VDR: Proactive element

1
Virtual Direction Routing (VDR) for Overlay
Networks Bow-Nan Cheng (RPI), Murat Yuksel (UNR),
Shivkumar Kalyanaraman (RPI)
VDR Details

• Motivation
• The explosion of peer-to-peer systems in recent
  years has prompted research into finding scalable
  and robust seeding and searching methods to
  support these overlay networks. Initial work
  relied on network flooding to find information
  and while robust, lacked scalability. In effort
  to scale large networks, many have looked at
  structured approaches to the problem by imposing
  some sort of structure to the network topology
  and routing based on that structure. To support
  search queries, a robust overlay network with
  routing policies must be in place as search fails
  to address the actual data traversal path. In
  much the same way, routing in overlay networks
  have evolved from pure flooding techniques to
  structured techniques. In our work, we attempt to
  drop the need for imposing a specific structure
  on the overlay network and introduce a technique
  to scalably route packets through an unstructured
  overlay network.

Evaluation Metrics / Scenarios
VDR Neighbor to Virtual Interface/Direction
Mapping
Metrics
Default Simulation Parameters

• Neighbors are either physical neighbors connected
  by interfaces or neighbors under a certain RTT
  latency away (logical neighbors)
• Neighbor to Virtual Interface Mapping
• Each neighbor ID is hashed to 160 bit IDs using
  SHA-1 (to standardize small or large IDs)
• The virtual interface assigned to the neighbor is
  a function of its hashed ID (Hashed ID number
  of virtual interfaces)

• Reachability Percentage of nodes reachable by
  each node in network
• State Complexity The total state info (
  spread) maintained in the network
• Average End-to-End Path Stretch Average VDR
  Path vs. Shortest Path
• Average Load Network-wide

30 8 6
Parameter Default Values
Nodes / of Virt Intf 50,000 / 8
Simulation Cycles 150
Churn Percentage 0 - 50 every 5 cycles
Seed/RREQ TTL 10 100 hops
Seed Entry Expiry 10 Cycles (under churn)
Number of Queries 1000 Randomly Gen.
26
15 8 7
30
10
15
10 8 2
1
2
0
3
10
5
1
7
4
68
6
5
15
Packetized Simulations with PeerSim Scenarios
26
30

• Effect of Seed/Query TTL on VDR, VDR-R, and RWR
• Effect of of Virtual Interfaces on VDR, VDR-R,
  and RWR
• Effect of Average of Neighbors on VDR, VDR-R,
  and RWR
• Effect of Network Churn on VDR, VDR-R, and RWR

Flooding
68
26 8 2
Normalized Flooding
68 8 4
VDR Proactive element
Virtual Direction Routing
Comparison Protocols
Paths from Rendezvous Nodes-to-Destination Nodes
are formed by periodically sending announcement
packets out orthogonal directions
VDR Random NB Send (VDR-R)

• VDR-R VDR with random neighbor forwarding (no
  biasing)
• RWR Data is seeded in 4 random walks and 4
  walkers are sent for search

Random Walk Routing (RWR)
Trends From Flood-based to Unstructured Scalable
10 1 9 26 1 25
10
10
Random Walk
26
1
Simulation Results
Hierarchy/Structured
Flood-based
Unstructured/Flat Scalable
67
48
1
2
1
2
1
2
0
3
0
3
0
3
1
10
5
7
7
7
4
4
4
6
6
6
15
68
5
28
5
55
5
22
5
30
14 1 13 22 1 21
5 1 4 13 1 12
13
14

• Structured vs. Unstructured Overlay Networks
• Unstructured P2P systems make little or no
  requirement on how overlay topologies are
  established and are easy to build and robust to
  churn
• Typical Search Technique (Unstructured Networks)
• Flooding / Normalized Flooding
• High Reach, Low path stretch, Not scalable
• Random Walk
• Need high TTL for high reach, Long paths,
  Scalable, but hard to find rare objects
• Virtual Direction Routing
• Globally consistent sense of direction (west is
  always west) ? Scalable interface to neighbor
  mapping
• Routing can be done similarly to ORRP
• Focus (for now)
• Small world approximations

Ex Seed Source Node 1
State Seeding State info forwarded in
orthogonal directions, biasing packets toward IDs
that are closer to SOURCE ID. Packets are
forwarded in virtual straight lines.
VDR Reactive element
Paths from Source Nodes-to-Rendezvous Nodes are
formed by sending route request (RREQ) packets
and waiting for route reply (RREP) packets. These
RREQ packets are sent on demand
Virtual Direction Routing
5 drop
10 12 2 26 12 15
15 drop
10
10
26
1
12 drop
67
48
1
2
1
2
1
2
Random Walk
0
3
0
3
0
3
1
10
13
7
7
7
4
4
4

• Conclusions
• VDR reaches 3.5 more nodes than VDR-R and 9
  more nodes than our modified random walk routing
  strategy (RWR)
• VDR shows a 3-4X reach retention rate going from
  0 to 50 network churn compared to VDR-R and
  RWR, showing itself to be much more robust to
  network churn
• VDR increases reach with fewer number of virtual
  interfaces because of its biasing technique.
  Gains disappear if the number of neighbors is
  smaller than the number of interfaces
• Increasing the number of neighbors generally
  increases reach and end-to-end path stretch
• VDR states are not well distributed and states
  and load is not spread evenly
• VDR paths exhibit high path stretch compared to
  shortest path but good path stretch compared to
  pure random walk

VDR Introduction
6
6
6
15
68
5
28
5
5
6
5
30
6 12 6 38 12 26
5 12 7 13 12 1
13
38
Ex Route Request Node 12 RREQ Source Node 1
VDR 2 Basic Primitives

• VDR Primitive
• Local sense of direction
• leads to ability to forward
• packets in opposite
• directions

Rendezvous Points
A

• Local directionality is sufficient to maintain
  forwarding of a packet on a straight line
• Two sets of orthogonal lines in a plane intersect
  with high probability even in sparse, bounded
  networks

Route Request RREQ packets are forwarded in
orthogonal directions, biasing packets towards
REQUESTED ID
Virtual view of VDR Route Request process Node 1
sends out a RREQ looking for Node 12. Once the
RREQ intersects a rendezvous ndoe, a RREP is sent
back. The virtual path of the data goes from the
source node to the rendezvous to the destionation
46
68
B
5
Rendezvous Node
RREQ Path
10
6
Question Can 1 hop neighbors in overlay networks
be consistently mapped to a local virtual
direction such that be forwarding in virtual
orthogonal lines, a high chance of intersection
(and search success) results?
30
1
13
26
38
RREP Path
2
Neighbor to Virtual Interface Mapping
Two Components of VDR
RREQ Node 12
48

• Relevant Publications
• B. Cheng, M. Yuksel, S. Kalyanaraman, Virtual
  Direction Routing for Overlay Networks,"
  Proceedings of IEEE International Conference on
  Peer-to-Peer Computing (P2P), Seattle WA,
  September 2009.
• This material is based upon work supported by the
  National Science Foundation under Grants 0627039,
  0721452, 0721612 and 0230787. Any opinions,
  findings, and conclusions or recommendations
  expressed in this material are those of the
  author(s) and do not necessarily reflect the
  views of the National Science Foundation.

Seed Path
Virtual Direction Routing

• Overlay Routing
• Proactive Element
• Reactive Element

12
VDR Route Request
Virtual View