Abstract
Data dissemination is a fundamental task in distributed computing. This paper studies broadcast problems in various innovative models where the communication network connecting n processes is dynamic (e.g., due to mobility or failures) and controlled by an adversary.
In the first model, the processes transitively communicate their ids in synchronous rounds along a rooted tree given in each round by the adversary whose goal is to maximize the number of rounds until at least one id is known by all processes. Previous research has shown a ⌈(3n1)/2⌉2 lower bound and an O(nlog log n) upper bound. We show the first linear upper bound for this problem, namely ⌈(1+√2) n1⌉ ≈ 2.4n.
We extend these results to the setting where the adversary gives in each round kdisjoint forests and their goal is to maximize the number of rounds until there is a set of k ids such that each process knows of at least one of them. We give a ⌈3(nk)/2⌉1 lower bound and a (π²+6)/6 n+1 ≈ 2.6n upper bound for this problem.
Finally, we study the setting where the adversary gives in each round a directed graph with k roots and their goal is to maximize the number of rounds until there exist k ids that are known by all processes. We give a ⌈3(n3k)/2⌉+2 lower bound and a ⌈(1+√2)n⌉+k1 ≈ 2.4n+k upper bound for this problem.
For the two latter problems no upper or lower bounds were previously known.
BibTeX  Entry
@InProceedings{elhayek_et_al:LIPIcs.ITCS.2023.47,
author = {ElHayek, Antoine and Henzinger, Monika and Schmid, Stefan},
title = {{Asymptotically Tight Bounds on the Time Complexity of Broadcast and Its Variants in Dynamic Networks}},
booktitle = {14th Innovations in Theoretical Computer Science Conference (ITCS 2023)},
pages = {47:147:21},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {9783959772631},
ISSN = {18688969},
year = {2023},
volume = {251},
editor = {Tauman Kalai, Yael},
publisher = {Schloss Dagstuhl  LeibnizZentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/opus/volltexte/2023/17550},
URN = {urn:nbn:de:0030drops175502},
doi = {10.4230/LIPIcs.ITCS.2023.47},
annote = {Keywords: broadcast, cover, kbroadcast, dynamic radius, dynamic graphs, oblivious message adversary, time complexity}
}
Keywords: 

broadcast, cover, kbroadcast, dynamic radius, dynamic graphs, oblivious message adversary, time complexity 
Collection: 

14th Innovations in Theoretical Computer Science Conference (ITCS 2023) 
Issue Date: 

2023 
Date of publication: 

01.02.2023 