FMA 101: Taking Things Apart to Make Them Even Better
This month, we continue our CableLabs 101 series by peeling back the next layer of the hybrid fiber-coax (HFC) distributed access network with a recently released specification called Flexible MAC Architecture (FMA). This technology isn’t as well known as DOCSIS®, Remote PHY or Coherent Optics, but it’s just as essential to make 10G a reality in the near future. Let’s take a closer look.
What Is FMA?
Without getting too technical, a big part of what we do involves analyzing how things work. We like to take things apart and see how we can reorganize or alter the components to build better, more efficient products. Essentially, that’s what innovation is all about! In this case, the “product” in question is the DOCSIS technology and the cable access network that delivers Internet to your home.
Some time ago, we figured out how to split key DOCSIS functions into two major pieces: the Media Access Control (MAC) function responsible for DOCSIS processing and the physical radio frequency function (PHY) responsible for DOCSIS signal generation. This initial split became known as Remote PHY, and you can read more about it in our previous blog post here. Subsequently, we built a complementary project involving the redistribution of these functions across the network to enable efficiencies in speed, reliability, latency and security. This newer project is FMA, which defines various ways of restructuring the MAC function’s management, control and data planes to support multi-gigabit data services of the future.
In September 2020, this extraordinary effort—involving thousands of work hours across the global cable industry—culminated in the specification. It’s a library of specifications that gives our industry vendors the technical means to develop interoperable products for our cable community, and it officially welcomes FMA into the 10G technologies toolkit.
How Does FMA Work and Why Do You Need It?
The Converged Cable Access Platform (CCAP)—a nearly decade-old technology—serves as a single platform for both video and broadband services. In a traditional CCAP architecture, all the major network functions, including the MAC layer functions we mentioned earlier, are unified at the headend. However, as consumers’ bandwidth consumption has continued to skyrocket with no sign of slowing down, the cable industry asked: Is there a better way to structure CCAP to prepare our networks for the needs of tomorrow?
The answer was yes.
That’s how the concepts of Remote PHY, Remote MAC-PHY and, eventually, FMA were born. By taking apart key CCAP functions and moving them to other places throughout the network (e.g., a fiber node), we can greatly reduce space and power demands at the headend, creating efficiencies that translate into faster network speeds, lower latencies and overall a better, and reliable cable access network.
Plus, FMA offers cable operators the ultimate flexibility to implement and deploy CCAP functionality in a way that makes the most sense for them. It fully supports the DOCSIS 4.0 requirements and, along with the other tools in the 10G arsenal, can help operators build adaptive and secure networks that can easily handle future demand.
How Does This Technology Affect You and Your Future?
Complete disaggregation of CCAP sounds great, but you might be asking yourself: “What’s in it for me?” As with any 10G technology that we’ll cover in this series, it’s always about improving the end user experience. All those technical efficiencies we talked about basically boil down to more room for data to go through the network at much faster speeds. This means more multi-gigabit services, low-latency applications such as ultra-realistic video experiences and overall a better quality of experience. One day soon, as we continue to build upon cutting-edge cable technologies like FMA, this will become reality.
The September 2020 FMA release is just a part of a much bigger initiative to completely virtualize cable access networks in the near future, so definitely stay tuned! In the meantime, we’ll continue taking things apart and putting them back together in new and better ways to take your connected experiences to the next level.
Remote PHY 101: Why the Industry Is Working Together to Take Things Apart
In our previous CableLabs 101 post about Distributed Access Architecture (DAA), we discussed the benefits of distributing key network functions throughout the cable access network to optimize its performance. Today, we delve deeper into Remote PHY—one of the earliest DAA solutions that cable operators are deploying to increase their network’s bandwidth and more.
What Is Remote PHY?
PHY stands for “physical radio frequency (RF) layer,” which delivers voice, video and data via the DOCSIS® protocol over the hybrid fiber-coax (HFC) network. Media Access Control (MAC) is an example of another CCAP layer that we’ll cover in our next CableLabs 101 post.
Prior to the introduction of the DAA concept, all CCAP functions, including PHY and MAC, were integrated at the Internet provider’s cable modem termination system (CMTS)—typically located at the headend or hub site—which sends and receives data to and from the modem in your home. This data exchange is the basis for how DOCSIS technology on HFC networks works. However, the integrated CCAP approach does not maximize the potential of the cable access network.
Once we figured out how to split the PHY and MAC functions, we were then able to distribute PHY closer to the end user, resulting in increased network capacity and greater speeds. You can refresh your memory about the benefits of DAA and Distributed CCAP Architecture (DCA) here.
Remote PHY was the first documented DCA specification that we officially released in 2015, followed by Flexible MAC Architecture (FMA), released in September 2020. These solutions are complementary and have similar benefits, giving cable operators the flexibility to architect their networks the way they see fit to support future high-bandwidth services. The specifications provide guidance to our industry vendors who are manufacturing Remote PHY–compatible equipment. Just like the other DOCSIS and Coherent Optics technologies, Remote PHY and the other DCA approaches are part of the 10G toolset.
How Does Remote PHY Work?
The Remote PHY specification defines ways to separate the physical RF layer from the MAC layer that remains at the headend and describes the interfaces between them. Let’s take a closer look at how it’s done.
