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.
Gearing Up for 10G: Download the Technical Brief on CableLabs’ Low Latency Technologies for DOCSIS Networks
If you’ve been following our blog and our recent 10G announcement, you know that one of the main areas of focus for us is latency. Achieving a near-zero latency on DOCSIS networks is one of the goals of the 10G initiative and is just as important as increasing speed or bandwidth. The success of future 10G networks that can support seamless communication and next-level interactive experiences like holodecks and 360° video is heavily dependent on finding technological solutions that decrease latency to imperceptible levels, delivering consistent, real-time responsiveness that our customers desire.
The good news is we are well on our way to getting there. So far we’ve released a number of specifications, including Low Latency DOCSIS (LLD) and Low Latency Mobile Xhaul (LLX), aimed at reducing latency in the DOCSIS networks that provide residential services and also serve as backhaul, midhaul and fronthaul (collectively known as xhaul) for mobile traffic.
Low Latency DOCSIS (LLD)
In modern households, there are often multiple applications and devices connected to the same network at the same time, sending and receiving a variety of traffic. Some, like streaming video and large file downloads, send repeated large bursts of data and expect the network to buffer and play-out those bursts, while others, like online gaming and voice chat, send traffic smoothly. Ordinarily, the traffic from the smooth senders is subjected to the widely varying buffering latency caused by the bursty senders. LLD technology is optimized for these two different types of traffic behavior, and decreases delays for smooth sending applications (many of which are latency-sensitive) without affecting the other traffic. Low Latency DOCSIS technology can support a consistent sub-1ms latency round-trip for the smooth sending applications, resulting in a much better network performance overall.
Low Latency Mobile Xhaul (LLX)
LLX leverages collaboration between the mobile network scheduler and the DOCSIS scheduler to provide a low latency xhaul solution that achieves a consistent DOCSIS upstream delay of just 1 to 2 milliseconds. LLX also defines a common quality of service framework for both mobile and DOCSIS so that the relative priorities of different traffic streams are maintained across the two systems. In the foreseeable future, deploying LLX technology will help solidify DOCSIS cable networks as the xhaul transport of choice, capable of supporting the latency requirements of 5G and beyond.
For more detail, please download the following member-only technical brief on Low Latency Technologies for DOCSIS Networks which includes information about sources of latency, how we address them, implementation strategies and more.
If you’re not yet a CableLabs member, find out how you can become one here.
Moving Beyond Cloud Computing to Edge Computing
In the era of cloud computing—a predecessor of edge computing—we’re immersed with social networking sites, online content and other online services giving us access to data from anywhere at any time. However, next-generation applications focused on machine-to-machine interaction with concepts like internet of things (IoT), machine learning and artificial intelligence (AI) will transition the focus to “edge computing” which, in many ways, is the anti-cloud.
Edge computing is where we bring the power of cloud computing closer to the customer premises at the network edge to compute, analyze and make decisions in real time. The goal of moving closer to the network edge—that is, within miles of the customer premises—is to boost the performance of the network, enhance the reliability of services and reduce the cost of moving data computation to distant servers, thereby mitigating bandwidth and latency issues.
The Need for Edge Computing
The growth of the wireless industry and new technology implementations over the past two decades has seen a rapid migration from on-premise data centers to cloud servers. However, with the increasing number of Industrial Internet of Things (IIoT) applications and devices, performing computation at either data centers or cloud servers may not be an efficient approach. Cloud computing requires significant bandwidth to move the data from the customer premises to the cloud and back, further increasing latency. With stringent latency requirements for IIoT applications and devices requiring real-time computation, the computing capabilities need to be at the edge—closer to the source of data generation.
What Is Edge Computing?
The word “edge” precisely relates to the geographic distribution of network resources. Edge computation enables the ability to perform data computation close to the data source instead of going through multiple hops and relying on the cloud network to perform computing and relay the data back. Does this mean we don’t need the cloud network anymore? No, but it means that instead of data traversing through the cloud, the cloud is now closer to the source generating the data.
Edge computing refers to sensing, collecting and analyzing data at the source of data generation, and not necessarily at a centralized computing environment such as a data center. Edge computing uses digital devices, often placed at different locations, to transmit the data in real time or later to a central data repository. Edge computing is the ability to use distributed infrastructure as a shared resource, as the figure below shows.
Edge computing is an emerging technology that will play an important role in pushing the frontier of data computation to the logical extremes of a network.
