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Berkeley COMPSCI 268 - Lecture Notes

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CS 268: Computer NetworkingL-5 Congestion Management andRouter Queues!Fair Queuing? Fair Queuing? Core-stateless Fair queuing? Assigned reading? CDKS90H Analysis and Simulation of a FairQueueing Algorithm, Internetworking: Researchand Experience? CSSQ98H Core-Stateless Fair Queueing:Achieving Approximately Fair Allocations inHigh Speed Networks!!"#r"i#w' (air*#ss' (air,-.#.i*/' Cor#,stat#3#ss (5' !th#r (5 "aria*ts"(air*#ss 7oa3s' 833ocat# r#so.rc#s :air3;' <so3at# i33,b#ha"#> .s#rs' ?o.t#r >o#s *ot s#*> #@A3icit :##>bacB toso.rc#' Sti33 *##>s #D# co*/#stio* co*tro3' Sti33 achi#"# statistica3 E.@i*/' !*# :3ow ca* :i33 #*tir# AiA# i: *o co*t#*>#rs' ForB co*s#r"i*/ ! sch#>.3#r *#"#r i>3#s 3i*B i:it has a AacB#t!!"at is (airness,- At /"at granularity,- (lo/s5 connections5 domains,- !"at if users "a:e different ;<<s=lin>s=etc?- S"ould it s"are a lin> fairly or Ae <CC fair,- DaEimiFe fairness indeE,- (airness G H!EiIJ=nH! EiJI KLfairnessLM- Nasically a toug" Ouestion to ans/er P tyQicallydesign mec"anisms instead of Qolicy- Rser G arAitrary granularity"DaESmin (airness- Allocate user /it" TsmallU demand /"at it/ants5 e:enly di:ide unused resources toTAigU users- (ormallyV- ;esources allocated in terms of increasing demand- Wo source gets resource s"are larger t"an itsdemand- Sources /it" unsatisfied demands get eOual s"areof resource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it-by-bit (() Single flow: clock ticks when a bit istransmitted. For packet i:) Pi ? length, Ai ? arrival time, Si ? begin transmittime, Fi ? finish transmit time) Fi ? SiCPi ? max (Fi-1, Ai) C Pi) Multiple flows: clock ticks when a bit from allactive flows is transmitted ! round number) Can calculate Fi for each packet if number offlows is know at all times) This can be complicated10Bit-by-bit (( Illustration) Not feasible tointerleave bits onreal networks) FQ simulates bit-by-bit ((!!!"e$"%e&' (a%$*e++' (a%$,-.e.%*g' 0o$e,+2a2e3e++ (5' !26e$ (5 "a$%a*2+!"(a%$ 5.e.%*g' 7app%*g 9%2,9:,9%2 +;6e<.3e o*2o pa;=e22$a*+>%++%o* +;6e<.3e' T$a*+>%2 pa;=e2 &%26 26e 3o&e+2 (% a2 a*:g%"e* 2%>e' @o& <o :o. ;o>p.2e (%A!"F" $llustrationFlow 1Flow 2Flow n$/23/24ariation: 6eighted Fair "ueuing (6F")!#=it-?