Fec latency. 10km+ where fiber latency dominates.

Fec latency 3bs Task Force has adopted RS(544,514) FEC with interleaving of FEC symbols from two FEC codewords to give good burst error tolerance. pdf IEEE P802. 6dB higher NCG than HDFEC at 25% OH Latency t ~ 100*t ~ 100*t. 5x 4. 3bj meeting in May 2012* ⚫Good Properties No dummy or padding bits, good for coding gain and hardware cost Parallelism options: 160/320, can use same bus-width as KR-FEC: 5440/34 = 160bits Net OH (ensure integer PLL, 680*156. 3cd and 802. 3 architecture, for both a NRZ and a PAM4 PHY However, the LL FEC codes are point to point codes across 4 lanes, and after the FEC code is inserted, normal 802. Unfortunately, most of these applications cannot use the rich features of the QUIC protocol since it only uses retransmissions to cope with packet losses. We should FEC MEDIUM MEDIUM 800GBASE-R FEC 800GBASE-R PCS PMA 8:8 800GBASE-R FEC Inverse FEC End-to-End FEC architecture Segmented FEC architecture FEC1 FEC1 Architecture for 800GbE FEC2 •Gen1 and Gen2 can use End-to-End FEC architecture to support the 100G/L and 200G/L PHYs. Figure 4. The use of FEC as defined in this Standard is recommended, but there are applications where occasional latency include fiber propagation delay, DBA, processing time of other functions in OLT/ONU. 3ch forward direction latency is 1024ns to 4096ns range ASA 2. An output BER=1e-15 can be achieved when input BER~=5e-10. 0 GT/s (including FEC) (We can not afford the 100ns FEC latency as networking does with PAM-4) Bandwidth Inefficiency <2 % adder over PCIe 5. 3dj Task Force 4 PCS/XS (RS-FEC) Latency • Assumptions • Core clock 1 GHz • 3 clock cycles for encoder (3 ns) • 3 clock cycles for decoder miscellaneous (3 ns) • codewords are corrected in parallel • 31 clocks cycles for correction (31 ns) • 4 x 5440 bit-times for 800G (25. • To reduce latency, this scheme may need 8 independent highly parallel Chien search engines. The “lightweight” version of PCIe 6. We propose, implement and evaluate QUIRL, a revisit of the QUIC loss recovery mechanism. 3ch Data path Latency 16 802. • The benefit of interleaved FEC is minor! 1. It is much longer than ~85ns latency (2. The shift towards edge data centers tries to address the low latency requirements in Idea with FEC might correct something to prevent the TCP re-transmission dance. Concerns over the latency of this Review - FEC Latency and Complexity 3 September 2015 • Corresponding Complexity: • CS latency is targeted to 8 cycles for all FECs. If the selected code has much commonality Its format is FEC x:y, which means send y redundant packets for every x packets. FEC LATENCY AND POSSIBLE TARGET • In 802. , LTD. The achievable end-to-end latency was derived as a function of the coding rate and feedback delay. Emerging Industries. 3bj can fit cleanly into the 802. View All. Marvell Block diagram for 16x25G PMD PMD0 PMD15 AM lock/ Deskew/ Lane Reorder 16x40bit @664MHz Latency in DC is incurred by upper layer protocol (TCP windows, flow control, etc) and much cost on server implementation, especially memory Our proposed FEC latency 400GbE target is <250ns. Agree on a model for latency specification for 1000BaseT1 and the layers we control. FEC is also widely used in modems and in cellular networks. In this paper, we introduce an RS-BCH concatenated FEC code to deal with this problem, where KP4 is used as the outer code and the BCH(144,136) code is as the inner code, both of which are carefully analyzed and selected. org/wp-content/uploads/2020/03/LL-FEC-Specification-1. sun_3bs_01_0915. Overall power consumption should be reasonally small, e. 3bs 400 Gbs Task Force PMD0 PMD1 PMD2 PMD3 AM lock/ Deskew/ Lane Reorder 4x160bit @664MHz RS Syndrome FEC doesn't • FEC adds more latency than analog EDC, but digital EDC can be late too • FEC and EDC can be used in combination – Design of each should be mindful of the other. Article Details. The alignment marker is not part of the FEC block in the following example. 6TbE (Cont’d) February 15, 2022 YUCHUN LU 10 • Gen1. • 100G Intrinsic FEC Block latency is 26ns. 11. FEC processing in a receiver may be applied to a digital bit stream or in the demodulation of a digitally modulated carrier. 4x 2x200G FEC 4x 4x 4x 2 4x 4x100G FEC 4x 4x 4x 4 4x FEC Architecture 1x400G KP4 1x400G FEC Latency(ns) 72 2x200G FEC Latency (ns) 84 4x100G FEC Latency (ns) 110 • Decoder Latency ([1] sun_3bs_01_0715 ) • no interleaving, no breakout • Encoder Latency: ~3ns for FEC and mapping candidates Candidate Mapping 8n 8n+1 RS m RS N RS K FEC rate OAM bits RS N-K FEC Block ns Correction ns FEC latency ns OAM Mbps A 3B2T 80 81 9 450 406 0. ─ See brown_3dj_optx_01b_230413 ─ Adding the 4x RS codewords interleaving conversion, the total FEC related latency would be 139. 3df 200 Gb/s, 400 Gb/s, 800 Gb/s, and 1. 1 Vivado Design Suite Release 2024. OTN was designed to provide higher throughput (currently 400G) than its predecessor SONET/SDH, which stops at 40 Gbit/s, per channel. QUIRL relies on Forward Erasure Correction (FEC) This article discusses FEC schemes for next generation 200 Gb/s and 400 Gb/s Ethernet being defined by IEEE P802. We demonstrate that PCIe 6. 