D y n a m i c L o a d B a l a n c i n g i n D i s t r i b u t e d V i r t u a l E n v i r o n m e n t s

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Dec 8, 2013 (3 years and 8 months ago)

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Dynamic Load Balancing in Distributed Virtual En vironmen
Stephan Man tler and Dieter Sc hmalstieg
Vienna Univ yofT ec hnology A ustria
f step j dieter g gu wienct
Abstract
This p ap er intr o duc es a new appr o ach for impr oving the sc alability of distribute d v onments
by using a c ombination of visibility cul ling for c ommunic ation and dynamic lo ad b alancing to ke ep
the system l o ad evenly distribute d F urther c ommunic ation optimizations as wel l as s ome p r eliminary
r esults ar epr esente d
tro duction message tering at run time T he en vironmen t is de
comp osed in to adjacen t parts whic h re a statically dis
In man y V irtual En vironmen ts there is a desire for
tributed o v er a net w ork f o s erv
h n um b ers of sim ultaneous p articipan ts within the
More sp ecially the system scalabilit yis no wnto
en vironmen t Ho w ev er these goals are defeated b y
longer limited b y n um ber of clien ts in the
limits of curren t soft w are and hardw are Increasing
load will degrade resp onsiv eness to the poin t vironmen t but the n ber of iclen ts that need to
the system is rendered useless T o o v ercome the re b e accoun ted or f b y one serv er T his s i without doubt
strictions distributed designs are needed that impro v e a drastic impro v emen t w er it is still p ossible for
the sc alability of the ystem s suc ha system to beecom o v erloaded as so on as
serv er reac hes its l imits ev en if the other computers
An optimal d esign will therefore minimize the com
are only v ery l igh tly loaded
m unication through a careful decomp osition of the
pap er tro duces an arc hitecture whic h
system additional computational ert can be used
aimed at aking t the scalabilit y of distributed virtual
to further reduce required comm unication ho w
vironmen ts one step further b y e ying dynamic
ev er care m b e t en that the increased pro essing c
lo ad b alancing k eep all serv ers v e
requiremen will not out w eigh impro v emen ts of
virtual w orld is decomp osed n i to regions he t distribu
distribution
tion nd hence the c ost of main tenance of whic his
An eien tnet w orking mec t p o
balanced among the a v ailable serv This arc hitec

is the se u of m ulticast comm unication I n addition
dirs from previous design b y allo wing a dy
to using a generic distributed approac h impro v
namic reconuration of the sim ulation sub d ivision
be obtained b y exploiting prop erties sp eci to
among serv ers including d atabase and net w ork con
the virtual vironmen t pplication a F or example if
nections Our approac h also allo ws to a nd v e
the ne vironmen t features ense d o cclusion suc hasin
serv ers at run time h is essen tial for In ternet
building in teriors the additional visibilit y i nformation
based applications
can b e used to reduce the n um b e r of essages m sen tto
h lien c t This reduction is t ypically p e rformed b ya
net w ork f o s erv ers eac h of whic h p ossesses geometry
A s ystem design with load balancing
nd th us visibilit y information ab out some part of
In order to k eep the system load distributed ev enly
the vironmen t w as the clien ts in part
o v connected hines sort of w orkload
As a c lien t an c see only a s mall fraction of the total
balancing to e place In the o v e of
n ber a v atars in suc h a system tering based
assigning a part of the en vironmen t to h serv er
up on visibilit y information greatly reduces the n um ber
an o v erloaded serv will to reduce its load b y
of messages that need to b e passed whic h leads to a
reducing the part of the w orld it has to handle while
signian t increase of the system scalabilit y
a serv noticing that has little or to do
F unkhouser describ ed an arc hitecture named R ING can request further w In this section w e outline

whic h uses static visibilit y information to p erform our system design whic hw as inspired b y the
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In
envir irtual
ersit
tsS Mantler and D Schmalstie g Dynamic L o ad Balancing n i istribute D d Virtual Envir onments
120
100
80
number of regions on server A
number of regions on server B
60
40
20
Figure R e gions a r etr ansferr e db etwe en servers to
number of clients on server A
number of clients on server B
b alanc e system lo ad
0
Experiment Time
Figure L o b alancing in action Initial ly server A
arc hitecture ut b is capable to include load balancing
to o many clients and gr ly p asses r e gions and
among erv s ers
clients to server B As clients move ab out r an
F or simplicit y eha v e limited the en vironmen tto
domly they b e c ome evenly distribute d over the world

a D epresen r tation whic h is suien t for the rep

and c seBt au or eturn some r e to A
resen tation of building in teriors Visibilit y anc b e de
termined from the o or ap with a fast o nhey

algorithm hci h allo ws rapid p o in toell and cell aluation and Results
toell visibilit y computation The w orld consists of a
W eha v e mplemen i ted a p rotot yp e of the as de
n b er f o djacen a t nonn tersecting con v ex p olygons
scrib e d i n the previous sections and are c urren tly p r e
where ac e h edge of the p lygon o can b e either transpar
forming exp rimen e ts to examine the reaction of the
en t represen ting an op en do or or o paque for w alls
vironmen tto eth c hange of parameters orld size
The ize s of t hese p olygons determines the gran ularit y
n um ber of serv n ber of clien ts directed clien t
of the load balancing
v emen t s v random w alk T osim ulate a large n um
ber of h participan ts and to be able to repro
The s imple h euristic that has b een used in our im
duce the test situation under c hanging conditions the
plemen tation tries to estimate the serv er load b yex
v emen t of the clien ts is trolled b y rob ot pro
amining he t n um ber of encli ts as w ell as the regions
whic h are able to explore the w orld
By trying to k eep the clien t coun tbloe w a ertain c lev el
in teraction Preliminary results sho w that our ap
the etn w ork tra and required computing p o w er can
proac h s i f easible and app ar e encouraging
b e limited the tendency to w ards k eeping the n um ber
of regions do wn tries to k eep an o therwise unloaded
T o c onclude t he presen ted system c an b e regarded
serv er ad surprises lik e a large n um ber of
as a ramew f ork for further studies This future w ork
clien tering its regions
be aimed at examining poetn tial heuristics and
p erformance optimizations as w ellasthe in tegration
If it is decided t hat load balancing is required the
of the system with other ongoing r esearc h
heuristic tries to c ho ose a region for transfer that will
bring t he most b ene for the serv er i t he one t hat
Ac kno wledgmen ts This pro ject i s s p onsored b yteh
will mo v e as man y clien as p ossible to other
Austrian Science F oundation FWF under con
serv er
n um b er PMA T
Naturally cu h ransfers t should not cause another
serv er to b come e o v erloaded and necessitate addi
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the
VRAIS
ulticast

tract
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