Tag: jitter

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Technology

Is Jitter the Problem?

Most people assume that when they have broadband issues they don’t have fast enough broadband speeds. But in many cases, problems are caused by high jitter and latency. Today, I’m looking at the impact of  jitter.

What is Jitter? Jitter happens when incoming data packets are delayed and don’t show up at the expected time or in the expected order. When data is transmitted over the Internet it is broken into small packets. A typical packet is approximately 1,000 bytes or 0.001 megabytes. This means a lot of packets are sent to your home computer for even basic web transactions.

Packets are created at the location originates a web signal. This might be a site that is streaming a video, sending a file, completing a voice over IP call, or letting you shop online. The packets are sent in the order that the original data stream is encoded. Each packet takes a separate path across the Internet. Some packets arrive quickly, while others are delayed for some reason. Measuring jitter means measuring the degree to which packets end up at your computer late or in the wrong order.

Why Does Jitter Matter? Jitter matters the most when you are receiving packets for a real-time transaction like a streaming video, a Zoom call, a voice over IP call, or a video connection with a classroom. Your home computer is going to do its best to deliver the transmissions on time, even if all the packets haven’t arrived. You’ll notice missing packets of data as pixelation or fuzziness in a video, or as poor sound quality on a voice call. If enough packets are late, you might drop a VoIP call or get kicked out of a Zoom session.

Jitter doesn’t matter as much for other kinds of data. Most people are not concerned if it takes slightly longer to download a data file or to receive an email. These transactions don’t show up as received on your computer until all (or mostly all) of the packets have been received.

What Causes Jitter? The primary cause of jitter is network congestion. This happens when places in the network between the sender and the receiver are sent more data packets than can be processed in real time.

Bandwidth constraints can occur anywhere in a network where there is a possibility of overloading the capacity of the electronics. The industry uses the word chokepoint to describe any place where data can be restricted. On an incoming data transmission, an ISP might not have enough bandwidth on the incoming backbone connection. Every piece of ISP network gear that routes traffic within an ISP network is a potential chokepoint – a common chokepoint is where data is handed off to a neighborhood. The final chokepoint is at the home if data is coming in faster than the home broadband connection can handle it.

A common cause of overloaded chokepoints is old or inadequate hardware. An ISP might have outdated or too-small switches in the network. The most common chokepoints at homes are outdated WiFi modems or older computers that can’t handle the volume of incoming data.

One of the biggest problems with network chokepoints is that any time that an electronics chokepoint gets too busy, packets can be dropped or lost. When that happens, your home computer or your ISP will request the missing packets be sent again. The higher the jitter, the more packets that are lost and must be sent multiple times, and the greater the total amount of data being sent through the network. With older and slower technologies like DSL, the network can get paralyzed if failed packets accumulate to the point of overwhelming the technology.

Contrary to popular belief, faster speeds don’t reduce jitter, and can actually increase it. If you have an old inadequate WiFi modem and upgrade to a faster technology like fiber, the WiFi model will be even more overwhelmed than it was with a slower bandwidth technology. The best solution to lowering jitter is for ISPs and customers to replace equipment that causes chokepoints. Fiber technology isn’t better just because it’s faster – it also includes technology that move packets quickly through chokepoints.

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The Industry

What We’ve Learned About Upload Bandwidth

Until the pandemic hit, I rarely thought about upload bandwidth. I mostly used upload bandwidth to send files to people, and I rarely cared if they received the files immediately – I was happy as long as files got sent. But the pandemic changed everything for millions of people. All of a sudden, homes were unable to function well due to problems with uploading.

The big change from the pandemic came when many millions of people were sent home to work while students were sent home to attend school remotely. It turns out that connecting to schools and offices requires steady and reliable upload bandwidth, and many homes found they didn’t have that. My consulting firm has done several surveys per month during the pandemic, and we routinely have seen that at least 30% of those working or schooling from home, including those using cable company broadband, say that their bandwidth was not adequate for the needs created by the pandemic. Homes that tried to accommodate multiple people working online at the same time had the worst experiences.

