TCP Switching: Exposing Circuits to IP

1. TCP Switching: Exposing Circuits to IP Pablo Molinero-Fernández Nick McKeown Stanford University

2. Outline Why might circuit switching be a good idea in the Internet? How might circuit switching be integrated in the Internet?

3. How the Internet Looks Like Today

4. How the Internet Really Looks Like Today SONET/SDH DWDM

5. How the Internet Really Looks Like Today Modems, DSL

6. PS is bandwidthefficient PS networks are robust Why Is the Internet Packet Switched in the First Place? Gallager: “Circuit switching is rarely used for data networks, ... because of very inefficient use of the links” Tanenbaum: ”For high reliability, ... [the Internet] was to be a datagram subnet, so if some lines and [routers] were destroyed, messages could be ... rerouted”

7. PS is bandwidthefficient PS networks are robust Are These Assumptions Valid Today? 10-15% average link utilization in the backbone [Odlyzko] SONET required to reroute in 50 ms vs. over 1 min for IP [Lavobitz]

8. Internet’s Performance Trends Processing power Link capacity

9. Fast Links, Slow Routers Processing Power Link Capacity (Fiber) Source: SPEC95Int; Prof. Miller, Stanford Univ.

10. Fast Links, Slow Routers Processing Power Link Speed (Fiber) 2x / 2 years 2x / 7 months Source: SPEC95Int; Prof. Miller, Stanford Univ.

11. Fewer Instructions Instructions per packet since 1996

12. How Can Circuit Switching Help the Internet? • Simple data path: • No buffering • No per-packet processing • Possible all-optical data path • Peak allocation of BW • No delay jitter Higher capacity switches Simple but strict QoS

13. Circuit sw Packet sw 99% of Circuits Finish Earlier Flow BW 1 Gb/s 10 Mb/s Avg latency 0.505 s 1 s Worst latency 1 s 1 s What Is the Performance of Circuit Switching? File = 10Mbit 100 clients 1 server 1 Gb/s x 100

14. Circuit sw Packet sw A big file can kill CS if it blocks the link Flow BW 1 Gb/s 10Mb/s+1Gb/s Avg latency 10.495 s 1.099 sec Worst latency 10.990 s 10.990 sec What Is the Performance of Circuit Switching? File = 10Gbit/10Mbit 100 clients 1 server 1 Gb/s x 99

15. No difference between CS and PS in core Circuit sw Packet sw Flow BW 1 Mb/s 1 Mb/s Avg latency 109.9s 109.9sec Worst latency 10,000 s 10,000 sec What Is the Performance of Circuit Switching? File = 10Gbit/10Mbit 100 clients 1 server 1 Gb/s x 99 1 Mb/s

16. Outline Why might circuit switching be a good idea in the Internet? How might circuit switching be introduced into the Internet?

17. Our Proposed Architecture • Create a separate circuit for each flow • IP controls circuits • Optimize for the most common case • TCP (90-95% of traffic) • Data (9 out of 10 pkts) TCP Switching

18. TCP Switching Exposes Circuits to IP IP routers TCP Switches

19. Source Router Router Router Destina-tion SYN SYN+ACK DATA Packets Packets Packets Packets TCP “Creates” a Connection

20. Source Boundary TCP-SW Core TCP-SW Boundary TCP-SW Destina-tion SYN ACCEPTED SYN+ACK ACCEPTED DATA Packets One Circuit Packets Let TCP Leave State Behind

21. State Management Feasibility • Amount of state • Minimum circuit = 64 kb/s. • 156,000 circuits for OC-192. • Update rate • About 50,000 new entries per sec for OC-192. • Readily implemented in hardware or software.

22. Software Implementation Results TCP Switching boundary router: • Kernel module in Linux 2.4 1GHz PC • Forwarding latency • Forward one packet: 21ms. • Compare to: 17ms for IP. • Compare to: 95ms for IP + QoS. • Time to create new circuit: 57ms.

23. Conclusion • PS seems unlikely to keep up with link speeds in the backbone. • CS becomes attractive in core • Higher capacity (optical) switches • Simple QoS • User response time comparable to PS • TCP Switching • Integrates CS and PS • Exploits our connection oriented use of Internet