Transcript PeerNet: Pushing Peer-to-Peer Down the Stack

PeerNet: Pushing Peer-to-Peer
Down the Stack
Jakob Eriksson, Michalis Faloutsos,
Srikanth Krishnamurthy
University of California, Riverside
What is PeerNet
• an approach to separate address and identity
– address reflects the node’s current location
– identifier remains the same
• a p2p-based network layer for large
networks
– an alternative to the IP layer
PeerNet Goals
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targeting large, wireless and mobile networks
emphasis on mobile nodes and p2p interactions
minimizing the need for manual configuration
favoring distributed and p2p solutions instead of
centralized solutions and node specialization
• localizing control overhead
...and Challenges
• while location-based addressing simplifies
routing, new challenges are created:
– consistent dynamic address allocation
– efficient node lookup service for finding
addresses for given identifiers
=> the project proposes distributed solutions
PeerNet Network layer (1/2)
• dynamic addressing, depending on the node’s current
location in the network
• addresses organized as a binary tree
• selecting addresses so that locality of communication is
guaranteed (subtree/area)
PeerNet Network Layer (2/2)
• Area invariant
– all nodes belong to a nested sequence of areas, one of
each level
– all nodes within an area share a unique address prefix
– l bit addresses  l area levels
– violating node resigns & rejoins
• Three major parts of the network layer
– address allocation
– routing
– node lookup
Address Allocation in General
• addresses assigned dynamically, preserving
the invariant
• goals:
– balancing the tree & effective utilization of
address space
– good physical connectivity within an area
– improving scalability & minimizing control
overhead
Address Allocation: Joining the
Network
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physical connection
requesting address
registering to node lookup service
moving node => new request & registration
Address Allocation: Details
• each node controls a range of addresses
• responding node splits its range in half
– joining node gets the lower half
– joining node’s address is the lowest address in that range
– nodes get evenly distributed in the address space
Address Allocation: Challenges
• 1. Keeping the tree balanced
– local congestion leads to address unavailability
– solution: proactively migrating nodes
• 2. Maximizing intra-area connectivity
– solution: nodes within an area have to be wellconnected by physical links
=> improves routing performance and tolerance
to link failures, desirable in mobile networks
Routing
• sender only needs to know the identifier of
the receiving node
• address provided by the lookup service
• packets include both the identifier and last
known address
– address rechecked along the route if necessary
Routing: Details
•routing one level at a time
•each step takes closer to destination in both topology and
address tree
• a distance vector type
approach:
– each node has l=log N
entries, one for each level
– each entry stores the next
hop to corresponding
sibling subtree
• destination address compared
to node address bit by bit,
MSB first, packet then
forwarded to corresponding
sibling subtree
Node Lookup Service (1/3)
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distributed node lookup for finding
addresses for given node identifiers
Storing lookup entries (id, addr)
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choosing a node with minimum xor-distance
(address XOR identifier)
Challenges
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node movement => address change => lookup
entries need to be updated or moved
Node Lookup Service (2/3)
• Solutions:
– Preserving locality of lookups
• multiple locations for lookup tables, chosen so that local
queries get local answers
• iterating from local scope to larger subtrees
– Creating locality of updates
• moving nodes change their low bits more often
storing LSB locally and MSB in remote nodes
remote nodes need less updating
MSB found first, query then forwarded to corresponding area
Node Lookup Service (3/3)
• Communication abstractions
– identifier mapping to multiple addresses
effective implementation of multicast/anycast
For example:
– multicast group id & group of receiving nodes
– service id & group of providing nodes
Further Directions of the Project
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security
performance issues
tree balancing and local connectivity
portability
leveraging various infrastructures
– tunneling through the Internet to connect PeerNets
– interconnection with Internet nodes
– TCP/IP emulation on PeerNet nodes
• actual data / results / comparison ?