This document describes Dynamic Performance Acceleration technology from XO Communications. It aims to optimize websites to reduce time-to-action, the amount of time until a user can interact with a page. It does this through techniques like prioritizing above-the-fold content, image combining, and script optimization. Dynamic Performance Acceleration analyzes pages and rewrites elements to accelerate loading without requiring changes from website owners. It provides these services through a global cloud platform with no hardware required.

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Dynamic Performance
Acceleration:
Reducing the browser bottleneck

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Table of Contents
What is Dynamic Performance Acceleration? ...................................................................................... 3
Historical delivery challenges ............................................................................................................... 3
Network reach ......................................................................................................................... 3
Datacenter consolidation ........................................................................................................ 3
Dynamic Websites ................................................................................................................... 4
Browser communication is the new bottleneck ............................................................... 4
Measuring Time‐to‐Action ................................................................................................................... 5
Different from Traditional CDN Services ............................................................................................. 5
Other Web Page Optimization Services .............................................................................................. 6
Dynamic Performance Acceleration Technology ................................................................................ 7
The XO Difference ............................................................................................................................... 8
Key Technology Features ........................................................................................................................ 8
Safe script postponing ............................................................................................................ 8
Viewport prioritization............................................................................................................ 8
Intelligent image combining ................................................................................................... 8
lnline frame rendering optimizations .................................................................................... 9
Javascript inlining .................................................................................................................... 9
Recursive cascading style sheet inlining ................................................................................ 9
Browser connection limit management ................................................................................ 9
Compression ............................................................................................................................ 9
Early resource loading ............................................................................................................ 9
Text replacement/insertion .................................................................................................... 9
XO CONTROL ...................................................................................................................................... 10
Summary ............................................................................................................................................ 10

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What is Dynamic Performance Acceleration?
The XO Dynamic Performance Acceleration solution is designed to optimize a customer's web
pages to enable faster Time-to-Action. Time-to-Action is the amount of time that elapses between
when a page begins to load and the time that an end user can interact with that web page. Dynamic
Performance Acceleration transparently optimizes the customer's web sites by rewriting elements of
the HTML page in such a way that it accelerates the page rendering process.
Dynamic Performance Acceleration is part of the Acceleration family of services specifically
designed to support dynamic web site acceleration:
• Basic Acceleration: Accelerate dynamic web sites through the use of a global caching and network
optimization to expedite the delivery of non-cacheable content.
• Premium Acceleration: A service offering that combines the benefits of the global
caching platform, network optimizations, and Dynamic Performance Acceleration
Technology targeted at B2C-based (business-to-consumer) applications.
• Mobile Acceleration: A service offering that takes advantage of Dynamic Performance
Acceleration Technology with special optimizations to support smart phone delivery for Apple
iPhone, iPad and Android-based handsets.
Application Acceleration can be utilized as a standalone service, in conjunction with dynamic
site acceleration, or in conjunction with third-party dynamic site acceleration solutions.
Historical delivery challenges
Network reach
Where is the delivery pain point? If we were to roll the Internet clock back ten years ago, in order to
deliver content to end users in an expeditious manner, one would have to have network presence
with over 8,000 different network providers to capture over 80% of the end user eyeball traffic. This
necessitated having multiple connections and lots of deployments in order to ensure end user
performance.
Fast forward to today. Network carrier and ISP consolidation has transformed the network landscape
and is impacting the need for large diverse network footprints. 80% of the world’s eyeball traffic can
now be reached with less than 1,000 network providers. The Internet is becoming a smaller place.
This phenomenon of network consolidation still does not mitigate the need for some form of network
acceleration. However, the major pain point in delivery has shifted given the improved speeds along
the Internet, network backbones and inter-carrier peering.
Datacenter consolidation
Underlying this trend towards network consolidation is the trend towards datacenter consolidation.
This gave rise to the WAN Optimization Controller (WOC) market andits service-based cousin that is

