Network Transceivers, Fiber Connectors, Copper Connectors, and Network Topologies

Transceiver is a combination of two words– “transmitter” and “receiver.” And these are usually combined within the same piece of equipment or the same component. A transceiver allows for modularity. You may have a switch like this one. You can see there are a number of open interfaces in this switch. You slide in the transceiver that’s appropriate for the media or the network type that you would like to use. And now that particular interface will operate with that particular configuration.

So if you need a copper configuration for Gigabit Ethernet, you slide in a copper Gigabit Ethernet transceiver. Or if you need a fiber-based 10-gig connection, you slide in a 10-gig fiber transceiver. This means that you can have every interface on this switch have a different type of media, depending on what transceiver you are planning to use.

There are different types of transceivers, different form factors, and different transceivers depending on the media. For example, if you are using an Ethernet switch, you need an Ethernet transceiver. If you’re using a Fibre Channel switch, then you will need a Fibre Channel transceiver. You can’t use Fibre Channel transceivers in an Ethernet switch or vice versa.

This means you get to decide what media type works best for your configuration. If you need copper connections, you can use a copper transceiver. And if you need fiber connections, you can use a fiber transceiver. And if you need to change those connections midway through your installation, you can remove the copper transceiver and replace it with a fiber transceiver. This type of modularity often comes at an additional cost. But it does provide you with a way to plug into whatever network type you might need.

One common transceiver type is the SFP type. This stands for Small Form-factor Pluggable. For example, you can plug in a fiber SFP and connect your fiber connections to that particular transceiver. But if you needed copper, you could easily slide in a copper SFP and plug in your RJ45 connector.

SFP’s are commonly associated with Gigabit Ethernet. So that’s 1 gigabit per second. There is an enhanced version of SFP called Enhanced Small Form-factor Pluggable, or SFP+. They look identical in size to an SFP, but they support much higher speeds, up to 16 gigabits per second. So if you have a 10-gig connection, then you’re probably using SFP+.

When you’re installing equipment into a rack that’s in a data center, you have a limited amount of space available. First, the equipment is only 19 inches wide. And the total amount of space available in the rack is limited by the amount of space you have in the data center. So we want to be sure that we can put as much connectivity into a single space as possible.

To that end, we’ve created the QSFP, or the Quad Small Form-factor Pluggable. This effectively allows you to have four times the amount of throughput into a space that’s very similar to that of an SFP. For example, an SFP in this form would be a Quad Small Form-factor Pluggable, or QSFP, which consists of four channels of SFP. So if one SFP is a 1 gigabit per second connection, a Quad SFP would be compatible with a 4-gigabit throughput.

The same thing applies for the SFP+. There is a Quad SFP+ that is a four-channel SFP+. Since it’s common to see a 10-gigabit connection on a single SFP+, a Quad SFP+ can support four of those, for a total throughput of 40 gigabits per second. This is where we start to see a benefit not only in the amount of space that we’re using inside of these devices, but we can take a single fiber connection and effectively extend four separate links over that single fiber. There’s cost benefit there for equipment and for the media itself.

Although the names are very similar, the form factors are slightly different between an SFP and SFP+ and a Quad SFP or Quad SFP+. On the left is an SFP or SFP+. Both the SFP and SFP+ use the same form factor, although the transceivers are obviously very different. The Quad SFP or Quad SFP+ also share the same form factor. But you can see it’s slightly larger than the traditional SFP or SFP+. Although it is slightly larger than an SFP, it’s not four times the size of an SFP. So we are getting an efficiency in space by using a Quad SFP or Quad SFP+.

When working with fiber optics, one of the first things you’ll notice is there are many different connector types. You have to make sure that you use the right connector type for the right connection.

A very common fiber connector type is the SC connector, or the Subscriber Connector. We also have other names that we associate with this connector. One is a square connector because the connector itself is rather square when you look at it. You might also see this referred to as a standard connector, although there are certainly other types of fiber connectors that you might use.

