Welcome!

Blog Feed Post

What is 25 Gigabit Ethernet and why would you want it?

In the past few weeks you may have seen several press releases and articles talking about 25 Gbit Ethernet. Just when you got used to ethernet speeds being a nice decimal based system where we simply add zeros every few years, someone threw in 40GbE a few years ago. And that’s ok, powers of two we can deal with, but 25? That just does not fit in our mental model of Ethernet.

SerDes

The driving force behind 25GbE Ethernet is actually fairly simple and straightforward. If you open up an ethernet switch (small, large, does not really matter), you will find that all the high speed components are connected using serial links called SerDes, the rather boring concatenation of SERializer and DESerializer. The serializer is a piece of logic that takes data to be transferred and serializes it, the deserializer sits on the receiving side and reconstructs the serial stream of bits back into data for the ultimate receiver. Between the two, there are some basic encoding mechanisms to keep their clocks synchronized, some basic framing and a few other things. Google for 64B/66B encoding if you really want to understand the gory details.

Gigabit and 10Gigabit ethernet runs over these SerDes connections between components. In a typical 10GbE Top of Rack like switch, the Ethernet switching chip (everyone has heard of Trident2 as the market leading chipset in use today), the actual ethernet ports are SerDes connections coming from the chip (128 of them for Trident2, each representing a 10GbE equivalent port). These connections are then used to connect to other Ethernet of fabric chips (in the case of chassis based systems), or directly to the cages SFP+ and QSFP optics plug into. Communication between an SFP+ in the front of the switch and the switching chip runs on top of one of these SerDes connections.

As you probably figured out, the components used in today’s switches all run SerDes with a clock rate around 12.5Ghz, providing that 10Gbit transfer rate between the components across each (allowing for the encoding overhead). Until recently, that speed was about the state of the art to run these serial links across short distances (this is all inside of a single device) within acceptable signal loss and cross talk ranges. Signal integrity is not one of my strong points, so that’s about the best explanation I will give you.

10 to 40 to 100

With that 10Gbit building block we have created higher speed interfaces. When you look at a 40GbE interface, it is constructed out of 4 parallel SerDes links between the Ethernet chip and the QSFP pluggable. Even when leaving the QSFP onto fiber, it takes 4 parallel 10Gbit streams to transport this to the receiving QSFP. The short reach QSFP interfaces use 4 pair of fiber between them, and their copper Direct Attach Cable (DAC) equivalent carry the same on several copper cables inside the big cable. Longer reach QSFP interfaces put the 4 10Gbit streams onto separate Wave Division Multiplexing (WDM) waves which can be carried over a single pair of fiber. This is part of the reason why QSFP optics are fairly expensive still, especially for longer distances. Distribution of the bits across these parallel paths is done on almost a bit by bit basis by the hardware and has nothing to do with the packet based distribution we know in Ethernet.

Similarly for the 100GbE interfaces that are available today, these are really constructed out of 10 parallel paths of 10Gbit streams. Similar to the 40GbE example above, these are carried across 10 pair of fiber, or multiplexed together into a single fiber. Of course that also comes at a cost.

In the past 2-3 years, technology has advanced to the point that 25Ghz SerDes have become economically viable, and all of the usual physics problems in signal integrity have found solutions. This now means that  we can push data 2.5 times as fast across those serial links, and ethernet chipsets due in the next year will start to have 25Ghz SerDes ports on them rather than 12.5Ghz ports. Once you have these ports, you can of course still run 10GbE across it, but you would not use all the capacity of that connection. 40GbE will then have the option to run across 2 parallel 25Ghz SerDes, rather than the 4 required today. And that translates into less cabling between devices. Similarly, 100GbE will move away from the current 10×10 implementations rather quickly to 4×25, for the very same reasons. Less parallel paths, less fibers, less optics, less everything.

