Avatar Mobility in 1 Wei Tsang Ooi Mehul Motani Huiguang Liang - - PowerPoint PPT Presentation

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Avatar Mobility in 1 Wei Tsang Ooi Mehul Motani Huiguang Liang - - PowerPoint PPT Presentation

Mar 02, 2024 438 likes •1.45k views

Avatar Mobility in 1 Wei Tsang Ooi Mehul Motani Huiguang Liang Ian Tay Ming Feng Neo National University of Singapore 2 My life is so great that I literally wanted a second one! - Dwight Schrute, The

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Avatar Mobility in

黃瑋璨 新加坡國立大學

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Wei Tsang Ooi Mehul Motani Huiguang Liang Ian Tay Ming Feng Neo National University of Singapore

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“My life is so great that I literally wanted a second one!”

  • Dwight Schrute,

The Office

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256x256 m regions.

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avatar mobility: who is where, when

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why do we care?

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research in systems support for NVE

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How to partition a world into regions and assign regions to servers considering

  • communication cost
  • hand-over rate
  • balancing server load

:

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How to predict avatar movement (end therefore what a user will see next)?

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AoI-based scheme

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How many connections? How stable are the connections?

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supernode-based scheme

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How to pick supernodes? How stable are the supernodes?

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how to simulate avatar mobility?

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random walk random waypoint clustered movement :

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  • r,

small-scale implementation

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no large-scale NVE available until recently

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482,594

residents logged in between 2-9 June 2008

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secondlife.com/whatis/economy-graphs.php

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  • collect mobility traces of

avatars in Second Life

  • what it means w.r.t. systems

design for NVEs?

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collecting traces

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how do avatars move inside a distributed virtual environment?

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how are avatars distributed within a region?

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how long do they stay at a location?

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do they move in groups?

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etc.

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FPS MMORPG NVE

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Linden, can we get access to the server traces?

No.

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  • Wrote our own client
  • Parses packets using libsecondlife
  • Insert bots into regions
  • Log positions of avatars every 10s
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difficulties

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running out of memory

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anti-bots policy

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  • ver crowded region
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inter-region tracking

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  • Wrote our own client
  • Parses packets using libsecondlife
  • Insert bots into regions
  • Log positions of avatars every 10s
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who is where, when (doing what)

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Freebies

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The Pharm

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Isis

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Ross

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Mobility Patterns

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Freebies: number of visits to a cell

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Freebies: average pause time in a cell

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Freebies: average speed in a cell

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Isis: number of visits to a cell

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caching/prefetching based on popularity of locations?

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Isis: average pause time in a cell

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pick supernodes from sticky location?

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Isis: average speed in a cell

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mobility model: random walk + pathway ?

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churn rate

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Reasonably high churn (up to 6/min)

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1 min 10 min 1 hr 2 hr

Highly skewed. Some stay for hours.

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cannot pick supernodes uniformly

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clustering of avatars

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meeting: encounter between two avatars (within each other AoI)

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Meet many different avatars.

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1 min 10 min 1 hr 2 hr

Most meetings are short.

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Meeting size is large.

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high overhead in maintaining AoI neighbors

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meeting stability: avg meeting size

  • ver

num of avatars met

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Wide range of stability

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  • ther tidbits
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little temporal variations

can use historical information to predict future

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rotate 18% of the time

Second Life’s prefetching is wasteful

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25-35% revisits the same region in a day

region-based caching?

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proxy-based texture caching

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why textures?

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62 - 81%

  • f traffic are textures
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316 MB

  • f textures in Isis
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64m 80o

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64m 80o

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403 TB

  • f textures retrieved

in Isis in a day

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SL servers texture proxy clients

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what caching algorithm to used?

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2Q

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FIFO LRU

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FIFO LRU cache miss

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FIFO LRU cache hit

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FIFO LRU cache hit

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FIFO LRU scan resistant

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3Q

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FIFO LRU Victim Buffer

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FIFO LRU cache hit Victim Buffer

(sorted by popularity)

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how to define popularity of texture?

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Freebies: number of visits to a cell

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little temporal variations

can use historical information to predict future

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popularity of texture = popularity of cell

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2Q 3Q OPT Ross 50 MB 0.58 0.62 0.70 Ross 25 MB 0.28 0.36 0.47 Freebies 50 MB 0.48 0.50 0.68 Freebies 25 MB 0.21 0.33 0.50

Per-byte Hit Rate

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conclusion

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understanding real avatar mobility is crucial to design good NVEs

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謝謝 歡迎發問及指教

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