To use an SC connector, it simply pushes into the connection and snaps in place with a lock. Once you have that connector in place, it’s not going to accidentally slip out of that connection. You first have to pull on the connector to unlock it, and then it can be removed from that interface. This is a common connector type, and if you’re plugging into a connection in a data center, you’re probably using some connections that are identified as SC.

The connectors themselves support individual fibers, but they’re often combined together into a pair because one of these is commonly used for transmit and the other is commonly used for receive.

Another common fiber connector is the LC, or Local Connector. This is slightly smaller than an SC connector, and as you can see, it has a clip on the top to lock it in place once you put it into the interface. This also means that it won’t accidentally get pulled out of an interface, and to remove it, you need to push down on the clip. That will release the lock and allow you to easily remove it from the interface. Instead of local connector, you might also see this referred to as a Lucent connector or a little connector.

The LC connector can also be combined in a pair– looks like this– and you can plug both of them in simultaneously. And again, one is used for transmit and the other used for receive.

Another fiber on our list is the ST connector. That stands for Straight Tip. It uses a bayonet connector. So you push it into an interface, give it a slight twist, and it is locked in place. This will not easily get removed from the interface unless you reverse that twist, and then you can remove it from the interface. When you’re working inside of a rack and there’s a large number of cables and fiber, it can be very easy to accidentally dislodge one of those connections. That’s why we have all of these different locking mechanisms for these different interface types.

Here’s a closer view of the ST connector. There is a protective ferrule around the fiber, which you can barely see in this picture, and you can easily see the bayonet connector where you would plug it in and twist it in place so that it is locked into that interface.

One of the challenges with the connector types that we’ve seen so far is that those fiber connections take up a lot of real estate. It would be a lot more efficient if we could put more fiber into a smaller connection, and there is a connector type for that called the MPO, which is Multi-fiber Push On. Inside the MPO are 12 individual fibers that are contained in that single cable connection. This also has a lock in place that’s very similar to the SC connector where you would push it in place, and you would have to pull it out slightly to unlock it from the interface. You might also see this connector referred to as an MTP. That name is provided by Corning, and they refer to this as an MTP MPO connector.

Here’s a side view of the connector. It has this lock on the top, and the individual fibers are these smaller dots you can barely see in this picture. If we look at it straight on with some light being sent through the fiber, you can see that all 12 of those fibers are much easier to see on the MPO connector.

One common copper connector we use on our networks today is an RJ11. This stands for Registered Jack type 11. It is a six-position connector, but we only use two conductors inside of this connector. Sometimes, you’ll see this referred to as a 6P2C, for 6 position 2 conductor.

We commonly associate an RJ11 connector with an analog telephone, but you’ll also see RJ11 used for DSL connections since those use exactly the same wires as a telephone connection. Here’s a better view of the RJ11 connector. And you can see the six positions– 1, 2, 3, 4, 5, 6 are clearly marked– but you notice that there are the two conductors in the middle that are used for RJ11.

If you’re using an ethernet connection, then you’re using an RJ45 connector. And this stands for Registered Jack type 45. It is an eight position connector with eight conductors inside, so we’re using all of the conductors available on an RJ45 connection. This is slightly larger than an RJ11 connector, and it’s what you would use if you’re plugging in an ethernet connection.

Here’s a device that has both RJ11 and RJ45 connectors on it. You can see this is a DSL connection that uses the RJ11, and these LAN connections, or ethernet connections, are using the RJ45. You can see that they’re very similar in shape, although the RJ11 is slightly smaller than the larger and wider RJ45.

If you’re using a cable modem connection, then you’re probably bringing coax connections and plugging it into a cable modem. And the connector that you’re probably using is the F-connector. The F-connector is a standard connection type. It usually has threads inside that allow you to fasten it very securely to the connector. And if you are using a cable modem, this is probably the connection type that you’re using from the cable television infrastructure.

This is also referred to as a DOCSIS connector. That stands for Data Over Cable Service Interface Specification. The connection that brings the signal is the single copper connection on the inside of the cable. This is what you would plug-in and screw into a cable modem using that F-connector connected to the coaxial cable.