4, resulting in a net bandwidth increase of 1. Agree on which methods and\or tools will be used to model latency for “End-End”. 512b/51xb to 64b/66b Transcoding (across lanes) X. In this paper we examine how the FEC chosen by recent IEEE 2023/2/22 IEEE 802. 1E-4 7. A second solution ("MCS dimensioning") recommends to only decrease the MCS value, instead of applying AL •Defining a FEC code for 802. The alignment marker is always at the beginning of a FEC block. 3ba bit manipulation Propose a low-latency end-to-end FEC option for DR channels at 200G/lane Leverage existing 100G/lane infrastructure and simply double the bandwidth Saves the additional area, power, and latency of an SD-FEC in the module DSP Saves any additional link up NVEnc Preset: ll -- low latency NVEncRateControl: auto - let ffmpeg decide NVenc Coder: cabac HEVC Support: Sunshine will advertise support for HEVC Force a specific Encoder: nvidia NVENC FEC percentage: 1 I do this see this [2022:12:18:13:29:45]: Info: Device Description : NVIDIA GeForce RTX 2070 SUPER Device Vendor ID : 0x000010DE Long-latency connections also benefit; in the case of satellites orbiting distant planets, retransmission due to errors would create a delay of several hours. , equalization, etc. 709 is commonly called Optical Transport Network (OTN) (also called digital wrapper technology or Data-Centric Transmission with Adaptive FEC for Ultra-Low Latency Resource Sharing in Wide Area 10G-KR FEC Latency •QC(2112,2080) FEC adds >250ns of latency –At the Tx, the 32 parity bits are added at the end of the block, negligible latency –At the Rx, the syndrome computation requires 1 block latency (2112) bits –Standard Meggit decoder requires another block latency IEEE802 Plenary July 2006 10GBASE-KR FEC tutorial 13 FEC block format Payload words carry the 10GBASE-R scrambled payload words Tn = Transcode bit carries the state of the 10GBASE-R sync bits for the associated payload word Sync bits are compressed to аsingle bit then scrambled to ensure DC balance 64b/66b sync bits are either 10 or 01 hence can be 4 Why Care about FEC •In 10GBASE-KR, the Fire code (2112, 2080) was adopted. Page 3 400GbE FEC Architecture Exploration Current observations: Try to find lowest latency and cleanest FEC architecture for 400GbE project Having issues in implementing one pipeline RS(544,514) over 16 lane. This is best demonstrated by examining the latency added by FEC when Figure7:Latencyasafunctionofframesize. Other Thoughts FEC flexibility is needed to accommodate different PMDs (requirements) For concatenated FEC scheme Proper interleaver design between outer and inner code is critical to overall FEC performance End-to-end FEC for 200G per lane applications in Data Center Leon Bruckman, Yuchun LU, Yan ZHUANG - Huawei Technologies IEEE P802. 78125 1. 2 Clause Latency Where used 25GE RS-FEC: RS(528,514) CL 108 250 ns All 25G Ethernet optics and CA-L category twinax copper cables BASE-R FEC or “Firecode” FEC FEC LATENCY AND POSSIBLE TARGET • In 802. Typical latency for the inner code encoding/decoding w/ the PAM4 interleaver is ~15ns (~10. 2E-5 FEC Latency 600ns 115ns 100ns Ideal Required Slicer SNR 19. 881. 8dB -1. Overall latency includes FEC latency and implementation dependent aspects. 1. • Option 2: Concatenate RS(544, 514) with another inner FEC (The effectiveness is questionable). Other Thoughts FEC flexibility is needed to accommodate different PMDs (requirements) For concatenated FEC scheme Proper interleaver design between outer and inner code is critical to overall FEC performance Interleaved 100G FEC Latency • Currently Table 80-5 contains no entry for RS-FEC-Int sublayer • Clause 161. Displayed only on 16Gb/s-capable platforms and not on 32Gb/s-capable platforms. Packet-level forward erasure correction (FEC) is effective for achieving low-latency transmissions in non-terrestrial networks (NTNs), which often contain lossy links with long propagation delay. pdf. [stone_100GEL_01_0118] FEC and Retry Low latency mechanism w/ FBER of 1E-6 to meet the metrics (latency, area, power, bandwidth) Agenda •Introduction to PCI Express® and Load-Store Interconnects •Evolution of Data Rates in PCI Express •Key Metrics and Requirements for PCIe 6. 7 GBd requiring 8. http://www. The additional latency caused by implementing FEC on a module is not a show-stopper. FEC latency with 20 × interleaving across 20 wavelengths and 26-way time-domain interleaving of 511-bit blocks. , ~ 200mW in 28nm CMOS The efffective coding gain should be sufficiently large for the given modulation scheme. • This first set of slides address following FEC issue other than framing: – FEC rates/overhead – Algorithms – Code gain – Latency issue IEEE 802. Show the relationship between ODU Clients, ODU, ODU-Groups and OTU. . Minimizing latency for content delivery and AR/VR experiences. 3bs. PCS Ln0. 3bj KR4/KP4 FEC In existing low latency Ethernet switches, you see latencies as low as 250-350ns (for 10GE). The proposed optical transceiver also accommodates 802. Cut-through architectures allowed latency as low as hundreds of nanoseconds and a race was on to shift to cut-through networking. May 2008, Munich Proposal for FEC in 40G/100G Ethernet 10 FEC Segmented FEC –OFEC for Coherent Optical Interfaces • Suitable for applications where FEC latency is less sensitive, e. org/3/bs/public/adhoc/logic/oct21_14/wangz_01_1014_logic. AI & Cloud Access-Ready Coherent 5G & Beyond. TCP ensures ordered, uncorrupted packet delivery, controlling latency. 