A Routing Scheme for ContentBased Networking

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A Routing Scheme for Content-Based Networking

• Antonio Carzaniga, Matthew J. Rutherford, and
  Alexander L. Wolf
• IEEE INFOCOM 2004

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Introduction

• Content-based Networking
• CBCB
• Protocol
• Optimization

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Content-Based Network

• point to point
• Application-level overlay consisting of client
  nodes and router nodes
• Connected by communication
• The content-based service consists of delivering
  a message to all the client nodes that advertised
  predicates matching the message.

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Content-Based Network

• A message content is structured as a set of typed
  attribute/value pairs
• A valid message, for example
• classalert, severity6, device-typeweb-se
  rver, alert-typehardware failure
• A predicate is a disjunction of conjunctions of
  constraints on individual attributes
• A valid predicate matching the message, for
  example
• alert-typeintrusion ?severitygt2
  ?classalert ?device-typeweb-server

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Content-Based Network

• Limiting the propagation of each message to only
  those nodes that advertised predicates matching
  the message

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Content-Based Network

• Define the content-based address of a node as a
  predicate a total boolean function p
• p(m) p over a message m
• If p(m)true , p selects a message m
• Cover relation
• p1 covers p2
• iff ?mp2(m)?p1(m)
• or
• iff selection(p2)?selection(p1)
• we note p2?p1 a indicates that p1covers p2

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What is a CBCB?

• Combined Broadcast and Content-Based
• 2 layers
• Broadcast
• It establishes a tree of broadcast
• The broadcast layer is necessary to make sure
  that a message flows from its source to all its
  destinations through loop-free and possibly
  minimal paths.
• Content-Based
• It trims the tree of broadcast
• The content-based layer is necessary to avoid
  sending a message towards nodes that are not
  interested in it.

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CBCB - protocol

• RA (Receiver Advertisements)
• RAs are issued by nodes periodically and/or when
  the node changes its local content-based address
  p0
• They spread out the conditions of the messages
  that are interested in receiving for the
  potentials publishers
• The structure of an RA packet is shown

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CBCB protocol - RA

• Protocol
• If pi to cover pRA ? RA is discarded
• If the pi not to cover the pRA
• the router computes the set of next-hop links on
  the broadcast tree rooted in r and forwards the
  RA along those links.
• the router updates its routing table, adding
  pRA to pi, computing pi? pi ? pRA.

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CBCB protocol -RA

• Example

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CBCB protocol -RA

• Consequence of protocol
• In the long run, this may cause an inflation of
  those content-based addresses.

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CBCB protocol -RA

• For example
• p6valuelt100
• p6valuelt50
• note 5 wants to send
• message with value70
• The network would maintain
• the forwarding state set by
• the first RA

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CBCB protocol SR/UR

• SR ( Sender Request)
• A router uses SR to pull
• content-based addresses
• from all receivers in order
• to update its routing table
• UR ( Update Reply)
• SR/UR protocol is designed to
• complement the RA protocol

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CBCB protocol SR/UR

• Objective
• It is intended to balance the effect of the
  address inflation caused by RAs
• It compensate for possible losses in the
  propagation of RAs
• Protocol
• Propagation of SR
• Made periodically
• A router processes an SR by forwarding it to
  downstream routers, and by generating a UR
• Each UR carries a predicate as well as the
  identifier of the SR

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CBCB protocol SR/UR

• Processing of SR/UR
• If a leaf router
• It sends a UR with its local address immediately
• If non-leaf router
• its UR by combining its own predicate p0 with
  those of the URs received from downstream
  routers, and then sends its URs upstream.
• The issuer of the SR processes incoming URs
• by updating its routing table
• an issuer receiving a UR carrying predicate pUR
  from interface i updates its routing table entry
  for interface i with pi ? pUR.

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CBCB protocol SR/UR

• Example

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CBCB Optimization

• Optimizations
• The SR may be quite expensive in terms of control
  traffic and computations within routers
• We reduce the amount of SR/UR traffic by reusing
  and caching update replies

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CBCB Optimization

• Caching and Reusing UR
• In some cases, a router may be able to use a UR
  requested by another router to update its own
  routing tables.
• The same router might also be able to cache that
  UR and use it later to immediately respond to
  another SR
• Cached UR allow routers to block the propagation
  of SR , greatly reducing SR/UR traffic

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Conclusion

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