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Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 5

Jean Tunis

This blog is the final installment in a 5-part series on APMdigest where I discuss web application performance and how new protocols like SPDY, HTTP/2, and QUIC will hopefully improve it so we can have happy website users.

Start with Web Performance 101: The Bandwidth Myth

Start with Web Performance 101: 4 Recommendations to Improve Web Performance

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 1

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 2

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 3

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 4

HTTP/2 Implementations

It has been almost a year since HTTP/2 has been a ratified standard. I talked about how widely support it is - only 4% of the top 2 million Alexa sites truly support it.

Does your website support it? What about your web host provider?

One place to check is the Google Chrome browser itself by going to Chrome Web Tools.


You can also check by doing a packet capture with Wireshark. Or go to tools.keycdn.com/http2-test.

By now, most web browsers support the new version of HTTP. The top five, Chrome, Firefox, IE/Edge, Opera and Safari all support HTTP/2, at least partially. The top two widely used web servers, Apache and Nginx, support it as well.

Previously, I mentioned a number of workarounds that developers used to make their websites faster with HTTP/1.1. Now with HTTP/2, some of these workarounds can actually degrade performance with HTTP/2 implementation.

The Unsharding

With only one connection per host that is allowed with HTTP/2, domain sharding can hurt a developer's attempt to improve performance. So if there was used previously, an upgrade to HTTP/2 means that the domains must be unsharded.

The Uncombine

Combining Javascript and CSS files into one file helped to reduce the amount of connections on HTTP/1.1. This is no longer needed with only one connection.

However, care must be taken with this. Doing this must be tested on a case-by-case basis. Some large files are able to compress better than smaller files. So it may not be to your advantage to uncombine the files if you have a lot of smaller files.

The Uninlining

Inlining scripts directly into the HTML was another way to reduce the number of connections and round-trips to the server. With HTTP/2, this is no longer needed with only one TCP connection.

HTTP/2 Pros & Cons

There are number of advantages of using HTTP/2, including:

■ Substantially and measurably improve end-user perceived latency over HTTP/1.1 using TCP

■ Address the head of line blocking problem in HTTP

■ Not require multiple connections to a server to enable parallelism, thus improving its use of TCP

■ Retain the semantics of HTTP/1.1, like header fields, status codes, etc.

■ Clearly define how HTTP/2.0 interacts with HTTP/1.x via new Upgrade header field

But, despite these advantages, there are still some disadvantages that the new protocol version has not addressed.

Some disadvantages are:

■ Unable to get around TCP head of line blocking, particularly during packet loss

■ TCP's congestion avoidance algorithm increases serialization delay

■ TLS connection setup still takes time

■ Binary format (for people like me) makes troubleshooting a bit more difficult, not being able to see plaintext, without TLS encryption keys

We Need to Be QUIC

So we see that we still have a number of limitations even with HTTP/2. Although, I have to admit, the last one is somewhat selfish.

One big limitation is the TCP protocol. Due to its connection-oriented nature, there's no getting around the head of line blocking and the time it takes to open and close the connection.

Google wanted a way around this, and in 2012 set out to develop a protocol that runs on top of UDP, which is connectionless protocol. The protocol is called Quick UDP Internet Connections, or QUIC. Another clever name by Google?

Clever or not, Google needed a protocol with quicker connection setup time and quicker retransmissions. Unlike TCP, UDP would allow for this. They wanted to take some of the benefits of the work done with SPDY, that ultimately went into the HTTP/2 standard, such as multiplexed HTTP communication, but running over UDP rather than TCP.

The main goal? To reduce overall latency across the Internet for a user's interactions.

QUIC implements various TCP features, but without the limitations, such as the round-trip time for connection setup, flow control, and congestion avoidance. With UDP's connectionless orientation, RTT is zero since UDP just starts sending data when it needs to rather than talking to the other side to ensure it's available to talk.

Where is QUIC?

The most common place I've come across QUIC being used is on YouTube.

Have you ever compared the speed of a YouTube video compared to some of the other providers like Wistia and Vimeo? Where I live, I'll be lucky to get 3Mbps from my ISP. Watching a video on YouTube rarely buffers. I can almost always count on buffering when watching a video hosted on Wistia or Vimeo. As you can see in the screenshot below, the protocol being used on YouTube is a mix of QUIC and SPDY.