We also changed a lot of other behavior during the pandemic that uses more upload bandwidth. Many who work from home started using software that automatically saves all work in the cloud. We started using collaborative software to connect to others working from home. And we began making Zoom calls to such an extent that this is now the largest use of upload broadband nationwide and has grown from practically nothing to consume over 15% of all upload broadband usage. Spending more time at home led millions to take up gaming – an activity that just started transitioning to the cloud before the pandemic.

We also got a stark reminder that broadband technologies are shared services. We saw that even homes with only one person working at home could suffer if the bandwidth for the whole neighborhood got bogged down from overuse.

It seems that everybody started collecting speed tests to figure out what was going wrong. Local governments, States, and the NTIA started gathering and looking at speed test results. We know that an individual speed test result is not reliable, but we’ve seen that masses of speed tests tell a great story about a given ISP in a given community.

We also learned that broadband networks vary by neighborhood – something that I don’t recall ever being discussed before the pandemic. Speed tests often showed that the performance of a cable company in a city could be drastically different by neighborhood. There have always been those who complained about cable company broadband, but they weren’t taken seriously by those in the same town that had adequate broadband. But we now often see some parts of cities with speeds drastically lower than the rest of the city – something cable companies have known about but never fixed.

We learned how awful rural broadband technologies can be when most rural folks had problems working and schooling from home. We figured this out when speed tests showed that rural upload speeds are often less than 1 Mbps.

Lately, I’ve been learning more about jitter, which measures the variance in broadband signal strength. Many people learned about jitter the hard way when they often got booted from school connections or Zoom calls when broadband signal strength fluctuated and hit a low point.

We also learned how the cable companies use the worst spectrum on a cable system to transmit upload speeds. They use spectrum inside the coaxial cables to transmit data, and the portion of the network used for upload is where natural interference from microwave ovens, small engines, and natural background radiation causes the most interference.

We’ve also learned that the pandemic has been good for the ISPs, although they aren’t talking about it. Millions of homes upgraded to faster broadband to try to get enough bandwidth during the pandemic. Unfortunately for many of them, their problem was not the download speeds, but the upload speeds, and the upgrade may not have brought much of a solution.

Categories
Technology

Jitter – A Measure of Broadband Quality

Most people have heard of latency, which is a measure of the average delay of data packets on a network. There is another important measure of network quality that is rarely talked about. Jitter is the variance in the delays of signals being delivered through a broadband network connection. Jitter occurs when the latency increases or decreases over time.

We have a tendency in the industry to oversimplify technical issues. We take a speed test and assume the answer that pops out is our speed. Those same speed tests also measure latency, and even network engineers sometimes get mentally lazy and are satisfied to see an expected latency number on a network test. But in reality, the broadband signal coming into your home is incredibly erratic. From millisecond to millisecond, the amount of data hitting your home network varies widely. Measuring jitter means measuring the degree of network chaos.

Jitter increases when networks get overwhelmed, even temporarily. Delays are caused in any network when the amount of data being delivered exceeds what can be accepted. There are a few common causes of increased jitter:

·         Not Enough Bandwidth. Low bandwidth connections experience increased jitter when incoming packets exceed the capacity of the broadband connection. This effect can cascade and multiply when the network is overwhelmed – being overly busy increases jitter, and the worse jitter then makes it even harder to receive incoming packets.

·         Hardware Limitations. Networks can bog down when outdated routers, switches, or modems can’t fully handle the volume of packets. Even issues like old or faulty cabling can cause delays and increase jitter.

·         Network Handoffs. Any network bottlenecks are the most vulnerable point in the network. The most common bottleneck in all of our homes is the device that converts landline broadband into WiFi. Even a slight hiccup at a bottleneck will negatively impact performance in the entire network.

All of these factors help to explain why old technology like DSL performs even worse than might be expected. Consider a home that has a 15 Mbps download connection on DSL. If an ISP were to instead deliver a 15 Mbps connection on fiber, the same customer would see a significant improvement. A fiber connection would avoid the jitter issues caused by antiquated DSL hardware. We tend to focus on speeds, but a 100 Mbps connection on a fiber network will typically have a lot less jitter than a 100 Mbps connection on a cable company network. Customers who try a fiber connection for the first time commonly say that the network ‘feels’ faster – what they are noticing is the reduced jitter.