The PHY layer of the CCAP system is placed in something called a Remote PHY Device (RPD). An RPD is a piece of equipment usually produced by a third-party cable vendor that contains all the PHY-related circuitry, as well as the pseudowire logic that connects back to the CCAP Core, which supports full DOCSIS functionality. In other words, all this rerouting on the back end is completely hidden from customers like you. Your network will function the same as before, only much faster because the PHY layer is now located much closer to where you live.
Speaking of location, the beauty of the Remote PHY architecture lies in its flexibility to place RPDs anywhere, including optical nodes closer to the network “edge”—a cable insider’s way of saying “closer to customers’ homes.” A single node can serve just a few blocks or even a single building; therefore, each customer modem connected to that node gets a bigger chunk of the bandwidth pie, so to speak. And, of course, more available bandwidth means better customer experience!
How Does This Technology Affect Me and My Future?
You might think that it makes no difference to you how your Internet provider’s CCAP is designed—and you would be right. What does matter, however, is the noticeable difference in your Internet quality, including how fast your apps work, how quickly you can download your movies or how much lag (or lack thereof) you experience when you play an online game with your friends. Looking forward to the near future, you may be using applications that utilize holographic displays, artificial intelligence, virtual rooms, 360° fully immersive entertainment experiences and other innovative technologies that require multi-gigabit bandwidth to function seamlessly.
This is why CableLabs and our partners in the cable industry are continuously inventing new ways to mine more bandwidth out of the available RF spectrum. Thanks to specifications like Remote PHY, FMA and others, we have all the pieces in place to deliver 10G symmetrical speeds—and more—to support future innovations. Now it’s just a matter of putting it all together.
Expanded Testing of Video Conferencing Bandwidth Usage Over 50/5 Mbps Broadband Service
As working from home and remote schooling remain the norm for most of us, we wanted to build on and extend our prior investigation of the bandwidth usage of popular video conferencing applications. In this post, we examine the use of video conferencing applications over a broadband service of 50 Mbps downstream and 5 Mbps upstream (“50/5 broadband service”). The goal remains the same, looking at how many simultaneous conferencing sessions can be supported on the access network using popular video conferencing applications. As before, we examined Google Meet, GoToMeeting, and Zoom, and this time we added Microsoft Teams and an examination of a mix of these applications. To avoid any appearance of endorsement of a particular conferencing application, we haven’t labeled the figures below with the specific apps under test.
We used the same network equipment from November. This includes the same cable equipment as the previous blog -- the same DOCSIS 3.0 Technicolor TC8305c gateway, supporting 8 downstream channels and 4 upstream channels, and the same CommScope E6000 cable modem termination system (CMTS).
The same laptops were also used, though this time we increased it to 10 laptops. Various laptops were used, running Windows, MacOS and Ubuntu – nothing special, just laptops that were around the lab and available for use. All used wired Ethernet connections through a switch to the modem to ensure no variables outside the control of the broadband provider would impact the speeds delivered (e.g., placement of the Wi-Fi access point, as noted below). Conference sessions were set up and parameters varied while traffic flow rates were collected over time. Throughout testing, we ensured there was active movement in view of each laptop’s camera to more fully simulate real-world use cases.
As in the previous blog, this research doesn’t take into account the potential external factors that can affect Internet performance in a real home -- from the use of Wi-Fi, to building materials, to Wi-Fi interference, to the age and condition of the user’s connected devices -- but it does provide a helpful illustration of the baseline capabilities of a 50/5 broadband service.
As before, the broadband speeds were over-provisioned. For this testing, the 50/5 broadband service was over provisioned by 25%, a typical configuration for this service tier.
First things first: We repeated the work from November using the 25/3 broadband service. And happily, those results were re-confirmed. We felt the baseline was important to verify the setup.
Next, we moved to the 50/5 broadband service and got to work. At a high level, we found that all four conferencing solutions could support at least 10 concurrent sessions on 10 separate laptops connected to the same cable modem with the aforementioned 50/5 broadband service and with all sessions in gallery view. The quality of all 10 sessions was good and consistent throughout, with no jitter, choppiness, artifacts or other defects noticed during the sessions. Not surprisingly, with the increase in the nominal upstream speed from 3 Mbps to 5 Mbps, we were able to increase the number of concurrent sessions from the 5 we listed in the November blog to 10 sessions with the 50/5 broadband service under test.
The data presented below represents samples that were collected every 200 milliseconds over a 5-minute interval (300 seconds) using tshark (the Wireshark network analyzer).
Conferencing Application: A
The chart below (Figure 1) shows total access network usage for the 10 concurrent sessions over 300 seconds (5 minutes) while using one of the above conferencing applications. The blue line is the total downstream usage, and the orange line is total upstream usage. Note that the total upstream usage stays around 2.5 Mbps which may be a result of running 10 concurrent sessions. Also, the downstream usage stays, on average, around 15 mbps, which leaves roughly 35 Mbps of downstream headroom for other services such as streaming video that can also use the broadband connection at the same time.
Figure 2 shows the upstream bandwidth usage of the 10 concurrent sessions and it appears that these individual sessions are competing amongst themselves for upstream bandwidth. However, all upstream sessions typically stay well below 0.5 Mbps -- these streams are all independent, with the amount of upstream bandwidth usage fluctuating over time.
