Rendezvous-Based CDN Server Selection for Cache-Aware Content Retrieval
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Solution Overview
Problem
Conventional CDN systems face inefficiencies in selecting optimal CDNs and content servers due to limited information about geographic location and cached content, leading to suboptimal content delivery.
Innovation Solution
A rendezvous system that utilizes a repeatable hash function to identify geographically proximate content servers based on content and location identifiers, ensuring consistent caching and efficient content retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CDN systems use limited information for server selection, then the system complexity is reduced, but the content delivery efficiency deteriorates
Solution Approach 1:
The system pre-computes and stores content location mappings in a content location service before requests arrive. This preliminary action allows the CDN to quickly resolve content locations without complex real-time computations, improving delivery efficiency while maintaining manageable system complexity through offline preparation.
Solution Approach 2:
A content location service acts as an intermediary between the CDN and client devices. This mediator receives content requests, performs location resolution using stored mappings, and returns appropriate server identifiers. The intermediary handles the complexity of content location tracking separately, allowing the core CDN system to remain relatively simple while achieving high delivery efficiency.
2Productivity
If the DNS selects servers based on geographic proximity only, then the selection process is simplified, but the content retrieval efficiency deteriorates when content is not cached at the selected server
Solution Approach 1:
The content location service maintains updated mappings between content identifiers and server locations based on caching status and location data. This feedback mechanism ensures that server selections are based on current content availability information, improving retrieval efficiency while keeping the selection process automated and simple through systematic information updates.
Solution Approach 2:
The system pre-establishes content location mappings that incorporate both geographic location and caching status information. By preparing this mapping data in advance, the server selection process becomes a simple lookup operation rather than a complex real-time decision process, maintaining ease of operation while improving content retrieval efficiency through accurate, pre-computed recommendations.
3Reliability
If multiple CDNs are used for content distribution, then the content availability is improved, but the difficulty of selecting the optimal CDN deteriorates due to limited information
Solution Approach 1:
The content location service serves as a centralized intermediary that manages content location information across multiple CDNs. It receives content requests, queries its stored mappings to determine the optimal CDN and server based on content identifier and location data, and returns the appropriate server identifier. This intermediary approach simplifies multi-CDN selection by centralizing the decision-making process and maintaining comprehensive content location information.
Solution Approach 2:
The content location service provides universal content resolution functionality that works across multiple different CDNs. It maintains a unified mapping system that can resolve content locations regardless of which CDN hosts the content, making the selection process consistent and simple while improving content availability through multi-CDN support.
Data Source
AI summary
Improved methods for retrieval of content from CDNs is provided that includes a rendezvous controller that receives information of an identification of content being requested and an estimated location of a content requesting device. Based on this information, the rendezvous system identifies a server within a CDN from which the requested content may be retrieved. The selected server may be based on a repeatable hash function such that the likelihood that the content being requested is cached at the selected server. Steering requests to a server of the CDN which may have the content cached may reduce the number of servers within the CDN with the same cached content, particularly for the highest requested content. The rendezvous system may then return a corresponding domain name associated with the selected server and that can be subsequently submitted to a DNS for resolution to the IP address of the identified server.