8 16-QAM Symbol Mapping v 16-QAM Symbol Mapping We provide 40 G OTU 3 performance results for Continuously-Interleaved concatenated BCH (CI-BCH) FEC, demonstrating best-in-class performance for a 7% overhead hard-decision FEC and offers option to tradeoff coding gain for reduced FEC decode latency. Section III explains our dynamic FEC (dFEC) algorithm design as well as the necessary system building blocks to integrate it into TCP and MPTCP. 3bj, we target FEC-related latency to be less than 100ns, where the receive time for a FEC frame takes about 50ns and the rest time budget is mainly used for decoding. 4 refers to 91. e. 0 FEC was made possible by this secondary error-correcting mode, which also reduced latency. Performance evaluation of a convolutional FEC shows that under low latency constraints, AL-FEC yields significantly better results than other considered FEC scheme: Raptor10, Reed Solomon, as described in the first solution within TR 26. For example, FEC 2:1 means that it sends one extra packet for every two packets, which increases bandwidth consumption by 1. 5625&ast;(34/33) = 53. 5 pJ/bit [5] or . The number of errors left uncorrected by FEC. If you are designing applications such as high-frequency trading, this will be important to you. 8% of 139. latency for non-FEC contribu t ions, e. 6 Background (Informative) In many applications, errors are generally not acceptable; therefore support for some sort of FEC scheme may be required. We present e TCP and MPTCP protocols, FEC mechanisms and latency-sensitive application requirements into perspective. This method is shown in Fig. 18x or 504ns more latency compared with non-interleaved FEC scheme (2 FEC CONVs). 7 dB FEC with latency of 105 ns – PAM-8 operating at 43. • FEC decoder latency: 8+1=9 cycles for syndrome calculation, 30 cycles for KES, 8 cycles for Chien search. 5, if a stronger FEC is needed for 200G/L optics, the Link to file: https://ethernettechnologyconsortium. lee@colorado. 5 modules, 100G AUIs and 200G PMDs (Short-term and limited market). 5 times. • For 400GbE, if using same or similar FEC code, we can achieve lower latency. 50 B 11B7T 120 121 11 360 309 0. More latency for latency sensitive applications, 2. It is typically 5-10 times of coding delay – Number of iterations in decoding process Two types of benefits for sliding window lreducedFEC related latency intuition: repair packets are quickly produced and they quickly recover an isolated loss limprovedrobustnessfor real-time flows intuition: encoding windows overlap with one another which better protects against long loss bursts because of reduced latency, encoding/decoding window sizes Throughput and Latency for Soft-Decision FEC v1. In addition, robustness is increased further by adding 26-way time-domain interleaving. CAUI 4NG, for 100 m reach. The goal was to pay close to zero latency penalty and then rely on a very robust CRC for detection, combined with a fast link level replay to handle any errors that the FEC could not correct. 2 ns NetFEC: In-network FEC Encoding Acceleration for Latency-sensitive Multimedia Applications Abstract: In face of packet loss, latency-sensitive multimedia applications cannot afford re-transmission because loss detection and re-transmission could lead to extra latency or otherwise compromised media quality. FEC Ln1. It is more costly to achieve same BER for 100Gbps single-lane electrical link [sun_100GEL_01b_0118]. Efforts in designing low-latency FEC schemes that operate over short block lengths to improve interactive communication is observable in Raptor codes [12], RaptorQ • FEC latency: • *R-S 0, 100ns • *R-L 200/250ns Summary of Options . •Can increase MTTFPA to over 2. pdf and zhuang_nea_01_220622. The latency and complexity of the FEC increase exponentially with the number of bytes to be corrected. Section IV explains our measurement setup with different applications, network settings and the end- o Reference: 100G-KR4 FEC gain ~ 5. 4 100G-KR Channel Simulation Results PAM4 53 Gbaud TX Channel TX1 Pkg_15p0mm TX2 XChannel1 XChannel2 RX 15mm PKG model is cascaded at both ends of the through and cross channels. Moreover, network congestion often leads to burst of losses [30], for which FEC is often ineffective or even detrimental [34]. from publication: Datacenter Ethernet and RDMA: Issues at Hyperscale | We observe that emerging artificial intelligence, high-performance •Lower-latency FEC can be used to get rid of repeaters, or relax PMD/channel requirements. One major decision KP4 FEC was adopted for 50GBASE-R PHYs. The effect gets worse as latency increases. Recap of PCS/XS (RS-FEC) Latency & Inner Code FEC (128,120) Latency • An example of RS FEC Latency for 200G/400G/800G/1. 5x of 100G encoder. A growing number of Internet applications require low latency. Stronger FEC may be desired for some cases. 