Figure 3 shows the downstream bandwidth usage for the 10 individual conference sessions. Each conference session typically uses between 1 to 2 Mbps. As previously observed with this application, there are short periods of time when some of the sessions use more downstream bandwidth than the typical 1 to 2 Mbps.
Conferencing Application: B
Figure 4 shows access network usage for 10 concurrent sessions over 300 seconds (5 minutes) for the second conferencing application tested. The blue line is the total downstream usage, and the orange line is total upstream usage. Note that the total upstream usage hovers around 3.5 Mbps. The total downstream usage is very tight, right above 10 Mbps.
Figure 5 shows the upstream bandwidth usage of the 10 individual conference sessions where all but one session is well below 1 Mbps and that one session is right at 2 Mbps. We don’t have an explanation for why that blue session is so much higher than the others, but it falls well within the available upstream bandwidth.
Figure 6 shows the downstream bandwidth usage for the 10 individual conference sessions clusters consistently around 1 Mbps.
Conferencing Application: C
Figure 7 shows access network usage for the 10 concurrent sessions over 300 seconds (5 minutes) for the third application tested. The blue line is the total downstream usage, and the orange line is total upstream usage. Note that the total upstream usage hovers right at 3 Mbps over the 5 minutes.
Figure 8 shows the upstream bandwidth usage of the 10 individual conference sessions where all stay well below 1 Mbps.
Figure 9 shows the downstream bandwidth usage for the 10 individual conference sessions. These sessions appear to track each other very closely around 2 Mbps, which matches Figure 7 showing aggregate downstream usage around 20 Mbps.
Conference Application: D
Figure 10 shows access network usage for the 10 concurrent sessions over 300 seconds (5 minutes) for the fourth application tested. The blue line is the total downstream usage, and the orange line is total upstream usage. Note that the total upstream usage hovers right at 5 Mbps over the 5 minutes, and there is no visible degradation to the conferencing sessions was observed.
Figure 11 shows the upstream bandwidth usage of the 10 individual conference sessions, where there is some variability in bandwidth consumed per session. One session (red) consistently uses more upstream bandwidth than the other sessions but remained well below the available upstream bandwidth.
Figure 12 shows the downstream bandwidth usage for the 10 individual conference sessions. These sessions show two groups, with one group using less than 1 Mbps of bandwidth and the second group using consistently between 2 Mbps and 4 Mbps of bandwidth.
Running All Four Conference Applications Simultaneously
In this section, we examine the bandwidth usage of all four conferencing applications running simultaneously. The test consists of three concurrent sessions from two of the applications and two concurrent sessions from the other two applications (once again a total of 10 conference sessions running simultaneously). The goal is to observe how the applications may interact in the scenario where members of the same household are using different conference applications at the same time.
Figure 13 shows access network usage for these 10 concurrent sessions over 300 seconds (5 minutes). The blue line is the total downstream usage, and the orange line is total upstream usage. Note that the total upstream usage once again hovers around 5 Mbps without any visible degradation to the conferencing sessions, and the downstream usage is pretty tight right above 10 Mbps.
Figure 14 shows the upstream bandwidth usage of the 10 individual conference sessions where several distinct groupings of sessions are visible. There were 4 different apps running concurrently. One session (red) consumes the most upstream bandwidth at averaging around 2 Mbps, whereas the other sessions use less, and some much less.
Figure 15 shows the downstream bandwidth usage for the 10 individual conference sessions across the four apps and, again, there are different clusters of sessions. Each of the four apps are following their own algorithms.
In summary, with a 50/5 broadband service, each of the video-conferencing applications supported at least 10 concurrent sessions, both when using a single conferencing application and when using a mix of these four applications. In all cases, the quality of the 10 concurrent sessions was good and consistent throughout. The 5 Mbps of nominal upstream bandwidth was sufficient to support the conferencing sessions without visible degradation, and there was more than sufficient available downstream bandwidth to run other common applications, such as video streaming and web browsing, concurrently with the 10 conferencing sessions.
DAA 101: A Flexible Approach to Better, Faster Cable Networks
This month, we’d like to share information about Distributed Access Architecture (DAA) and how cable operators are using it to build the 10G networks of the future. In our previous posts about DOCSIS® and Coherent Optics technologies, we touched on some of the components of the cable hybrid fiber-coax (HFC) network, such as the headend and fiber nodes, but of course, there’s much more to it. Today, we’ll take a closer look at the functionality of the cable access network and how it can be distributed between various components to optimize network performance.
What Is Distributed Access Architecture?
DAA isn’t a single technology but rather an umbrella term that describes the network architecture cable operators use to future-proof their access networks. This network evolution involves moving various key network functions that are traditionally located at the cable operator’s hub site (or headend) closer to customers’ homes—while also leveraging signal-quality improvements inherent with digital optics and the ubiquity of Ethernet. In addition, closer is better because it reduces the amount of hardware at the headend and creates efficiencies in network speed, reliability, latency and security.
