Tag Archives: active Ethernet

Designing for Growth

I live in Asheville, North Carolina, where a lot of the neighborhoods like mine have been here for a long time. In fact, most of the houses in my neighborhood were built one hundred years ago – and there are plenty of neighborhoods that are older.

I also live in a city that has been booming over the last decade or two. There have been a lot of new houses built at the fringe of the City and a lot of infill construction where somebody has built a house on almost every vacant lot in the City. Folks are even starting to build houses in what used to be their backyard. I also know of a half dozen multi-dwelling buildings and complexes being built.

This kind of growth means that there is a lot of stress on the existing utilities. Both the electric grid and water system were built for a smaller city, yet each has been expected to somehow accommodate the outward and infill expansion. As you might expect, the over-taxed utilities are showing the strain. There seem to be electrical outages almost every time we have serious rain. We have a few major problems every year with the water system.

Our telecom networks are not immune from growth problems. The Charter cable network clearly has occasional problems. The company never explains problems, but it’s not hard to imagine that there are neighborhoods where the cable network is overloaded due to growth. I also imagine that the Charter network is a hodge-podge of different neighborhoods built over time – it is not one big ubiquitous network but rather a patchwork of smaller networks built in different decades that are all grafted together. That means different generations of coaxial cable, different sizes of cable nodes, and different schemes and designs of taps and amplifiers.

The growth story in Asheville is mild compared to some of the places I’ve lived in my life. In the early 80s, I lived a block outside of the Dallas city limits in Richardson, Texas. At that time, there wasn’t a whole lot in Richardson, which was the outer northern fringe of the suburbs. North of Richardson were places like Plano, which I remember as having a few bars and a rodeo, but which was mostly open country. Today, the Dallas suburbs spread far north of where I used to live forty years ago.

My latest electrical outage made me think about designing fiber networks for growth. There will surely be some fiber networks built with grant funding in rural areas that, over the next fifty years, will be overrun by urban expansion. How easy will it be to expand fiber networks in areas with fast growth?

Passive PON networks are the best at handling growth. The good analogy for thinking of a PON network is to envision one of the many board games that are based upon hexagons. PON technology can handle growth by adding new hexagons as long as the ISP can get enough bandwidth to feed the new neighborhood. A PON network can theoretically handle nearly unlimited growth. If an existing hexagon adds a lot of new homes, it’s just as easy to add new PON core OLTs.

This is not to say that PON networks can’t get into trouble with fast growth. If there had been a PON network in Richardson in the 1980s, there would be a good chance that expansion happened so quickly that there would not have been enough extra fibers in the network to fully handle growth. It’s almost certain that if PON had been in Richardson in the 1980s, there would have been several upgrades to the backbone fiber feeding the neighborhoods to get enough broadband to satisfy customer demand.

Active Ethernet networks have a harder time handling runaway growth. Since there is a last-mile fiber for every customer, it’s not hard to envision adding more homes than existing fiber can handle. There is no real issue expanding active Ethernet into new greenfield neighborhoods, but fast infill growth might mean building new neighborhood fiber at some point.

Not all fiber networks are alike. I know some ISPs today that are building what I consider to be slim fiber networks, meaning a network with a minimum of extra fibers. The chances are that in most rural places this will be okay – but it means a lot of future investment in areas where growth shows up unexpectedly. And that means that it’s going to be important to be served by an ISP that is ready and willing to invest in keeping up with growth. We’ve seen copper and coaxial networks deteriorate when the network owner wouldn’t spend the needed capital.

I am positive that the city planner in Richardson in 1980 did not foresee that Richardson would become a densely populated inner suburb today – or if they did, nobody believed them. Fifty years is a long time, and I’m positive that some of the folks building rural fiber networks will be equally surprised by the growth. But they can make growth easier with some early planning during the original design.