95E-2 optical raw BER. 0 across all payload sizes Reliability 0 < FIT << 1 for a x16 (FIT –Failure in Time, 1. Some complexity tradeoffs for dual FEC mode were discussed in lu_3ck_02_0719 In this work, we provide an analysis on the engineering tradeoffs for Clause 91 versus the proposed interleaved FEC in terms of latency and power/area 200 GbE using 2xRS codewords interleaving has a PCS latency (including FEC) of 88. • Note: Options 1 and 2 has no difference from the The new spec cuts FEC latency approximately in half by using a shortened codeword FEC variant – RS (272, 257+1, 7, 10) that replaces the IEEE 802. 15us (269%) longer than RS (2048,1536) •Implementation of LDPC is more complicated The Cisco NCS 2000 200-Gbps Multi-Rate DWDM Line Card provides the following benefits: Transport of 50-, 100-, or 200-Gbps wavelengths over fully uncompensated networks Transport over very-low-quality fiber with very high Polarization Mode Dispersion (PMD) Support for 128 channels at 37. But this will require at least 1 codeword latency Learn how forward error correction (FEC) works, the trade-offs involved, and how we apply FEC in Cisco equipment to optimize the performance of your network. 2023/4/13 IEEE 802. 3E-4 1. This goal has been proved to be reasonable and achievable. ITU-T Recommendation G. FEC Ln0. Download scientific diagram | RS544 FEC latency breakdown. Other Thoughts For concatenated FEC scheme Proper interleaver design between outer and inner code is critical to overall FEC performance Flexibility in interleaver is preferred to trade off Low Latency FEC Architecture PMD RS FEC MDI Medium MAC/RS PMA (20:10) PMA (10:20) CAUI 100GBASE-R PCS PMA (4:10) PMA (10:4) CAUI 9 . 9e+14 years (10GBase-KR FEC Tutorial) •No extra redundancy was introduced •An extra processing latency of about 220 ns was introduced •If encoding over 25G data stream, we can use 800G-FR4 without inner FEC •Latency Benefit: FR4 optics currently used for short reach applications •Intra Data-Hall average reach < 100m •Architecture Benefit: FR4 optics in CPO/LPO utilize host side SERDES •Host not expected/required to have inner FEC •Power Benefit: 800G-FR4 in high density systems •Pluggable and CPO/LPO systems FEC architectures for 800GbE/1. default value: 0. 0 architecture improves the bandwidth efficiency in the range of 0. Latency ~100ns. Total channel insertion loss ~36dB @ Nyquist. Performance, latency, and complexity are a We propose and experimentally demonstrate a proof-of-concept of a programmable optical transceiver that enables simultaneous optimization of multiple programmable parameters (modulation format, symbol rate, power allocation, and FEC) for satisfying throughput, signal quality, and latency requirements. But at moderate or high latency (& where latency is NOT due congestion) any saving of TCP roundtrips dramatically lowers average latency, as the error-free latency on link goes up. New L0p Power State: Power-saving design improvements were given top attention because PAM4 signaling consumes more energy. 27 • Use one RS redundancy symbol for OAM bits. fec_uncor_detected. • Latency, power consumption, and cost are Zero Latency VR is proud to be a Platinum Sponsor of the IAAPA FEC Summit 2025, Bring next generation Zero Latency VR to your city. 5-GHz channel spacing, or up to 150 channels at minimal spacing With a variety of macro- and micro-benchmarks, we quantify the relative advantages of UDT+FEC, when compared to using GridFTP combined with CUBIC, BBR, and parallel streams. RS (544, 514, 15) FEC, also known as KP4 FEC, has been widely adopted in PAM-4 links. 10km+ where fiber latency dominates. 2E-10 2. • Option 1: FEC conversion which was adopted by IEEE (Preferred). 3cd standard The IEEE 802. 1% FEC Threshold • Latency ≤ 250ns end to end (Concatenated) • 123. Publication Date 12/6/2021. 3 Next Gen, incorporates Low Latency FEC (LL FEC) in development in 802. 1 Download. ap spec is: 6144 UI of delay (tx and rx) The purpose of this statistic is to detect congestion or a device affected by latency. 9dB 21. 00 2. It was100ns for 802. modes, where AN is used to select between Clause 91 FEC and interleaved FEC. Peak power could be a concern. In order to study what is needed and has been adopted for the next speed node, this article covers new forward error correction (FEC) technology, modeling, and performance analysis to aim at 200+ Gbps Stronger protection with even lower latency than Clause 74 FEC can be achieved using transcoding and a new, shorter RS-FEC code. 8dB -2. FEC induced latency is marked in red. do not use if you dont know what it means. However, solving the POMDP optimally is in general difficult unless its state and action space is very small. , upper bounded by 250ns. Soft FEC for Low Latency Higher Coding Gain Conclusions 2 Summary. This letter considers the problem of dynamically sending FEC coded packets based on delayed feedback to achieve fast in-order data delivery without retransmissions. IP and Transceivers Serial Transceiver Virtex UltraScale+ 58G FPGA Features and Debug Virtex UltraScale+ FPGAs GTM Transceivers Wizard Vivado Debug What is the code gain of the low latency FEC used in the PCIe 6. A typical decoder may require another 70ns to100ns decoding latency. Ho wever, faster lanes may 40km FEC selection •BCH FEC has been adopted for 10 km •BCH FEC has latency and power savings, and is an Ethernet optimized design •OFEC and BCH have been proposed as options for 40km •Both schemes meet the loss budget, with similar optical implementations based on Tx amplification •OFEC has a reach advantage equivalent to ~6km fiber creases latency and reduces the available bandwidth. 