Click here to close now.




















Welcome!

Microservices Expo Authors: Elizabeth White, Joe Pruitt, Lori MacVittie, Jason Bloomberg, AppDynamics Blog

Related Topics: Microservices Expo, Java IoT, Linux Containers, IoT User Interface, @CloudExpo, @BigDataExpo

Microservices Expo: Article

Understanding Application Performance on the Network | Part 6

The Nagle Algorithm

In Part V, we discussed processing delays caused by "slow" client and server nodes. In Part VI, we'll discuss the Nagle algorithm, a behavior that can have a devastating impact on performance and, in many ways, appear to be a processing delay.

Common TCP ACK Timing
Beyond being important for (reasonably) accurate packet flow diagrams, understanding "normal" TCP ACK timing can help in the effective diagnosis of certain types of performance problems. These include those introduced by the Nagle algorithm, which we will discuss here, and application windowing, to be discussed in Part VII.

A slightly simplified but useful rule of thumb is as follows:

A receiving node will:

  • Acknowledge every second packet immediately
  • Acknowledge a single packet if the Delayed ACK timer expires before a second packet arrives

The Delayed ACK timer typically defaults to 200 milliseconds, at least on Microsoft platforms.

While this behavior is quite common, you may encounter differences; for example, changing the ACK frequency to every packet is an approach to circumventing certain problems, while shorter Delayed ACK timers may be observed in non-Microsoft environments.

ACK every second packet, or a single packet after the Delayed ACK timer expires

The Nagle Algorithm
The Nagle algorithm was designed to help reduce network overhead by delaying the transmission of a small packet (i.e., <MSS) until all previously transmitted packets have been acknowledged. The goal was to prevent a node from transmitting many small packets if the application delivers data to the socket rather slowly. The usefulness of the algorithm and the frequency with which it is applied have both diminished dramatically; however, you may still encounter it, as the option still exists in most environments.

To begin to understand the impact of the Nagle algorithm, consider a request or reply flow; chances are, the size of the payload in the flow is not an exact multiple of the MSS. Therefore, the last packet of the flow will be smaller than the MSS. With Nagle enabled, this last packet will not be transmitted until the previous (penultimate) packet has been acknowledged. In the best case, the penultimate packet represents an even-numbered packet in the flow, triggering an immediate acknowledgement from the receiver which in turn "releases" the final small packet. In this case, the Nagle penalty is equal to one network round-trip for the entire flow. Should the penultimate packet be an odd-numbered packet, it will not be acknowledged by the receiver until the Delayed ACK timer expires; the penalty becomes one network round-trip plus approximately 200 milliseconds.

The HTTP reply includes two data packets; the last packet is not sent until the earlier packet has been acknowledged. The Delayed ACK timer adds about 200 milliseconds to the transmission of the reply.

For more network tips click here for the full article

More Stories By Gary Kaiser

Gary Kaiser is a Subject Matter Expert in Network Performance Analysis at Compuware APM. He has global field enablement responsibilities for performance monitoring and analysis solutions embracing emerging and strategic technologies, including WAN optimization, thin client infrastructures, network forensics, and a unique performance management maturity methodology. He is also a co-inventor of multiple analysis features, and continues to champion the value of software-enabled expert network analysis.

