|By Gary Kaiser||
|July 28, 2014 07:00 AM EDT||
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
WebSocket is effectively a persistent and fat pipe that is compatible with a standard web infrastructure; a "TCP for the Web." If you think of WebSocket in this light, there are other more hugely interesting applications of WebSocket than just simply sending data to a browser. In his session at 18th Cloud Expo, Frank Greco, Director of Technology for Kaazing Corporation, will compare other modern web connectivity methods such as HTTP/2, HTTP Streaming, Server-Sent Events and new W3C event APIs ...
Feb. 12, 2016 09:00 AM EST
SYS-CON Events announced today that Men & Mice, the leading global provider of DNS, DHCP and IP address management overlay solutions, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. The Men & Mice Suite overlay solution is already known for its powerful application in heterogeneous operating environments, enabling enterprises to scale without fuss. Building on a solid range of diverse platform support,...
Feb. 12, 2016 06:00 AM EST Reads: 247
The (re?)emergence of Microservices was especially prominent in this week’s news. What are they good for? do they make sense for your application? should you take the plunge? and what do Microservices mean for your DevOps and Continuous Delivery efforts? Continue reading for more on Microservices, containers, DevOps culture, and more top news from the past week. As always, stay tuned to all the news coming from@ElectricCloud on DevOps and Continuous Delivery throughout the week and retweet/favo...
Feb. 12, 2016 05:00 AM EST Reads: 232
How is your DevOps transformation coming along? How do you measure Agility? Reliability? Efficiency? Quality? Success?! How do you optimize your processes? This morning on #c9d9 we talked about some of the metrics that matter for the different stakeholders throughout the software delivery pipeline. Our panelists shared their best practices.
Feb. 12, 2016 04:00 AM EST Reads: 113
In a previous article, I demonstrated how to effectively and efficiently install the Dynatrace Application Monitoring solution using Ansible. In this post, I am going to explain how to achieve the same results using Chef with our official dynatrace cookbook available on GitHub and on the Chef Supermarket. In the following hands-on tutorial, we’ll also apply what we see as good practice on working with and extending our deployment automation blueprints to suit your needs.
Feb. 12, 2016 04:00 AM EST
Sensors and effectors of IoT are solving problems in new ways, but small businesses have been slow to join the quantified world. They’ll need information from IoT using applications as varied as the businesses themselves. In his session at @ThingsExpo, Roger Meike, Distinguished Engineer, Director of Technology Innovation at Intuit, showed how IoT manufacturers can use open standards, public APIs and custom apps to enable the Quantified Small Business. He used a Raspberry Pi to connect sensors...
Feb. 12, 2016 03:45 AM EST Reads: 344
Let’s face it, embracing new storage technologies, capabilities and upgrading to new hardware often adds complexity and increases costs. In his session at 18th Cloud Expo, Seth Oxenhorn, Vice President of Business Development & Alliances at FalconStor, will discuss how a truly heterogeneous software-defined storage approach can add value to legacy platforms and heterogeneous environments. The result reduces complexity, significantly lowers cost, and provides IT organizations with improved effi...
Feb. 12, 2016 03:45 AM EST Reads: 264
The cloud promises new levels of agility and cost-savings for Big Data, data warehousing and analytics. But it’s challenging to understand all the options – from IaaS and PaaS to newer services like HaaS (Hadoop as a Service) and BDaaS (Big Data as a Service). In her session at @BigDataExpo at @ThingsExpo, Hannah Smalltree, a director at Cazena, will provide an educational overview of emerging “as-a-service” options for Big Data in the cloud. This is critical background for IT and data profes...
Feb. 12, 2016 02:30 AM EST Reads: 224
Father business cycles and digital consumers are forcing enterprises to respond faster to customer needs and competitive demands. Successful integration of DevOps and Agile development will be key for business success in today’s digital economy. In his session at DevOps Summit, Pradeep Prabhu, Co-Founder & CEO of Cloudmunch, covered the critical practices that enterprises should consider to seamlessly integrate Agile and DevOps processes, barriers to implementing this in the enterprise, and pr...
Feb. 12, 2016 02:00 AM EST Reads: 438
If we look at slow, traditional IT and jump to the conclusion that just because we found its issues intractable before, that necessarily means we will again, then it’s time for a rethink. As a matter of fact, the world of IT has changed over the last ten years or so. We’ve been experiencing unprecedented innovation across the board – innovation in technology as well as in how people organize and accomplish tasks. Let’s take a look at three differences between today’s modern, digital context...