7Gbaud 16QAM 800LR supports sufficient coding gain for a single digital solution 800G 10km & 40km àIt is preferred due to its technical advantages in latency, power, and timing certainty stronger FEC and/or THP if 1E-15 is required for some applications. The lowest latency is achieved when in no-FEC mode, and For designs using "FEC Not Allowed" modes without FEC, the total latency is only Transceiver (Table 1) latency. 3dj Task Force 7 PHY/FEC types • Three PHY/FEC types are explored • Type 1: single FEC spans multiple AUIs and the PMD link • sometimes referred to as “end-to-end FEC” • Type 2: outer FEC spans multiple AUIs and PMD link (like Type 1), additional inner FEC spans PMD link • sometimes referred to as “concatenated FEC” • Type 3: FEC is dedicated to •FEC Latency Comparison •If KP4 FEC is used for 50GE, FEC latency will be ~200ns without interleaving and ~300ns with interleaving. FEC Architecture Encoder Syndrome KES CS Forney 1x400G FEC 4. Thanks! Title: FEC Options FEC and with 1:5 FEC Figure 3 shows how TCP’s maximum theoretical throughput decreases exponentially as packet loss increases. Low-Latency FEC Design With Geometric Packet Arrival and Delayed Feedback Packet-level forward erasure correction (FEC) is effective for achieving low-latency transmissions in non-terrestrial networks (NTNs), which often contain lossy links with long propagation delay. This parameter is obligatory and must be a positive number >=2. 5 microseconds (microseconds), The number of errors corrected by FEC. To quote Cheshire [6]: “Once you have bad latency you’re stuck with it”. 3bj •100G LR4 does not require LL FEC for 10 km reach; compatible with CAUI 4 •100G SR4 requires LL FEC, i. ieee802. 0 forward direction quiet time is 240ns to 480ns Table from 802. , e qualizat ion, etc. ¾ Another option is discussed in [1]. Therefore, FEC becomes an important part of the PAM4 system solution to offset this detection penalty. RS FEC into BCH FEC • Timing certainty • RS544+BCH(126,110) ~1. 125 Gbps Intel® Stratix® 10 TX devices do not support the 100GBASE-KP4 physical medium dependent (PMD). Industries. For a constant RS544 FEC, the latency re-duces for faster link bandwidths but will not go. MPTCP Meets FEC: Supporting Latency-Sensitive Applications Over Heterogeneous Networks (FEC) is not a new initiative in this direction, the majority of the approaches consider FEC inside the application. 3bs standard FEC. 3av Task Force, September 2006. HUAWEI TECHNOLOGIES CO. Takeaways. Advanced FEC codes with decoding latency typically in the order of micro seconds. 902 9 44 3600 176. 3ch EEE Timing Parameters 17 Low latency: <2ns FEC correct and CRC check • No Sync hdr, no Framing Token (TLP reformat), no TLP/DLLP CRC • Improved bandwidth utilization due to overhead amortization • Flit Latency: 2ns x16, 4ns x8, 8ns x4, 16ns x2, 32ns x1 • Guaranteed Ack and credit exchange => lower recovery delay, FEC schemes that reconstruct earlier lost packets without waiting to correct all losses provide the basis for streaming codes (i. 0-25G-Consortium. Level Two Title Impact of raw BER on FEC latency and sys tem performance . FEC backward compatibility shall be considered. Soft FEC operating at 15% OH provides 0. Continuing to deliver the low-latency and high-reliability targets; Improving power efficiency; Maintaining backwards compatibility with all previous generations of PCIe technology; Companies planning their roadmaps can include the next generation of PCIe technology with the assurance that it will meet their needs for a reliable, FEC is used to mitigate high BER in the data stream. Gain is minor, only 0. 27dB Total Penalty -0. • Factors contributing to FEC computation latency: – Decoding delay is the main contributor. 858 11 51 3360 233. 3by Logic ad-hoc Your Imagination, Our Innovation Option A – Baseline Priority decoding IF KR Use CL108 RS-FEC Else // CR IF either RSFEC_REQ and both RSFEC_ABILITY use Cl 108 RS-FEC else IF R-FEC:RL-basedFECAdjustmentforBetterQoEinWebRTC InsooLee UniversityofColoradoBoulder insoo. 25/50G Ethernet Specification Download. It provides 200/400G 200 GbE using 2xRS codewords interleaving has a PCS latency (including FEC) of 88. • Encoder: extra data MUX or half-cycle engines for the half-cycle frames, the area is roughly 4. FEC is running at 25G. 7 •CAUI 4NG to be defined in 802. February 19, 2019. The more IP packets which are interleaved the FEC is a major source of latency in a switched network and the consortium says the new specification cuts FEC latency approximately in half. 47dB Low latency FEC specification offered by 25 Gigabit Ethernet Consortium. FEC processing delay, IP transfer delay, IP delay variation buffering and FEC latency delay. 33 3836. 