High Performance Browser Networking

1. Network performance fundamentals: Latency and bandwidth

Speed is a feature, and in fact, for some applications it is the feature.

Latency matters more than bandwidth. In most cases, the performance of web applications is limited by latency, not bandwidth. Latency is the time it takes for a message to travel from its point of origin to the point of destination, while bandwidth is the maximum throughput of a logical or physical communication path.

Factors affecting latency:

• Propagation delay (distance)
• Transmission delay (data size)
• Processing delay (network equipment)
• Queuing delay (network congestion)

Reducing latency is crucial for improving user experience, as humans perceive delays as small as 100-300 milliseconds. To optimize performance, focus on:

• Minimizing round trips
• Moving data closer to the client (e.g., using CDNs)
• Leveraging caching and compression techniques

2. TCP and UDP: The building blocks of internet communication

TCP provides the abstraction of a reliable network running over an unreliable channel.

TCP ensures reliable, ordered delivery. Transmission Control Protocol (TCP) is optimized for accurate delivery rather than timely delivery. It includes features like flow control, congestion control, and error checking, making it suitable for applications that require all data to arrive intact.

Key TCP concepts:

• Three-way handshake
• Slow-start algorithm
• Congestion avoidance

UDP offers speed over reliability. User Datagram Protocol (UDP) is a simpler, connectionless protocol that provides a low-latency and loss-tolerating connection. It's often used for real-time applications like video streaming and online gaming.

UDP characteristics:

• No guarantee of delivery or ordering
• No connection state or congestion control
• Lower overhead and latency

3. The evolution of HTTP: From 0.9 to 2.0

HTTP 2.0 will make our applications faster, simpler, and more robust—a rare combination.

HTTP has constantly evolved to meet web needs. The Hypertext Transfer Protocol (HTTP) has undergone significant changes from its inception to the current HTTP/2 version. Each iteration has brought improvements in performance, functionality, and efficiency.

HTTP evolution timeline:

• HTTP/0.9 (1991): Simple, one-line protocol
• HTTP/1.0 (1996): Added headers, methods, and status codes
• HTTP/1.1 (1997): Introduced keep-alive connections, pipelining
• HTTP/2 (2015): Multiplexing, header compression, server push

HTTP/2 addresses many limitations of its predecessors, offering:

• Full request and response multiplexing
• Header compression
• Server push capabilities
• Prioritization of requests

These improvements significantly reduce latency and increase page load speeds, especially for complex web applications.

4. TLS: Securing web communications

Security and performance are not mutually exclusive, and TLS can be optimized to minimize its impact on web application performance.

TLS provides encryption, authentication, and integrity. Transport Layer Security (TLS) is the protocol responsible for securing communications on the web. It ensures that data exchanged between clients and servers remains private and unaltered.

Key components of TLS:

• Handshake protocol: Authenticates parties and negotiates cryptographic parameters
• Record protocol: Encrypts and transmits application data

While TLS adds some overhead to web communications, several optimization techniques can minimize its impact:

• TLS session resumption
• TLS false start
• OCSP stapling
• Elliptic curve cryptography

Implementing these optimizations can significantly reduce the latency introduced by TLS, ensuring both security and performance.

5. Mobile networks: Challenges and optimizations

The performance of your application, especially the first load and the "time to render" depends directly on how this dependency graph between markup, stylesheets, and JavaScript is resolved.

Mobile networks present unique challenges. Mobile networks introduce additional complexities due to higher latencies, lower bandwidths, and less stable connections compared to fixed networks. Understanding these challenges is crucial for optimizing web applications for mobile users.

Key mobile network characteristics:

• Variable latency and bandwidth
• Radio Resource Control (RRC) state transitions
• Power consumption considerations

Optimization strategies for mobile:

• Minimize and batch network requests
• Implement efficient caching mechanisms
• Use compression for data transfers
• Optimize images and media for mobile devices
• Leverage offline capabilities (e.g., Service Workers)

By adapting web applications to the unique constraints of mobile networks, developers can significantly improve performance and user experience for mobile users.

6. Browser APIs: XMLHttpRequest, Server-Sent Events, and WebSockets

The fastest network request is a request not made.

Modern browsers offer powerful networking APIs. Web developers have access to a variety of APIs for efficient network communication, each suited for different use cases.

Comparison of browser networking APIs:
XMLHttpRequest (XHR):

• Traditional method for AJAX requests
• Supports both sending and receiving data
• Limited by same-origin policy (unless using CORS)

Server-Sent Events (SSE):

• Enables server-to-client real-time updates
• Unidirectional (server to client only)
• Automatically handles reconnection

WebSockets:

• Provides full-duplex, bidirectional communication
• Low latency, suitable for real-time applications
• Requires special server support

Choosing the right API depends on the specific requirements of your application. For real-time updates, SSE or WebSockets are often more efficient than polling with XHR. However, XHR remains useful for traditional request-response patterns.

7. WebRTC: Enabling peer-to-peer communication in browsers

WebRTC is much more than just another browser API.

WebRTC revolutionizes browser-based communication. Web Real-Time Communication (WebRTC) allows direct peer-to-peer communication between browsers, enabling applications like video calling, file sharing, and collaborative editing without the need for plugins or third-party software.

Key components of WebRTC:

• MediaStream: Handles audio and video capture
• RTCPeerConnection: Manages peer connections and data transfer
• RTCDataChannel: Enables arbitrary data exchange between peers

WebRTC uses UDP as its transport protocol, prioritizing low latency over guaranteed delivery. It incorporates several other protocols to handle various aspects of peer-to-peer communication:

• ICE, STUN, and TURN for NAT traversal
• DTLS for securing data transfers
• SCTP and SRTP for multiplexing and congestion control

While WebRTC opens up new possibilities for web applications, it also introduces complexities in terms of connection establishment and NAT traversal. Developers need to carefully consider these aspects when implementing WebRTC-based features.

Last updated: April 11, 2025