’re modeling the different outside network and the internal LAN, their gymnasium was in the attic, which seemed inconvenient in terms of bringing all those weights up there. But I also noticed the set of hanging gymnast rings from the ceiling of the attic and I thought, “Wow, these are some serious health nuts that live in that house”.

Matt Dodd (24:01):

Yeah. And think about it: if you put the gym in the attic, then you’ve got to work to get to the gym, but it’s nice when you leave the gym, right?              Whereas you guys, you have gyms in the basement, but we don’t have basements here. We have cellars. Now, going down the stairs, it’s easy, right? And I do a workout downstairs. I’ve got to walk upstairs, or get in the elevator.

Justin Kennington (24:23):

Sure, I just can’t wait to see you on the hanging rings sometime.

Justin Kennington (27:32):

We’re down to time here, Matt. So I think we should tell people that our next show is two weeks from right now. It’s called “Using Fiber Optics in Pro AV Applications”. We have our first special guest. Right, Matt? He’s a friend of yours.

Matt Dodd (28:02):

Yeah. Gary Vlaeminck from Cleerline Technology Group is a dear friend of mine.

Let’s stick around for the aftershow.

Justin Kennington (28:21):

We’ll see you in one minute. Bye.


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