Multicast Assisted Unicast Delivery for Live Content
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Solution Overview
Problem
Current content delivery methods using HTTP(S) for live events result in inefficient network usage due to unicast traffic peaks, which can degrade user experience and overwhelm Content Delivery Network servers, as they do not effectively utilize multicast for identical content delivery to multiple clients.
Innovation Solution
Implementing a 'Multicast Assisted Unicast Delivery' (MAUD) method where responses from a content server are separated into client-specific and common components, with the former sent over unicast and the latter over multicast, using proxy servers to regenerate and deliver the complete response to clients, allowing for authentication token updates and session-specific information preservation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If unicast HTTP requests are used for content delivery to multiple clients, then each client can receive individualized content with session-specific information, but network traffic peaks occur and network efficiency deteriorates
Solution Approach 1:
The response from the content server is segmented into two components: a first component containing session-specific information delivered via unicast, and a second component containing common content delivered via multicast. This segmentation allows the system to simultaneously preserve individualized client information while achieving efficient multicast distribution of identical content to multiple clients, thereby resolving the contradiction between reliability of session information delivery and network productivity.
2Productivity
If multicast is used for content delivery to multiple clients, then network efficiency improves and traffic peaks are reduced, but session-specific information and authentication tokens cannot be delivered individually
Solution Approach 1:
The response is divided into a first component for unicast delivery containing authentication tokens and session-specific data, and a second component for multicast delivery containing the common content. This segmentation enables the system to achieve high network efficiency through multicast while simultaneously ensuring reliable delivery of session-specific information through unicast channels.
Solution Approach 2:
A network node acts as an intermediary that receives the segmented response components, regenerates the complete response by combining them, and delivers it to the client. This intermediary enables the coordination between unicast and multicast paths, ensuring that session-specific information and common content are properly integrated and delivered together to the client.
3Productivity
If Proxy X sends entire response over multicast, then network efficiency improves, but authentication and session management become impossible
Solution Approach 1:
Proxy X segments the response into a first component containing authentication-related session-specific information and a second component containing the common content. The first component is sent via unicast to the specific client, while the second component is sent via multicast to multiple clients. This segmentation preserves authentication capability while achieving network efficiency through multicast.
Data Source
AI summary
Described is a method of delivering content over a network using an approach referred to as “Multicast Assisted Unicast Delivery” (MAUD), as a multicast network is used to assist, rather than substituting for, an otherwise unicast path. Content is requested by client devices from a content server over unicast. The responses containing the requested content are separated into two components: a first component containing elements that are specific to individual client devices (for example session specific data), and a second component that is common to all client devices (typically this is the video content being requested). The first component can be delivered over unicast and the second component over multicast. Identifiers are introduced into each of the first and second components to aid recombination of the components to form the original responses. The separation and recombination are handled by suitably configured proxy servers.