Feb. 12, 2016 01:45 AM EST Reads: 233
The principles behind DevOps are not new - for decades people have been automating system administration and decreasing the time to deploy apps and perform other management tasks. However, only recently did we see the tools and the will necessary to share the benefits and power of automation with a wider circle of people. In his session at DevOps Summit, Bernard Sanders, Chief Technology Officer at CloudBolt Software, explored the latest tools including Puppet, Chef, Docker, and CMPs needed to...
Feb. 12, 2016 01:30 AM EST Reads: 347
Cognitive Computing is becoming the foundation for a new generation of solutions that have the potential to transform business. Unlike traditional approaches to building solutions, a cognitive computing approach allows the data to help determine the way applications are designed. This contrasts with conventional software development that begins with defining logic based on the current way a business operates. In her session at 18th Cloud Expo, Judith S. Hurwitz, President and CEO of Hurwitz & ...
Feb. 12, 2016 12:00 AM EST Reads: 281
Data-as-a-Service is the complete package for the transformation of raw data into meaningful data assets and the delivery of those data assets. In her session at 18th Cloud Expo, Lakshmi Randall, an industry expert, analyst and strategist, will address: What is DaaS (Data-as-a-Service)? Challenges addressed by DaaS Vendors that are enabling DaaS Architecture options for DaaS
Feb. 11, 2016 10:45 PM EST Reads: 371
One of the bewildering things about DevOps is integrating the massive toolchain including the dozens of new tools that seem to crop up every year. Part of DevOps is Continuous Delivery and having a complex toolchain can add additional integration and setup to your developer environment. In his session at @DevOpsSummit at 18th Cloud Expo, Miko Matsumura, Chief Marketing Officer of Gradle Inc., will discuss which tools to use in a developer stack, how to provision the toolchain to minimize onboa...
Feb. 11, 2016 10:00 PM EST Reads: 124
Microservices are a type of software architecture where large applications are made up of small, self-contained units working together through APIs that are not dependent on a specific language. Each service has a limited scope, concentrates on a specific task and is highly independent. This setup allows IT managers and developers to build systems in a modular way. In his book, “Building Microservices,” Sam Newman said microservices are small, focused components built to do a single thing very w...
Feb. 11, 2016 06:00 PM EST
SYS-CON Events announced today that Catchpoint Systems, Inc., a provider of innovative web and infrastructure monitoring solutions, has been named “Silver Sponsor” of SYS-CON's DevOps Summit at 18th Cloud Expo New York, which will take place June 7-9, 2016, at the Javits Center in New York City, NY. Catchpoint is a leading Digital Performance Analytics company that provides unparalleled insight into customer-critical services to help consistently deliver an amazing customer experience. Designed...
Feb. 11, 2016 05:00 PM EST Reads: 395
With the proliferation of both SQL and NoSQL databases, organizations can now target specific fit-for-purpose database tools for their different application needs regarding scalability, ease of use, ACID support, etc. Platform as a Service offerings make this even easier now, enabling developers to roll out their own database infrastructure in minutes with minimal management overhead. However, this same amount of flexibility also comes with the challenges of picking the right tool, on the right ...
Feb. 11, 2016 04:15 PM EST Reads: 185
SYS-CON Events announced today that Interoute, owner-operator of one of Europe's largest networks and a global cloud services platform, has been named “Bronze Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2015 at the Javits Center in New York, New York. Interoute is the owner-operator of one of Europe's largest networks and a global cloud services platform which encompasses 12 data centers, 14 virtual data centers and 31 colocation centers, with connections to 195 ad...
Feb. 11, 2016 03:45 PM EST Reads: 418
SYS-CON Events announced today that Alert Logic, Inc., the leading provider of Security-as-a-Service solutions for the cloud, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. Alert Logic, Inc., provides Security-as-a-Service for on-premises, cloud, and hybrid infrastructures, delivering deep security insight and continuous protection for customers at a lower cost than traditional security solutions. Ful...
Feb. 11, 2016 02:45 PM EST Reads: 444
SYS-CON Events announced today that Commvault, a global leader in enterprise data protection and information management, has been named “Bronze Sponsor” of SYS-CON's 18th International Cloud Expo, which will take place on June 7–9, 2016, at the Javits Center in New York City, NY, and the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Commvault is a leading provider of data protection and information management...
Feb. 11, 2016 01:30 PM EST Reads: 444