Welcome!

IBM Cloud Authors: Yeshim Deniz, Elizabeth White, Pat Romanski, Liz McMillan, Stefan Bernbo

Related Topics: @DevOpsSummit, Containers Expo Blog, @DXWorldExpo

@DevOpsSummit: Article

Compression: Making the Big Smaller and Faster (Part 1) | @DevOpsSummit #DevOps #WebPerf

The sharing of information in a fast and efficient manner has been an area of constant study and research

Compression: Making the Big Smaller and Faster (Part 1)
By Nilabh Mishra

How important is data compression? The sharing of information in a fast and efficient manner has been an area of constant study and research. Companies like Google and Facebook have spent a lot of time and effort trying to develop faster and better compression algorithms. Compression algorithms have existed since the ’70s and the ongoing research to have better algorithms proves just how important compression is for the Internet and for all of us.

The Need for Data Compression
The World Wide Web (WWW) has undergone a lot of changes since it was made available to the public in 1991. Believe it or not, the copy of the world’s first website can still be browsed here. Back then, webpages were very simple. Today, they are increasingly more complex and there is an evident need to have compression algorithms that are lossless, fast, and efficient.

There are several best practices that help optimize page load times. Here is a blog from that discusses webpage optimization. In this article, we will spend some time understanding the basics of compression and how it works. We will also cover a new type of compression method called “Brotli” in the second part of this blog.

Encoding and Data Compression
Let’s start by understanding what data encoding and compression are:

The word “compression” comes from the Latin word compressare, which means to press together. “Encoding” is the process of placing a sequence of characters in a specialized format that allows efficient data storage as well as transmission. Per Wikipedia: “Data compression involves encoding information using fewer bits than the original representation.

Compression plays a key role when it comes to saving bandwidth and speeding up your site. Modern day websites involve a lot of HTTP requests and responses between the client (the browser) and the server to serve a webpage. With an overall increase in the number of HTTP requests and responses, it becomes important to ensure that these transfers are taking place at a fast and efficient rate.

HTTP works on a request-response model, as demonstrated below:

In this case, we are not using any compression method to compress the response being sent by the server.

  • The browser sends an HTTP request asking for the Index.html page
  • The server looks for the requested file and responds with the requested resource and a 200 OK HTTP status message
  • The browser receives the server’s response and renders the page

As we can see, in this case there is no compression involved. The server responded with a 300 KB file (index.html page). If the file size was bigger, it would have taken more time for the response to be sent on the wire and this would have increased the overall page load time. Please note that we are currently looking only at a single HTTP response. Modern websites receive hundreds of such HTTP responses from the server to render a webpage.

The image below shows the same HTTP request – response between the browser and the server, but in this case, we use compression to reduce the size of the response being sent by the server to the browser.

Today, complex and dynamic websites generate hundreds of HTTP requests/responses. This made it important to have a system which would ensure fast and efficient data transfer between the server and the browser. This is when compression algorithms like Deflate and Gzip came into existence.

Introduction to Gzip
Gzip is a compression method that is used to make files smaller for storage and faster transmission over the network. Gzip is one of the most popular, powerful, and effective ways of compressing data and it can reduce the file size by up to 70%.

Gzip is based on the DEFLATE algorithm, which in turn is a combination of LZ77 and Huffman coding. Understanding how LZ77 works is essential to understand how compression methods like DEFLATE and Gzip work.

LZ77
Developed in the late ’70s by Abraham Lempel and Jacob Ziv, the LZ77 method of compression looks for sequences of characters that recur in a text. It performs compression by replacing the recurring occurrences of strings using pointers that backreference identical strings, previously encountered in the text, that needs to be compressed.

The pointer or backreference is of the form <relative jump, length>, where relative jump signifies how many bytes are there between the current occurrence of the string and its last occurrence and length is the total number of identical bytes found.

Now let us understand this better with the help of an example. Assume, there is a text file with the following text:

As idle as a painted ship, upon a painted ocean.

In this file, we see the following strings: “as” and “painted” occurring multiple times. What LZ77 method does is, it replaces multiple occurrences of strings with the notation: <relative jump, length>.

So using LZ77, the text will get encoded in the following way:

As idle <8,2> a painted ship, upon a <21,7> ocean.

To encode the text, we took the following steps:

  1. Looked at the string and tried to find occurrences of the same “string” or “substrings”.
  2. Replaced multiple occurrences of a string with the notation: <relative jump, length>; The two strings: “as” and “painted” were replaced the multiple occurrences of the strings with <relative jump, length>.
  3. The string “painted” which would have earlier occupied 7 bytes (i.e. the number of characters in the word: “painted”) X 1 byte = 7 bytes was compressed to occupy only 2 bytes. 2 bytes or 16 bits is the size of the pointer or backreference.

HUFFMAN Coding
Huffman Coding is another lossless data compression algorithm. The frequency of occurrence of a string in a text file or pixels in images form the basis of Huffman coding. To get a deeper understanding of this algorithm, read this detailed tutorial that clearly explains how Huffman Coding works.

All modern browsers support Gzip compression for HTTP Requests. With Gzip, one of the most important question is what to compress. It works best with text-based resources like static HTML, CSS files and JavaScript resources but is not very efficient for already compressed resources such as Images. To support Gzip, the server must be configured to allow gzip compression.

The image above shows the impact Gzip compression can have on a text-based resource like a JavaScript file. In this case, we ran 2 instant tests using Catchpoint to the URL: https://code.jquery.com/jquery-3.2.1.js.