Contrast that to the screenshot I took from Wistia's site, below.


They are still largely using HTTP/1.1. They're not even on HTTP/2 yet. I'm sure they are doing a number of other things to make their web properties faster, but that explains to me why I rarely get any buffering on YouTube compared to Wistia.

Conclusion

If the speed with which SPDY was tested and went into the HTTP/2 standard, which took about three years from SPDY draft release to HTTP/2 draft release, is it possible that we could have a replacement for the TCP protocol on the web in the next couple of years? This should be interesting and exciting!

Jean Tunis is Senior Consultant and Founder of RootPerformance.

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Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 5

Jean Tunis

This blog is the final installment in a 5-part series on APMdigest where I discuss web application performance and how new protocols like SPDY, HTTP/2, and QUIC will hopefully improve it so we can have happy website users.

Start with Web Performance 101: The Bandwidth Myth

Start with Web Performance 101: 4 Recommendations to Improve Web Performance

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 1

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 2

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 3

Start with Web Performance and the Impact of SPDY, HTTP/2 & QUIC - Part 4

HTTP/2 Implementations

It has been almost a year since HTTP/2 has been a ratified standard. I talked about how widely support it is - only 4% of the top 2 million Alexa sites truly support it.

Does your website support it? What about your web host provider?

One place to check is the Google Chrome browser itself by going to Chrome Web Tools.


You can also check by doing a packet capture with Wireshark. Or go to tools.keycdn.com/http2-test.

By now, most web browsers support the new version of HTTP. The top five, Chrome, Firefox, IE/Edge, Opera and Safari all support HTTP/2, at least partially. The top two widely used web servers, Apache and Nginx, support it as well.

Previously, I mentioned a number of workarounds that developers used to make their websites faster with HTTP/1.1. Now with HTTP/2, some of these workarounds can actually degrade performance with HTTP/2 implementation.

The Unsharding

With only one connection per host that is allowed with HTTP/2, domain sharding can hurt a developer's attempt to improve performance. So if there was used previously, an upgrade to HTTP/2 means that the domains must be unsharded.

The Uncombine

Combining Javascript and CSS files into one file helped to reduce the amount of connections on HTTP/1.1. This is no longer needed with only one connection.

However, care must be taken with this. Doing this must be tested on a case-by-case basis. Some large files are able to compress better than smaller files. So it may not be to your advantage to uncombine the files if you have a lot of smaller files.

The Uninlining

Inlining scripts directly into the HTML was another way to reduce the number of connections and round-trips to the server. With HTTP/2, this is no longer needed with only one TCP connection.

HTTP/2 Pros & Cons

There are number of advantages of using HTTP/2, including:

■ Substantially and measurably improve end-user perceived latency over HTTP/1.1 using TCP

■ Address the head of line blocking problem in HTTP

■ Not require multiple connections to a server to enable parallelism, thus improving its use of TCP

■ Retain the semantics of HTTP/1.1, like header fields, status codes, etc.

■ Clearly define how HTTP/2.0 interacts with HTTP/1.x via new Upgrade header field

But, despite these advantages, there are still some disadvantages that the new protocol version has not addressed.

Some disadvantages are:

■ Unable to get around TCP head of line blocking, particularly during packet loss

■ TCP's congestion avoidance algorithm increases serialization delay

■ TLS connection setup still takes time

■ Binary format (for people like me) makes troubleshooting a bit more difficult, not being able to see plaintext, without TLS encryption keys

We Need to Be QUIC

So we see that we still have a number of limitations even with HTTP/2. Although, I have to admit, the last one is somewhat selfish.

One big limitation is the TCP protocol. Due to its connection-oriented nature, there's no getting around the head of line blocking and the time it takes to open and close the connection.

Google wanted a way around this, and in 2012 set out to develop a protocol that runs on top of UDP, which is connectionless protocol. The protocol is called Quick UDP Internet Connections, or QUIC. Another clever name by Google?

Clever or not, Google needed a protocol with quicker connection setup time and quicker retransmissions. Unlike TCP, UDP would allow for this. They wanted to take some of the benefits of the work done with SPDY, that ultimately went into the HTTP/2 standard, such as multiplexed HTTP communication, but running over UDP rather than TCP.

The main goal? To reduce overall latency across the Internet for a user's interactions.

