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Low latency for DCI and mobile applications

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At ECOC 2019, Jörg-Peter Elbers talked strategies and technologies for ensuring the low levels of latency needed in tomorrow's mobile and data center interconnect networks.

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Low latency for DCI and mobile applications

  1. 1. Low latency for DCI and mobile applications Jörg-Peter Elbers ECOC 2019 Why and how?
  2. 2. © 2019 ADVA Optical Networking. All rights reserved.22 Is low latency just another …
  3. 3. © 2019 ADVA Optical Networking. All rights reserved.33 Mobile network infrastructure Real-time (mobile) applications High-frequency trading (HFT) High-performance computing A few examples Low latency – Where do we need it? “A one-millisecond advantage in trading applications can be worth USD 100 million a year.”
  4. 4. 4 © 2019 ADVA Optical Networking. All rights reserved. Confidential. Low latency in DCI applications
  5. 5. © 2019 ADVA Optical Networking. All rights reserved.55 Applications require a maximum latency and controlled latency variation Low latency is more than just fast transmission … Framing FEC Link control Frame forwarding Switching Address lookup Packet forwarding Routing TCP windowing Flow control Packet retransmission Application Presentation Session Less latency More latency 1 2 3 4 5 6 7 Speed-up in high-frequency trading broker's contribution exchange response time round trip time order processing time 2007 2010500ms 450ms 850ms 100ms 10ms 30ms 60ms 250µs
  6. 6. © 2019 ADVA Optical Networking. All rights reserved.66 Latency close to fiber propagation delay (5µs/km) Straight line connection Minimization of equipment delay 1300km link for HFT, approx. 13ms round-trip time … but transmission line can be critical Chicago Futures market New York NYSE, NASDAQ
  7. 7. © 2019 ADVA Optical Networking. All rights reserved.77 10G transparent regenerator-based design performs best Directions to beat the fiber delay: µwave, free-space optics, low-latency fibers Low-latency design considerations [B. Teipen et al., ECOC’12] X p dr X p dr X p dr X p dr X p dr X p dr 10G transparent 0.70µs X p dr X p dr 100G OTN + SD-FEC 15.24µs 100G OTN + SD-FEC * 11.44µs (* reduced number of iterations) FBGFBG FBGFBGFBGFBGFBGFBGFBG X p dr X p dr 10G OTN 3.09µs 10G OTN + GFEC 9.39µs Tab. 2: Latencies for system building blocks System Component Latency Simple transparent 10G Regen 10 ns Optical Mux/Demux 20 ns Raman Amplification 30 ns DCM (grating) 50 ns 10 Gb/s OTN line card 2.0 μs 100 Gb/s OTN line card w/ equalization ~ 9 μs 10 Gb/s 5.6dB NECG G.709 FEC 6.3 μs 100 Gb/s 11.1dB NECG SD-FEC ~5.6 μs Recipe for low latency: Limit excess fiber and electronic processing 10 span system, 20dB loss per span
  8. 8. © 2019 ADVA Optical Networking. All rights reserved.88 Rule of thumb: a few µs per network element Ethernet aggregator latencies – examples [iCirrus paper Fronthaul Evolution: From CPRI to Ethernet“, OFT 2015]
  9. 9. 9 © 2019 ADVA Optical Networking. All rights reserved. Confidential. Low latency in mobile applications
  10. 10. © 2019 ADVA Optical Networking. All rights reserved.1010 ~10ms round-trip time~1ms round-trip time ~5ms round-trip time Very low latency Low latencyUltra low latency There will not be a one-size-fits-all configuration Latency determines location of RAN functions RU: radio unit DU: distributed unit CU: central unit MEC: multi-access edge computing UPF: user plane function RU: radio unit DU: distributed unit CU: central unit MEC: multi-access edge computing UPF: user plane function RU: radio unit DU: distributed unit CU: central unit MEC: multi-access edge computing UPF: user plane function ~1000 sites ~100 sites ~10 sites ~1000 sites ~100 sites ~10 sites ~1000 sites ~100 sites ~10 sites Source: NGMN Overview on 5G RAN Functional Decomposition
  11. 11. © 2019 ADVA Optical Networking. All rights reserved.1111 Ethernet is simplest; TDM-PON, FlexE and OTN add additional protocol layers 5G transport layer stack options Optical underlay Backhaul Fronthaul F1 Fx eCPRI CPRI IEEE1914.3 NGS1 Timingandsync Ethernet 802.1 CM Grey optics WDM Fiber TDM-PON FlexE2.1 or OTN OAMandserviceassurance