Jitter can be deadliest to real-time connections – most people aren’t concerned about jitter if means it takes a little longer to download a file. But increased jitter can play havoc with an important Zoom call or with maintaining a TV signal during a big sports event. It’s easiest to notice jitter when a real-time function hesitates or fails. Your home might have plenty of download bandwidth, and yet broadband connections still fail because small problems caused by jitter can accumulate to make the connection fail.

ISPs have techniques that can help to control jitter. One of the more interesting ones is to use a jitter buffer that grabs and holds data packets that arrive too quickly. It may not feel intuitive that slowing a network can improve quality. But recall that jitter is caused when there is a time delay between different packets in the same transmission. There is no way to make the slowest packets arrive any sooner – so slowing down the fastest ones increases the chance that Zoom call packets can be delivered evenly.

Fully understanding the causes of jitter in any specific network is a challenge because the causes can be subtle. It’s often hard to pinpoint a jitter problem because it can be here one millisecond and gone the next. But it’s something we should be discussing more. A lot of the complaints people have about their broadband connection are caused by too-high jitter.

Categories
The Industry

The Reality of Rural Broadband

I recently saw the results of several rural surveys that probably tell the best story about the state of rural broadband. The two areas being studied are far apart geographically, but they are similar in many ways. The areas are both rural and are not near to a metropolitan area. The areas have some modest manufacturing and some modest amount of tourism, but neither in a big way. Both areas included some small towns, and a few of these towns have cable TV. And in both places, the customers in the rural area have poor broadband choices. These are not small isolated pockets of people, and the two surveys cover nearly 20,000 homes.

If you listen to FCC rhetoric it’s easy to think that rural broadband is improving – but in areas like these you can’t see it. These areas have both were supposed to get some upgrades from CAF II – but from what the locals tell me there have been zero improvements so far. The CAF program still has a few years to go, so perhaps there will be some modest improvement in rural DSL.

For now, the broadband situation in these areas is miserable. There are homes with DSL with speeds of a few Mbps at best, with some of the worst speeds hovering at dial-up speeds. One respondent to a survey reported that it took 8 hours to download a copy of Microsoft Office online.

The other broadband choices are also meager. Some people use satellite broadband but complain about the latency and about the small data caps. These areas both have a smattering of fixed wireless broadband – but this is not the modern fixed wireless you see today in the open plains states that delivers 25 Mbps or faster broadband. Both of the areas in the surveys are heavily wooded with hilly terrain, and fixed wireless customers report seeing speeds of 1-2 Mbps. There are a number of homes using their cell phones in lieu of home broadband – an expensive alternative if there are school kids or if any video is watched. There were customers who reported using public hotspots in nearby small towns. And there were a number of households, included many with school kids who have given up and who have no broadband – because nothing they’ve tried has worked.

As would be expected in rural areas, slow speeds are not the only problem. Even homes that report data speeds that should support streaming video complain that streaming doesn’t work. This indicates networks with problems and it’s likely the networks have high latency, are full of jitter, or are over-subscribed and have a lot of packet loss. People don’t really judge the quality of their broadband connection by the speed they get on a speed test, but instead by the ability to do normally expected activities on the Internet.

Many of these homes can’t do things that the rest of us take for granted. Many report the inability to stream video – even a single stream. This is perhaps the biggest fallacy in the way the FCC measures broadband, because they expect that a house getting a speed like 5 Mbps ought to be able to do most needed tasks. In real life the quality of many rural connections are so poor that they won’t stream video. Many people in these areas also complained that their Internet often froze and they had to constantly reboot – something that can kill large downloads or kill online sessions for school or work.

One of the biggest complaints in these areas was that their network only supported one device at a time, meaning that members of the family have to take turns using the Internet. I picture a family with a few school kids and can see how miserable that must be.

The surveys produced a long list of other ways that poor broadband was hurting households. Number one was the inability of people to work at home. Many people said they could work at home more often if they had broadband. A few respondents want to start home businesses but are unable to because of the poor broadband. Another common complaint was the inability for kids to do schoolwork, or for adults to pursue college degrees on line.

The problems many people reported were even more fundamental than these issues. For instance, there were households saying that they could not maintain a good enough connection to bank online or pay their bills online. There were respondents who say they can’t shop online. Many households complained that they couldn’t offload cellular data at home to WiFi, driving up their cellular bills. A number of homes would like to cut the cord to save money but can’t stream Netflix as an alternative to cable.