Key Drivers of Edge Computing:
- Plummeting cost of computing elements
- Smart and intelligent computing abilities in IIoT devices
- A rise in the number of IIoT devices and ever-growing demand for data
- Technology enhancements with machine learning, artificial intelligence and analytics
Benefits of Edge Computing
Computational speed and real-time delivery are the most important features of edge computing, allowing data to be processed at the edge of network. The benefits of edge computing manifest in these areas:
Moving data computing to the edge reduces latency. Latency without edge computing—when data needs to be computed at a server located far from the customer premises—varies depending on available bandwidth and server location. With edge computing, data does not have to traverse over a network to a distant server or cloud for processing, which is ideal for situations where latencies of milliseconds can be untenable. With data computing performed at the network edge, the messaging between the distant server and edge devices is reduced, decreasing the delay in processing the data.
Pushing processing to edge devices, instead of streaming data to the cloud for processing, decreases the need for high bandwidth while increasing response times. Bandwidth is a key and scarce resource, so decreasing network loading with higher bandwidth requirements can help with better spectrum utilization.
From a certain perspective, edge computing provides better security because data does not traverse over a network, instead staying close to the edge devices where it is generated. The less data computed at servers located away from the source or cloud environments, the less the vulnerability. Another perspective is that edge computing is less secure because the edge devices themselves can be vulnerable, putting the onus on operators to provide high security on the edge devices.
What Is Multi-Access Edge Computing (MEC)?
MEC enables cloud computing at the edge of the cellular network with ultra-low latency. It allows running applications and processing data traffic closer to the cellular customer, reducing latency and network congestion. Computing data closer to the edge of the cellular network enables real-time analysis for providing time-sensitive response—essential across many industry sectors, including health care, telecommunications, finance and so on. Implementing distributed architectures and moving user plane traffic closer to the edge by supporting MEC use cases is an integral part of the 5G evolution.
Edge Computing Standardization
Various groups in the open source and standardization ecosystem are actively looking into ways to ensure interoperability and smooth integration of incorporating edge computing elements. These groups include:
- The Edge Computing Group
- CableLabs SNAPS programs, including SNAPS-Kubernetes and SNAPS-OpenStack
- OpenStack’s StarlingX
- Linux Foundation Networking’s OPNFV, ONAP
- Cloud Native Compute Foundation’s Kubernetes
- Linux Foundation’s Edge Organization
How Can Edge Computing Benefit Operators?
- Dynamic, real-time and fast data computing closer to edge devices
- Cost reduction with fewer cloud computational servers
- Spectral efficiency with lower latency
- Faster traffic delivery with increased quality of experience (QoE)
The adoption of edge computing has been rapid, with increases in IIoT applications and devices, thanks to myriad benefits in terms of latency, bandwidth and security. Although it’s ideal for IIoT, edge computing can help any applications that might benefit from latency reduction and efficient network utilization by minimizing the computational load on the network to carry the data back and forth.
Evolving wireless technology has enabled organizations to use faster and accurate data computing at the edge. Edge computing offers benefits to wireless operators by enabling faster decision making and lowering costs without the need for data to traverse through the cloud network. Edge computation enables wireless operators to place computing power and storage capabilities directly at the edge of the network. As 5G evolves and we move toward a connected ecosystem, wireless operators are challenged to maintain the status quo of operating 4G along with 5G enhancements such as edge computing, NFV and SDN. The success of edge computing cannot be predicted (the technology is still in its infancy), but the benefits might provide wireless operators with critical competitive advantage in the future.
How Can CableLabs Help?
CableLabs is a leading contributor to European Telecommunication Standards Institute NFV Industry Specification Group (ETSI NFV ISG). Our SNAPS™ program is part of Open Platform for NFV (OPNFV). We have written the OpenStack API abstraction library and contributed it to the OPNFV project at the Linux Foundation—“SNAPS-OO”—and leverage object oriented software development practices to automate and validate applications on OpenStack. We also added Kubernetes support with SNAPS-Kubernetes, introducing a Kubernetes stack to provide CableLabs members with open source software platforms. SNAPS-Kubernetes is a certified CNCF Kubernetes installer that is targeted at lightweight edge platforms and scalable with the ability to efficiently manage failovers and software updates. SNAPS-Kubernetes is optimized and tailored to address the need of the cable industry and general edge platforms. Edge computing on Kubernetes is emerging as a powerful way to share, distribute and manage data on a massive scale in ways that cloud, or on-premise deployments cannot necessarily provide.
5G — The Beginning of an Exhilarating Journey
“5G” is the next step for the evolution of wireless technology beyond “4G-LTE” with the 2018 and 2020 Olympics acting as powerful Incentives for vendors to accelerate their product development.