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sometimes referred to as Dynamic Site Acceleration (DSA)in an attempt to compensateforthereduced
geographicdatacenterfootprint. As customers look to support fewer, larger datacenter deployments, it
has a side effect of losing geographic presence. WOC and DSA capabilities help to fill that void by
providing end users with performance that can be comparable to having a local datacenter without the
expense and operational challenges that come with maintaining multiple physical datacenter facilities
and systems. However, in most domestic markets, the network effect is not that strong.
In domestic markets, things like presentation layer optimizations such as GZIP compression play a
larger role in improving dynamic content performance; however, with trans-Atlantic/trans-Pacific long-
haul requests, the network effect can be more pronounced. As customers continue to consolidate and
virtualize their infrastructure, it gives rise to the need for some form of presentation layer acceleration.
Dynamic Websites
The corporate industry trend is to webify traditional back office systems. Part of this desire is to use
cheaper local Internet connections rather than more expensive point-to-point connections. By
decommissioning dedicated branch-to-branch and branch-to-headquarters connectivity and migrating to
HTTP-based applications, versus fat-client server-based applications, companies have more flexibility
with rolling out new features without having to force new end user downloads, offering improved security
through centralized application management, as well as faster time to market. As these dynamic,
mission-critical applications move to the Internet, the user base becomes more sensitive to performance
lag as they use the Internet for their communications backbone. This paradigm is forcing businesses to
address the performance lag for their highly dynamic HTTP-based applications.
With the rise of online commerce as a viable revenue channel to corporations, B2C web sites have
become a more important component in driving top-line revenue growth in corporate boardrooms across
the globe. Hence, more attention and money is being thrown at the web channel in order to drive more
sales and adoption. Along with this trend, B2C websites have become more dynamic, incorporating both
personalized and customized information about the end user in an attempt to provide a more engaging
brand experience, helping to retain customers and drive online adoption. As Internet commerce and
portals have started to come of age, the infrastructure required to support these dynamic applications
have become more complex and expensive to manage. Along with the data center consolidation trend
previously mentioned, complex database-driven websites can greatly benefit from data center
consolidation with less infrastructure to maintain globally. With consolidation, databases don't need to be
synchronized across vast distances, mitigating concurrency issues, as well as simplifying disaster
recovery planning. The other side of the coin is that having centralized applications running over the
Internet creates end user performance issues. Having some sort of web acceleration technology has
been a useful tool in overcoming some of the application performance challenges as a result of the
increased use of dynamic content.
Browser communication is the new bottleneck
The end user web browser is based on the HTTP protocol which is over twenty years old.
Advancements have been made in the browser engine's rendering capability; however, not much
has changed to alter the underlying HTTP protocol to improve end users Time-to-Action. Content
Delivery Networks using DSA or WOC devices can only address so much through network
acceleration and dropping off the content at the closest edge cache server point to an end user. The
end user's browser still has to render the page. Most HTML web pages are comprised of over eighty
objects and five different domain names: images, cascading style sheets, javascripts, third-party

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ads, tracking beacons, etc. Most browsers fetch objects in some synchronous fashion with no
priority as to which objects it should fetch to render the page. This leads to an interesting side effect
that impacts the Time-to-Action. When a browser receives a javascript element, the browser pauses
content retrieval while the browser engine interprets the javascript to determine what to do next.
Delivering the objects from an edge server cache does not change this browser-based behavior,
which impacts the last byte download time and the Time-to-Action. The browser cannot render the
page faster even if the objects get there faster – unless there is help. This is where Web Page
Optimization (WPO) capabilities come into play.
Measuring Time-to-Action
Typical web performance benchmarking services like Keynote and Gomez are often used to evaluate
the end user experience. These synthetic tests are often performed from network backbones and
download the content, measuring the DNS lookup time, first byte download, payload download time,
etc. in an effort to ascertain how long it takes to download the objects on a web page. Do end users
really download content at backbone network speeds? Of course not, but as an industry we have come
to accept these tests as a barometer to benchmark performance.
In reality, these tests are measuring how long it takes to last byte download regardless of what actually is
needed for the end user to interact with the page. Web Page Optimization (WPO) is different. It is about
measuring Time-to-Action – how soon can an end user interact with the web page and what elements
comprise the visible field of view? How long it takes to download non-visible elements is largely irrelevant
to the end user experience. Benchmarking browser render time is more impactful to determine the end
user experience.
Different from Traditional CDN Services
Content Delivery Networks (CDNs) can play a vital role in improving the end user experience. They
typically are caching/off-loading common reference objects on the edge caches, while they route
optimize non-cacheable requests back to the origin. This does help improve the end user experience:
but its impact is somewhat muted with respect to the Time-to-Action for an end user. Most WOC/DSA-
type services optimize the network layer transport and attempt to offload some of the common objects
on a page, but they don't do anything to help the browser more effectively render the HTML for the end
user.
In regional delivery markets where content is largely localized, WPO can be a more effective technology
solution for customers as the regional network effect that traditional WOC/DSA services are designed to
address are not really the main pain points in delivery time. WPO addresses the end user experience by
reducing the number of round trips an end user needs to make in order to render the page. Fewer round
trips equates to better performance.
In certain situations, the optimal setting may be using a combination of traditional WOC/CDN-based
content acceleration solutions in conjunction with some form of WPO. WPO reduces the connection and
improves the last mile interaction; while the network optimizations and caching components can be used
to effectively limit the interaction with the customer's origin web infrastructure and expedite non-cachable
content back to the customer's datacenter for long-haul connections.

