CSCI578 Team Project

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CSCI578 Team Project

• Using Alfa in modeling SIENA connector

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Team Member

• Sang-Yun, Lee (lee3_at_usc.edu)
• Won-Hyung, Lee (wonhyungl_at_usc.edu)
• Inhwan, Cha (icha_at_usc.edu)
• Dongwoo, Won (dwon_at_usc.edu)

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Motivation (1)

• Check the scalability expressiveness of SIENA
• Classification of Event-Based
  Infrastructure

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Motivation (2)

• Validation of the suitability of Alfa
• Is it rich enough to describe the important parts
  of SIENA architecture ?
• Is it the valid mapping ?
• Is it better than drawing a block-diagram ?

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Approach for Motivation

• Study SIENA
• Study Alfa
• Come up with evaluation criteria
• Compose the important aspects of SIENA using
  ViSAC
• Analyze the result
• Conclusion

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SIENA

• Scalable Internet Event Notification Architecture
• Publish/Subscribe event-notification service
• Advertisement of Routing Information
• Content-based vs. Channel-based
• Pattern Matching
• Routing/Forwarding
• Covering Relation

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Alfa

• An Assemble Language For software Architecture
• Framework for understanding/constructing
  style-based software architectures from
  architectural primitives.
• DATUM, PARTICLE, OUTPUT, INPUT, INTERFACE,
  TWOWAY, DUCT, RELAY, BIRELAY
• HOLDS, RELEASES, SEND, RECEIVE, HANDLE, REPLY,
  CREATE, CONNECT, DISCONNECT
• ViSAC

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SIENA Connector (aspects)

• Publish and Subscribe
• Advertisement
• Pattern Matching
• Forwarding and Routing
• Proxy in Wireless Environment
• Server Interconnection Topology

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Publish and Subscribe (1)

• Follows traditional PS style
• Clients objects of interest, interested parties
• Use access points of clients local server to
  publish and subscribe

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Publish and Subscribe in Alfa
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Advertisement

• Traditional publish/subscribe protocol extension
• advertise object of interest inform event of
  service of notifications it might publish
• unadvertise advertisement remain in effect
  until cancelled
• Define source address of notifications
• cf.subscription define destination address of
  notifications in routing tables

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Advertisement in Content-based Routing Protocol

• Push mechanism based on receiver
  advertisement(RA)
• Issued by nodes periodically when local
  content-based address changes
• RA packet carry content-based address issuer id

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Advertisement in Content-based Routing Protocol
(2)

• Combined broadcast and content-based protocol
• Content-based RA ingress filtering
• - If covers, drop. If not goto 2
• 2. Broadcast RA propagation
• 3. Routing table update

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Advertisement in Alfa
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Pattern Matching (1)

• Two main architecture concerns in SIENA
  expressiveness vs. scalability
• Pattern should be rich enough (expressiveness)
• Processing Patterns should be optimize-able
  efficient-able (scalability)
• Lets investigate SIENA is able..

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Pattern Matching - Semantics

• Notification, Filter, Pattern

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Pattern Matching Semantics (2)

• The building block is called a attribute filter
  - (Type, Name, Operation, Value)- (String,
  Software Architecture News, Contains, Alfa)
• Notification can be - (Type, Name, Value) -
  Operation implicitly defined as "- (String,
  Software Architecture News, Alfa
  comes with visual modeling tool, now.)
• Filter is conjunction of attribute filters, that
  is - (att-filter AND att-filter AND ..) -
  Subscription and Advertisement are basically the
  form of filter.- Consumer and Publisher need to
  be knowledge about attribute name ahead of
  time
• Anyone wonders about Pattern ? Let me know we
  can explain.

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Pattern Matching Semantics (3)Covering
Relationship

• Processing of Publication match with Filter
  should be done reasonably fast. Also, limited
  space to store filters.(More on this in
  Forwarding part.)
• Optimization Strategy Filter/Pattern can cover
  another Filter/Pattern
• - This covering relationship is used in
  optimization of forwarding table by merging
  two filters if one covers the other.
• Possible Problem Too much merging can cause the
  problem Inflation that is when the selection of
  pattern widen too much that it doesnt filter and
  cause the flooding of notification of the
  network. (More on this in Routing part.)

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Pattern Matching Class Diagram of SIENA
Semantics (Implementation Level)
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Pattern Matching aspect in Alfa (1)
Core SIENA Layer
Between SIENA low level Communication layer and
Core SIENA
Communication Mechanisms Layer
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Pattern Matching aspect in Alfa (2)
Covering Relation used in this
Pattern Matching happening here
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Pattern Matching aspect in Alfa (3) - Doubt

• Semantics of SIENA will be used in all of 3
  particles. How to show this in Alfa ?? Or is this
  not important to show in the architecture level
  ??
• We can just assume the particle has knowledge of
  SIENA Semantics internally ??
• But, in the object oriented programming such as
  Java, the Semantics is encapsulated in Class and
  to use the instance is created to access. Should
  we show this kind of details in Alfa ??
• One of conditions of Alfa primitives is
  Primitives should be implemental in a computer
  program. So, what approach Alfa will take in
  terms of the code generation with previous case ?