Which then leaves the question, if there is this basic 25Ghz building block that we intend to use for 40GbE and 100GbE, why would we not want to use it in and by itself for 25GbE. As a single signal, it would provide a 2.5 performance boost in an SFP+ form factor without doing anything complicated. It’s like taking 10GbE and simply run it faster, one the hardest part has been solved, running a serial signal that fast.

And then there is 25

And there is your long winded but rather straightforward reason for 25Gbit Ethernet. Independent of ethernet, serial I/O technology has created an extremely useful building block that runs much faster than its predecessor. IEEE in its standardization of 100GbE already assumed 25Ghz serial I/O capabilities and has layered its definition of 100GbE on top it (the 10×10 available today is mostly a placeholder, make sure you ask your vendor what flavor of 100GbE they provide). But that same IEEE never went back to re-apply that 25Ghz technology to 10GbE and 40GbE and turn it into 25GbE and 50GbE. With lots of the foundational work done as part of the 100GbE specifications, this is not the tremendous 4-5 year effort that most IEEE standards efforts take.

The vendor industry has taken it on themselves to move this along outside of IEEE with a 25GbE consortium. There are several parts and components required to create complete 25GbE ethernet solutions. The ethernet chips will start to have them within a year, we then also need pluggable optics and perhaps even Direct Attach Cables to support the native 25GbE and its 50GbE sister, and of course server NIC cards need to support this as well. This is one of these efforts that requires a relatively small development across all of these components (emphasis on relatively) with a fairly quick 2.5x performance payoff at the end. As a consumer, 25GbE and 50GbE provide will provide you with a substantial performance boost in your datacenter server and storage environment with less cabling at a cost that in my opinion will get to small premiums over 10GbE fairly quickly over the next few years.

At Plexxi we fully support the 25GbE efforts, there is very little if anything negative associated with the push to productization. We will quickly embrace ethernet chipsets that support 25Ghz SerDes and the optical components that help us drive our optical fabric to higher capacities. The IEEE has always been the one and only standardization body for anything Ethernet, but it has been sent a clear message by the industry to move a lot faster. I have no doubt that that same industry will drive 25GbE to commercial success because it just makes sense.

[Today's fun fact: Over 50 percent of your body heat is lost through your head and neck. That is a very useful fact for us here in the Northeast.]

The post What is 25 Gigabit Ethernet and why would you want it? appeared first on Plexxi.

Read the original blog entry...

More Stories By Marten Terpstra

Marten Terpstra is a Product Management Director at Plexxi Inc. Marten has extensive knowledge of the architecture, design, deployment and management of enterprise and carrier networks.