  12. 12. © 2019 ADVA Optical Networking. All rights reserved.1212 With eCPRI, 5G goes Ethernet eCPRI leverages Eth transport & OAM and offers ~10x reduction in bandwidth
  13. 13. © 2019 ADVA Optical Networking. All rights reserved.1313 Maximum latency on the data path plus accurate timing delivery eCPRI latency and timing requirements CoS Traffic Max. one- way frame delay Use case Max. one- way frame loss ratio High25 User plane (fast) 25µs Ultra-low latency applications 10-7 High100 100µs Full LTE or NR performance High200 200µs Installations with long fiber links High500 500µs Large latency installations Medium User plane (slow), C&M plane (fast) 1ms All 10-7 Low C&M plane 100ms All 10-6 Category Maximum time error |TE| at UNI Maximum time alignment error TAE between antenna ports T-TSC in radio equipment T-TSC in transport network T-TSC with |TEmax|=70n s (Class B) T-TSC with |TEmax|=15n s A+ (relative) n/a n/a 20ns 65ns A (relative) n/a 60ns 70ns 130ns B (relative) 100ns 190ns 200ns 260ns C (absolute) 1100ns 3µs
  14. 14. © 2019 ADVA Optical Networking. All rights reserved.1414 Limiting latency variation in x-haul network Low-latency timing-accurate mobile x-haul based on SDN-enabled 100G Ethernet aggregator RoE BH TrafficAnalyzer 10G 100G100G 10G 1GIEEE 1588v2 PTP (grand master) IEEE 1588v2 PTP slave (probe) 10G10G 10G10G 10G 10G BBU GNSS RRH PTP 10G 10G Central Office Remote Node … RoE RoE NETCONF/YANG Controller 100G100G FUSION IP Core MAC 100G PHY MAC 10G PHY MAC 10G BH … x6…8 10G PHY 100G MAC100G PHY FUSION IP Core MAC MAC 100G Aggregator Node (time sensitive) 1G PTP 100GMAC 100G PHY 10G PHY MAC10G FH 10G FH … x4 1G PHY 10G PHY … 10G 10G … Backhaul Service Configuration and Monitoring … … … PTP TrafficEmulator … Traffic Generator 100G Transport Node (time sensitive) … … SM GST 100GbE ingress treated as GST FH bounded delay aggregation Dagg = Store-fw MTU@10G + serve all other streams (F  1) MTU@100Gbps + transmission of packet MTU@100Gbps 100G 1G Paper Tu3B.3 Fronthaul traffic (1522 Byte MTU): • <3.1µs agg+deagg latency (1µs from MAC/PHY) • <0.6µs transit node latency • 5µs per fiber-km PTP traffic: • <±75ns time error (w/o additional means) Best demo award
  15. 15. © 2019 ADVA Optical Networking. All rights reserved.1515 Low latency (mobile) application Video surveillance demo at EUCNC 2019 Virtual machine Video management system Compute node AMEN (access metro edge node) Virtual machine Video analytics Compute node MCEN (metro core edge node) Core networkRemote client Fixed camera Metro network controlled by NFV network service Demonstrated here separately with partially emulated data plane (ROADMs, transceivers, …) PTZ camera High bandwidth video and low latency control traffic
  16. 16. 16 © 2019 ADVA Optical Networking. All rights reserved. Confidential. Summary
  17. 17. © 2019 ADVA Optical Networking. All rights reserved.1717 Conclusions Required latency and its value depends on the application The network is only one contributor Lower latency is often about simplification Trade-off between dedicated solutions and economies of scale More network layers may help short-term but can block future evolution Latency becomes additional network dimensioning parameter If you cannot measure it, you cannot monetize it
  18. 18. Thank you IMPORTANT NOTICE The content of this presentation is strictly confidential. ADVA Optical Networking is the exclusive owner or licensee of the content, material, and information in this presentation. Any reproduction, publication or reprint, in whole or in part, is strictly prohibited. The information in this presentation may not be accurate, complete or up to date, and is provided without warranties or representations of any kind, either express or implied. ADVA Optical Networking shall not be responsible for and disclaims any liability for any loss or damages, including without limitation, direct, indirect, incidental, consequential and special damages, alleged to have been caused by or in connection with using and/or relying on the information contained in this presentation. Copyright © for the entire content of this presentation: ADVA Optical Networking. jelbers@advaoptical.com

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