The INSTANCE II project
Frank T. Johnsen,
University of Oslo
Overview
Introduction
Application area and project goal
Overlay network example
Partial caching
Simulations
The road ahead
Introduction
INSTANCE II builds on ideas from
INSTANCE and KOMMSYS.
INSTANCE is short for intermediate storage
node concept (basically a proxy).
The original project was Pål Halvorsen’s
Ph.D. work.
His kernel optimizations enhanced the
proxy’s throughput.
What is INSTANCE II?
A distribution infrastructure.
Work is done on the middleware level networking issues and cooperation between
proxies.
Focus is on mixed media rather than pure
VoD.
The project is financed by NFR.
Application
The application area for INSTANCE II is mixed
media in a News-on-demand (NoD) scenario.
Important differences from VoD:
–
–
User interaction
Structure
Our news story assumptions:
–
–
A news item may consist of several different objects.
The relationship between objects is described by a
presentation plan.
Goal
The project goal:
–
Enhanced delivery of mixed media content.
Shall be achieved by:
–
–
CDN with a reconfigurable overlay network (Trude
Hafsøe), and
partially caching proxies in this overlay (me).
An overlay network
A physical network
–
–
Nodes (squares) and
links (lines).
An overlay network
A physical network
–
–
Nodes (squares) and
links (lines).
Some nodes are part of
the CDN (red).
An overlay network
An overlay network
–
–
The participating nodes
(red).
Virtual links between
nodes (blue dotted
lines).
Note that virtual links
are independent of
physical links!
An overlay network
12
7
12
16
The overlay links can
be chosen according to
some criterion, for
example latency.
An overlay network
500
X
12
12
16
The overlay links can
be chosen according to
some criterion, for
example latency.
If something happens
the values will change.
An overlay network
X
12
30
12
16
The overlay links can
be chosen according to
some criterion, for
example latency.
If something happens
the values will change.
This might trigger an
automatic
reconfiguration.
An overlay network
In INSTANCE II we
have different QoS
classes.
This warrants multiple
overlay networks
spanning the same
nodes.
Our CDN
Why use an overlay network?
–
–
–
Easy to deploy and maintain.
Possibility for application level multicast.
Enables third parties (not ISPs) to offer enhanced
services to their users.
We envision one hosting CDN spanning
multiple ISPs.
What is partial caching?
Different types of partial caching:
–
–
Time domain
Quality domain
We want to introduce structure as well.
Caching with structure
Structure expresses relationships between
multimedia objects.
We will have two kinds of structure:
–
–
Structure between objects
Structure within objects
We assume that a proxy utilizing knowledge about
structure will be more efficient than a proxy that does
not.
I am looking into such a scheme for our scenario.
Caching with structure
Structure between objects:
–
For example that they are always retrieved:
together,
after one another, or
as an alternative to the other.
–
They are a part of the same presentation plan.
Structure within objects:
–
An example is layered video.
Caching with structure
Advantages of NoD:
–
–
–
Known structure.
Re-use of elements.
Interaction and access patterns.
Structure caching example:
–
Branched VoD
Each branch is eligible for caching.
A master degree student is looking into this.
Is this smart?
Remains to be proven:
–
The CPU overhead may render it useless in a real
system.
My approach:
–
–
Simulate it and estimate the overhead.
Compare the performance gains to a simple yet
relatively good reference algorithm, i.e., LRU.
The road ahead
Now:
–
Test hypothesis with a discrete event simulation.
Next step:
–
Integrate this with the reconfigurable overlay
network, and then add proxy cooperation to the
model.
Simulation ideas
SERVER
− infinite disk space
Other assumptions:
–
− zero delay
− unlimited bandwidth
–
PROXY
− finite disk space
− zero delay
− unlimited bandwidth
CLIENT
–
–
The proxy has the
presentation plan and does
not need to retrieve this.
A presentation plan has a
unique ID.
A media object (i.e. an
object in a presentation)
has a unique ID.
The probability of accessing
a news story (a
presentation) is Zipf-like.
The next step
S
P
The INSTANCE II CDN:
–
–
P
P
–
–
P
Server (S) and proxies
(P) in an automatically
reconfigurable overlay
network.
Clients (small squares)
connected to proxies.
Routing of packets
according to QoS class.
Proxy cooperative
caching.
Highlights
INSTANCE II
–
–
–
–
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Multi-ISP hosting CDN.
Automatically reconfigurable overlay network.
Partial caching with structure.
A distribution infrastructure for mixed media.
Focus on interactive NoD.
Thanks for your attention!
Questions?
Ask and be enlightened!