Overlay Networking Research @NTG

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Overlay Networking Research_at_NTG

• Srinivasan Seetharaman
• Fall 2006

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Overlay Networks

• Overlay networks help overcome functionality
  limitations of the Internet by forming a virtual
  network on top of the IP network.
• Overlay nodes collaborate to offer multiple
  services
• Multicast (Ex ESM, Overcast)
• Alternate paths (Ex RON, Detour, X-Bone,
  Brocade)
• Customized forwarding (Ex I3, Scattercast)
• QoS (Ex OverQoS, SON)
• Name resolution, Intelligent routing

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Overlay Networks (contd.)

• Typical features
• Overlay routing is independent of IP layer
  routing(Possibly with functionality overlap)
• End-system overlays (Ex Skype), or Service
  overlays (Offer services to actual end-systems)
• Each Overlay link is actually an IP route between
  the two overlay nodes
• Each Overlay path is comprised of one or more
  Overlay links, inline with a certain objective

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Example Latency-Optimized paths
A
50ms
D
20ms
20ms
C
B
Relaying

• Potential for selfish behavior. Impact varies
  based on the
• percentage of overlay traffic
• scale of overlay networks

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What can go wrong?

1. Overlay routes can violatenative layer polices-
   Srini ICNP06
2. Extra load on native linkscausing bottleneck
   issues.Serious issue when nativelayer wants
   load balance.- Srini Ongoing
3. Failure detected by both layers and rerouted
   twice,with each rerouting disrupting the
   optimality of the previous.- Srini Infocom06

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What can go wrong? (contd.)

1. Sub-optimal performance becauseof lack of
   cooperation. Potentiallya chicken-and-egg
   problem- Srini Hotnets05
2. Topology (NodesLinks)placement is tricky-
   Jinliang Infocom06, Sridhar Ongoing, YongZhu
   Infocom06
3. Overlay routing can clash with TCP congestion
   control- Ruomei Ongoing

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1. BGP Policy Violations

• Example violation over Planetlab and its benefit
• 6.3ms lower latency 10.48 gain
• Transit policy is violated in the above example.
  Harvard Univ pays its provider unnecessarily and
  unavoidably.

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3. Dual Rerouting
G
2
3

• Consider a native link failure in CE
• Only overlay link AE is affected.
• The native path AE is rerouted over F (ACE ?
  ACFDE)

A
I
3
2
4
E
OVERLAY
NATIVE
G
B
I
A
8
F
C
H

Cost
Overlay recovery 8
D
E
Original 2
Native Rerouting 2
Overlay rerouting 4
Time
Native Failure
Native Recovery
Native Repair
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4. ESM-Friendly Native Network

• Reduce extra copies on some links

• No extra copies on each link
• Latency to reach C is less If there were
  native layer support

A
D
New packet replication capability
Similar in spirit to REUNITE, Packet reflection
C
B
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What can go right?

• 0. The services listed earlier, viz. QoS,
  Multicast, resilience, intelligent routing,
  security
• Improve performance of TCP using schemes like
  Overlay-TCP- Pradnya Networking05
• Improve services offered at the native layer by
  deploying them at the overlay layer (Ex Name
  resolution)- Sridhar Ongoing
• Creating improved service-based architectures and
  end-system driven functionalities- Anyone
  interested?

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References

• Jinliang Fan, Mostafa Ammar, "Dynamic
  Reconfiguration of Service Overlay Networks,"
  IEEE INFOCOM, 2006. PDF
• Yong Zhu and M. Ammar, "Algorithms for assigning
  substrate network. resources to virtual network
  components," IEEE INFOCOM, 2006. PDF
• Pradnya Karbhari, M.Ammar, E. Zegura, "Optimizing
  End-to-End Throughput for Data Transfers on an
  Overlay-TCP Path", IFIP Networking, 2005. PS
• S. Seetharaman and M. Ammar, "Characterizing and
  Mitigating Inter-domain Policy Violations in
  Overlay Routes," IEEE ICNP, 2006. PDF
• S. Seetharaman and M. Ammar, "On the Interaction
  between Dynamic Routing in the Overlay and Native
  Layers," IEEE INFOCOM, 2006. PDF
• S. Seetharaman and M. Ammar, "Overlay-Friendly
  Native Network A Contradiction in Terms?," ACM
  HOTNETS IV, 2005. PDF