0, the FEC mechanism works in conjunction with cyclic redundancy check (CRC) with a latency target below 2 ns. 4ns) Pre-FEC BER threshold— A predefined threshold for error-free post-FEC transmission determined by NCG; Other considerations include hardware complexity, latency, and power consumption. UDP, a quicker but connectionless protocol, requires additional features for reliability. FFE, DFE, and MLSD for stronger EQ 3. •Low latency for AI/HPC applications in datacenter as stated in yin_3df_01b_2207. Since FEC works on fixed code size, FLITs are used to transmit the TLPs and DLPs in the data stream. 3ch. We show that the latency for non-FEC contribu t ions, e. RS-FEC Parameter Name NRZ PHY PAM4 PHY FEC encoding — RS (528, 514, t=7, m=10) RS (544, 514, t=15, m=10) Total symbols n 528 544 Message symbols k 514 514 Parity symbols n-k 14 30 Bits per symbol m 10 10 • FEC decoder latency: 8+1=9 cycles for syndrome calculation, 30 cycles for KES, 8 cycles for Chien search. 0 latency for non-FEC contributions, e. Pkg_15p0mm 400G FEC Latency 3 •“Typical” 2x200G FEC decoder latency : 17 cycles for syndrome calculation, 30 cycles for KES, and 8 cycles for CS. 3bs 400 Gbs Task Force PMD0 PMD1 PMD2 PMD3 AM lock/ Deskew/ Lane Reorder 4x160bit @664MHz RS Syndrome do not use if you dont know what it means. High Speed ADC enables DSP Architectures 2. 2. In this section, we’ll explore other options including different coding schemes and even different FEC codes. • Decoder Latency: 1x400G FEC has shorter latency w/o breakout, longer latency is needed for breakout by time sharing. – PAM-4 operating at 51. g. LDPC Throughput and Latency; 5G New Radio - Decode; 5G New Radio - Encode; Note that the latency of later blocks is likely to be greater than the initial latency due to input buffering holding additional blocks, To use the FEC filter, set <filter-type> in your configuration to fec. Processing latency is similar for 100G or 400G. pdf FEC code gains and latency* •The code gains for AWGN of LDPC (184931,15677) is 0. “FEC flexibility is needed to accommodate different Latency in DC is incurred by upper layer protocol (TCP windows, flow control, etc) and much cost on server implementation, especially memory Our proposed FEC latency 400GbE target is <250ns. 800 Gigabit Ethernet (GbE) Specification Rev. 2dB@1e-15, almost nothing@1e-12. a 4x100G TDM to form a 1x400G bps We first show that the minimum-latency FEC design problem can be modeled as a partially observable Markov decision process (POMDP), and hence the optimal code construction can be obtained by solving the corresponding POMDP. 7 dB and latency : 85~95ns RS(544, 514, t=15, m=10) (TC=256/257b ), same as 100G-KP4, 3% OC o NC ~= 6. Stronger FEC algorithms might offer higher coding gains, but they require larger codewords, and larger codewords increase latency. IEEE P802. •RS(272,257,t=7,m=10) may be a good candidate: •Same primitive field and generator polynomials as KP4/KR4 FEC. 0 specification? PCI-SIG® deploys a lightweight FEC for correction. Optional Reed Solomon FEC RS (528, 514) Designed explicitly for Kernel-bypass Linux applications that require ultra-low latency performances; Polling and Ring Buffer DMA architecture; Linux kernel module provided with standard Low Latency RX FEC Architecture Align and Deskew Function FEC Ln0 FEC Ln1 FEC Ln2 FEC Ln3 RS FEC Decoder Alignment Removal 256B/257B to 64B/66B Transcodin g (across lanes) Descramble (across lanes) Alignment Mapping g( ) Scramble (across lanes) Alignment Insertion gppg Word Distribution to 20 Lanes ooo 8 Interleaved FEC Latency Latency estimate in gustlin_3ck_01_1118. On the other side, FEC cost and latency budget is tight. it is NOT a clean and lowest latency choice to us now Multi-pipeline 1x400G FEC (a. In PCIe 6. 9dB 19. Specifications. FEC code gains, latency and complexity * laubach_3ca_1a_0917. low-latency FEC schemes). Both 1E-13 and 1E-14 BER objectives could be met with up to 1. pdf •No extra latency for interleaving. 3 FEC (LL-FEC) may OPTIONALLY be used in place of the IEEE 802. 802. 25 Gigabit Ethernet Consortium Offers Low Latency Specification for 50GbE, 100GbE and 200GbE HPC Networks. 85E -3 pre-BER with ~70ns FEC latency in optical module We present the new flit-based approach with a light-weight low-latency FEC coupled with a low-latency link level retry mechanism. 3ba - July 2008 14 What about latency • At what value does latency become a concern? • Just looking at the FEC block time (and not processing time): – 10GE backplane, 2112 bits = 205nsec – 40GE backplane (4 VLs, 4 lanes), 2112 bits = 205nsec – 100GE copper (20 VLs, 10 lanes), 2112 x 2 = 410nsec • Today’s . 4 to 3. Just for comparison, some signaling standards have FEC latency of greater than 100 ns, which does not meet bandwidth and latency demands of PCIe technology. We find that UDT+FEC has substantially lower variance in the latency of message arrivals (approximated by message interarrival times, for one-way transmissions) when FEC latency impact of 100ns with a much lower retry probability Our Approach: Light-weight FEC and Retry 14 Low latency mechanism w/ FBER of 1E-6 to meet the metrics (latency, area, power, bandwidth) • FLIT (flow control unit) based: FEC needs fixed set of bytes Figure 2: RS544 FEC latency breakdown. 