For the first test run, we did not specify any encoding to be used by passing the custom header: Accept-Encoding: identity along with the request. The first image shows no Content-Encoding being passed for the request.

In the second image, the browser is sending Accept-Encoding:zip, for which the server is sending zipped file as the response.

We can clearly see how Gzip can drastically compress the files to improve data transmission rate over the wire.

Catchpoint’s Scheduled tests also highlight the difference between compressed and not-compressed content loading on webpages.

In the screenshot above, we see the difference in downloaded bytes for static content (CSS, JavaScript) when using G-zip vs. when not using any encoding.

Brotli Compression
A new compression method called Brotli was introduced not too long ago. The Brotli compression algorithm is optimized for the web and specifically for small text documents. We will discuss more about this compression method and what is has to offer to the World Wide Web community in the second part of the article.

The post Compression: Making the Big Smaller and Faster (Part 1) appeared first on Catchpoint's Blog - Web Performance Monitoring.

More Stories By Mehdi Daoudi

Catchpoint radically transforms the way businesses manage, monitor, and test the performance of online applications. Truly understand and improve user experience with clear visibility into complex, distributed online systems.

Founded in 2008 by four DoubleClick / Google executives with a passion for speed, reliability and overall better online experiences, Catchpoint has now become the most innovative provider of web performance testing and monitoring solutions. We are a team with expertise in designing, building, operating, scaling and monitoring highly transactional Internet services used by thousands of companies and impacting the experience of millions of users. Catchpoint is funded by top-tier venture capital firm, Battery Ventures, which has invested in category leaders such as Akamai, Omniture (Adobe Systems), Optimizely, Tealium, BazaarVoice, Marketo and many more.

IoT & Smart Cities Stories
Recently, REAN Cloud built a digital concierge for a North Carolina hospital that had observed that most patient call button questions were repetitive. In addition, the paper-based process used to measure patient health metrics was laborious, not in real-time and sometimes error-prone. In their session at 21st Cloud Expo, Sean Finnerty, Executive Director, Practice Lead, Health Care & Life Science at REAN Cloud, and Dr. S.P.T. Krishnan, Principal Architect at REAN Cloud, discussed how they built...
When talking IoT we often focus on the devices, the sensors, the hardware itself. The new smart appliances, the new smart or self-driving cars (which are amalgamations of many ‘things'). When we are looking at the world of IoT, we should take a step back, look at the big picture. What value are these devices providing. IoT is not about the devices, its about the data consumed and generated. The devices are tools, mechanisms, conduits. This paper discusses the considerations when dealing with the...
Bill Schmarzo, author of "Big Data: Understanding How Data Powers Big Business" and "Big Data MBA: Driving Business Strategies with Data Science," is responsible for setting the strategy and defining the Big Data service offerings and capabilities for EMC Global Services Big Data Practice. As the CTO for the Big Data Practice, he is responsible for working with organizations to help them identify where and how to start their big data journeys. He's written several white papers, is an avid blogge...
Business professionals no longer wonder if they'll migrate to the cloud; it's now a matter of when. The cloud environment has proved to be a major force in transitioning to an agile business model that enables quick decisions and fast implementation that solidify customer relationships. And when the cloud is combined with the power of cognitive computing, it drives innovation and transformation that achieves astounding competitive advantage.
Machine learning has taken residence at our cities' cores and now we can finally have "smart cities." Cities are a collection of buildings made to provide the structure and safety necessary for people to function, create and survive. Buildings are a pool of ever-changing performance data from large automated systems such as heating and cooling to the people that live and work within them. Through machine learning, buildings can optimize performance, reduce costs, and improve occupant comfort by ...
René Bostic is the Technical VP of the IBM Cloud Unit in North America. Enjoying her career with IBM during the modern millennial technological era, she is an expert in cloud computing, DevOps and emerging cloud technologies such as Blockchain. Her strengths and core competencies include a proven record of accomplishments in consensus building at all levels to assess, plan, and implement enterprise and cloud computing solutions. René is a member of the Society of Women Engineers (SWE) and a m...
JETRO showcased Japan Digital Transformation Pavilion at SYS-CON's 21st International Cloud Expo® at the Santa Clara Convention Center in Santa Clara, CA. The Japan External Trade Organization (JETRO) is a non-profit organization that provides business support services to companies expanding to Japan. With the support of JETRO's dedicated staff, clients can incorporate their business; receive visa, immigration, and HR support; find dedicated office space; identify local government subsidies; get...
With 10 simultaneous tracks, keynotes, general sessions and targeted breakout classes, @CloudEXPO and DXWorldEXPO are two of the most important technology events of the year. Since its launch over eight years ago, @CloudEXPO and DXWorldEXPO have presented a rock star faculty as well as showcased hundreds of sponsors and exhibitors! In this blog post, we provide 7 tips on how, as part of our world-class faculty, you can deliver one of the most popular sessions at our events. But before reading...
Digital Transformation: Preparing Cloud & IoT Security for the Age of Artificial Intelligence. As automation and artificial intelligence (AI) power solution development and delivery, many businesses need to build backend cloud capabilities. Well-poised organizations, marketing smart devices with AI and BlockChain capabilities prepare to refine compliance and regulatory capabilities in 2018. Volumes of health, financial, technical and privacy data, along with tightening compliance requirements by...
"Avere Systems deals with data performance optimization in the cloud or on-premise. Even to this day many organizations struggle with what we call the problem of data gravity - 'Where should I put the data?' - because the data dictates ultimately where the jobs are going to run," explained Scott Jeschonek, Director Cloud Solutions at Avere Systems, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.