An Overlay Data Plane for PlanetLab Andy Bavier, Mark Huang, and Larry Peterson Princeton University

Overlay networks Purpose-built virtual networks that use the existing Internet for transmission The Internet was once deployed as an overlay on top of the telephony network Choose “better” routes than the underlying Internet Route around failure, congestion Improve throughput and delay Extend network architecture E.g., multi-path routing, multicast, DHT-based routing, VoIP overlay Internet

PlanetLab is… A platform for overlay network research Worldwide consortium of universities and companies Running 550 widely-distributed nodes Supporting hundreds of simultaneous projects

PlanetLab Slices Slice = set of distributed virtual machines (VMs) PlanetLab is a shared infrastructure

PlanetLab Node View Each VM looks like a Linux account Limited root access Install software Raw sockets Initialization scripts VM is user-space only, shared kernel Linux-based VMM Node Mgr Local Admin VM 1 VM 2 VM n …

Our vision: ROCK Routing Overlay Construction Kit (ROCK) Build, debug, deploy, and maintain routing overlays… In a (user-space) slice on PlanetLab State-of-the-art components Framework Embody our expertise with both PlanetLab and overlays Wrappers allow the components to work together Customize components using hooks Tools to configure, deploy, and monitor resulting overlays Goal: typing “make” deploys a fully-functional overlay on PlanetLab

ROCK components 1. Information plane: network topology and conditions 2. Forwarding engine: forward packets within the overlay 3. Ingress point: where packets from clients enter the overlay 4. Egress point: where packets exit the overlay 5. Control plane: computes and adds routes to the forwarding engine Information plane Ingress point Fwd engine Egress point The Internet Control plane Data plane

ROCK IP data plane Component: Click modular software router Click elements process, forward, queue, drop, schedule, and account IP packets Runs as a user process or kernel module We added Click elements for: Tunneling via UDP sockets and VPN (PPTP/GRE) connections Network address translation (NAT) using “safe raw sockets”

Initializing the data plane PL1PL2PL3 VPN tunnel (e.g., PPTP) UDP tunnels NAT DestNext hopInterface PL3UDP PL1UDP DestNext hopInterface NAT PL2UDP DestNext hopInterface PL2UDP VPN

Applications Right now: network games Know locations of clients and server, network topology Create a static overlay, e.g., using low-latency, high- bandwidth links Projects for CS networking class Plug in a dynamic control plane, build a useful service on PlanetLab Devise a way to find “better” routes Attract real users all around the world Crazy idea: Build a virtual ISP?

Summary ROCK is a work-in-progress Click-based IP data plane released Still needed: Control plane examples Monitoring, visualization tools More users and feedback! PlanetLab: ROCK: WikiWord: OverlayToolkit

PlanetLab performance Test data plane performance on PlanetLab using netperf All machines on a LAN Summary: Each overlay node adds about 1ms to RTT Throughput of about 4.5Mbps What’s the bottleneck on TCP throughput? PlanetLab machines are heavily loaded Most have outgoing bandwidth capped at 10Mbps Overlay hops RTT (ms)TCP thru (Mbps) None One Two4.5 Three5.54.5