Routing in Delay Tolerant Networks

Transcription

1 Rouing in Dlay Tolran Nworks Primary Rfrnc: S. Jain K. Fall and R. Para Rouing in a Dlay Tolran Nwork SIGCOMM 04 Aug. 30-Sp Porland Orgon USA Sudn lcur by: Soshan Bali (748214) mail : sbali@ic.ku.du For EECS 800: Survivabl Rsilin and Disrupion Tolran Nworking Univrsiy of Kansas Novmbr

2 Oulin Moivaion: DTN rouing problm xampl Rouing wih zro knowldg (FC) Rouing wih parial knowldg (MEDEDEDLQEDAQ) Rouing wih compl knowldg (LP) Simulaion Rsuls Conclusion Novmbr Soshan Bali 2

3 DTN rouing problm (xampl) LAN ` DTN Gaway Inrn 6 hrs Congsion: - Bundl will b droppd Bundl will wai unil nx conac (whr will salli b?) ` 2 hrs Salli connciviy 1 hr afr arrival of bundl Novmbr Soshan Bali 3

4 Knowldg oracls Absrac knowldg oracls ar abl o answr qusions Conacs Summary Oracl: Aggrga saisics (.g. avg. waiing im unil nx conac for an dg) Conacs Oracl: Knowldg of all conacs for all dgs a all ims Quuing Oracl: Insananous quu lnghs of all nods Traffic Dmand Oracl: Prsn and fuur raffic dmand Novmbr Soshan Bali 4

5 Rouing wih zro knowldg Firs conac (FC) No knowldg oracls ar usd Forward along a randomly chosn dg (from availabl conacs) If no conacs availabl wai for firs conac Problms Mssag may no mak progrss owards h dsinaion Sourc Dsinaion Loops (spcially whn frqun conacs prsn among a s of nods) No provision o rou around congsion Improvmns Incorpora sns of rajcory o rou owards dsinaion Us pah vcor yp approach o avoid loops Novmbr Soshan Bali 5

6 Rouing wih parial knowldg MED ED EDLQ EDAQ On or mor of oracls: conacs summary conac and quuing Pah ha minimizs dlay incrass dlivry probabiliy Dijksra s algorihm finds minimum-cos pah Coss assignd o dgs o rflc simad dlay of mssag in aking ha dg Dijksra s algorihm hn finds h minimum-dlay pahs Algorihms diffr in h way coss ar assignd Coss may b Tim invarian (MED) Tim varying (ED EDLQ EDAQ) Limiaion of his mhod Only singl pah may b drivd Novmbr Soshan Bali 6

7 Inpu : G = Oupu : L 1: Q 2 : L Rouing wih parial knowldg Modifid Dijksra s algorihm ( V E) s T w( ) { V} [] s 0 L[] v v V _ s.._ v s _ Q {}_ do L _ u Q _ b _ h _ nod _ s _ L[] u = min x Q L[] x Q = Q {} u for _ ach _ dg _ E s _ = ( u v) _ do s if _ L[] v > ( L[] u + w( L[] u + T ))_ hn L[] v L[] u + w( L[] u + T ) 3: whil 4 : 5 : 6 : 7 : 8 : 9 : nd _ if 10 : nd _ for 11: nd _ whil Diffrn Novmbr Soshan Bali 7 T 1 2 [ u] = 1 2 L + u u u u u v ( L[ u] T ) = w + T + 1 T T [ v] = L +

8 Rouing wih parial knowldg Minimum Expcd Dlay (MED) Uss h conacs summary oracl Edg coss ar im-invarian (avrag im unil nx conac) Cos of an dg is avg. waiing im + prop. + ransmission dlay Rou of a mssag indpndn of im Problms No mchanism o rou around congsion Whn dirc conac bcoms availabl mssag sill wais for... pr-compud nx-hop Improvmns Modify pr-compud rou in ransi whn a conac bcoms availabl Novmbr Soshan Bali 8

9 Novmbr Soshan Bali 9 Rouing wih parial knowldg Tim-varying coss ED EDLQ and EDAQ assign im-varying coss L m is h mssag siz s is h nod assigning h cos ( ) ( ) s m w w ' = ( ) ( ) ( ) ( ) ( ) ( ) ( ) + = + = = " " min ' ' ' ' x s Q m dx x c s m d s m s m w m ( ) s Q ( ) m s '

10 Rouing wih parial knowldg Earlis Dlivry (ED) Conacs oracl is usd Quuing informaion is no usd Rous ar loop fr (Dijksra s algorihm) Rous drmind a sourc and fixd (sourc rouing) Mssags may b droppd du o congsion Will work good whn Quus in pah ar mpy Conac capaciy is high (quus mpid in ngligibl im) Will no work good whn ( s) = 0 Q Mssags in quu conac may nd bfor mssag is sn Disasrous bcaus conac in nx hop may b missd Coninuing on rou compud arlir may no b opimal Novmbr Soshan Bali 10

