1. Routing in Multiple Layers: Opportunities and Challenges
Mostafa Ammar, Srinivasan Seetharaman
Networking and Telecommunications Group
College of Computing
Georgia Institute of Technology

2. Overlays P2P Nets Service Overlays
Application Layer X (X= multicast, QoS, …)
Virtual Networks (a la PlanetLab, VINI, GENI)

3. Overlays like to do routing!
Their raison d’etre
Performance reasons
Fault recovery reasons
Resource management
To “battle” lower layer

4. Multi-Layer Routing C E B C E F H A G D B A C E F H B D G OVERLAY2
No knowledge of each other. Causing increase in perceived freedom E F H B
NATIVE IP
LAYER D G

5. Challenge 1: Objective Mismatch
Conflict in objective between the two layers
AS policy violation C
OVERLAY1
LAYER E F H A G D B A C
PROVIDER
Policy violation E F H B
NATIVE IP
LAYER
CUSTOMER D G

6. Challenge 2: Functionality overlap
Each layer performs rerouting, with no knowledge of which layer leads to optimal restoration
Overlay rerouting C
OVERLAY1
LAYER E F H A G D A B A C
Functionality overlap and suboptimality E F H X
Failure B
NATIVE IP
LAYER D G
Native rerouting

7. Challenge 3: Coexistence issues
In reality, coexistence is required between:
overlay and legacy apps.
overlay and other overlay apps C
OVERLAY1
LAYER E F H A G D B A C
Conflict between layers and between entities in the same layer that share resources. Unfortunately, this grim picture is here to stay and not contrived. The ISPs need to be prepared. E F H B
NATIVE IP
LAYER D G

8. Challenge 4: Unconstrained Design
Higher level of perceived freedom as you go up
No knowledge of physical constraints & optimal placement
Essential nodes C E F
OVERLAY1
LAYER H A G D B A C E F H B
NATIVE IP
LAYER D G

9. Virtual network assignment (VNA)
Problem Statement
Allowing virtual networks (VNs) to be assigned to the substrate network efficiently and on-demand
Tasks
Assign VNs to the substrate
Achieve low and balanced load on both substrate nodes and links
Importance
Allows for accommodating more VNs with limited resources
Helps to handle dynamic situation
In our envisioned scenario, DVN demands would arrive at different time instances and request to set up virtual networks (VNs) with different topologies and lifetimes. Allowing VNs to be assigned to the substrate network efficiently and on-demand is desirable for the following reasons:
• Increasing efficiency in the substrate resource utilization would allow the substrate network to accommodate more VNs with limited resources and reduce hot spots or congestion.
• On-demand assignment means that the assignment for each VN is determined based on the current network situation as the demand arrives. Given that DVN demands can arrive at any moment and the SNP would not have information regarding future arrivals, it is important for the SNP to be able to make the assignment decision in response to each individual demand as they arrive.
A special case of the VN assignment problem can be formulated as an unsplittable flow problem which is NP-hard. Therefore, the VN assignment problem is intrinsically difficult and heuristics will be used to solve the problem.

10. Research Opportunities
Layer-aware design of protocols in all layers
Sufficient incentive for inter-layer awareness
Level of awareness and cooperation needs to determined
Improves co-existence/resource sharing
Virtual network (resource) assignment
Resource management
Intelligent placement
Efficient reconfiguration
Multi-layer testbed
that allows control of multiple layers
That helps meter actual user experience