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@MicroservicesExpo Stories
"ProfitBricks was founded in 2010 and we are the painless cloud - and we are also the Infrastructure as a Service 2.0 company," noted Achim Weiss, Chief Executive Officer and Co-Founder of ProfitBricks, in this SYS-CON.tv interview at 16th Cloud Expo, held June 9-11, 2015, at the Javits Center in New York City.
Node.js is an open source runtime environment for server-side and network based applications. Node.js contains all the components needed to build a functioning website. But, you need to think of Node.js as a big tool box. As with any other art form, going to the tool box over and over to perform the same task is not productive. The concept of tool reuse is used in all forms of artistry and development is no exception.
One of the ways to increase scalability of services – and applications – is to go “stateless.” The reasons for this are many, but in general by eliminating the mapping between a single client and a single app or service instance you eliminate the need for resources to manage state in the app (overhead) and improve the distributability (I can make up words if I want) of requests across a pool of instances. The latter occurs because sessions don’t need to hang out and consume resources that could ...
What we really mean to ask is whether microservices architecture is SOA done right. But then, of course, we’d have to figure out what microservices architecture was. And if you think defining SOA is difficult, pinning down microservices architecture is unquestionably frying pan into fire time. Given my years at ZapThink, fighting to help architects understand what Service-Oriented Architecture really was and how to get it right, it’s no surprise that many people ask me this question.
The Internet of Things. Cloud. Big Data. Real-Time Analytics. To those who do not quite understand what these phrases mean (and let’s be honest, that’s likely to be a large portion of the world), words like “IoT” and “Big Data” are just buzzwords. The truth is, the Internet of Things encompasses much more than jargon and predictions of connected devices. According to Parker Trewin, Senior Director of Content and Communications of Aria Systems, “IoT is big news because it ups the ante: Reach out ...
Cloud Migration Management (CMM) refers to the best practices for planning and managing migration of IT systems from a legacy platform to a Cloud Provider through a combination professional services consulting and software tools. A Cloud migration project can be a relatively simple exercise, where applications are migrated ‘as is’, to gain benefits such as elastic capacity and utility pricing, but without making any changes to the application architecture, software development methods or busine...
"We got started as search consultants. On the services side of the business we have help organizations save time and save money when they hit issues that everyone more or less hits when their data grows," noted Otis Gospodnetić, Founder of Sematext, in this SYS-CON.tv interview at @DevOpsSummit, held June 9-11, 2015, at the Javits Center in New York City.
Growth hacking is common for startups to make unheard-of progress in building their business. Career Hacks can help Geek Girls and those who support them (yes, that's you too, Dad!) to excel in this typically male-dominated world. Get ready to learn the facts: Is there a bias against women in the tech / developer communities? Why are women 50% of the workforce, but hold only 24% of the STEM or IT positions? Some beginnings of what to do about it! In her Opening Keynote at 16th Cloud Expo, S...
"We've just seen a huge influx of new partners coming into our ecosystem, and partners building unique offerings on top of our API set," explained Seth Bostock, Chief Executive Officer at IndependenceIT, in this SYS-CON.tv interview at 16th Cloud Expo, held June 9-11, 2015, at the Javits Center in New York City.
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at @ThingsExpo, James Kirkland, Red Hat's Chief Arch...
Sysdig has announced two significant milestones in its mission to bring infrastructure and application monitoring to the world of containers and microservices: a $10.7 million Series A funding led by Accel and Bain Capital Ventures (BCV); and the general availability of Sysdig Cloud, the first monitoring, alerting, and troubleshooting platform specializing in container visibility, which is already used by more than 30 enterprise customers. The funding will be used to drive adoption of Sysdig Clo...
Auto-scaling environments, micro-service architectures and globally-distributed teams are just three common examples of why organizations today need automation and interoperability more than ever. But is interoperability something we simply start doing, or does it require a reexamination of our processes? And can we really improve our processes without first making interoperability a requirement for how we choose our tools?
The Software Defined Data Center (SDDC), which enables organizations to seamlessly run in a hybrid cloud model (public + private cloud), is here to stay. IDC estimates that the software-defined networking market will be valued at $3.7 billion by 2016. Security is a key component and benefit of the SDDC, and offers an opportunity to build security 'from the ground up' and weave it into the environment from day one. In his session at 16th Cloud Expo, Reuven Harrison, CTO and Co-Founder of Tufin,...
How do you securely enable access to your applications in AWS without exposing any attack surfaces? The answer is usually very complicated because application environments morph over time in response to growing requirements from your employee base, your partners and your customers. In his session at @DevOpsSummit, Haseeb Budhani, CEO and Co-founder of Soha, shared five common approaches that DevOps teams follow to secure access to applications deployed in AWS, Azure, etc., and the friction an...
JavaScript is primarily a client-based dynamic scripting language most commonly used within web browsers as client-side scripts to interact with the user, browser, and communicate asynchronously to servers. If you have been part of any web-based development, odds are you have worked with JavaScript in one form or another. In this article, I'll focus on the aspects of JavaScript that are relevant within the Node.js environment.
Discussions about cloud computing are evolving into discussions about enterprise IT in general. As enterprises increasingly migrate toward their own unique clouds, new issues such as the use of containers and microservices emerge to keep things interesting. In this Power Panel at 16th Cloud Expo, moderated by Conference Chair Roger Strukhoff, panelists addressed the state of cloud computing today, and what enterprise IT professionals need to know about how the latest topics and trends affect t...
Digital Transformation is the ultimate goal of cloud computing and related initiatives. The phrase is certainly not a precise one, and as subject to hand-waving and distortion as any high-falutin' terminology in the world of information technology. Yet it is an excellent choice of words to describe what enterprise IT—and by extension, organizations in general—should be working to achieve. Digital Transformation means: handling all the data types being found and created in the organizat...
In the midst of the widespread popularity and adoption of cloud computing, it seems like everything is being offered “as a Service” these days: Infrastructure? Check. Platform? You bet. Software? Absolutely. Toaster? It’s only a matter of time. With service providers positioning vastly differing offerings under a generic “cloud” umbrella, it’s all too easy to get confused about what’s actually being offered. In his session at 16th Cloud Expo, Kevin Hazard, Director of Digital Content for SoftL...
"Vicom Computer Services is a service provider and a value-added reseller and we provide technology solutions, infrastructure solutions, security and management services solutions," stated Amitava Das, Chief Technology Officer at Vicom Computer Services, in this SYS-CON.tv interview at 16th Cloud Expo, held June 9-11, 2015, at the Javits Center in New York City.
Containers are changing the security landscape for software development and deployment. As with any security solutions, security approaches that work for developers, operations personnel and security professionals is a requirement. In his session at DevOps Summit, Kevin Gilpin, CTO and Co-Founder of Conjur, will discuss various security considerations for container-based infrastructure and related DevOps workflows.