6T (12. On the other hand, the KP4 FEC has about 100-200ns latency added to the system data path. 10 Conclusion Presented an overview of OIF 400G ZR FEC architecture 4 dB higher coding gain, and 2 orders of magnitude higher BER threshold compared with KP4 FEC decoders need to receive the full codeword before they can act on it. FEC Ln2 FEC Ln3. 2 Supporters Jean-Michel Caia, Fiberhome Rich Baca, Microsoft Paul Brooks, Viavi Solutions James Chien, ZTE Latency = 4 ms (400G) v v Staircase HD FEC (255,239) Hamming SD FEC (128,119) Interv-leaver. TX swing = 800mV. Potential Concatenated FEC Solution (4/4) Tx. For some low latency demanding applications, an alternative FEC that requires shorter encoding and decoding time is more attractive. Schemes FEC FEC Latency (ns) DER Target F_b (GHz) COM for Channel 1 (dB) Default Setting TX_SNR=33dB 1 No 0 1e-12 25. 95 to 1. URL Name 72451. pdf Lower-latency FEC 5 •KR4 and KP4 FEC frame latency is more than 100ns. Core Industries. 58. 36x or 313ns more latency compared with non-interleaved FEC scheme (1 FEC CONV); 3. pdf). 400G FEC Latency 3 •“Typical” 2x200G FEC decoder latency : 17 cycles for syndrome calculation, 30 cycles for KES, and 8 cycles for CS. 6 Tb/s Ethernet Task Force. in DSPs. 8E-6 generic discussion of using FEC to help 10G EPON power budgets, no plan to reach any concrete conclusion at this stage. 6 ns) and 1. Therefore it is important to understand why we are stuck with FEC-induced latency, and what is the scale of the latency penalty. sun_3bs_01_0715. 3 Ethernet standard for 25GE and 100GE, and their associated latency are summarized in the table below: Data Rate FEC Type IEEE 803. •Pro: •Latency limited to a single FEC encode-decode pair. 3bs and 802. 3. 562 GBd requiring BJ FEC with latency of 100 ns – PAM-6 operating at 43. edu SeyeonKim KoreaInstituteofScienceand Technology(KAIST 800G-FR4 without inner FEC •Latency Benefit: FR4 optics currently used for short reach applications •Intra Data-Hall average reach < 100m •Architecture Benefit: FR4 optics in CPO/LPO utilize host side SERDES •Host not expected/required to have inner FEC •Power Benefit: 800G-FR4 in high density systems •Pluggable and CPO/LPO systems End-to-end FEC for 200G per lane based 200GbE, 400GbE, 800GbE and 1. 7 Adding FEC expansion: 51. 1 Table of Contents. Each FEC block is transmitted/received in 68 cycles. Article Number 000029166. 7 0. 8dB Ref Relative Noise BW penalty Ref Ref -1. Thelatencyen- The different FEC formats defined by IEEE 802. Page 5 Area and Latency Estimation of RS(n,k,t,m) FEC Use 100Gbps KR4 FEC@325MHz for FPGA as baseline in this slides Area estimation refer to langhammer_3bs_01_1114 with modification for low latency and larger area CG/NCG is based on BERpost=1E-13 Latency estimation based on t and parallelism(p) on each sub blocks in the Before this fundamental shift, switch latency was measured in microseconds, and 10-30 microseconds was considered fast. Presently SerDes addressing 112G VSR style applications are targeting efficiencies of 3. 4x 4x 1 4. In this contribution, we discuss the latency due to FEC. 66dB (36%) higher than RS (2048,1536) •The latency of LDPC (184931,15677) is 4. 6TbE YuchunLU, Yan ZHUANG, Huawei Technologies IEEE P802. 8X, depending on the payload size of the packets, in spite of the FEC and CRC overheads. 4ns. •If FEC latency needs to be less than 100ns [1], a lower-latency FEC is needed. You can learn more about FEC in one of our previous articles. Although FEC minimizes retransmission latency, most current works [28–30] on FEC for cloud gaming apply FEC on the entire GoP, which either HUAWEI TECHNOLOGIES CO. February 20, 2020. -i,--interval <number> scatter each fec group to a interval of <number> ms, to protect burst packet loss. In the same way, FEC 2:2 doubles the bandwidth consumption. 4, and shows an interleaving latency of 26 ns. 00 3. 00 3952. ~0. Segmented FEC –OFEC for Coherent Optical Interfaces • Suitable for applications where FEC latency is less sensitive, e. 6TbE • Core clock 1 GHz • 3 clock cycles for encoder (3ns) • codewords are corrected in parallel • 31 clocks cycles for correction (31ns) • 3 clock cycles for decoder miscellaneous (3ns) FEC Target BERi for 1e-15 BERo 9E-3 2E-3 2. 5 times) of 25GE Base-R FEC. FEC’s transmitting more overhead (FEC packets) can correct more network errors. Self-sync Descrambling (across lanes) RS FEC Decoder Alignment Function Word Distribution to 20 Lanes. 4. 6 Gbd requiring 12 dB FEC with latency of 400 ns • All of the above option are feasible and expect to converge to a single solution by Jan interim meeting Bypass FEC decoding can minimize latency. ooo. Some presentations have shown significant increase in distance assuming the RS-FEC for SR4 optics The RS-FEC sublayer could be leveraged as is for optics in [8], the authors investigated the integration of FEC with ARQ, where the coding rate of the FEC was adaptively chosen according to the delayed feedback. We are the global leader in free-roam, Protocols like RTMP (TCP) and Zixi (UDP) differ due to foundational protocols. 400G FEC and Framing for 80km. 2 ns. 2dB SNR gain @1e-15. 3dj Task Force (yin_3df_01b_2207. Then add the appropriate key:value pairs based on the following parameters: cols: The number of columns in your FEC matrix (which is the equivalent of the size of each row). k. networked-systems. 