@-?it AA BCampleFF10Flow 1(arriHing)Flow 2transmitting3utputFF2FF5FF8Flow 1 Flow 23utputFF10Kannot preempt pacMetcurrentl@ ?eing transmitted15!ela% Allocation- .e/0ce /ela% for flo3s 0sing less than fair share- A/7ance finish times for so0rces 3hose 90e0es /raintemporaril%- Sche/0le <ase/ on =i instea/ of >i- >i ? Pi A maB C>iDEF AiG ! =i ? Pi A maB C>iDEF Ai D !G- If Ai I >iDEF con7ersation is acti7e an/ ! has no effect- If Ai J >iDEF con7ersation is inacti7e an/ ! /eterminesho3 m0ch histor% to taKe into acco0nt- Infre90ent sen/ers /o <etter 3hen histor% is 0se/16>air L0e0ing Tra/eoffs- >L can control congestion <% monitoring flo3s- NonDa/apti7e flo3s can still <e a pro<lem O 3h%P- CompleB state- R0st Keep 90e0e per flo3- Sar/ in ro0ters 3ith man% flo3s Ce.g.F <acK<one ro0tersG- >lo3 aggregation is a possi<ilit% Ce.g. /o fairness per /omainG- CompleB comp0tation- Classification into flo3s ma% <e har/- R0st Keep 90e0es sorte/ <% finish times- >inish times change 3hene7er the flo3 co0nt changes!i#$%##i&'()&**+',#- ./a'%1a/i,y(&3(3ai/'+##- 4+$5a' i#*(6#7( 8&1i$y(!(9i11(#++(,5i#( i'(:&;- <a/d(,&(%'d+/#,a'd- )&*81+xi,y(?(5&9(@ad(i#(i,A1"18B6+/6i+9- Cai/'+##- Cai/DE%+%i'F- )&/+D#,a,+1+##(C:- B,5+/(C:(6a/ia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ge &o()e* +e,a./o*0 1o2/)o* ea3, f5o6 / )o 7ea8(*e /)8 a**/.a5*a)e 9*/:0 !;1< of *a)e0 =o2>3o28)a2) !;1< 3o28)a2)0 e>T@A 6,e*e T B 3(**e2) /2)e*a**/.a5C A B 3o28)a2)0 De5p8 a"ap) )o "/ffe*e2) pa3Fe) 8/Ge8 a2" a**/.a5pa))e*280 &a)e /8 a))a3,e" )o ea3, pa3Fe)22Ho*e &o()e* +e,a./o*0 Aeep )*a3F of fa/* 8,a*e *a)e !0 I23*ea8/2g ! "oe8 2o) /23*ea8e 5oa" 9J: KL = M!0 J9!: B "/ 7/29*/C !: ! 6,a) "oe8 ),/8 5ooF 5/FeN0 Pe*/o"/3a55L (p"a)e !0 Aeep )*a3F of 3(**e2) a**/.a5 *a)e0 P25L (p"a)e ! /f e2)/*e pe*/o" 6a8 3o2ge8)e" o*(23o2ge8)e"0 Q*op p*oKaK/5/)L fo* pa3Fe) B 7aR9S> !@*C T:2"F #s. Alpha+ew alpha. [lin2ed capacit6]r1 r2 r3old alphaalphaF2#=stimating Fair @hareA +eed F(!) D capacit6 D .A .anEt 2eep map of F(!) #alues ! would reHuire perflow stateA @ince F(!) is conca#eI piecewise-linearA F(0) D 0 and F(!) D current accepted rate D FcA F(!) D Fc/ !A F(!new) D . ! !new D !old M ./FcA Nhat if a mista2e was madeOA Forced into dropping pac2ets due to Puffer capacit6A Nhen Hueue o#erflows ! is decreased slightl625!ther 'ssues* +unishing fire-hoses 2 wh45* 6as4 to 8eep trac8 of in a F< scheme* >hat are the real edges in such a scheme5* Must trust edges to mar8 traffic accuratel4* Bould do some statistical sampling to see ifedge was mar8ing accuratel4Ciscussion Bomments* 6Dponential aEeraging* Fatenc4 properties* Gand-waE4 numHers* Irusting the edge26!"!"#r"i#&' (airn#ss' (air,-u#uing' 0or#,stat#l#ss (5' !t6#r (5 "ariantsStoc6astic (air 5u#uing' 0o9put# a 6as6 on #ac6 pac;#t' <nst#a= of p#r,flo& -u#u# 6a"# a -u#u# p#r6as6 ?in' @n aggr#ssi"# flo& st#als traffic fro9 ot6#rflo&s in t6# sa9# 6as6' 5u#u#s s#r"ic#= in roun=,ro?in fas6ion' Aas pro?l#9s &it6 pac;#t siB# unfairn#ss' M#9orD allocation across all -u#u#s' E6#n no fr##


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Berkeley COMPSCI 268 - Lecture Notes

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