Latest Stories
"We do one of the best file systems in the world. We learned how to deal with Big Data many years ago and we implemented this knowledge into our software," explained Jakub Ratajczak, Business Development Manager at MooseFS, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
Traditional IT, great for stable systems of record, is struggling to cope with newer, agile systems of engagement requirements coming straight from the business. In his session at 18th Cloud Expo, William Morrish, General Manager of Product Sales at Interoute, will outline ways of exploiting new architectures to enable both systems and building them to support your existing platforms, with an eye for the future. Technologies such as Docker and the hyper-convergence of computing, networking and...
Using new techniques of information modeling, indexing, and processing, new cloud-based systems can support cloud-based workloads previously not possible for high-throughput insurance, banking, and case-based applications. In his session at 18th Cloud Expo, John Newton, CTO, Founder and Chairman of Alfresco, described how to scale cloud-based content management repositories to store, manage, and retrieve billions of documents and related information with fast and linear scalability. He addres...
You want to start your DevOps journey but where do you begin? Do you say DevOps loudly 5 times while looking in the mirror and it suddenly appears? Do you hire someone? Do you upskill your existing team? Here are some tips to help support your DevOps transformation. Conor Delanbanque has been involved with building & scaling teams in the DevOps space globally. He is the Head of DevOps Practice at MThree Consulting, a global technology consultancy. Conor founded the Future of DevOps Thought Leade...
An edge gateway is an essential piece of infrastructure for large scale cloud-based services. In his session at 17th Cloud Expo, Mikey Cohen, Manager, Edge Gateway at Netflix, detailed the purpose, benefits and use cases for an edge gateway to provide security, traffic management and cloud cross region resiliency. He discussed how a gateway can be used to enhance continuous deployment and help testing of new service versions and get service insights and more. Philosophical and architectural ap...
By 2021, 500 million sensors are set to be deployed worldwide, nearly 40x as many as exist today. In order to scale fast and keep pace with industry growth, the team at Unacast turned to the public cloud to build the world's largest location data platform with optimal scalability, minimal DevOps, and maximum flexibility. Drawing from his experience with the Google Cloud Platform, VP of Engineering Andreas Heim will speak to the architecture of Unacast's platform and developer-focused processes.
Wooed by the promise of faster innovation, lower TCO, and greater agility, businesses of every shape and size have embraced the cloud at every layer of the IT stack – from apps to file sharing to infrastructure. The typical organization currently uses more than a dozen sanctioned cloud apps and will shift more than half of all workloads to the cloud by 2018. Such cloud investments have delivered measurable benefits. But they’ve also resulted in some unintended side-effects: complexity and risk. ...
To Really Work for Enterprises, MultiCloud Adoption Requires Far Better and Inclusive Cloud Monitoring and Cost Management … But How? Overwhelmingly, even as enterprises have adopted cloud computing and are expanding to multi-cloud computing, IT leaders remain concerned about how to monitor, manage and control costs across hybrid and multi-cloud deployments. It’s clear that traditional IT monitoring and management approaches, designed after all for on-premises data centers, are falling short in ...
Serveless Architectures brings the ability to independently scale, deploy and heal based on workloads and move away from monolithic designs. From the front-end, middle-ware and back-end layers, serverless workloads potentially have a larger security risk surface due to the many moving pieces. This talk will focus on key areas to consider for securing end to end, from dev to prod. We will discuss patterns for end to end TLS, session management, scaling to absorb attacks and mitigation techniques.
We are seeing a major migration of enterprises applications to the cloud. As cloud and business use of real time applications accelerate, legacy networks are no longer able to architecturally support cloud adoption and deliver the performance and security required by highly distributed enterprises. These outdated solutions have become more costly and complicated to implement, install, manage, and maintain.SD-WAN offers unlimited capabilities for accessing the benefits of the cloud and Internet. ...
"We focus on SAP workloads because they are among the most powerful but somewhat challenging workloads out there to take into public cloud," explained Swen Conrad, CEO of Ocean9, Inc., in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
The deluge of IoT sensor data collected from connected devices and the powerful AI required to make that data actionable are giving rise to a hybrid ecosystem in which cloud, on-prem and edge processes become interweaved. Attendees will learn how emerging composable infrastructure solutions deliver the adaptive architecture needed to manage this new data reality. Machine learning algorithms can better anticipate data storms and automate resources to support surges, including fully scalable GPU-c...
The vast majority of businesses now use cloud services, yet many still struggle with realizing the full potential of their IT investments. In particular, small and medium-sized businesses (SMBs) lack the internal IT staff and expertise to fully move to and manage workloads in public cloud environments. Speaker Todd Schwartz will help session attendees better navigate the complex cloud market and maximize their technical investments. The SkyKick co-founder and co-CEO will share the biggest challe...
Machine learning provides predictive models which a business can apply in countless ways to better understand its customers and operations. Since machine learning was first developed with flat, tabular data in mind, it is still not widely understood: when does it make sense to use graph databases and machine learning in combination? This talk tackles the question from two ends: classifying predictive analytics methods and assessing graph database attributes. It also examines the ongoing lifecycl...
The Founder of NostaLab and a member of the Google Health Advisory Board, John is a unique combination of strategic thinker, marketer and entrepreneur. His career was built on the "science of advertising" combining strategy, creativity and marketing for industry-leading results. Combined with his ability to communicate complicated scientific concepts in a way that consumers and scientists alike can appreciate, John is a sought-after speaker for conferences on the forefront of healthcare science,...