Alibaba Cloud Workspace uses Adaptive Streaming Protocol (ASP), a device-cloud synergy protocol built to deliver high-quality, low-latency interactive sessions. A device refers to an Alibaba Cloud Workspace terminal. This topic describes how ASP works and how it compares to the High-definition Experience (HDX) protocol, including a comparison of management capabilities for ASP-based and HDX-based cloud computers.
Benefits
ASP provides excellent performance, high reliability, and enhanced security for streaming. The ASP technical design integrates graphics command streams, graphics streams, and audio and video streams. The ASP protocol integrates multiple key technologies, such as image analysis, encoding, live streaming media, and network quality of service (QoS) optimization. The protocol also supports multi-platform SDKs.
ASP is built around three technical layers, each targeting a specific performance challenge:
Intelligent streaming engine
The engine detects the type of content being rendered — static content such as documents and web pages, or dynamic content such as video and games — and selects the appropriate streaming method automatically. This applies to both regular and GPU-accelerated cloud computers.
Advanced compression algorithm
Cloud computer screens typically show mixed content: computer-generated text and UI elements alongside camera-captured photos or video. No single codec handles both optimally. ASP classifies content regions using image analysis and applies targeted encoding to each. Only changed regions are transmitted, which reduces bandwidth usage while preserving image quality.
High-quality network transmission
Three common network problems affect streaming quality: jitter degrades real-time interaction, audio and video calls consume bandwidth unevenly, and congestion on unstable connections causes packet loss. ASP addresses all three:
A virtual multi-channel mechanism (via multiplexing) lets a single connection send packets by priority.
At the transport layer, ASP dynamically applies Quality of Service (QoS) policies, predicts available bandwidth, and performs congestion control using either Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) depending on conditions. By default, UDP is used because it delivers better performance on high-latency or unstable networks. If UDP cannot be established, TCP is used automatically.
A caching mechanism optimizes audio on both upstream and downstream channels.
Multi-client SDKs
ASP SDKs are available across all major platforms — Windows, macOS, Linux, Web, Android, and iOS — and are built on shared underlying resources. Each SDK includes modules for packet analysis, session management, I/O events (upstream), and image, audio, and video stream decoding.
Protocol comparison
The following table compares ASP and HDX across capabilities, graphics, multimedia, networking, SDK support, and supported guest operating systems. Features marked Yes (ASP only) are exclusive to ASP; features marked Yes (HDX only) are exclusive to HDX.
| Category | Feature | ASP | HDX |
|---|---|---|---|
| Basic capabilities | Downstream links: content streaming | Yes | Yes |
| Upstream links: data reporting from terminals | Yes | Yes | |
| Regular cloud computers | Yes | Yes | |
| GPU-accelerated cloud computers | Yes | Yes | |
| Virtual multi-channel mechanism | Yes | Yes | |
| Bidirectional copy of text or images | Yes | Yes | |
| Bidirectional copy of files | Yes | Yes | |
| Custom configurations on terminals | Yes | No | |
| Graphics | Joint Photographic Experts Group (JPEG) encoding | Yes | Yes |
| Image caching | Yes | Yes | |
| Dirty region update | Yes | Yes | |
| Encoding compression by region | Yes | Yes | |
| Lossless file compression | Yes | Yes | |
| Video stream | Yes | Yes | |
| Multi-display | Yes | Yes | |
| Resolution adjustment | Yes | Yes | |
| Watermarking | Yes | Yes | |
| Configurations of image display quality | Yes | Yes | |
| Stream division (stream collaboration) | Yes | No | |
| Relative mouse | Yes | Yes | |
| Multimedia | Opus encoding | Yes | Yes |
| H.264 encoding | Yes | Yes | |
| H.265 encoding | Yes | Yes | |
| Audio encoding | No | Yes | |
| Audio and video call | Yes | Yes | |
| Audio and video redirection | Yes | Yes | |
| Regional video stream encoding | Yes | Yes | |
| Full-screen video stream encoding | Yes | Yes | |
| Browser content redirection | No | Yes | |
| Windows media redirection | No | Yes | |
| Network | TCP-based reliable transmission | Yes | Yes |
| UDP-based unreliable transmission | Yes | Yes | |
| Automatic reconnection upon network downtime | Yes | Yes | |
| Display of bandwidth and latency | Yes | Yes | |
| SDK | Windows | Yes | Yes |
| macOS | Yes | Yes | |
| Linux | Yes | Yes | |
| Web | Yes | Yes | |
| Android | Yes | Yes | |
| iOS | Yes | Yes | |
| Guest OS | Windows Server 2016 | Yes | Yes |
| Windows Server 2019 | Yes | Yes | |
| Windows Server 2022 | Yes | No | |
| Ubuntu Linux | Yes | Yes |
Key differentiators
The following features differ between ASP and HDX:
Custom configurations on terminals (ASP only): Administrators can configure ASP-based terminals directly, without going through the cloud computer.