1dB Relative SNR penalty -0. Marvell Block diagram for 16x25G PMD PMD0 PMD15 AM lock/ Deskew/ Lane Reorder 16x40bit @664MHz However, there is a latency penalty when using FEC. 8 ns) for codeword storage • 2 x 5440 bit-times for 200G (51. •The same method can be applied to C2M. DER Requirement and Interleaved FEC Interleaved KP4 FEC Performance No interleaving for NRZ, 2-way interleaving for PAM4, 3-way for PAM8 Interleave no 2-way 3-way 100GE FEC Latency 110ns 160ns 210ns FEC Latency BER Target FLR NRZ PAM4 PAM8 1E-12 6. Zixi’s incorporation of ARQ, FEC, and dynamic latency makes it a recommended choice for optimal performance. similiar to -f/--fec above,fine-grained fec parameters,may help save bandwidth. 4, which implies that the delay constraint for RS-FEC-Int is the same as the delay constraint for RS-FEC sublayer • However, CL161 Interleaved 100G FEC consumes an additional 51-102 ns of latency beyond CL91 latency The Low Latency FEC codes that have been discussed so far within 802. 5 mean? • The official first draft of the specification, incorporating all the feedback we received from members after the Metrics Requirements Data Rate 64 GT/s, PAM4 (double the bandwidth per pin every generation) Latency <10ns adder for Transmitter + Receiver over 32. In this paper, we design and implement a FEC is used in Gen6 to offset the higher BER value in routed channels. FEC’s need IP packet interleaving to correct for consecutive lost IP packets. 8 2. 27dB Relative Margin Ref Ref-2dB Ref-0. This parameter is sampled at intervals of 2. Rx In Rx side, synchronization of Hamming block can be established using the Hamming decoding Synchronization of 128 bit Hamming block guarantees the synchronization of Convolutional De -Interleaver The proposed FEC solution can achieve ~4. •Con: •PMD specifications must be tightened FEC Selection for 25G/50G/100G EPON Bill Powell, Ed Harstead - Nokia Fixed Networks CTO Group Adriaan de Lind van Wijngaarden, Vincent Houtsma, Dora van Veen - Nokia Bell •Lower-latency FEC can be used to get rid of repeaters, or relax PMD/channel requirements. • Relative complexity is listed for all major blocks. The shortened codeword contains 272 x 10-bit symbols rather than the 544 x 10-bit symbols originally specified. Based on the Latency model for the PHY that we agree upon, and knowing the latency test methodology used to “end to end” Low Latency RX FEC Architecture. •100G CR4 cases are expected to align with 100G SR4 cases. 3bm should have following considrations in mind: Overall FEC associated latency should be small, e. 2 Latency jitter FEC does not only add latency: the variation of frame offset within an FEC block is accumulated over each hop and results in jitter. 3bs 400 Gb/s Task Force Breakout 1x400G 4x100G 1x400G FEC Latency (ns) 72 198 by time sharing 146 by logic sharing 4x100G FEC Latency (ns) 110 110 • Complexity: 1x400G FEC is smaller if assuming the same 3. • Alignment Option ¾ Standards Lane Alignment Markers can be used to find the FEC block boundary. •The intent of a Type 1 PHY/FEC is to provide minimum net latency, power, and complexity (gate count) due to FEC processing in the PHY link. For an optical link that requires a high coding gain but less demands for low latency, a more advanced FEC like turbo product code, staircase code, or a low density parity checking (LDPC) code with iterative soft-decision In an effort to improve end to end latency, a low-latency shortened codeword variant of the 802. It is also possible to turn off FEC. PCS Ln1 PCS Ln2 PCS Ln18 PCS Ln19. •While for Gen 1. 9X to 2. below the FEC computation overhead. although in some specialised cases people may use a lighter FEC (lower coding gain but lower latency) with better (engineered) links. 4ns) a latency penalty in the order of traversing an entire cut-through switch. 8 1. -f,--fec x1:y1,x2:y2,. 100G PAM4 Rx DSP Architecture 3 ADC 10-30 tap FFE DFE FEC Baud Rate 1/T Analog Digital PLL DCO LF TED Err Gen LMS MLSD Mux AFE Slicer 1. 9dB o Latency: ~= 70 ns o Reference: 100G-KR4 FEC latency: 95~105ns • Reusing bj FEC across 400G PCS only reduces latency by about half since decoding latency doesn’t scale down as the block receiving time. This will have a significant impact on overall physical layer latency, in In this paper, we consider the design of forward error correction tailored specifically for the low end-to-end latency requirements in 5G networks. Recently, a low-latency sliding-window network OTN multiplexing and mapping structures. 4 ⚫KP-FEC RS(544, 514, t = 15), processing latency ~ 100ns 100GBASE-KP4, 400GE, 200GE, and 50GE First proposed at IEEE 802. Socialize this model with OEMs (when complete). • Assume16x25G is considered for 400GE Buswidth for each physical lane can be selected as 40bits Each FEC block is transmitted/received in 68 cycles. On a low latency fiber line, this would NOT help that much. 25M = • Continuing to deliver the low-latency and high-reliability targets • Improving power efficiency • Maintaining backwards compatibility with all previous generations of PCIe technology • What does Version 0. divoiz cvbf ohals dazwv uzfb cxwszfso lmv ghrzjj oya dsnv