Welcome!

Microservices Expo Authors: Elizabeth White, Liz McMillan, Jason Bloomberg, Anders Wallgren, Derek Weeks

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

Microservices Expo: Article

Understanding Application Performance on the Network | Part 3

TCP Slow-Start

In Part II, we discussed performance constraints caused by both bandwidth and congestion. Purposely omitted was a discussion about packet loss - which is often an inevitable result of heavy network congestion. I'll use this blog entry on TCP slow-start to introduce the Congestion Window (CWD), which is fundamental for Part IV's in-depth review of Packet Loss.

TCP Slow-Start
TCP uses a slow-start algorithm as it tries to understand the characteristics (bandwidth, latency, congestion) of the path supporting a new TCP connection. In most cases, TCP has no inherent understanding of the characteristics of the network path; it could be a switched connection on a high-speed LAN to a server in the next room, or it could be a low-bandwidth, already congested connection to a server halfway around the globe. In an effort to be a good network citizen, TCP uses a slow-start algorithm based on an internally-maintained congestion window (CWD) which identifies how many packets may be transmitted without being acknowledged; as the data carried in transmitted packets is acknowledged, the window increases. The CWD typically begins at two packets, allowing an initial transmission of two packets and then ramping up quickly as acknowledgements are received.

At the beginning of a new TCP connection, the CWD starts at two packets and increases as acknowledgements are received.

The CWD will continue to increase until one of three conditions is met:

Condition

Determined by

Blog discussion

Receiver's TCP Window limit

Receiver's TCP Window size

Part VII

Congestion detected (via packet loss)

Triple Duplicate ACK

Part IV

Maximum write block size

Application configuration

Part VIII

Generally, TCP slow-start will not be a primary or significant bottleneck. Slow-start occurs once per TCP connection, so for many operations there may be no impact. However, we will address the theoretical case of a TCP slow-start bottleneck, some influencing factors, and then present a real-world case.

The Maximum Segment Size and the CWD
The Maximum Segment Size (MSS) identifies the maximum TCP payload that can be carried by a packet; this value is set as a TCP option as a new connection is established. Probably the most common MSS value is 1460, but smaller sizes may be used to allow for VPN headers or to support different link protocols. Beyond the additional protocol overhead introduced by a reduced MSS, there is also an impact on the CWD, since the algorithm uses packets as its flow control metric.

We can consider the CWD's exchanges of data packets and subsequent ACKs as TCP turns, or TCP round trips; each exchange incurs the round-trip path delay. Therefore, one of the primary factors influencing the impact of TCP slow-start is network latency. A smaller MSS value will result in a larger number of packets - and additional TCP turns - as the sending node increases the CWD to reach its upper limit. It is possible that with a small MSS (536 Bytes) and high path delay (200 msec) that slow-start might introduce 3 seconds of delay to an operation as the CWD increases to a receive window limit of 65KB.

How Important Is TCP Slow-Start?
While significant, even a 3-second delay is probably not interesting for large file transfers, or for applications that reuse TCP connections. But let's consider a simple web page with 20 page elements, averaging about 120KB in size. A misconfigured proxy server prevents persistent TCP connections, so we'll need 20 new TCP connections to load the page. Each connection must ramp up through slow-start as content is downloaded. With a small MSS and/or high latency, each page component will experience a significant slow-start delay.

For more network performance insight from click here for the full article.

More Stories By Gary Kaiser

Gary Kaiser is a Subject Matter Expert in Network Performance Analytics at Dynatrace, responsible for DC RUM’s technical marketing programs. He is a co-inventor of multiple performance analysis features, and continues to champion the value of network performance analytics. He is the author of Network Application Performance Analysis (WalrusInk, 2014).

