8 ms·
Designing 100G optical connections
- thomseddon 10y agoIf you're wondering what this kind of optic costs the rest of us: http://www.fs.com/products/65219.html http://www.fs.com/products/65219.html (£1,081) Although you'd pay at least 10-20x that if it had a big vendor name on the top.
- ericd 10y agoHa awesome! Is this switch-to-switch only, or are there 100 gig optical connectors for servers as well? I like the 2 km max cable run length.
- erentz 10y agoYou use CWDM4 for switch to switch. Cheaper/easier to use DAC cables for switch to server connections. Though I don't know anyone doing 100G to server yet, so you'd more likely be using DAC breakout cables to deliver 25G to the server.
- ericd 10y agoCool, thanks for the info. Wondering if this is remotely worth it for a home computing cluster yet.
- shouldbworking 10y agoLinux can route traffic over 40G on regular hardware as long as packet sizes are fairly large >~150 bytes. I would guess that serving static assets from ram would be able to saturate that on a single machine
- gonzo 10y ago150 bytes is a fairly small payload. I think you dropped a 0. kernel bypass will get you line rate 40gbps w/64 byte packets. We've been showing IPsec over 40g links during the past week. https://twitter.com/netgateusa/status/853694461456646144 https://twitter.com/netgateusa/status/853694461456646144
- shouldbworking 10y agoNeat! I've heard you can get line rate on slightly bigger packets without bypass using IPVS with direct return since it bypasses part of handling. In a lot of scenarios the big pipe is right at the load balancer so this is useful.
- shaklee3 10y agoYou can do 40gbe even if packet sizes are small using any kernel bypass technique and multiple cores. Mellanox claims up to 130Mpps.
- shouldbworking 10y agoIs this just blind forwarding or does that include some decent routing logic? I've looked into kernel bypass but I keep shying away because it seems to proprietary, especially the virtualized flavor which seems to be Intel only
- shaklee3 10y agoBlind forwarding. It's left to the application to do everything.
- en4bz 10y ago100G, probably not unless you are extremely wealthy and you have a burning desire to be destitute. 40G is definitely doable for a homelab. Used 40Gbe adapters are roughly $200 and DAC cables are < $100. QSPF+ Switches are much harder to find used and/or cheap though. This means that p2p solutions or ring networks are generally preferred unless you are wealthy. If you want fiber, which you don't need for a homelab, you pay the prices listed above.
- jsjohnst 10y agoAgree with other commenters, not sure what the 2.5x increase in traffic would open for you in a home setting. I use 40gb fiber between switches on opposite ends of my place and 10gb connections between switch and computers and I've always found something else to be my bottleneck, not the internal network itself. I can saturate my wifi network easily though (I've got a $20k retail Aruba wifi network, yet still not enough). I buy most of my gear used so it's not that expensive (would've been very expensive retail), but still overkill unless your a network nerd (like me) or are doing something out of your home you likely should be using a DC.
- ericd 10y agoYeah, I think 10 G will be more than good enough for now. Thanks for the info!
- thomseddon 10y agoLooks like you can get 100Gb NICs for servers e.g. https://www.hpe.com/uk/en/product-catalog/servers/server-adapters/pip.hpe-100gb-1-port-op101-qsfp28-x8-pcie-gen3-with-intel-omni-path-architecture-adapter.1008830960.html https://www.hpe.com/uk/en/product-catalog/servers/server-ada... (Intel, Mellanox etc also seem to have their own) On the distance, there are other specs that support 100Gb up to 20km on there!
- ericd 10y agoHaha for when you need another DC that's sort of across town, or you're trying to add artificial latency intra DC with enormous coils of fiber. Not too unreasonably expensive - roughly in line with a GeForce 1080, and that's after the Official HP Hardware markup. I wonder how much the switch/cabling is...
- penagwin 10y ago> trying to add artificial latency intra DC with enormous coils of fiber. Do people really do this?! (I don't have DC experience, serious question)
- ericd 10y agoHeh like the peers said, it was a reference to what IEX does.
- snowwindwaves 10y agoAt least one stock exchange has: https://en.m.wikipedia.org/wiki/IEX https://en.m.wikipedia.org/wiki/IEX
- Dylan16807 10y agoI believe that's a reference to IEX's magic shoebox. 61 kilometers of cable that provide 350 microseconds of delay for stock market voodoo purposes.
- walrus01 10y agoThere are Intel chipset single and dual port 100GbE pci-express 3.0 NICs with good Linux kernel support in v4.8+.
- drewg123 10y agoMy understanding is that this is just a qsfp28 transceiver using a new optical format. There have have been 100GbE server NICs for almost two years (Mellanox ConnectX 4, using mlx5 driver) using QSFP28. We've been using them with great success at Netflix in our flash storage appliances. We are able serve well over 90Gb/s from single machines with these NICs using our tuned/enhanced FreeBSD and nginx.
- shouldbworking 10y ago> We are able serve well over 90Gb/s from single machines with these NICs using our tuned/enhanced FreeBSD and nginx. Incredible
- shaklee3 10y agoCan you describe why you choose freebsd over Linux+DPDK? I realize freebsd has the fast path built in, but I would think it's lacking in other areas.
- toast0 10y agoJust wondering, what kind of things do you think FreeBSD is lacking in? Regardless of those things, the OpenConnect boxes are doing a pretty small subset of possible server tasks, it's basically serving static content from disk, and updating the static content occasionally. This is a task that FreeBSD has been excelling at, since basically forever. FreeBSD is a pretty stable target to tweak on as well, Netflix moved TLS bulk encryption into sendfile(), which helps avoid the transitions from kernel to user space, but by putting more stuff in kernel space, rather than the DPDK method of putting more stuff in user space. They've continued to tweak sendfile, which I imagine helped them get up to nearly 100Gbps out. I haven't had the pleasure of running 100G network, but I had to do very little tuning to saturate 10G with FreeBSD on http download site, and TLS cpu was the primary thing holding me back when moving it to https. Bulk download was moved away from my team before I got new servers with 2x10G and fancier processors, so I was never able to see if I could saturate that too :(
- drewg123 10y agoWe're pretty much the opposite of DPDK. Rather than moving stuff out of the kernel, we move stuff into it. We're actually moving stuff like TLS encryption into the kernel -- see our kernel TLS papers at AsiaBSDCon We do all of our stack "traditionally", in the kernel, whereas DPDK moves things into userspace. By using a traditional stack with async sendfile in the kernel, we benefit from the VM page cache, and reduce IO requirements at peak capacity. There are no memory to memory copies, very little kernel/user boundary crossing, and no AIO. Using single-socket Intel Xeon E5-2697A v4, we serve at 90Gb/s using roughly 35-50% CPU (which will increase as more and more clients adopt HTTPS streaming). There is no question that FreeBSD is lacking in a number of areas. For example, device support is a constant struggle.
- jpmattia 10y agoNote that "100G optical connections" is physically implemented as "4x25G optical connections". The 4 wavelengths are coarsely spaced, which allows cheaper optical components to be employed. (As opposed to long-haul optics, where it is economical to squeeze many more wavelengths on the same fiber with costlier optics.)
- kpil 10y agoI must say that I'm fascinated by the fact that each bit is around 1 cm long while in transit, at near the speed of light (in vacuum.) Single channel 100 GB would mean 2-3 mm long bits. Imagine that :-)
- walrus01 10y agoSingle channel 100GbE is already done, but not with OOK, it's coherent modulated qpsk, 16qam or 64qam single wavelength. But wider channel size in THz occupied than a single channel 1550 10GbE single wavelength OOK circuit.
- Dylan16807 10y agoAnd even 1cm at light speed is still a good 7 thousand cycles long at these frequencies.
- walrus01 10y agoBecause it's 25 Gbps electrically per lane, this also allows for economies of scale with new 25 GbE optical and direct attach NICs for servers, where 10GbE is not enough, but 100 is too costly. There is some good documentation and reference links on 25GbE on Wikipedia for anyone who is curious. This also allows for one 100GbE top of rack switch port to be broken out into 4x25GbE individual connections. So if you have a 1.5RU 32-port 100GbE top of rack switch it can serve up to 120 servers, leaving two 100GbE ports free for uplink.
- myrandomcomment 10y agoThe other issue that people miss here is the physical board that the switch ASIC is on. People might want to google SerDes and XAUI. The simplified bit here is back in the day first 10G you had 4 x 3.25G lanes. So for example for the Fulcrum FM4000 (24x10G) you had 64 traces on the board, 4 to each port. For something like the Broadcom Trident+ which could do 64 ports of 10G you have 256 traces. For each 10G there are 4 and they have to line up to the nm on the board unless you wanted to use a PHY and / or retimers. Arista shipped the 1st PHYless design of this. Less parts, higher MTBF, less heat and also less latency (phy add latency). To do 40G you would need 16 of the 3.25 (yuk). Things moved to 4x10G lanes and you got 40G ports. With the 25G Ethernet the lanes moved to 4x25G so you get 100G ports. Anyway random stuff if anyone is interested. Yes I know I am mixing the Serdes and XAUI stuff but this is a simpler view just talking about the lanes from the chip. Google will give great answers if you want to dig deeper.
- en4bz 10y agohttp://www.cwdm4-msa.org/ http://www.cwdm4-msa.org/ No where does this mention Facebook as a founding member. This dates back to at least 2015. > We created a 100G single-mode optical transceiver solution, and we're sharing it through the Open Compute Project. What gives? Looks to me like someone may be taking more credit than they deserve. EDIT: > The starting point for this specification is the CWDM4 MSA, a standard that was agreed upon in 2014 by several optical transceiver suppliers. It uses a wider wavelength grid (CWDM = 20 nm spacing) and, for many of the different technology approaches, does not require a cooler inside the module to keep the laser wavelength stable. So Facebook took something that already existed. Tweaked it slightly by relaxing the constraints so that it works in the data-center only.
- walrus01 10y ago4 x 25Gbps has been around for years but in larger form factors like CFP, cfp2, etc. The main difference here is they're using commodity lasers from China and Taiwan sources with prism to do 4 x 20nm width channels between qsfp28 optics. For reference: https://en.wikipedia.org/wiki/QSFP https://en.wikipedia.org/wiki/QSFP The next step down in size will be to sfp/sfp+ dimensions. I can see it coming, a qsfp is already a lot smaller than a first generation 100GbE CFP.
- walrus01 10y agoThe big difference is that it is lower cost than the 4x25 cwdm msa because it is specced for 500m reach through normal g.652.d singlemode and a reasonable number of clean, properly terminated sc and lc/UPC patch panels. Not specced to work at 2000 metres.
- madengr 10y agoThe OCP link loss is 3.5 dB @ 500m, which would be 9.5 dB @ 2000m. The MSA is 5 dB @ 2000m, so where is the additional loss coming from in the OCP spec? Different connectors?
- ADefenestrator 9y agoIt's coming from loosened tolerances. Higher/lower temperatures may mean higher loss. I'm assuming there's a bit more tolerance in the alignment of the up optics/connectors as well. So, if you get lucky it might well be 5db@2km, but it's not guaranteed/required by spec.
- z3t4 10y agoThis high bandwidth enables some interesting consumer services. The speed is also very good, like less then a millisecond over 10km, which is ten times faster then from your computer to the monitor.