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Other Web Page Optimization Services
There are many different flavors of Web Page Optimization (WPO) in the market today ranging from
server plug-ins to hardware appliances deployed at a datacenter. Below are some areas of interest that
customers need to consider when choosing a WPO vendor:
• Scalability: How does the solution scale for seasonal or unplanned load? Do you need to
deploy more dedicated appliances? If your page volume goes beyond a certain level, do you
need to spend more CapEx?
• Resource Utilization: HTML page transformation can be expensive in terms of memory and CPU
utilization. If you are using a web server plug-in, what effect does that have on your web server's
effectiveness?
• WPO Capabilities: What types of optimizations can the WPO platform offer? Do you need to pre-
process anything?
• Dynamic Content: Some WPO services are designed to optimize over time. The more they see
patterns emerge, the more they optimize the web page; however, many web sites today are
dynamic and constantly changing. When a web page is always changing, WPO technology that
relies on pattern matching never sees the same thing twice, so it is never able to achieve its
optimal state.
• One-size-fits-all approach: All browser technology is not the same. What works well for Internet
Explorer does not necessarily work well for Firefox or Chrome. Some WPO tools only focus on
one type of optimization and do not customize the experience based on the browser type.
• Availability: How does the WPO platform ensure service availability? Do you need to
deploy multiple machines in order to ensure uptime?
• Mobile Acceleration: Does the WPO vendor do anything to help support mobile delivery? Hyper
growth in the smart phone category continues to outpace new desktop PCs sales. WPO vendor
support varies based on capability and efficacy.
• Secure Delivery: Secure Socket Layer (SSL) delivery is an important part of any web site
performing B2B or B2C transactions; however, some WPO vendors do not support delivery of
Web pages over SSL. What good is having a WPO service that can't address your secure
delivery needs?
• Development Resources: Implementing best practices for WPO is something that can be done
with careful HTML programming effort, know-how, and time; however, optimizing page delivery
across a wide range of end user browser environments for an ever-changing website is
something that most customers would rather avoid as it is resource and time-consuming. Using
some sort of WPO capability to automatically leverage WPO best practices is often a better use
of time and money.

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Dynamic Performance Acceleration Technology
Application Acceleration incorporates Website Performance Optimization (WPO) functionality
through a series of technologies, blending both the art and the science of WPO in a seamless
service offering. XO encapsulates these techniques under the moniker of Dynamic Performance
Acceleration. Dynamic Performance Acceleration (DPA) is specifically designed to optimize dynamic
web pages without impairing the user experience or requiring any end user browser plug-ins.
Dynamic Performance Acceleration impacts the Time-to-Action. The diagram below illustrates this
concept. In a normal end user browser to web server exchange, requests are made in a serial fashion –
one after another until the page is loaded. With Dynamic Performance Acceleration, objects are
prioritized so that the visible objects are requested first, while hidden objects are downloaded after the
end user's browser viewport, aka above the fold, has been rendered. This content transformation takes
place transparently without content owners having to manipulate their HTML code. The result? The end
user can see and interact with a web page much more quickly. In the illustration below, the web page
loaded in 6.1 seconds without Dynamic Performance Acceleration (DPA). However, with XO DPA, the
same page loads in 3.7 seconds. An important distinction because every second counts when a user is
waiting on your site. Each second the user is kept waiting increases the likelihood that the user will
abandon your page without interacting.

8. The XO Difference
Application Acceleration is different from other WPO solutions both architecturally and
technologically. Like other XO Cloud delivery services, Application Acceleration is sold as
a software-as-a-service model so there is no hardware to deploy, no server plug-ins that
need to be tied into a Web server and best of all, no CapEx. XO integrates into the
delivery path as a proxy server whereby traffic is directed to the Application Acceleration
platform by way of a canonical name (CNAME) via a DNS directive. As a result,
Application Acceleration provides customers with a global platform, with no single point
of failure, enabling elastic functionality for on-demand scalability. As your website
grows, the Application Acceleration platform just seamlessly expands to fit your needs;
furthermore, because Application Acceleration is executed as a service, customers get
to take advantage of new capabilities as the market evolves – future proofing your web
site to always take advantage of the latest WPO advancements. No software upgrades
to plan or purchase, thus reducing maintenance costs, management overhead and
headaches.
More importantly, Application Acceleration has been optimized to perform dynamic WPO
optimizations to provide the industry's fastest Time-to-Action. This manifests itself in higher
end user conversions on your site, improved end user experiences, and reduced site
abandonment – leading to increased site stickiness and website adoption.
Key TechnologyFeatures
Safe script postponing
Safe script postponing controls the execution of things, like javascript. Safe script
postponing seamlessly delays scripts with no adverse effect on HTML page rendering.
Web pages retain their original look and behavior.
Viewport prioritization
Viewport prioritization conditions the browser to request certain objects before others.
This is done in an effort to improve the Time-to-Action for the above-the-fold end user
experience. This technology can also be used to promote certain objects so they render
first, e.g. third-party advertisement scripts.
Intelligent image combining
Dynamic Performance Acceleration has the ability to combine images into larger payload
downloads that some people refer to as image “spriting”. Intelligent image combining is an
example of the art and science of WPO at work. If one were to try to optimize the last byte
download experience, one could combine all the objects on a page into a single large
object for download and let the end user's browser decompose the image sprite;
however, combining all the images into a single resource has an adverse effect on Time-
to-Action as inevitably objects that are below the fold and not necessary for the viewport
are being downloaded. The magic of the XO Dynamic Performance Acceleration