In a nutshell, CableLabs’ DAA technology solutions give cable operators the ability to cost-efficiently redesign their access networks in stages, when and how they see fit. Because all providers’ business objectives are different, CableLabs has designed several DAA approaches they can leverage. Ultimately, it’s all about building a robust 10G network that not only supports the needs of today’s gig consumers but also anticipates tomorrow’s high-rate applications such as holodecks, artificial intelligence (AI), virtual reality (VR) and more.
Let’s take a look at one particular embodiment of DAA, known as Distributed CCAP Architecture (DCA).
How Does Distributed CCAP Architecture Work?
In a traditional HFC network architecture, the operator’s hub—or headend—is connected via fiber to the fiber node in your geographical region. In the fiber node, the optical signal is converted to a radio frequency (RF) signal that travels via a coaxial cable to the cable modem in your home. The key functions responsible for the transmission of data and device access are placed at either end of the operator’s access network—the hub and the modem—like bookends.
In 2015, CableLabs figured out how to split the key DOCSIS network functions into two components: a Media Access Control (MAC) layer that’s responsible for how devices in a network gain access to the network, and a Physical (PHY) layer, a physical component that’s responsible for the transmission and reception of data. Decoupled, these components can now be partially or fully moved from the headend into a fiber node closer to subscribers’ homes, resulting in increased network capacity, greater speeds, lower latency and so on. That’s the basis for DCA.
How Can Distributed CCAP Architecture Help Build Better Networks?
Distributing key DOCSIS network functions out of the headend and closer to subscribers’ homes comes with many benefits. Primarily, it allows operators to:
- Maximize Their Network’s Potential
DCA allows cable operators to take full advantage of the gigabit capabilities of Coherent Optics and DOCSIS 3.1 technology, including Full Duplex DOCSIS and Low Latency DOCSIS. This means their networks will have more than enough bandwidth to support the latest-generation products for years to come.
- Achieve a Better-Quality RF Signal
With distributed architecture, the RF signal that usually originates in the regional hub can now originate in the optical node, closer to the subscriber’s home, thus reducing distortion and creating a more seamless user experience.
- Increase Network Reliability
Because the main functions of the network no longer need to be housed at the headend, the access network can be redesigned so that fewer homes are connected to any single optical node (where the fiber and coax portions of the network meet). This means that if there’s an outage, it will affect fewer customers, ultimately increasing the reliability of the overall network.
- Expand RF Spectrum in the Future
Because DCA solutions are easily customizable and budget-friendly, they provide new opportunities for cable operators to expand their RF spectrum (basically maximizing the capacity of the coax portion of the HFC network) to support future services.
How Does This Technology Affect Me and My Future?
Widespread adoption of DCA, and importantly the superset of capabilities provided by DAA, is essential to creating the 10G future that we’re all looking forward to. And although it might seem that DAA only provides cost-effective solutions for cable companies, ultimately the real beneficiary is you, the customer. By reimagining and reinventing cable access infrastructure, we’re finding greater efficiencies that translate into more powerful networks. These networks will enable a wave of new, innovative services that will transform the way we live, learn, work and play.
Just like DOCSIS technology, Coherent Optics and other technologies that we’ll be covering in our 101 series, DAA is another piece of the puzzle responsible for propelling cable’s HFC networks into the new decade and beyond. Stay tuned for another installment—coming soon!
10G: Enhancing the Power of Human Connection
If 2020 has taught us anything, it’s that connectivity is essential to our wellbeing and happiness. It fosters a sense of belonging—whether it’s to our family, our school, our company or just a random group of like-minded souls. And it’s not so much about the internet or the devices we use—it’s about experiences and staying connected to what matters most. That’s the ultimate goal of 10G.
In the last three decades, cable connection speeds increased from 9600 bps to 1 gig—now available to over 80% of U.S. homes! This has transformed our lives, giving us unparalleled access to the information we need, restructuring the way we conduct our businesses and communicate with others, anytime, anywhere around the world. And still, we’re nowhere near maximizing our networks’ potential. In the near future, 10G networks that are up to 100 times faster than what we have today will open doors to a whole new era of innovation, including autonomous vehicle fleets, holographic media, in-home telehealth solutions, immersive entertainment experiences and much more.
What will that mean for us? Will the seamless inner workings of our networks and smart devices help us lead healthier, happier and more fulfilling lives? Will this technology be able to take care of mundane and time-consuming tasks so we can focus on ourselves and our loved ones? We bet it will! We are now standing on the brink of an exciting new frontier, powered by super-fast, reliable and secure HFC networks.
To see more about what this means for changing people’s connected lives, check out this video:
Latency 101: Getting From There to Here
Welcome back, once again, to the CableLabs 101 series! In our most recent post, we discussed the fiber portion of the hybrid fiber-coax (HFC) network, as well as the coherent optics technology that’s widely considered to be the hyper-capacity future of internet connectivity. Today, we’ll focus on a topic of growing importance for many of the new applications in development—a topic that significantly impacts the user experience even if it’s not well known. That topic is latency.
What Is Latency?
Simply put, latency means delay.
In our post about coherent optics technology, we pointed out how quickly light can travel through a piece of fiber-optic cable: an astonishing 128,000 miles per second. However, as incredibly fast as that is, it still takes time for light to carry information from one point to another.
