Soft-TTL: Time-Varying Fractional Caching

Jasper Goseling, Osvaldo Simeone

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Standard time-to-live (TTL) cache management prescribes the storage of entire files, or possibly fractions thereof, for a given amount of time after a request. As a generalization of this approach, this letter proposes the storage of a time-varying, diminishing, fraction of a requested file. Accordingly, the cache progressively evicts parts of the file over an interval of time following a request. The strategy, which is referred to as soft-TTL, is justified by the fact that traffic traces are often characterized by arrival processes that display a decreasing, but non-negligible, probability of observing a request as the time elapsed since the last request increases. An optimization-based analysis of soft-TTL is presented, demonstrating the important role played by the hazard function of the inter-arrival request process, which measures the likelihood of observing a request as a function of the time since the most recent request.
Original languageEnglish
Pages (from-to)18-21
Number of pages4
JournalIEEE Networking Letters
Issue number1
Publication statusPublished - 23 Nov 2018


  • Caching
  • TTL
  • content delivery network
  • hazard rate
  • 22/4 OA procedure


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