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Pattern Matching aspect in Alfa (4) Role Playing

• Scenario 1 We are backtracking from the
  implementation to the architecture. We found Java
  classes that are the representation of SIENA
  Semantics and these classes are used in
  everywhere. How does this map to Architecture or
  Alfa ? Does it map to many interfaces and many
  Input and Output portals corresponding to each
  function call to this Java class ? How about the
  instance of this Java class ?
• Scenario 2 What if the Semantic of SIENA is
  changed ? For example, the structure of the
  Filter is changed ? Will our architecture (in
  terms of Alfa) be able to tell us parts of SIENA
  we should pay attention to ?

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Filter class is dependent of 11 other classes
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How about Notification class ?
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Forwarding and Routing (1)

• Subscription-based forwarding- Forwarding table
  information is built with subscriptions (filters
  from consumers)
• Advertisement-based forwarding- Forwarding table
  information is built with advertisements (filters
  from publisher)
• Prototype mainly deals with Subscription-based
  forwarding- Possibly one mechanism can be more
  efficient over the other depends on the type of
  value-in applications you are trying to have on
  the top of SIENA. (software administration, stock
  market analysis, network management, middleware
  technologies, business process, security
  monitors, service discovery and etc).

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(No Transcript)
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Forwarding and Routing in Alfa (1)
Again, SIENA Core Layer!
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Forwarding and Routing in Alfa (2)
1) Event comes
Routing aspect
The repository style (blackboard)
Table Information is stored here (Data
component)
Selective Table
Indexed Table
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Routing Protocol
Handles the routing events and act accordingly
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Proxy in Wireless Environment

• To support the movement of clients between access
  points of a distributed publish/subscribe system.
• Dont want to lose messages/Automated Routing
  Info Change.
• Implemented by Mobility Proxy and Mobility Proxy
  Object

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The Mobility Service

• When a client is connected, just receive messages
  directly.
• (b) When a client is disconnected, Proxy will
  receive messagesinstead of that client.

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Functionality of Mobility Service

• Move-out function
• You move out to somewhere and leave your baggage
  in the storage.
• It is called right before a client is
  disconnected to store its subscription data into
  its local mobility proxy.
• It will be implemented power management daemon or
  a network connectivity daemon level on the
  clients side.
• Move-in function
• You move in to somewhere and want to take back
  your baggage from the storage.
• It is called when a client reaches its
  destination(storage) to get data to its local
  mobility proxy.

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Move-out Function
Proxy Object
Client

Buffer
(2)
(7)
P/S System
(3)
Mobility Service Lib
(5)
(Local)Mobility Proxy
(6)
(4)
Subscription Repository

• How it works
• Right before a client is disconnected( See Red
  Arrows )
• Move-out function in Mobility Service Library is
  called
• It sends all its subscription data to its
  Mobility Proxy
• Mobility Proxy stores subscription data from the
  client
• Invoke a proxy object for the client.
• The proxy object in the local Mobility Proxy
  subscribe instead of the client( Follow Blue
  Arrows)
• P/S system will send subscribed messages to the
  Mobility Proxy.
• All messages from P/S System will be stored into
  the mobility proxy objects buffer.
• The client is disconnected.

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Move-in Function
Client
.
(8)
(1)
(3)
queue
Mobility Service Lib
Remote Mobility Proxy
(2)
(6)
Move-out Proxy
.
(4)
(5)
(7)
Local Mobility Proxy
Move-in Proxy

• Client finds its last connected Mobility Proxy to
  get its last information(messages subscription)
  used.
• Ping the last connected Mobility Proxy with its
  last connected address information
• Remote Mobility Proxy responds
• Client request move-in function call
• Newly connected Mobility Proxy(Local Mobility
  Proxy) will send a request to receive data from
  the remoteMobility Proxy
• Messages in the remote Mobility Proxy are
  downloaded to the local Mobility Proxy
• Client gets messages from the local Mobility
  Proxy.
• Proxy Object in the remote Mobility Proxy is
  removed.

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Wireless Environment in Alfa
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Server Interconnection Topology

• Conceptually, the service can have
• Hierarchical Server Topology
• Acyclic Peer-to-Peer Server Topology
• Generic peer-to-peer server Topology

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3 Topologies
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Hierarchical Topology (good side)

• Only one up-stream server and treat him specially
  (that is your master)
• You can treat other down-stream server as clients
  (simplifies your design)
• Simpler Forwarding/Routing Protocols can be used
  (no cycle means no duplicate packet coming back)

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Hierarchical Topology (bad side)

• Server shut down, (in the prototype)
• before its shutdown, return the master address to
  its down-stream servers and clients
• Server crashes unexpectedly or link failure
• No mechanism (backup server)
• Bottom line
• Continuing research topic in Content-Based
  Networking

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Server Topology in Alfa
Up-stream
Used instances to show the server topology
Deployed at your workstation
Down-stream
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Conclusion

• SIENA is evolving architecture
• Problem with scalability
• Alfa is suitable
• Block diagram as analysis tool
• Helps to refine the architecture

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Conclusion 2

• Alfa is not suitable
• Kind of awkward to express procedure calls
  (invocation) with no parameter. When procedure
  calls are used to pass the execution control with
  no parameter. Input, output and duct need to be
  drawn with no actual datum transfer.
• Many architectures in distributed computing
  carefully present the design of data component
  (such as address scheme, semantics and etc),
  components, protocol (interaction of components)
  and then topology of components. Alfa lacks in
  expressing data component and topology aspect of
  architecture.

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Future Work

• Source Code comparison
• C2, Prism-MW comparison