Optics in Routers: Switch Fabric Architecture

1. 2R/3 Linecard 1 Linecard 1 Fixed Laser/Modulator Detector 1 1 1 1 1 1 Linecard 2 Linecard 2 l l  R/2  R/2  R/2  R/2 R/N R/N R/N R/N R/N 1 1 Ingress Linecard 1 1 N 1 1 Midstage Linecard 1 l l l l , , Egress Linecard 1 2 2 2 2 2 2 R R R R R R l l 1 2 1 2 Linecard 1 Linecard 1 2 2 2 1 l l … … N N l l 3 3 3 3 3 Linecard 3 Linecard 3 3 N N l l 1 1 2 1 Ingress Linecard 2 l l 2 2 Midstage Linecard 2 , l l , l Egress Linecard 2 l Passive mesh Linecard 2 Linecard 2 1 2 1 2 2 2 2 3 … l l … NxN WGR N N l l N N 2R/N Ingress Linecard N Midstage Linecard N Egress Linecard N l l 1 1 N N-1 N N l l l l , , l l 1 2 1 2 Linecard N • Additional spreading stage with MEMS Linecard N R/N 2 2 1 N l R/N l … … N N Passive mesh l l N N StaticMEMS 4R/3 Linecard 1 2x3Crossbar 2x3Crossbar Linecard 1 4R/3 4R/3 Linecard 2 Linecard 2 2R/3 Linecard 3 2x3Crossbar 2x3Crossbar Linecard 3 4R/3 Shang-Tse (Da) Chuang, Isaac Keslassy, Nick McKeownStanford University Switch Fabric Design Goals Optics in Routers: Switch Fabric Architecture Passive Mesh WGR Based Solution R R • Design a switch fabric • For load-balancing and switching stages • 625 ports of 2x160 Gbps • Features: • Scalability • Flexibility: arbitrary addition and deletion of linecards (due to upgrades/failures) Cyclic Shift Cyclic Shift No more arbitrations, no more reconfigurations! Problem 1: Scalability to 625 Linecards Problem 2: Missing Linecards Problem 1: Scalability to 625 Linecards • Mesh needs N2 connections • Problem when N=625 • Idea: use mesh between groups of linecards Linecard Mesh: Scalability & Flexibility Issues From Linecard Mesh to Group Mesh Problem 2: Missing Linecards • Each linecard spreads 2R amount of traffic among N linecards • Each connection carries 2R/N • If one linecard fails, needs to spread 2R among (N-1) linecards: connection capacity not enough • Idea: use permutations that reconfigure only when linecard arrangement changes 8R/3 Linecard 1 Crossbar Crossbar Linecard 1 Linecard 2 Linecard 2 4R/3 4R/3 Linecard 3 Crossbar Crossbar Linecard 3 2R/3 100Tbps Packaging Hybrid Switch Fabric Group Mesh using Static MEMS Optical Switch Fabrics Static MEMS Electronic Switches Fixed Lasers Optical Receivers Electronic Switches 1 1 GxG MEMS Linecard 1 Linecard 1 2 2 LxM Crossbar MxL Crossbar Linecard 2 3 3 Linecard 2 1 M M Linecard L Linecard L 25 25 GxG MEMS 25 25 Group 1 Group 1 1 1 2 Linecard 1 Linecard 1 2 2 LxM Crossbar MxL Crossbar 25 25 Linecard 2 3 3 Linecard 2 25 25 GxG MEMS M M Linecard L Linecard L 3 Rack 2 Rack 1 Rack 24 Rack 25 Group 2 Group 2 1 1 Optical Modules Linecard 1 Linecard 1 2 2 LxM Crossbar MxL Crossbar Electronic Crossbars Linecard 2 3 3 Linecard 2 GxG MEMS M M Linecard L Linecard L 25 160 Gb/s Linecards M Group G Group G Racks of Linecards