When you look the raw data behind these kinds of surveys you quickly see the real issues with lack of broadband. In today’s society, not having home broadband literally takes a home out of the mainstream of society. It’s one thing to look at the national statistics and be told that the number of homes without broadband is shrinking. But it’s an entirely different story when you see what that means for the millions of homes that still don’t have adequate broadband. My guess is that some of the areas covered by these surveys show as underserved on the FCC maps – when in fact, their broadband is so poor that they are clearly unserved, ignored and forgotten.

Categories
The Industry

Verizon’s Case for 5G, Part 3

Ronan Dunne, an EVP and President of Verizon Wireless recently made Verizon’s case for aggressively pursuing 5G. In this blog I want to examine the two claims based upon improved latency – gaming and stock trading.

The 5G specification sets a goal of zero latency for the connection from the wireless device to the cellular tower. We’ll have to wait to see if that can be achieved, but obviously the many engineers that worked on the 5G specification think it’s possible. It makes sense from a physics perspective – a connection of a radio signal through air travels for all practical purposes at the speed of light (there is a miniscule amount of slowing from interaction with air molecules). This makes a signal through the air slightly faster than one through fiber since light slows down when passing through fiberglass by 0.83 milliseconds for every hundred miles of fiber optic cable traversed.

This means that a 5G signal will have a slight latency advantage over FTTP – for the first few connection from a customer. However, a 5G wireless signal almost immediately hits a fiber network at a tower or small cell site in a neighborhood, and from that point forward the 5G signal experiences the same latency as an all-fiber connection.

Most of the latency in a fiber network comes from devices that process the data – routers, switches and repeaters. Each such device in a network adds some delay to the signal – and that starts with the first device, be it a cellphone or a computer. In practical terms, when comparing 5G and FTTP the network with the fewest hops and fewest devices between a customer and the internet will have the lowest latency – a 5G network might or might not be faster than an FTTP network in the same neighborhood.

5G does have a latency advantage over non-fiber technologies, but it ought to be about the same advantage enjoyed by FTTP network. Most FTTP networks have latency in the 10-millisecond range (one hundredth of a second). Cable HFC networks have latency in the range of 25-30 ms; DSL latency ranges from 40-70 ms; satellite broadband connections from 100-500 ms.

Verizon’s claim for improving the gaming or stock trading connection also implies that the 5G network will have superior overall performance. That brings in another factor which we generally call jitter. Jitter is the overall interference in a network that is caused by congestion. Any network can have high or low jitter depending upon the amount of traffic the operator is trying to shove through it. A network that is oversubscribed with too many end users will have higher jitter and will slow down – this is true for all technologies. I’ve had clients with first generation BPON fiber networks that had huge amounts of jitter before they upgraded to new FTTP technology, so fiber (or 5G) alone doesn’t mean superior performance.

The bottom line is that a 5G network might or might not have an overall advantage compared to a fiber network in the same neighborhood. The 5G network might have a slight advantage on the first connection from the end user, but that also assumes that cellphones are more efficient than PCs. From that point forward, the network with the fewest hops to the Internet as well the network with the least amount of congestion will be faster – and that will be case by case, neighborhood by neighborhood when comparing 5G and FTTP.

Verizon is claiming that the improved latency will improve gaming and stock trading. That’s certainly true where 5G competes against a cable company network. But any trader that really cares about making a trade a millisecond faster is already going to be on a fiber connection, and probably one that sits close to a major internet POP. Such traders are engaging in computerized trading where a person is not intervening in the trade decision. For any stock trades that involve humans, a extra few thousandths of a second in executing a trade is irrelevant since the human decision process is far slower than that (for someone like me these decisions can be measured in weeks!).

Gaming is more interesting. I see Verizon’s advantage for gaming in making game devices mobile. If 5G broadband is affordable (not a given) then a 5G connection allows a game box to be used anywhere there is power. I think that will be a huge hit with the mostly-younger gaming community. And, since most homes buy broadband from the cable company, lower latency with 5G ought to be to a gamer using a cable network, assuming the 5G network has adequate upload speeds and low jitter. Gamers who want a fiber-like experience will likely pony up for a 5G gaming connection if it’s priced right.

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