Stream division / stream collaboration (ASP only): ASP supports splitting a stream across multiple rendering paths for collaborative workflows.
Windows Server 2022 (ASP only): HDX does not support Windows Server 2022 as a guest operating system.
Browser content redirection and Windows media redirection (HDX only): HDX offloads browser media and Windows Media Player playback to the client endpoint for local rendering.
Audio encoding (HDX only): HDX supports audio encoding; ASP does not.
Management capability comparison
The following table compares management features for ASP-based and HDX-based cloud computers.
| Category | Feature | ASP (Windows) | ASP (Linux) | HDX (Windows) | HDX (Linux) |
|---|---|---|---|---|---|
| Basic policy | Network transfer | Yes | Yes | No | No |
| Image quality control | No | No | Yes | Yes | |
| Printer redirection | Yes | No | Yes | Yes | |
| USB redirection | Yes | No | Yes | Yes | |
| Webcam redirection | Yes | No | No | No | |
| Screen recording audit | Whole-process | Yes | Yes | Yes | No |
| Interval-based | Yes | Yes | Yes | No | |
| Operation-triggered | Yes | Yes | Yes | No | |
| Session lifecycle listening | Yes | Yes | No | No | |
| Audio | Yes | Yes | No | No | |
| Cloud computer | Scheduled task upon inactivity | Yes | No | No | No |
| Session | Session management | Yes | No | No | No |
| Monitoring | Session disconnection | Yes | No | No | No |
| Session logoff | Yes | No | No | No | |
| Message sending | Yes | No | No | No | |
| Applications | Yes | No | No | No | |
| Remote assistance | Yes | No | No | No | |
| AD office network | Conditional forwarders and trust relationships | See note below |
Feature details
Network transfer: ASP-based cloud computers use UDP/TCP adaptive mode. UDP is used by default, which delivers better performance on weak or high-latency networks. If UDP cannot be established, TCP is used automatically. Available only for ASP-based cloud computers.
Image quality control: Controls the image display quality of Enterprise Graphics cloud computers. Available only for HDX-based cloud computers.
Printer redirection: Lets end users use local printers on cloud computers.
USB redirection: Lets end users use local USB devices on cloud computers.
Webcam redirection: Lets end users use local webcams on cloud computers. Supported only on ASP-based Windows cloud computers.
Whole-process screen recording: The EDS system records all user operations for the duration of a session — from connection to disconnection.
Interval-based screen recording: Records during a configured time window only. The recording starts when end users connect and stops when they disconnect. Operations outside the window are not recorded.
Operation-triggered screen recording: Recording is triggered by specific end-user operations.
Session lifecycle listening: Records all user operations from session establishment to session close. Available only for ASP-based cloud computers.
Audio recording: Records audio output from cloud computers during screen recording sessions. Available only for ASP-based cloud computers.
Scheduled task upon inactivity: Triggers a configured task when no mouse or keyboard input is detected for a set period. Available only for ASP-based Windows cloud computers.
Session management: Manages the logical connection between an end user and a cloud computer. Enabling this feature greatly improves cloud computer utilization. Available only for ASP-based Windows cloud computers.
Session disconnection: When an active session is closed, the session remains resumable if the end user reconnects within a configured time window. Available only for ASP-based Windows cloud computers.
Session logoff: When an end user closes a session, unsaved data is deleted. A new session starts on the next connection. Available only for ASP-based Windows cloud computers.
Message sending: Sends messages to end-user sessions. Available only for ASP-based Windows cloud computers.
Applications: Lets administrators view all applications used by end users. Available only for ASP-based Windows cloud computers.
Remote assistance: Lets administrators initiate remote assistance for end users. Available only for ASP-based Windows cloud computers.
Conditional forwarders and trust relationships (AD office network): If no conditional forwarder and trust relationship are configured for an AD office network, only ASP-based cloud computers can be created. If both are configured, either ASP-based or HDX-based cloud computers can be created. The available protocol is determined by these AD network configurations.