Imagine for a moment that you’re reading this blog post on a computer in New York City. That would mean you’re about 1,600 miles away from the CableLabs offices here in Colorado. If we assume that the entire network between you and our offices is made of fiber (which is close enough to true for our purposes), it would take a minimum of 0.0125 seconds—or 12.5 milliseconds (12.5 ms)—for the text to travel from our server to your computer.
That’s not a lot of time, but distance is not the only source of delay—and those delays can add up.
For example, to read this post, you had to click a link to view it. When you clicked that link, your computer sent a request to our server asking for the article. That request had to travel all the way to Colorado, which also took the same minimum of 12.5 ms. If you put the two times together, you get a round-trip time (the time it takes to go somewhere and back), which in our case would be a minimum of 25 ms. That’s a longer amount of time, but it’s still pretty small.
Of course, the server can’t respond instantly to your request. It takes a moment for it to respond and provide the correct information. That adds delay as well.
In addition, these messages have to traverse the internet, which is made up of an immense number of network links. Those network links are connected by a router, which routes traffic between those links. Each message has to hop from router to router, using the Internet Protocol to find its way to the correct destination. Some of those network links will be very busy, and others won’t; some will be very fast, and some might be slower. But each hop adds a bit more delay, which can ultimately add up and become noticeable—something you might refer to as lag.
Let’s try a little experiment to illustrate what we’re talking about.
If you’re on a Windows computer, select Start, Programs, Accessories, Command Prompt. Doing so will open up a window in which you can type commands.
First, try typing the following: ping www.google.com
After you hit Enter, you should see some lines of text. At the end of each line will be a “time” in milliseconds (ms). That’s the amount of time it took for a ping request to get from your computer to Google’s server and for a response to come back, or the round-trip latency. Each value is likely different. That’s because each time a ping (or any message) is sent, it has to wait a small but variable amount of time in each router before it’s sent to the next router. This “queuing delay” accumulates hop-by-hop and is caused by your ping message waiting in line with messages from other users that are traversing that same part of the internet.
Next, try typing the following: tracert www.google.com
You should see more lines of text. The first column will show a hop number (the number of hops away that point is), the next three will show times in milliseconds (since it checks the latency three times) and the final column will show the name or the address of the router that’s sending you the message. That will show you the path your request took to get from you to the Google server. You’ll notice that even as close as it is (and as low as your latency might be), it had to hop across a number of routers to get to its destination. That’s how the internet works.
(Note that you might have some fields show up as an asterisk [*]. That’s not a problem. It simply means that the specific device is configured not to respond to those messages.)
If you’re on a Mac, you can do the same thing without needing a command prompt: Just search for an application on your computer called Network Utility. To send a ping in that app, click on the Ping tab, type in www.google.com and click the Ping button. Similarly, to check the route, click on the Traceroute tab, type in the same website name and click the Trace button.
What Is Low Latency?
A term you might have heard is low latency. This term has been getting more and more attention lately. In fact, the mobile industry is touting it as an essential aspect of 5G. But what exactly is low latency, and how does it relate to our definition of latency?
The reality is that there’s no formal definition of what qualifies as low latency. In essence, it simply means that latency is lower than it used to be, or that it’s low enough for a particular application. For example, if you’re watching a streaming video, low latency might mean having the video start in less than a second rather than multiple seconds.
However, if you’re playing an online game (or perhaps using a cloud gaming service), you need the latency to be low enough so that you don’t notice a delay between moving your controller and seeing the resulting movement on your screen. Experiments have shown that anything above about 40ms is easily noticeable, so low latency, in this case, might mean something even lower than that.
How Do We Achieve Low Latency?
Reducing latency requires us to look at the sources of latency and try to figure out ways to reduce it. This can include smarter ways to manage congestion (which can reduce the “queuing delay”) and even changing the way today’s network protocols work.
Reducing latency on cable networks is something CableLabs has been working on for many years—long before it became a talking point for 5G—and we’re always coming up with new innovations to reduce latency and improve network performance. The most recent of these efforts are Low Latency DOCSIS, which can reduce latency for real-time applications such as online gaming and video conferencing, and Low Latency Xhaul, which reduces latency when a DOCSIS network is used to carry mobile traffic.
How Does Low Latency Affect Me and My Future?
Achieving low latency opens the door to do things in near real-time: to talk to friends and family as if they were close by, to interact in online worlds without delays and to simply make online experiences quicker and better. In the long term, when combined with the higher-capacity networks currently in development, low latency opens the door to new technologies like immersive interactive VR experiences and other applications that have not been invented yet.
The future looks fast and fun.
Coherent Optics 101: Coming at You at 0.69c
Welcome back to the CableLabs 101 series! In our previous post, we discussed the basic components of a typical hybrid fiber-coax (HFC) cable network infrastructure and the role of DOCSIS® technology in data transmission over the coaxial portion of the network. Today, we’ll focus on the fiber portion of the HFC network, as well as the coherent optics technology that’s widely considered to be the hyper-capacity future of internet connectivity.
What Is Coherent Optics Technology?