A Strategy for Upgrading GPON

I’ve been asked a lot during 2018 if fiber overbuilders ought to be considering the next generation of PON technology that might replace GPON. They hear about the newer technologies from vendors and the press. For example, Verizon announced a few months ago that they would begin introducing Calix NGPON2 into their fiber network next year. The company did a test using the technology recently in Tampa and achieved 8 Gbps speeds. AT&T has been evaluating the other alternate technology, XGS-PON, and may be introducing it into their network in 2019.

Before anybody invests a lot of money in a GPON network it’s a good idea to always ask if there are better alternatives – as should be done for every technology deployed in the network.

One thing to consider is how Verizon plans on using NGPON2. They view this as the least expensive way to deliver bandwidth to a 5G network that consists of multiple small cells mounted on poles. They like PON technology because it accommodates multiple end-points using a single last-mile fiber, meaning a less fiber-rich network than with other 10-gigabit technologies. Verizon also recently began the huge task of consolidating their numerous networks and PON gives them a way to consolidate multi-gigabit connections of all sorts onto a single platform.

Very few of my clients operate networks that have a huge number of 10-gigabit local end points. Anybody that does should consider Verizon’s decision because NGPON2 is an interesting and elegant solution for handling multiple large customer nodes while also reducing the quantity of lit fibers in the network.

Most clients I work with operate PON networks to serve a mix of residential and business customers. The first question I always ask them is if a new technology will solve an existing problem in their network. Is there anything that a new technology can do that GPON can’t do? Are my clients seeing congestion in neighborhood nodes that are overwhelming their GPON network?

Occasionally I’ve been told that they want to provide faster connections to a handful of customers for which the PON network is not sufficient – they might want to offer dedicated gigabit or larger connections to large businesses, cell sites or schools. We’ve always recommended that clients design networks with the capability of large Ethernet connections external to the PON network. There are numerous affordable technologies for delivering a 10-gigabit pipe directly to a customer with active Ethernet. It seems like overkill to consider upgrading the electronics to all customers to satisfy the need of a few large customers rather than overlaying a second technology into the network. We’ve always recommended that networks have some extra fiber pairs in every neighborhood exactly for this purpose.

I’ve not yet heard an ISP tell me that they are overloading a residential PON network due to customer data volumes. This is not surprising. GPON was introduced just over a decade ago, and at that time the big ISPs offered speeds in the range of 25 Mbps to customers. GPON delivers 2.4 gigabits to up to 32 homes and can easily support residential gigabit service. At the time of introduction GPON was at least a forty-times increase in customer capacity compared to DSL and cable modems – a gigantic leap forward in capability. It takes a long time for consumer household usage to grow to fill that much new capacity. The next biggest leap forward we’ve seen was the leap from dial-up to 1 Mbps DSL – a 17-times increase in capacity.

Even if somebody starts reaching capacity on a GPON there are some inexpensive upgrades that are far less expensive than upgrading to a new technology. A GPON network won’t reach capacity evenly and would see it in some neighborhood nodes first. The capacity in a neighborhood GPON node can easily be doubled by cutting the size of the node in half by splitting it to two PONs. I have one client that did the math and said that as long as they can buy GPON equipment they would upgrade by splitting a few times – from 32 to 16 homes and from 16 homes to 8 homes, and maybe even from 8 to 4 customers before they’d consider tearing out GPON for something new. Each such split doubles capacity and splitting nodes three times would be an 8-fold increase in capacity. If we continue on the path of seeing household bandwidth demand double every three years, then splitting nods twice would easily add more than another decade to the life of a PON network. In doing that math it’s important to understand that splitting a node actually more than doubles capacity because it also decreases the oversubscription factor for each customer on the node.

AT CCG we’ve always prided ourselves on being technology neutral and vendor neutral. We think network providers should use the technology that most affordably fits the needs of their end users. We rarely see a residential fiber network where GPON is not the clear winner from a cost and performance perspective. We have clients using numerous active Ethernet technologies that are aimed at serving large businesses or for long-haul transport. But we are always open-minded and would easily recommend NGPON2 or XGS-PON if it is the best solution. We just have not yet seen a network where the new technology is the clear winner.