Another common connector used for coax is a BNC connector. This is a Bayonet connector, that’s what the b stands for, where you push it into the connector and twist it slightly to lock it in place. The NC in the BNC connector stands for Neill-Concelman. This stands for Paul Neill from Bell Labs and Carl Concelman from Amphenol. They both were involved in creating this standard for a BNC connection.

If you’re bringing in a WAN connection or any other type of coax, it’s very possible you might use a BNC connection to lock this in place. That is one of the benefits of using BNC, is that you’re able to push the connector in and twist it, and it’s not going to easily remove itself from that connection. You would need to untwist before removing that from the interface.

Here’s a close up view of the BNC interfaces on a device. You could see where you would plug-in the BNC connector. You twist that connector slightly and it’s locked in place onto that device.

Networks can connect to each other in many different ways. And in this video, we’re going to look at a number of different network topologies and how those different network topologies can be deployed in an enterprise network. This can be very useful during the planning process, where you’re designing the network. It’s also useful during the troubleshooting process so that you can tell how different networks are connected to other networks. This is also useful during the troubleshooting process so that you can visually see how one network might connect to and send data to another network.

Let’s start this conversation with one of the most popular network topologies in use. That would be a star network. Sometimes you may hear this referred to as a hub-and-spoke network. This is what we use in most large networks to connect devices together. There’s a central device that is used as the central networking component. And then everyone on the network is all connecting to that same central device.

A good example of a star network, or a hub-and-spoke network, is one that we have with switched Ethernet. Our Ethernet switch sits in the middle of the network. And all of the other devices connect to that same Ethernet switch. If each of these spokes around the network would like to communicate with each other, they all must communicate through this central hub.

A mesh network design is when one location or device connects to another location or device over more than one network connection. This means that we can have one link communicating to another. And it might follow one path to get to that location. Or it may follow an alternate path to be able to get to that location.

One reason we design a network this way is so that if one link in the mesh was to fail, we can use one of the other links to complete that communication. We might also perform load balancing over these links, where half of the data is sent over one connection, and the other half of the data is sent over a different connection. Although we can certainly design mesh networks for local area networks, we often see them deployed in wide area networks so that we can maintain connectivity to a remote site regardless of what network connection might be available.

If you were to look at a large enterprise network, you would notice there are a number of different architectures all being used in different parts of the network. And when we combine all of those together, we’ve created a hybrid network. One part of the network might be a star network. Another part of the network may be point to point. And a third part of the network might be a mesh network. Once we combine all of these together, we’ve created a hybrid architecture.

Many data centers take advantage of a spine and leaf architecture. This is where you would have individual switches at the top that are the spine of the network. There would be switches in the middle that are leaf networks. And then you would have different devices connect to the leaf.

You’ll notice that the spine network is connected to all of the leafs. And the leafs are connected to each of the spines. However, those leaf switches do not connect directly to each other. And the spine switches also do not connect directly to each other. This works very well for an architecture we use in many data centers, known as top-of-rack switching. In top-of-rack switching, every rack has a leaf switch at the top of every physical rack. We would then connect all of the physical devices in that rack to the leaf switch that is at the top of that rack.

This keeps your cabling very simple because all of your cabling is self-contained within that same rack. There is redundancy because you have this rack connected to multiple spines. This also increases the overall performance of the network because we’re no more than one switch away from any other device in the data center.

If your data center only has a handful of racks, this may be a relatively inexpensive way to connect all of these devices together. But when you have tens or hundreds or even thousands of racks in a data center, you would need a separate switch for every rack. And of course, the cost of that will increase for each rack you have in the network.

When looking around the network, you may find some wide area network connections that are point to point. And as the name implies, there is a single point connected to a single point. This was a very common design on older wide area networks, where you would use something like a T1 or a T3 connection. We refer to those as point-to-point T1 or point-to-point T3. We might also use this design in local area networks. If you work on a campus, you can connect one building to another over two connections. And the connection between those two buildings would be a point-to-point connection.