A few weeks ago, I travelled to San Francisco to chair a session at the new IEEE SDN-NFV conference and to participate in a panel session at the IEEE 5G Summit taking place in Silicon Valley that same week. I have long been convinced that NFV and SDN would be key enabling technologies for 5G. My panel role was to talk about how the international standards effort around NFV and SDN would support innovation in the 5G space.
In the weeks preceding the conference, Verizon had announced plans for “5G” field tests. As a consequence, demand to attend the 5G Summit was much greater than the organizers had originally anticipated resulting in the event shifting to a larger venue. There was a capacity crowd of greater than 300 academic and industry researchers along with a sprinkling of business development types.
Industry initiatives to define the target for 5G have identified eight key requirements for the technology:
- 1-10Gbps connections to end points
- 1ms end-to-end round trip delay (latency)
- 1000x bandwidth per unit area
- 10-100x number of connected devices
- Perception of 99.999% availability
- Perception of 100% coverage
- 90% reduction in network energy usage
- 10-year battery life for low power devices
We have all seen the impact that broadband connectivity combined with smart devices has had on our lives. Imagine the possibilities if this ambitious target could be realized!
Innovation in a 5G World
As the conference progressed, I became more and more excited about the innovation possibilities in a 5G-enabled world. There were a number of very informative presentations during the day, but the talk that made the most impact on me was the keynote by Professor Gerhard Fettweiss from the 5G Lab. I was floored by his vision for a “Tactile Internet” illustrated with powerful video demonstrations that showed if network latency (round trip delay) could be reduced below 10ms, the potential for machine to machine and human to machine interactions would become limitless. A surgeon undertaking remote surgery was one example, self-driving vehicles with real-time network assisted object tracking another. Of course safeguards would need to be in place to deal with loss of connectivity or faults, but you get the idea.
I am convinced the “Tactile Internet” will spawn a myriad of applications in every field of human endeavor. Many of which we cannot even conceive of yet. However a fellow delegate remarked that he didn’t think Gerhard’s vision would be realized any time soon. In my view he missed the point - a compelling vision is the critical first step for any new ecosystem to get started and I am sure that key elements of the tactile internet vision will be realized sooner than people think. The enabling technologies exist today. They just need to be brought together in the right way with standards that facilitate open innovation.
Other keynotes including those from AT&T and Google reinforced my impression that we are on the cusp of an unprecedented era of innovation driven by low latency, high bandwidth wireless connectivity embodied in what is being termed “5G” — but having far greater implications than simply wireless connectivity.
Back to reality and my panel, which was the final event of the conference. We were challenged with answering the imponderable question “what is 5G”. None of us was able to come up with an answer that satisfied the moderator since 5G is a far richer vision than simply an increase in wireless bandwidth or a 5G icon appearing on a smartphone handset.
What CableLabs is doing in this Space
The cable network will provide an ideal foundation for 5G because it is ubiquitous and already supports millions of Wi-Fi nodes in places where the majority of wireless data is consumed. It has high capacity for both Access and Backhaul. It is highly reliable and has low intrinsic latency because it is based on optical fiber which penetrates deep into the access network feeding wideband coaxial cables reaching all the way to the end-user premises. Moreover, it is a multi-node remotely powered access topology ideally suited to support the connection of the large number of small cells close to homes and businesses that will be needed for 5G.
A multi-faceted CableLabs R&D program is addressing the key technologies required for 5G. For example, we are developing end-to-end architectures based on SDN and NFV technologies that will provide the efficiencies and resource flexibility and adaptability required for 5G. We are studying the co-existence of wireless technologies and we have joined with leading industry organizations such as NYU WIRELESS to evaluate how spectrum in the millimeter wave region combined with the cable network will provide an economical foundation for 5G. CableLabs participated in the recent 3GPP RAN 5G Workshop where we outlined the CableLabs vision for converged broadband and wireless networks.
It is exhilarating to think that the 5G journey is only just beginning and it is going to be incredibly exciting because we will be visualizing how to architect a dynamically configurable 5G network based on the existing cable network and bringing it all together to serve the needs of cable operators and their customers world-wide.
Watch this space for blogs from my CableLabs wireless colleagues, and consider attending our new Inform[ed]: Wireless conference in New York in April.
Don Clarke is a Principal Architect at CableLabs working in the Virtualization and Network Evolution group.
Tuesday, April 13, 2016
8:30am to 6:00pm
New York City