1. Internet In A Slice
Andy Bavier
CS461 Lecture

2. Internet in a slice (IIAS)
Goal: run multiple “virtual” internets on PlanetLab
Experimentally evaluate proposed changes to the Internet’s core software
Demonstrate scalability and robustness
Carry real traffic on behalf of real users worldwide
Handle real-world instability and failures

3. Overlays A network built on top of a network Key idea: tunneling
Examples
VPN
Multicast
Resilient Overlay Network (RON)

4. How to build an overlay? Requirements
Packet forwarding engine
Allow clients to opt-in to overlay (overlay ingress)
Communicate with servers that don’t participate in the overlay (overlay egress)
Routing scheme (control plane)
First three form overlay’s data plane

5. User Opt-in
Client
Server
NAT

6. IIAS data plane First step towards IIAS vision
Built using the Click modular router project
You plug in your own control plane to make it all work

7. Click modular router
Open-source, standards-compliant software router from MIT
Click elements
Process, forward, schedule packets
Written in C++
Arrange elements into a graph using a simple configuration language

8. Click example Destination Out 1.2.0.0/16 0 3.4.5.0/24 1 default 2
/16 0
/24 1
default
ToSocket(UDP, , 4700)
FromSocket(UDP, , 4700)
LinearIPLookup 1 2
ToSocket(UDP, , 4700)
Discard

9. Example overlay
Build an overlay that carries traffic over Internet2 as far as possible
Internet2 connects most universities
Ingress: local I2 node
Egress: I2 node close to destination
By default, traffic between ingress and egress will be carried by I2

10. Example Overlay Servers NAT PlanetLab nodes at other universities PPTP
tunnel
UDP
tunnels
Princeton
PlanetLab
node
WinXP laptop
Internet2

11. Overlay ingress Overlay = VPN
PPTP = Microsoft’s proprietary VPN protocol
Client connects to ingress using GRE/PPTP tunnel
Ingress assigns a private IP address to client
All of the client’s packets are sent into the overlay
WinXP laptop
PPTP
tunnel
Princeton
PlanetLab
node

12. Overlay routing Route within overlay based on destination
Server -> egress
Client -> ingress
IP packets tunneled over I2 using UDP
In example, every node is an ingress or egress
Princeton
PlanetLab
node
nodes at other
universities
UDP
tunnels
Internet2

13. Overlay egress Egress nodes use NAT
Rewrite source IP address, UDP/TCP port
Reply from server to egress, routed through overlay back to client
Note: switching egress nodes breaks connections
Servers
NAT
PlanetLab
nodes at other
universities

14. IIAS control plane Where do the overlay routes come from?
Static configuration
Edit a config file, type “make”
Assumes clients, servers, and routes all known in advance
Better: dynamically add nodes, routes based on changing network conditions

15. Resilient overlay network
Utah
MIT
Explain overlays
Utah Company
Cable Modem

16. RON Strategy Measure all links between nodes Compute path properties
Determine best route
Forward traffic over that path

17. Potential projects Plug in an interesting control plane
RON, one-hop source routing, ESM, …
Measurement, visualization tools
Show the control plane in action
SpecOverlay05
Performance, robustness, adapting to changing network conditions, …

18. More information IIAS paper Wiki: https://wiki.planet-lab.org/
Topic: InternetInASlice
Feel free to add to it
Click:
RON: