NIC光網卡.pdf

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1、OCP Global Summit October 18,2023|San Jose,CADavid Piehler,Dell TechnologiesNIC PhotoNICsSYM-ContentThe NIC gateway between the network and compute resourcesOCP 3.0Home for silicon photonics/co-packaged optics(CPO)?MaybeLinear pluggable optics(LPO)at home in the NIC?LikelyThe NIC of tomorrowAgendaSY

2、M-ContentShowing NIC placement(things can re-rearranged)OIF taxonomy ComputeIOCompute MemoryComputeComputeNetwork Interface CardNetworkComputeEthernetPCIefocus of the remaining talks in this sessionServer TrackSERVEROCP NIC in 2023:800G,PCIe Gen6&Test IntegrationDamien Chong,Technical Lead,MetaHemal

3、 Shah,Distinguished Engineer and Architect,BroadcomJason Rock,Distinguished Member Technical Staff,Dell TechnologiesI cant give a NIC talk at OCP and not mention OCP 3.0.The Open Compute Project has standardized the NIC form factor,a huge benefit for the industryOCP NIC rev 3.0 is all over this even

4、t.OCP 3.0(NIC)Thursday 19 October,2:40pm-3:00pm|SJCC-Concourse Level-220BPassive copper direct attach cables(DACs)have been the most used for ToR switch-to-server NIC connectivity.Limited to 3 4(?)meters at 100G per lane.Length also depends on cable gauge(thickness)Enough for one rack of servers.Low

5、est cost.Active electrical(retimed)copper cables(AECs)can go a little farther.7 meters at(8 100G)OSFP112 with 26 AWG cable.Lower cost.Optics,either active optical cable(AOCs)or transceivers are needed for anything longer.Todays NICToRswitchserversNIC=a home for CPO?From:Moray McLaren(Microsoft)Optic

6、a Industry Summit,26 October 2022Recall:#1 CPO solves a power dissipation problem associated with chip-to-module distance.also CPO may have other benefits(cost)A few years ago,I thought:Unlikley,as CPO economics pay off when you have to integrate many lanes.NICs need at most a few lanes.Today,NIC ba

7、ndwidth expansion surge due to AI.Multiple(high-speed)lanes are needed(e.g.8 100G PAM4)Slow and wide thinking may use even more lanes.But there is another,surprising competitor linear pluggable optics(LPO).NIC=a home for CPO?Linear pluggable optics(LPO)DSPserdesdriverTIAopticsDSPserdesdriverTIAoptic

8、sanaloglineardriverTIAopticsanalog lineardriverTIAopticshostDSPserdeshostDSPserdeshostDSPserdeshostDSPserdesSWITCHSWITCHhostelectricalchannelhostelectricalchannelhostelectricalchannelhostelectricalchannelstandard high-speed linklinear,direct-drive,un-retimed linkpluggable optical transceiveroptical

9、fiberoptical fiberDSP serdes:high-power dissipation,high cost most of the power dissipation,most of the cost of moduleanalog linear:low-power dissipation,lower cost,lower latency 15 dB 15 dBCPO-like power reduction without the baggageIn the end,power dissipation(pJ/b)numbers are similar.Trade-off of

10、 long trace length(LPO)vs.external(pluggable)laser source(CPO)Baggage:Only reason to move from pluggables to CPO is for lower power,right?From:Bechtolsheim,OFC-2023(session M4D)(lower for VCSEL-based transceivers)(linear pluggable optics)(co-packaged optics)LPO critical issuesLittle published data l

11、ots of folkloreSeems to work across many optical transceiver types VCSEL,EML,SiPh,TFLNMost successful with highly-advanced,DSP-based SerDess.Sensitive to chip-to-module loss and SI(?)How to specify interoperability?Inner workings of DSP-based serdes are highly proprietary.No ones giving up their sec

12、ret sauce.Specifications in process at OIF.Interoperability across all IEEE-compliant 100GbE(PAM4)ports/receptacles seems an almost unbounded problem.First movers will solve a well-defined,well-bounded problem.With LPO,optics are already near to the NIC serdes.LPO distance/link penalty is small.How

13、much technical advantage would CPO have by comparison?(NPO=near package optics)For NICs,LPO=NPOFrom:Lusted and Bentley,“Server NIC trace lengths,”July 2018 https:/www.ieee802.org/3/ck/public/18_07/lusted_3ck_01a_0718.pdfHistogram comes from 40 Intel NICs(OCP and PCIe)with 10G and 25G/lane 1-2 inches

14、(2.5 5.1 cm)A worked examplePower savings,with and without LPOtotal bandwidthtypical adaptor power without optics(W)fully-loaded optics power wthDSP-based pluggable(W)fully loaded optics powerwith LPO(W)optics/total power ratioDSP-based pluggableoptics/total power ratio(LPO)NICx400 Gb/s167243.8%12.5%Will be specified by OCP.Will eventually be all-optical.The network-side will be something like Ethernet via linear pluggable optics.The ultimate host-side optical solution will be informed by todays talks which follow.The NIC of tomorrowOCP Global Summit|October 18,2023|San Jose,CA