QUIC implements various TCP features, but without the limitations, such as the round-trip time for connection setup, flow control, and congestion avoidance. With UDP's connectionless orientation, RTT is zero since UDP just starts sending data when it needs to rather than talking to the other side to ensure it's available to talk.

Where is QUIC?

The most common place I've come across QUIC being used is on YouTube.

Have you ever compared the speed of a YouTube video compared to some of the other providers like Wistia and Vimeo? Where I live, I'll be lucky to get 3Mbps from my ISP. Watching a video on YouTube rarely buffers. I can almost always count on buffering when watching a video hosted on Wistia or Vimeo. As you can see in the screenshot below, the protocol being used on YouTube is a mix of QUIC and SPDY.


Contrast that to the screenshot I took from Wistia's site, below.


They are still largely using HTTP/1.1. They're not even on HTTP/2 yet. I'm sure they are doing a number of other things to make their web properties faster, but that explains to me why I rarely get any buffering on YouTube compared to Wistia.

Conclusion

If the speed with which SPDY was tested and went into the HTTP/2 standard, which took about three years from SPDY draft release to HTTP/2 draft release, is it possible that we could have a replacement for the TCP protocol on the web in the next couple of years? This should be interesting and exciting!

Jean Tunis is Senior Consultant and Founder of RootPerformance.

Hot Topics

The Latest

According to Auvik's 2025 IT Trends Report, 60% of IT professionals feel at least moderately burned out on the job, with 43% stating that their workload is contributing to work stress. At the same time, many IT professionals are naming AI and machine learning as key areas they'd most like to upskill ...

Businesses that face downtime or outages risk financial and reputational damage, as well as reducing partner, shareholder, and customer trust. One of the major challenges that enterprises face is implementing a robust business continuity plan. What's the solution? The answer may lie in disaster recovery tactics such as truly immutable storage and regular disaster recovery testing ...

IT spending is expected to jump nearly 10% in 2025, and organizations are now facing pressure to manage costs without slowing down critical functions like observability. To meet the challenge, leaders are turning to smarter, more cost effective business strategies. Enter stage right: OpenTelemetry, the missing piece of the puzzle that is no longer just an option but rather a strategic advantage ...

Amidst the threat of cyberhacks and data breaches, companies install several security measures to keep their business safely afloat. These measures aim to protect businesses, employees, and crucial data. Yet, employees perceive them as burdensome. Frustrated with complex logins, slow access, and constant security checks, workers decide to completely bypass all security set-ups ...

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Cloudbrink's Personal SASE services provide last-mile acceleration and reduction in latency

In MEAN TIME TO INSIGHT Episode 13, Shamus McGillicuddy, VP of Research, Network Infrastructure and Operations, at EMA discusses hybrid multi-cloud networking strategy ... 

In high-traffic environments, the sheer volume and unpredictable nature of network incidents can quickly overwhelm even the most skilled teams, hindering their ability to react swiftly and effectively, potentially impacting service availability and overall business performance. This is where closed-loop remediation comes into the picture: an IT management concept designed to address the escalating complexity of modern networks ...

In 2025, enterprise workflows are undergoing a seismic shift. Propelled by breakthroughs in generative AI (GenAI), large language models (LLMs), and natural language processing (NLP), a new paradigm is emerging — agentic AI. This technology is not just automating tasks; it's reimagining how organizations make decisions, engage customers, and operate at scale ...

In the early days of the cloud revolution, business leaders perceived cloud services as a means of sidelining IT organizations. IT was too slow, too expensive, or incapable of supporting new technologies. With a team of developers, line of business managers could deploy new applications and services in the cloud. IT has been fighting to retake control ever since. Today, IT is back in the driver's seat, according to new research by Enterprise Management Associates (EMA) ...

In today's fast-paced and increasingly complex network environments, Network Operations Centers (NOCs) are the backbone of ensuring continuous uptime, smooth service delivery, and rapid issue resolution. However, the challenges faced by NOC teams are only growing. In a recent study, 78% state network complexity has grown significantly over the last few years while 84% regularly learn about network issues from users. It is imperative we adopt a new approach to managing today's network experiences ...

Image
Broadcom

From growing reliance on FinOps teams to the increasing attention on artificial intelligence (AI), and software licensing, the Flexera 2025 State of the Cloud Report digs into how organizations are improving cloud spend efficiency, while tackling the complexities of emerging technologies ...