Breaking the Barrier Of 2 for the Competitiveness of Longest Queue Drop

Antonios Antoniadis, Matthias Englert , Nicolaos Matsakis, Pavel Vesely

Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

1 Citation (Scopus)
42 Downloads (Pure)

Abstract

We consider the problem of managing the buffer of a shared-memory switch that transmits packets of unit value. A shared-memory switch consists of an input port, a number of output ports, and a buffer with a specific capacity. In each time step, an arbitrary number of packets arrive at the input port, each packet designated for one output port. Each packet is added to the queue of the respective output port. If the total number of packets exceeds the capacity of the buffer, some packets have to be irrevocably rejected. At the end of each time step, each output port transmits a packet in its queue and the goal is to maximize the number of transmitted packets.
The Longest Queue Drop (LQD) online algorithm accepts any arriving packet to the buffer. However, if this results in the buffer exceeding its memory capacity, then LQD drops a packet from the back of whichever queue is currently the longest, breaking ties arbitrarily. The LQD algorithm was first introduced in 1991, and is known to be 2-competitive since 2001. Although LQD remains the best known online algorithm for the problem and is of practical interest, determining its true competitiveness is a long-standing open problem. We show that LQD is 1.707-competitive, establishing the first (2-ε) upper bound for the competitive ratio of LQD, for a constant ε > 0.
Original languageEnglish
Title of host publication48th International Colloquium on Automata, Languages, and Programming (ICALP 2021)
PublisherDagstuhl
Number of pages20
ISBN (Electronic)978-3-95977-195-5
DOIs
Publication statusPublished - 2021
Event48th International Colloquium on Automata, Languages, and Programming, ICALP 2021 - Online Conference
Duration: 12 Jul 202116 Jul 2021
Conference number: 48

Conference

Conference48th International Colloquium on Automata, Languages, and Programming, ICALP 2021
Abbreviated titleICALP 2021
CityOnline Conference
Period12/07/2116/07/21

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