Cable’s HFC networks are “fiber-rich,” which means they’re composed mostly of fiber—a bundle of very thin, hair-like strands of glass or plastic wire. Fiber is light, durable, and most importantly, capable of transmitting a lot of data over very long distances incredibly quickly. Light travels through a vacuum at 186,282 miles per second, a universal constant that scientists denote as “c.” Although light traveling through fiber optic cable moves a little slower than that (69 percent of the speed of light in a vacuum, or 0.69c), it’s still incredibly fast at over 128,000 miles per second. That’s fast enough for a single burst of light to circle the earth more than five times in a single second.
Until recently, signals in a typical HFC network were transmitted over fiber using analog technologies: an electrical radio frequency signal would be converted to an analog optical signal, transmitted over fiber optic cables, and then converted back to an electrical signal at the fiber node. With the advent of Distributed Access Architecture technologies, which will help cable operators cost-effectively add more capacity to their networks, that same fiber is being re-used to carry digital signals rather than analog ones.
The digital fiber technology being deployed today in access networks uses an “on-off keying” approach, in which a transmitter rapidly turns the laser on and off to send a signal; each pulse can signal a single bit of digital information (a 1 or a 0). Coherent optics adds further dimensions to the optical signal to carry more information simultaneously: rather than just pulsing the light on and off, it uses other properties of light (e.g., amplitude, phase and polarization) to carry multiple bits with each burst of information rather than just one bit. That can increase the data-carrying capacity of a single fiber by as much as 70 times, compared with non-coherent technology.
How Has This Technology Evolved?
Coherent optics technology is not new. It’s been used for over 10 years in long-haul fiber networks that span thousands of miles between cities and countries. More recently, as the cost of coherent optics technology has come down and speeds have gone up (from forty to now hundreds of gigabits per second) it has seen growing deployment in metropolitan or regional networks. The one remaining frontier has been the access network—such as in a cable HFC network, which has a large number of relatively short links, requiring a very low-cost solution.
It was for this reason that CableLabs embarked on an effort to define the use of coherent optics for cable access networks: to define requirements specific to access networks, thereby promoting interoperability, scale and competition. All this reduces the cost of this technology to the point at which it could be used widely to grow the capacity of cable operator fiber networks.
This vision was realized with the publication of our initial Point-to-Point (P2P) Coherent Optics specifications (released in June 2018), which defined how to send 100 Gigabits per second (Gbps) on a single wavelength, and how to send up to 48 wavelengths on a single fiber. That was followed by our version 2 specifications (released in March 2019), which defined interoperable operations at 200 Gbps per wavelength, doubling the capacity of the network. And both specifications included support for another key technology called Full Duplex Coherent Optics, which doubles the capacity of each fiber yet again while enabling the cost-effective use of a single fiber rather than the normal fiber pair.
How Does This Technology Affect Me and My Future?
When you think about current technology trends and predictions for the future, you’ll notice a common thread. Future innovations—like holograms, 360° virtual reality (VR), artificial intelligence and so on—will all require super high-capacity, low-latency networks that can transmit a ton of data very, very quickly. We’re not talking about just long-haul networks between cities and countries, but everywhere.
This is why cable companies started investing in the expansion of their fiber infrastructure and fiber optic technology decades ago. By focusing on “fiber deep” architectures—a fancy term for bringing fiber closer to subscribers’ homes—and using technologies such as coherent optics to mine even more bandwidth out of the fiber that we already have in the ground today, we can ensure that our cable networks continue meeting the requirements of current and future innovations. Thanks to those efforts, you’ll be able to one day enjoy your VR chats in “Paris,” work in a “holo-room” and much, much more.
Cable Broadband: From DOCSIS 3.1® to DOCSIS 4.0®
In 1997, CableLabs released the very first version of Data Over Cable Service Interface Specification (DOCSIS ® technology) that enabled broadband internet service over Hybrid Fiber-Coaxial (HFC) networks. Ever since, we’ve been making improvements, greatly enhancing network speed, capacity, latency, reliability and security with every new version. Today, cable operators use DOCSIS 3.1 technologies to make 1 Gbps cable broadband services available to 80% of U.S. homes, easily enabling 4K video, seamless multi-player online gaming, video conferencing and much more. Although there is still a significant runway for DOCSIS 3.1, CableLabs has been hard at work developing the next version – DOCSIS 4.0, which was officially released in March of 2020 and further advances the performance of HFC networks. Let’s take a look.
First, let’s talk about upstream speeds. DOCSIS 4.0 technology will quadruple the upstream capacity of HFC network to 6 Gbps—compared to the 1.5 Gbps that is available with DOCSIS 3.1. While current cable customers still download significantly more data than they upload, upstream data usage is on the rise. In the near future, advanced video collaboration tools, VR and more, will require even more upstream capacity. DOCSIS 4.0 also provides more options for operators to increase downstream speeds, with up to 10 Gbps of capacity. It has been designed to support the widespread availability of symmetric multigigabit speed tiers through full-duplex and extended-spectrum technologies that move us closer to our 10G goal.
In addition to faster speeds, DOCSIS 4.0 will also deliver stronger network security through enhanced authentication and encryption capabilities and more reliability due to the Proactive Network Maintenance (PNM) improvements. It is a great leap toward 10G, setting the stage for a series of subsequent enhancements that will all work together to help us build the future that we always dreamed of.
