1. CS 740: Advance Computer Networks Hand-out on Router Design
02/07/2007

2. ISLIP Scheduling Example

3. ISLIP (cont.)

4. What Limits Router Capacity?
Approximate power consumption per rack
Power density is the limiting factor today

5. Multi-rack Routers Reduce Power Density
Crossbar
Linecards
Switch
Linecards

6. Question
Instead, can we use an optical fabric at 100Tb/s with 100% throughput?
Conventional answer: No
Need to reconfigure switch too often
100% throughput requires complex electronic scheduler.

7. If Traffic is Uniform… R R
R/N In
Out R R In R In

8. Two-stage Load-Balancing SwitchR R R In
R/N
Out
R/N
Out
R/N
R/N
R/N
R/N R
R/N
R/N R R In
Out
R/N
R/N
R/N
R/N
R/N
R/N R R R
R/N
R/N In
R/N
R/N
Load-balancing stage
Switching stage
100% throughput for weakly mixing, stochastic traffic
[C.-S. Chang, Valiant]

9. In Out In In R R 1 R R 2 R R 3 3 3 3 R/N R/N R/N R/N R/N R/N R/N R/N

10. Passive and Almost Zero Power
Static WDM Switching
A, A, A, A
B, B, B, B
C, C, C, C
D, D, D, D
4 WDM channels,
each at rate 2R/N
Array
Waveguide
Router
(AWGR)
Passive and Almost Zero Power A In
Out
A, B, C, D In
Out B In
Out C D In
Out

11. 100 Tb/s router: Linecard Dataflow2 2
l1, l2,.., lN R
WDM R lN
WDM l1 lN R
l1, l2,.., lN 2 1 3 1 1 1 1 2 3 4 R
WDM l1 lN
l1, l2,.., lN
Out 1 1 1 1 1