Lecture: 7 Energy Efficiency in Optical Networks Ajmal Muhammad, Robert Forchheimer Information Coding Group ISY Department

Outline Introduction to Energy Issue Network Device’s Power Profile Access, metro & core networks Approaches to low Energy Networking Energy Saving Strategies Core, metro & access networks

Motivation Two main factors that drive the quest for “Green” networking (1) Reduction of CO2 emission The ICT (Information and Communications Technology) sector is responsible for 2.0% of the global greenhouse emissions, estimated by ITU (International Telecommunication Union). (2) Reduction of operational cost Power consumption of the ICT (Information and Communications Technology) accounted for the 4% of the global energy consumption BAU: Business-As-Usual ECO: Eco Sustainable 50 % of CO2 emission is due to the production stage 45% due to the usage stage 5% due to recycling/disposal stage For European Telecom network infrastructures

Terminal versus Network Power Consumption Typical current mobile terminal power consumption is 0.83Wh per day (including battery charger and terminal). The corresponding network power consumption is 120Wh. The ratio is 150:1 and therefore the network power consumption is the main contributor to CO2 and effort has to be directed at the network primarily. Significant research effort has gone into extending the mobile terminal battery life by optimizing and reducing its power utilization from 32Wh per day in 1990 to 0.83Wh per day in 2008, a factor of 38. In comparison the network power consumption has received little attention to date.

Power Consumption of Access Networks Mobile access is becoming dominant access technology Any where, any time, any service Mobile is least energy efficient ~25 W/user @ 10 Mb/s PON is most efficient ~7 W/user PON: Passive optical Network HFC: Hybrid fiber coaxial PtP: Point to point FTTN: Fiber to the node or neighborhood

Network Segmentation

Key Components Access Network Metro Network Customer home terminal ADSL modem, ONU…. Access network field equipment PON splitter, DSLAM, RF amps… Central office equipment OLT, gateway, switch, base station,… Access Network Metro Network

Key Components: Core Network Core routers & switched Number of router hops Long haul & submarine optical WDM transport EDFAs, Raman Amps, transmit & receive units, etc. TDM and WDM cross connects & OADM

Photonic Versus Electronic Switching Photonic switching has much lower energy consumption compared to electronic switching. It has been shown that the power needed per bit for switching is 100 to 1000 times higher in an electronic semiconductor switch as compared to a photonic switch.

Data Centers and Content Servers

Access, Metro, Core Power Consumption PON based access network - power consumption estimates are 10W for optical network units (ONU) and 100W for optical line terminal (OLT) which resides in an edge node. Edge router in the metro, for example Cisco 12816, with capacity 160Gb/s consumes 4.21 kW. Efficiency= 26.5nJ/bit Core router, such as Cisco CRS-1 with 640 Gb/s capacity consumes 1020 kW. Efficiency= 17nJ/bit WDM systems connecting the edge nodes to the core node consume 1.5 kW for every 64 wavelengths. Typically one multi-wavelength amplifier is required per fibre, consuming around 6W. The WDM terminal systems connecting core nodes consume 811 W for every 176 channels, while each intermediate line amplifier consumes 622 W for every 176 channels.

Router Power Consumption Dominated by router forwarding engines Power driver: IP look-up/forward engine I/O- optical transport: is lower in power Consumption than switch fabric

Outline Approaches to Low Energy Networking Introduction to Energy Issue Network Devices Power Profiles Access, metro, core network components Approaches to Low Energy Networking Energy Saving Strategies Core, metro, access networks

Approaches to low Energy Networking Modulate capacities of processing engines and of network interfaces, to meet actual traffic loads and requirements Introduce and design: More energy efficient elements for network devices Optimize the internal organization of devices Reduce devices intrinsic complexity levels Smartly and selectively drive unused network/device portions to low standby mode 1 2 3

Network Domain Utilization Internet traffic profile Networks are provisioned with resources for worse case scenario

Energy Saving in Core Networks Approaches Selectively turn down network elements - Energy efficient protocols Energy efficient network architecture Energy efficient routing Green routing

Energy Efficient Protocols Sleep & standby states Network devices enter low power state when not in use Can apply to systems and sub-systems Need to ensure network presence is retained use network connection proxy with sleep protocol Need to account for state transition energy and time May have multiple lower energy states IEEE Energy Efficient Ethernet (802.3az) Low power idle mode when no packets are being sent Approved Sept. 2010 Currently applies to copper interface only; not optical

Example: Exploiting Sleep Mode off: not used must be active to support working lightpath can be set to sleep

Dynamic Rate Adaptation Modify capacity of network devices in response to traffic demands Change clock frequency, processor voltage Power = C x Voltage2 frequency Slower speed to reduce power consumption 100 Mb/s uses 10-20 W less than 10GE, 4 W less than 1GE Need to allow transition time between rates Dynamic rate adaptation and standby states can be combined

Sleep Mode for Dynamic Networks Some nodes are selected to go to sleep according to the traffic flow and their location in the network topology When nodes go to sleep, they can still transmit and receive traffic but they cannot route traffic A node which is the only neighbour for another node cannot go to sleep Some traffic flows will have to take longer routes, i.e., energy is saved at the expense of QoS If the network blocking probability exceeds the acceptable (service) blocking probability threshold, the most recent node to sleep wake up

Energy Efficient Network Architecture Architectures that reduce the number of router hops Optical bypass Layer 2 rather than Layer 3 where possible Without optical bypass: All traffic goes to IP layer for processing ~10nJ per bit Allow aggregation of incoming traffic flow Statistical multiplexing Layer 3 Layer 2

Architecture: Bypass Option With bypass: TDM Layer Some traffic streams processed at TDM layer ~ 1nJ per bit WDM Layer Some traffic streams processed at WDM layer < ~ 0.1nJ per bit Switching wavelengths

Energy Efficient Routing Network with Dedicated Path Protection Energy-unaware Routing Energy-aware Routing

Energy Efficient Routing Network with Shared Path Protection Energy-unaware Routing Energy-aware Routing

Green Routing

Energy Saving in Metro Networks Reduce Regeneration PIC: Peripheral Interface Controller WSS: Wavelength Selective Switch ROADM: Reconfigurable Optical Add Drop Multiplexer

Energy Efficient Traffic Grooming DXC: Digital cross-connect OXC: Optical cross-connect FG: First Generation SH: Single-hop MH: Multi-hop

Network simplification Energy Efficiency in Access Networks Remove Layers Today IP ATM PSTN DPCN PDH SDH - mesh MSH DSL KiloStream Fibre Copper DWSS British Telecom network architecture today More power 21CN IP/MPLS Fibre & Copper MSAN Call Control Content WWW ISP Multi - service access Converged core Current thinking. No implementation assurances Wireless Ethernet Backhaul Other CPs I/connects Future Plan Less power Network simplification

From PON to Long Reach-PON

The Ring-and-Spur LR-PON Two dimensional coverage for failure protection Reusing the existing metro rings Cost-effective extended coverage integrated system less active sites low CapEx and OpEx