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ACM Program. Lang."],"published-print":{"date-parts":[[2023,10,16]]},"abstract":"<jats:p>Early programming models for software-defined networking (SDN) focused on basic features for controlling network-wide forwarding paths, but more recent work has considered richer features, such as packet scheduling and queueing, that affect performance. In particular,<jats:italic>PIFO trees<\/jats:italic>, proposed by Sivaraman et al., offer a flexible and efficient primitive for<jats:italic>programmable<\/jats:italic>packet scheduling. Prior work has shown that PIFO trees can express a wide range of practical algorithms including strict priority, weighted fair queueing, and hierarchical schemes. However, the semantic properties of PIFO trees are not well understood.<\/jats:p><jats:p>This paper studies PIFO trees from a programming language perspective. We formalize the syntax and semantics of PIFO trees in an operational model that decouples the scheduling policy running on a tree from the topology of the tree. Building on this formalization, we develop compilation algorithms that allow the behavior of a PIFO tree written against one topology to be realized using a tree with a different topology. Such a compiler could be used to optimize an implementation of PIFO trees, or realize a logical PIFO tree on a target with a fixed topology baked into the hardware. To support experimentation, we develop a software simulator for PIFO trees, and we present case studies illustrating its behavior on standard and custom algorithms.<\/jats:p>","DOI":"10.1145\/3622845","type":"journal-article","created":{"date-parts":[[2023,10,16]],"date-time":"2023-10-16T15:41:29Z","timestamp":1697470889000},"page":"1338-1362","update-policy":"https:\/\/doi.org\/10.1145\/crossmark-policy","source":"Crossref","is-referenced-by-count":5,"title":["Formal Abstractions for Packet Scheduling"],"prefix":"10.1145","volume":"7","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6803-9767","authenticated-orcid":false,"given":"Anshuman","family":"Mohan","sequence":"first","affiliation":[{"name":"Cornell University, Ithaca, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4677-8902","authenticated-orcid":false,"given":"Yunhe","family":"Liu","sequence":"additional","affiliation":[{"name":"Cornell University, Ithaca, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6557-684X","authenticated-orcid":false,"given":"Nate","family":"Foster","sequence":"additional","affiliation":[{"name":"Cornell University, Ithaca, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6068-880X","authenticated-orcid":false,"given":"Tobias","family":"Kapp\u00e9","sequence":"additional","affiliation":[{"name":"Open University of the Netherlands, Heerlen, Netherlands \/ University of Amsterdam, Amsterdam, Netherlands"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8007-4725","authenticated-orcid":false,"given":"Dexter","family":"Kozen","sequence":"additional","affiliation":[{"name":"Cornell University, Ithaca, USA"}]}],"member":"320","published-online":{"date-parts":[[2023,10,16]]},"reference":[{"key":"e_1_2_1_1_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jalgor.2004.04.004"},{"key":"e_1_2_1_2_1","volume-title":"SP-PIFO: Approximating Push-In First-Out Behaviors using Strict-Priority Queues","author":"Alcoz Albert Gran","unstructured":"Albert Gran Alcoz , Alexander Dietm\u00fcller , and Laurent Vanbever . 2020. 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