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technology is to know what elements are required to render the above-the-fold
experience and combine only those image resources necessary to render the viewport –
dynamically.
lnline frame rendering optimizations
lnline frames is a technique that some web developers use to incorporate elements from
different sources into a single page. Dynamic Performance Acceleration contains
functionality to specifically optimize inline frame rendering to optimize the Time-to-Action.
Javascript inlining
Waiting on javascripts to be processed by the end user browser is one of the largest
elements attributed to longer last byte download times. To mitigate this effect, Dynamic
Performance Acceleration has the ability to dynamically and in real-time inline scripts into
the web page itself. This reduces network, server, and browser processing latencies
associated with external script fetching – all with the goal of improving the Time-to-Action.
Recursive cascading style sheet inlining
As with the Javascript inlining function, Dynamic Performance Acceleration has the ability
to inline cascading style sheets (CSS) into the base HTML page. This is done to improve
the Time-to-Action by eliminating superfluous requests and wait time.
Browser connection limit management
Not all browsers exhibit the same behaviors. Some browsers are able to support two
simultaneous connections, while others can support six or more. Dynamic Performance
Acceleration knows the capabilities of the most popular browser types and in turn is able
to override the default parameters and fool the browser into believing it has more
connections available, allowing the end user's browser to download more multiple
resources via the many connections. New browser support is added as new standards
emerge.
Compression
Compression is a very common performance optimization, but is often not used because
it can be CPU intensive. Dynamic Performance Acceleration has the ability to compress
content by MIME type as a way to reduce the overall payload size that the end user's
browser needs to download, thus improving performance.
Early resource loading
Browser think time can sometimes impact when resources load. Application Acceleration
ensures end user browsers can fetch resources as soon as page loading commences, so
as to eliminate unnecessary delays and improving Time-to-Action.
Text replacement/insertion
Dynamic Performance Acceleration also has the ability to dynamically replace and inject
code into the HTML page. This can be useful to place tracking or campaign beacons into

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a web page. Text replacement can also be used as a means to alter hard-coded
elements in a page, such as changing HTTP to HTTPS, to ensure that end users do not
get security browser warnings.
XO CONTROL
The Application Acceleration client extranet site, CONTROL, provides customers with the
functionality they need in order to self-provision and report on their Application
Acceleration service. Using a wizard-like workflow, customers can tune and manipulate
their Application Acceleration configuration. Configuration changes are propagated to the
production network in less than five minutes, allowing customers to do rapid prototyping,
as well as adjustments to their production environment in near real-time.
Summary
Application Acceleration is a Software-as-a-Service (SaaS) solution designed to provide
customers with a transparent and scalable solution to enable Web Page Optimization
(WPO) to reduce the end user Time-to-Action. By optimizing the web page experience for
the end user, organizations may see a range of benefits including:
• Improved Conversion Rates: Customers may see an improvement in their conversion rates
as a result of the improved Time-to-Action. Because end users can interact with the web site
faster, they are less likely to get frustrated and leave.
• More Page Views: For ad supported sites, optimizing the Time-to-Action translates to more page
views, and the more pages viewed, the more money you have the opportunity to earn.
• Enhanced User Experience: Customers have a very short attention span if a web site is
slow. Improving the Time-to-Action helps protect your brand and leaves your audience with
a positive impression.
• Stickiness/Adoption: When the perceived page load time is fast, end users are more likely to
linger on your web site. This gives you more of an opportunity to sell, promote, and/or drive
uptake of your online service.
• Reduce Abandonment: A shorter Time-to-Action will keep users on your web site and
less likely to abandon shopping carts. If users are engaged with your brand, you keep
them away from the competition.
Application Acceleration can be purchased as a standalone capability or as part of a
complementary WOC/DSA service. Whether your needs are regional, mobile, or
international, Application Acceleration fills a role that no other technology solution can
compare to in terms of scalability, ease of use, and technological capability.

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The HTTP protocol in the end user's browser is the new bottleneck of the Internet. Using XO
Application Acceleration is the latest technology in your arsenal to over overcome the
limitations of the end user browser.
To learn more, please visit www.xo.com/SuperchargeYourContent or contact an XO representative at
888-349-0134.