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'''Blue''' is ana [[scheduling discipline]] for the [[network scheduler]] developed by graduate student Wu-chang Feng for Professor [[Kang G. Shin]] at the [[University of Michigan]] and others at the [[Thomas J. Watson Research Center]] of [[IBM]] in 1999.<ref name="mich">{{Cite journal |title=BLUE: A New Class of Active Queue Management Algorithms |author1=Wu-chang Feng |author2=Dilip D. Kandlur |author3=Debanjan Saha |author4=Kang G. Shin |yeardate=April 1999 |month=April |url=http://www.eecs.umich.edu/techreports/cse/99/CSE-TR-387-99.pdf |publisher= University of Michigan |workjournal= Computer Science Technical Report |issue=CSE–TR–387–99 |accessdate= June 8, 2013 }}</ref>
==Functioning==
Like [[random early detection]] (RED), itBlue operates by randomly dropping or marking packet with [[explicit congestion notification]] mark before the transmit buffer of the [[network interface controller]] overflows. In contrary toUnlike RED, however, it requires little or no tuning onto thebe partperformed ofby the network administrator. A Blue queue maintains a drop/mark probability ''p'', and drops/marks packets with probability ''p'' as they enter the queue. Whenever the queue overflows, ''p'' is increased by a small constant ''p<sub>di</sub>'', and whenever the queue is empty, ''p'' is decreased by a constant ''p<sub>id</sub> < p<sub>di</sub>''.
If the mix of traffic on the interface does not change, ''p'' will slowly converge to a value that keeps the queue within its bounds with full link utilization.
===Stochastic fair Blue===
The main flaw of Blue, which it shares with most single-queue queueing[[queuing disciplinesdiscipline]]s, is that it does not distinguish between [[Traffic flow (computer networking)|traffic flows]], but treats all flows as a single aggregate. Therefore, a single aggressive flow can push packets out of the queue belonging to other, better behaved, flows.
Stochastic fair Blue (SFB) is a stochastically fair variant of Blue which hashes flows and maintains a different mark/drop probability for each hash value. Assuming no hash collisions, SFB is able to provide a fair share of buffer space for every flow. In the presence of hash collisions, SFB is only stochastically fair.<ref>{{CitationCite book|author1=Wu-Chang Feng |author2=Dilip D. Kandlur |author3=Debanjan Saha |author4=Kang G. Shin |title=Proceedings IEEE INFOCOM 2001. Conference on Computer Communications. Twentieth Annual Joint Conference of the IEEE Computer and Communications Society (Cat. No.01CH37213) |chapter=Stochastic Fairfair Blueblue: anA queue management algorithm for enforcing fairness |url=http://www.thefengs.com/wuchang/blue/41_2.PDF |journaldate=Proceedings of INFOCOMApril 2001 |year=2001 |month=April |pages=1520–1529 |doi=10.1109/INFCOM.2001.916648 |accessdate= June 8, 2013 |volume=3|isbn=978-0-7803-7016-6 |citeseerx=10.1.1.11.4235 |s2cid=5902623 }}</ref>
Unlike other stochastically fair queuing disciplines, such as SFQ ([[Stochastic Fairness QueueingQueuing]]), SFB can be implemented using a [[bloom filter]] rather than a [[hash table]], which dramatically reduces its storage requirements when the number of flows is large.
When a flow's drop/mark probability reaches 1, the flow has been shown to not react to congestion indications from the network. Such an inelastic flow is put in a "[[penalty box]]", and rate-limited.
===Resilient stochastic fair Blue===
Many scheduling algorithms, including the fairness-aimed ones, are notably vulnerable to spoofing [[distributed denial-of-service]] (DDoS) attacks. A resilient stochastic fair Blue (RSFB) algorithm was proposed in 2009 against spoofing DDoS attacks. The basic idea behind RSFB is to record the responsive normal TCP flows and rescue their dropped packets. RSFB algorithm is effective in preserving the TCP throughput in the presence of spoofing DDoS attacks.<ref name=RSFB>{{Cite journalbook |authorauthor1= Changwang Zhang, |author2=Jianping Yin, and |author3=Zhiping Cai |name-list-style=amp |url= http://sites.google.com/site/cwzhangres/home/files/RSFBaResilientStochasticFairBluealgorithmagainstspoofingDDoSattacks.pdf |title= RSFB: a Resilient Stochastic Fair Blue algorithm against spoofing DDoS attacks |workjournal= International Symposium on Communication and Information Technology (ISCIT) |year= 2009 |pages= 1566-15671566–1567 |isbn= 978-1-4244-4521-9 |accessdate= June 8, 2013 }} [http://portal.acm.org/citation.cfm?id=1789954.1790341 Abstract]</ref>
==Implementations==
==References==
{{Reflist}}
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[[Category:Packets (information technology)]]
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