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Tue, 14 Jul 2009 13:58:40 +0200Tue, 14 Jul 2009 13:58:40 +0200Deciding the FIFO stability of networks in polynomial time
http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/6675
FIFO is the most prominent queueing strategy due to its simplicity and the fact that it only works with local information. Its analysis within the adversarial queueing theory however has shown, that there are networks that are not stable under the FIFO protocol, even at arbitrarily low rate. On the other hand there are networks that are universally stable, i.e., they are stable under every greedy protocol at any rate r < 1. The question as to which networks are stable under the FIFO protocol arises naturally. We offer the first polynomial time algorithm for deciding FIFO stability and simple-path FIFO stability of a directed network, answering an open question posed in [1, 4]. It turns out, that there are networks, that are FIFO stable but not universally stable, hence FIFO is not a worst case protocol in this sense. Our characterization of FIFO stability is constructive and disproves an open characterization in [4].Maik Weinardworkingpaperhttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/6675Tue, 14 Jul 2009 13:58:40 +0200The effects of local randomness in the adversarial queueing model
http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/6671
We study the effect of randomness in the adversarial queueing model. All proofs of instability for deterministic queueing strategies exploit a finespun strategy of insertions by an adversary. If the local queueing decisions in the network are subject to randomness, it is far from obvious, that an adversary can still trick the network into instability. We show that uniform queueing is unstable even against an oblivious adversary. Consequently, randomizing the queueing decisions made to operate a network is not in itself a suitable fix for poor network performances due to packet pileups.Yann Lorion; Maik Weinardworkingpaperhttp://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/6671Tue, 14 Jul 2009 11:29:57 +0200