11 Rouing wih parial knowldg Earlis Dlivry wih Local Quuing (EDLQ) Conacs oracl is usd Local quu occupancy is akn ino accoun ( s) Q ( s* ) daa_ quud_ for a _ im if _ = = 0 ohrwis Q accouns only for quuing a ougoing dgs of currn nod Hlps rou around congsion a firs hop Unlik ED r-compu rou a vry hop Problm May rsul in rouing loops Improvmn Us pah vcors o avoid loops Problm Lik ED mssags migh g droppd bcaus of buffr ovrrun Novmbr Soshan Bali 11

12 Rouing wih parial knowldg Earlis Dlivry wih All Quus (EDAQ) Conacs and Quuing oracls usd Insananous quu sizs across nir opology a any poin of im ar usd ( s) = daa_ quud_ for a _ im a _ nod_ s Q Lik ED mssags ar sourc roud Problm Congsion losss may occur bcaus EDAQ is oblivious o buffr sizs Novmbr Soshan Bali 12

13 Rouing wih compl knowldg LP formulaion LP formulaion is discussd in papr Objciv funcion is o minimiz h avrag dlay Conacs Quuing and Traffic oracls ar usd Buffr sizs ar assumd o b known Evn for a vry simpl opology compuaion im is abou 8 minus.. on a 8 procssor P3 machin No fasibl o compu rous in ral-im for ralisic opologis Novmbr Soshan Bali 13

14 Simulaion Sup Scnario 1: Rouing o a rmo villag Dialup: 4Kbps (availabl 11AM o 6PM) LEO salli (posiion drmind by racking sofwar) Moorbik (2 hrs on way bandwidh o/from moorbik 1Mbps can sor up-o 128 MBys in USB sick) Mssags: villag o ciy 1KB rvrs dir. 10KB low load = 200 mssags pr day high load = 1000 mssags mssags gnrad for on day simulaion im = 2 days Novmbr Soshan Bali 14

15 Simulaion Rsuls Scnario 1: Rouing o a rmo villag MED rous all daa ovr dialup (bs avrag dlay im-invarian) ED: mos daa salli rs dialup (moorbik no usd: salli crossings lss han 2 hrs) FC prforms ok for simpl opology (all pahs lad o h ciy) Congsion awar schms us moorbik a high loads ED and MED rmain sam a low and high loads (no congsion awar) Boh ED and MED suffr bcaus of no bing congsion awar EDLQ and EDAQ avrag dlay prformanc is clos o LP Novmbr Soshan Bali 15

16 Simulaion Sup Scnario 2: a nwork of ciy buss Map of San Francisco usd for bus movmns of 20 buss Bus sop whn bus maks a urn o a nw sr Sop im 0 o 5 mins uniform disribud Bus spd m/sc uniform disribud Buss communica whn in radio rang: dfaul = 100m Mssags gnrad for 12 hrs 20 random sourc dsinaion pairs chosn in ach hour Each sourc bus snds 200 mssags o is dsinaion in 1 hr Mssags injcd simulanously a a randomly chosn im in h 1 hr inrval This rprsns bursy raffic Load=Traffic dmand/conac volum Evn wih a load lss han 1 nwork may b congsd (mssag has o ravrs mulipl hops conacs may b prsn bu no raffic o uiliz hm) Load is changd by changing h conac volum (chang conac bandwidh or chang conac duraion radio rang) Dfaul sorag capaciy=100mb dfaul link bandwidh =100Kbps Novmbr Soshan Bali 16

17 Simulaion Rsuls Scnario 2: a nwork of ciy buss Chang load: bandwidh basd Low loads: dlay dos no chang problm is conacs no bandwidh Highr loads: hr is congsion EDAQ EDLQ prform br Vry high load: mos no dlivrd Avrag dlay dcrass wih incras in radio rang High radio rang buss in conac highr prcn of im Diffrnc in algorihms mor pronouncd whn connciviy is inrmin Novmbr Soshan Bali 17

18 Conclusion EDEDLQEDAQ ouprform FCMED: boh dlay and dlivry raio ED prforms wors han EDLQEDAQ: congsion miigaion Prformanc diffrnc mor pronouncd whn conacs inrmin EDLQ and EDAQ prformanc comparabl LP canno compu rous in ral-im Papr assums ha knowldg oracls ar prsn Ralizing knowldg oracls in ral-world is a big problm (wih frqun disconncs and high dlays) Algorihms may b usful in spcial cas scnarios whr conacs can b prdicd Novmbr Soshan Bali 18