Optics in Routers Switch Fabric Architecture ShangTse Da

Optics in Routers: Switch Fabric Architecture Shang-Tse (Da) Chuang, Isaac Keslassy, Nick Mc. Keown Stanford University Switch Fabric Design Goals Passive Mesh § Design a switch fabric 1 2 3 § For load-balancing and switching stages § 625 ports of 2 x 160 Gbps R R Cyclic Shift WGR Based Solution 1 2 3 R/N 1 2 3 Passive mesh § Features: § Scalability § Flexibility: arbitrary addition and deletion of linecards (due to upgrades/failures) 1 2 3 2 R/N Fixed Laser/Modulator l 1 Linecard 1 l 2 l 1 Linecard 2 l 2 1 2 3 2 l 1 Linecard N l 2 N Problem 1: Scalability to 625 Linecards § Idea: use mesh between groups of linecards l 1, l 3 Nx. N WGR … l N N N 1 l. N l 1 l 2 Linecard 2 2 l. N l 1 l 2 N-1 l 1, l 2 1 …l N Linecard N l. N Problem 2: Missing Linecards R/N R/2 R § Mesh needs N 2 connections § Problem when N=625 2 2 l 1, l 2 N …l N l 1 l 2 Linecard 1 N l 1, l 2 2 …l N l. N Passive mesh 1 1 l 1, l 2 1 …l N l. N No more arbitrations, no more reconfigurations! Problem 1: Scalability to 625 Linecards 1 Detector Ingress Linecard 1 Midstage Linecard 1 Egress Linecard 1 R R Ingress Linecard 2 Midstage Linecard 2 Egress Linecard 2 R R Ingress Linecard N Midstage Linecard N Egress Linecard N R R/N R/2 § Additional spreading stage with MEMS Linecard Mesh: Scalability & Flexibility Issues Problem 2: Missing Linecards § Each linecard spreads 2 R amount of traffic among N linecards § Each connection carries 2 R/N § If one linecard fails, needs to spread 2 R among (N-1) linecards: connection capacity not enough 2 R/3 Linecard 1 8 R/3 Linecard 1 Linecard 2 From Linecard Mesh to Group Mesh Crossbar Linecard 2 4 R/3 Linecard 1 Crossbar Linecard 3 4 R/3 Linecard 3 Crossbar 2 R/3 § Idea: use permutations that reconfigure only when linecard arrangement changes Hybrid Switch Fabric Group Mesh using Static MEMS Electronic Switches Linecard 2 4 R/3 Linecard 2 Linecard 3 4 R/3 2 x 3 Crossbar 2 R/3 2 x 3 Crossbar 4 R/3 2 Lx. M Crossbar 2 x 3 Crossbar Linecard 2 Linecard 3 3 2 Lx. M Crossbar Linecard 2 Lx. M Crossbar Group G 3 M Linecard 2 25 25 Linecard L Rack 1 Mx. L Crossbar Rack 24 Linecard 1 Optical Modules Linecard 2 Electronic Crossbars Linecard L 25 160 Gb/s Linecards Group G Racks of Linecards 2003 C 2 S 2 Annual Review 25 25 Group 2 2 M Mx. L Crossbar M 2 Gx. G MEMS 25 Linecard 1 2 3 Gx. G MEMS Linecard L 1 1 M Linecard L 2 Linecard 2 Group 1 1 3 Mx. L Crossbar 25 3 Group 2 Linecard 1 3 Optical Switch Fabrics Linecard 1 2 M 3 M Linecard L 1 Gx. G MEMS 1 Linecard 1 Optical Electronic Receivers Switches 1 Group 1 Linecard 2 Gx. G MEMS M Linecard L Linecard 1 Static MEMS Fixed Lasers 1 Linecard 1 Static MEMS Linecard 1 100 Tbps Packaging Rack 25