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

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

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

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

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

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

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

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

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.

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