Testing Bandwidth Usage of Popular Video Conferencing Applications
This year we have seen a shift toward working and learning from home and relying more on our broadband connection. Specifically, most of us use video conferencing for work, school and everyday communications. With that in mind, we looked at how much video conferencing a broadband connection can support.
In the U.S., the Federal Communications Commission (FCC) defines broadband to be a minimum of 25 Mbps downstream and 3 Mbps upstream. So, we started there. The investigation looked at how many simultaneous conferencing sessions can be supported on the access network using popular software including Google Meet, GoToMeeting, and Zoom. The data gathering used typical settings and looked at both upstream and downstream bandwidth usage from and to laptops connected by ethernet cable to a modem connected to a wired broadband connection. To avoid any appearance of endorsement of a particular conferencing application, we have not labeled the figures below with the specific apps under test.
Since this is CableLabs, we used DOCSIS® cable broadband technology. A Technicolor TC8305c gateway was used, which is a DOCSIS 3.0 modem supporting 8 downstream channels and 4 upstream channels. Note that this modem is several years old and not the current DOCSIS 3.1 technology. The modem was connected through the cable access network to a CommScope E6000 cable modem termination system (CMTS).
Laptops used ethernet wired connections to the modem to ensure no variables outside the control of the service provider would impact the speeds delivered, and conferences were set up and parameters varied while traffic flow rates were collected over time. Various laptops were used, running Windows, MacOS and Ubuntu – nothing special, just laptops that were around the lab and available for use.
Most broadband providers over-provision the broadband speeds delivered to customers’ homes – this is for assorted reasons including considering protocol overhead and ensuring headroom in the system to handle unexpected loads. For this testing, the 25/3 service was over-provisioned by 25%, a typical configuration for this service tier.
At a high level, we found that all three conferencing solutions could support at least five concurrent sessions on five separate laptops connected to the same cable modem with the above 25/3 broadband service and with all sessions in gallery view. The quality of all five sessions was good and consistent throughout, with no jitter, choppiness, artifacts, or other defects noticed during the sessions.
This research doesn’t take into account the potential external factors that can affect Internet performance in the home, from the placement of Wi-Fi routers, to building materials, to Wi-Fi interference, to the age and condition of the user’s connected devices, but it does provide a helpful illustration of the baseline capabilities of 25/3 broadband.
The data is presented below where samples were collected every 200 milliseconds using tshark (the Wireshark network analyzer).
Conferencing Application: A
The chart below (Figure 1) shows access network usage for the five concurrent sessions over 300 seconds (five minutes) for one of the above conferencing applications. The blue line is the total downstream usage, and the orange line is total upstream usage. Note that the upstream usage stays below 2 Mbps over the five minutes.
Figure 2 shows the upstream bandwidth usage of the five individual conference sessions where each is below 0.5 Mbps.
Figure 3 shows the downstream bandwidth usage for the five individual conference sessions.
Conferencing Application: B
Figure 4 shows access network usage for five concurrent sessions over 300 seconds (five minutes) for the next conferencing application tested. The blue line is the total downstream usage, and the orange line is total upstream usage. Note that the upstream usage hovers around 3 Mbps as each conference session attempts to use as much upstream bandwidth as possible.
Figure 5 shows the upstream bandwidth usage of the five individual conference sessions where each is below 1 Mbps, though the individual sessions sawtooth up and down as the individual conference sessions compete for more bandwidth. This is normal behavior for applications of this type, and did not have a negative impact on stream quality.
Figure 6 shows the downstream bandwidth usage for the five individual conference sessions.
Conferencing Application: C
Figure 7 shows access network usage for the five concurrent sessions over 300 seconds (five minutes) for the third of the applications tested. The blue line is the total downstream usage, and the orange line is total upstream usage. Note that the total upstream usage hovers around 3 Mbps over the five minutes.
Figure 8 shows the upstream bandwidth usage of the five individual conference sessions where each is below 1 Mbps, though the individual sessions sawtooth up and down as the individual conference sessions compete for more bandwidth. This is normal behavior for applications of this type, and did not have a negative impact on stream quality.
Figure 9 shows the downstream bandwidth usage for the five individual conference sessions. Note the scale of this diagram is different because of higher downstream bandwidth usage.
In summary, each of the video conferencing applications supported at least five concurrent sessions over the 25/3 broadband connection. The focus of this analysis is upstream bandwidth usage, and all three video conferencing technologies manage the upstream usage to fit within the provisioned 3 Mbps broadband speed. For at least two of the conferencing applications, there was also sufficient available downstream speed to run other common applications, such as video streaming and web browsing, concurrently with the five conferencing sessions.
Areas of Future Study
Conferencing services have enhanced modes that allow for higher definition video but that also uses more bandwidth. These modes place additional load on the broadband connection and may reduce the number of simultaneous conferences.
An interesting finding is that upstream bandwidth usage out of a home can depend on how other conference participants choose to view the video. Gallery mode uses lower bit rate thumbnail pictures of participants and is the most efficient for a conference. “Pinning” a speaker’s video can cause higher bandwidth out of a home. In addition, users that purchase add-on cameras that provide higher definition video than the camera included with their laptop may see higher upstream usage.