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
The proper isolation of resources is essential for multi-tenant environments. The traditional approach to isolate resources is, however, rather heavyweight. In his session at 18th Cloud Expo, Igor Drobiazko, co-founder of elastic.io, will draw upon their own experience with operating a Docker container-based infrastructure on a large scale and present a lightweight solution for resource isolation using microservices. He will also discuss the implementation of microservices in data and applicat...
Join IBM June 8 at 18th Cloud Expo at the Javits Center in New York City, NY, and learn how to innovate like a startup and scale for the enterprise. You need to deliver quality applications faster and cheaper, attract and retain customers with an engaging experience across devices, and seamlessly integrate your enterprise systems. And you can't take 12 months to do it.
This is not a small hotel event. It is also not a big vendor party where politicians and entertainers are more important than real content. This is Cloud Expo, the world's longest-running conference and exhibition focused on Cloud Computing and all that it entails. If you want serious presentations and valuable insight about Cloud Computing for three straight days, then register now for Cloud Expo.
SYS-CON Events announced today that Stratoscale, the software company developing the next generation data center operating system, 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. Stratoscale is revolutionizing the data center with a zero-to-cloud-in-minutes solution. With Stratoscale’s hardware-agnostic, Software Defined Data Center (SDDC) solution to store everything, run anything and scale everywhere...
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,...
You deployed your app with the Bluemix PaaS and it's gaining some serious traction, so it's time to make some tweaks. Did you design your application in a way that it can scale in the cloud? Were you even thinking about the cloud when you built the app? If not, chances are your app is going to break. Check out this webcast to learn various techniques for designing applications that will scale successfully in Bluemix, for the confidence you need to take your apps to the next level and beyond.
Digital means customer preferences and behavior are driving enterprise technology decisions to be sure, but let’s not forget our employees. After all, when we say customer, we mean customer writ large, including partners, supply chain participants, and yes, those salaried denizens whose daily labor forms the cornerstone of the enterprise. While your customers bask in the warm rays of your digital efforts, are your employees toiling away in the dark recesses of your enterprise, pecking data into...
SYS-CON Events announced today that DatacenterDynamics has been named “Media 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. DatacenterDynamics is a brand of DCD Group, a global B2B media and publishing company that develops products to help senior professionals in the world's most ICT dependent organizations make risk-based infrastructure and capacity decisions.
With DevOps becoming more well-known and established practice in nearly every industry that delivers software, it is important to continually reassess its efficacy. This week’s top 10 includes a discussion on how the quick uptake of DevOps adoption in the enterprise has posed some serious challenges. Additionally, organizations who have taken the DevOps plunge must find ways to find, hire and keep their DevOps talent in order to keep the machine running smoothly.
Between the mockups and specs produced by analysts, and resulting applications built by developers, there exists a gulf where projects fail, costs spiral, and applications disappoint. Methodologies like Agile attempt to address this with intensified communication, with partial success but many limitations. In his session at 18th Cloud Expo, Charles Kendrick, CTO & Chief Architect at Isomorphic Software, will present a revolutionary model enabled by new technologies. Learn how business and devel...
Call it DevOps or not, if you are concerned about releasing more code faster and at a higher quality, the resulting software delivery chain and process will look and smell like DevOps. But for existing development teams, no matter what the velocity objective is, getting from here to there is not something that can be done without a plan. Moving your release cadence from months to weeks is not just about learning Agile practices and getting some automation tools. It involves people, tooling and ...
The notion of customer journeys, of course, are central to the digital marketer’s playbook. Clearly, enterprises should focus their digital efforts on such journeys, as they represent customer interactions over time. But making customer journeys the centerpiece of the enterprise architecture, however, leaves more questions than answers. The challenge arises when EAs consider the context of the customer journey in the overall architecture as well as the architectural elements that make up each...
APIs have taken the world by storm in recent years. The use of APIs has gone beyond just traditional "software" companies, to companies and organizations across industries using APIs to share information and power their applications. For some organizations, APIs are the biggest revenue drivers. For example, Salesforce generates nearly 50% of annual revenue through APIs. In other cases, APIs can increase a business's footprint and initiate collaboration. Netflix, for example, reported over 5 bi...
As the software delivery industry continues to evolve and mature, the challenge of managing the growing list of the tools and processes becomes more daunting every day. Today, Application Lifecycle Management (ALM) platforms are proving most valuable by providing the governance, management and coordination for every stage of development, deployment and release. Recently, I spoke with Madison Moore at SD Times about the changing market and where ALM is headed.
If there is anything we have learned by now, is that every business paves their own unique path for releasing software- every pipeline, implementation and practices are a bit different, and DevOps comes in all shapes and sizes. Software delivery practices are often comprised of set of several complementing (or even competing) methodologies – such as leveraging Agile, DevOps and even a mix of ITIL, to create the combination that’s most suitable for your organization and that maximize your busines...
These days I mostly make my living as a consultant. Consultants in general are probably not the best loved group in the world. It is common to think of consultants wafting-in to your organization, telling you things that you already know and advising you to “change your culture”, whatever that means. Subsequently they depart, no-doubt with a fat fee, and leave you as you were before with the same problems and no progress made.
Struggling to keep up with increasing application demand? Learn how Platform as a Service (PaaS) can streamline application development processes and make resource management easy.
In the rush to compete in the digital age, a successful digital transformation is essential, but many organizations are setting themselves up for failure. There’s a common misconception that the process is just about technology, but it’s not. It’s about your business. It shouldn’t be treated as an isolated IT project; it should be driven by business needs with the committed involvement of a range of stakeholders.
New Relic, Inc. has announced a set of new features across the New Relic Software Analytics Cloud that offer IT operations teams increased visibility, and the ability to diagnose and resolve performance problems quickly. The new features further IT operations teams’ ability to leverage data and analytics, as well as drive collaboration and a common, shared understanding between teams. Software teams are under pressure to resolve performance issues quickly and improve availability, as the comple...
The goal of any tech business worth its salt is to provide the best product or service to its clients in the most efficient and cost-effective way possible. This is just as true in the development of software products as it is in other product design services. Microservices, an app architecture style that leans mostly on independent, self-contained programs, are quickly becoming the new norm, so to speak. With this change comes a declining reliance on older SOAs like COBRA, a push toward more s...