A “101” on DOCSIS® Technology: The Heart of Cable Broadband
Welcome to the first installment of our CableLabs 101 series about a suite of breakthrough technologies that are instrumental in the path toward the cable industry’s 10G vision—a new era of connectivity that will revolutionize the way we live, work, learn and play. These technologies work together to further expand the capabilities of cable’s hybrid fiber coaxial (HFC) network by increasing connection speeds and capacity, lowering latency and enhancing network reliability and security to meet cable customers’ needs for many years to come.
What Is DOCSIS?
Initially released by CableLabs in 1997, DOCSIS—or Data Over Cable Service Interface Specification—is the technology that enables broadband internet service over an HFC network, now used by hundreds of millions of residential and business customers around the globe. It is essentially the set of specifications that allows different cable industry vendors to design interoperable cable modems (the piece of network equipment that sits in the home) and cable modem termination systems (CMTSs—the network equipment that sits in the cable operator’s hub site). The CMTS is a head-end traffic controller that routes data between the modem in the home and the internet.
DOCSIS technology helped usher in the era of broadband and “always on” internet connections, enabling a wave of innovation that continues to this day. With DOCSIS technology, internet customers were no longer forced to use dial-up solutions that tied up home phone lines and probably caused a significant spike in family feuds. The DOCSIS solution changed everything. Not only did it allow for an “always-on” cable connection (no dial-up required!), it was also significantly faster than dial up. We’ll talk about connection speed—along with capacity, latency and other network performance metrics—and how they affect you a little later in this article.
How Does It Work?
DOCSIS technology governs how data is transmitted over the HFC network. To understand how it works, we need to start with the HFC network—the physical infrastructure that most cable companies use to provide high-speed internet connectivity to their customers. As the name suggests, the HFC network is composed of two parts: the fiber optical network and the coaxial network. HFC networks are predominantly fiber, as illustrated in our recent blog post. The remaining portion of the HFC network is coaxial cable. The coaxial network is connected to the optical fiber network at a “fiber node,” where the (fiber) optical signals are converted to radio frequency electrical signals for transmission over the coaxial network to the subscriber’s home. The HFC network seamlessly transmits data from the CMTS to your cable modem (we call this “downstream” or “download” traffic) or from your modem back to the CMTS (“upstream” or “upload”). In turn, the CMTS is connected to the internet via a set of routers in the service provider’s network.
Think of the HFC network as a “highway” and the data as traffic moving in “lanes” in either direction. In the downstream direction, DOCSIS devices translate the data from the internet into signals carried on the fiber optic portion of the HFC network and then down the coaxial network to your modem. On the upstream, the data that you upload is sent back up the network on a separate upstream “lane.” Traditionally, this “highway” has had more lanes dedicated to the downstream traffic than upstream, which matches current customer traffic patterns. All of this is about to change with the 10G vision, which strives toward symmetrical upstream and downstream service speeds.
How Has This Technology Evolved?
DOCSIS technology has come a long way since 1997. Over the years, it has undergone a few iterations, through versions 1.0, 1.1, 2.0 and 3.0 to 3.1. As DOCSIS has evolved, it has gotten faster by adding more lanes in each direction and it has become more energy-efficient as well. Along the way, several additions to the base technology have been continuously added. These include enabling lower latencies, increased security of the traffic, and tools to make the network more reliable. Today’s cable networks leverage DOCSIS 3.1 technology, which has enabled the widespread availability of 1 Gbps cable broadband services, allowing us to easily enjoy services like 4K video, faster downloads, seamless online gaming and video calls.
DOCSIS 4.0, released in March 2020, is another stepping stone toward that 10G vision. It will quadruple the upstream capacity to 6 Gbps, to match changing data traffic patterns and open doors to even more gigabit services, such as innovative videoconferencing applications and more. DOCSIS 4.0 equipment is still in the process of being developed and is seeing great progress each day toward device certification. Once certification is complete, cable vendors will start mass-producing DOCSIS 4.0-compatible equipment. With the widespread deployment of DOCSIS 4.0 technology, cable operators will have the ability to offer symmetrical multigigabit broadband services over their HFC networks.
How Does This Technology Affect Me and My Future?
All this talk about connection speeds, low latency, reliability and other performance metrics matter to us technologists because it’s how we gauge progress. But it’s so much more than giga-this and giga-that. These metrics will directly impact your future in a real, tangible way.
Over the past two decades, high-speed internet connectivity went from an obscure tech geek novelty to an important part of modern life. We are now streaming in 4K, collaborating on video chat, playing online games with people around the world, driving connected cars and so on. Continuous advancements in DOCSIS technologies are helping make this reality possible by increasing download and upload speeds, lowering latency—or lag—for a more seamless experience, and improving reliability and security to protect our online information.
DOCSIS 4.0 technology will enable symmetrical multigigabit services, ushering in a new wave of innovation across industries and applications, including healthcare, education, entertainment, collaboration technologies, autonomous vehicles and many more. In the near future, we will see advanced health monitoring services, immersive learning and work applications, visually rich VR/AR, holodecks, omnipresent AI assistants and other game-changing innovations that we haven’t even thought of yet. In many ways, the reach and flexibility of cable’s HFC infrastructure is the backbone of our 10G future, and DOCSIS—in combination with other advanced network technologies—is key to helping us reach this Near Future.