SFP SFP+ SFP28 and Why You Need DAC in Your Rack!

tom here from one systems and we're going to talk about direct attach copper some fiber modules and why these are a better fit than your standard twisted pair cables that you want to run when you're running them inside of your network stack where your data center or just in a rack in general unless there's a couple long distance runs and you may want to use these fiber modules now all this is coming out of to focus in on these cables in particular and their use cases because i did a video breaking down what cables are used where but of course there's a lot of expanded information i wanted to add but was out of scope of that other video that i'll leave linked down below to we dive into when exactly we do use these and why we use these and latency and speed is a big thing power usage well someone's going to point out that these can go 10 gig and this can go 10 gig so speed versus the latency that's where the challenge really comes in of course the efficiency of using these so they will go the same speed but the latency is going to make an overall better experience for using them and there's some real technical reasons why and we'll dive into those details here before we do if you'd like to learn more about me and my company head over to lawrences.com if you'd like to hire a share project including network consulting there's a hires button right at the top if you want to support this channel in other ways just affiliate links down below to get you deals and discounts on products and services we talk about in this channel and we'll start right here with 10 g base t versus sfp versus stack which to choose free data center despite this being from november of 2015 and it being currently august of 2021 this still holds up and this is the latency debate but a very relevant one latency and power are going to be two really big factors that play into why you want to use these cables now this is the relevant sentence right here the five standard specifies 2.6 microseconds for the transmit received pair and the size of the block requires a latency to be less than 2 microseconds sfp uses simplified electronics without encoding and is typical latency around 300 nanoseconds per link and then they have a chart that breaks that down now for the simplified version the electronics it takes to take these twisted pairs and this is a cat6 cable and the shielding goes up with the higher grade cables all the way up to your cat eight having a lot of extra shielding around here to eliminate any potential interference what they're doing is they have a series of electronics that does signaling down this and we twist the pairs around each other and put insulation on them to prevent the degradation or interference with that signal that is a lot of electronics that has to do a bunch of differential calculations to make sure that the data on one end is getting through to the data on the other end and all the bits come out exactly perfect they're never perfect but the electronics makes the perception that they're perfect and the data then flows with your direct attached copper simplified electronics means they're not doing any of those differentials so without those differentials happen to be done although we lose the ability to go over distance we save on latency because there's not that extra step that something has to go through of turning it into the type of signaling that this needs and breaking it back down to a simple signal on the other side by eliminating the extra components we've simplified the connection we've lowered the amount of power the other advantage and it does take a significant not even poe just the amount of power it takes to do that signaling and push this across and this allows for a less expensive card and less expensive switches both in power expense and in actual cost because there's less electronics needed to operate these to get the data to where it needs to be all right now let's dive a little deeper when i see deeper i really just mean in choosing the different type of dac versus aoc cables as this came up when people said well you mentioned dac but you didn't specifically see aoc i kind of look at them the same but i know they're different i they will look and present mostly the same the direct attach cable is compromised of a twin x copper cable terminated with in the different sfp versions three different types here passive copper active copper active optical cable and these are when you use what so passive dac cable like the short one i had less than seven meters is going to be just twin x copper cable uses very small amount of wattage and kind of the use is top of rack tor not like the tor protocol but top of rack is what that stands for or your adjacent racks same thing here you have tor and adjacent racks again for these because it depends on how far those adjacent racks are so if their adjacent racks are pretty much next to each other you could connect these your active deck cables a little bit more expensive but go up to 7 to 15 meters active optical cables active out cables i don't have one here for presentation but essentially what an aoc cable is is your fiber module and the fiber all mated together in one and what that allows you to do is not have to worry about whether or not someone would have any loose connections or any dirt getting into connections or buying the cable and the module and plugging them all in together it comes as a fused unit that looks the same as far as these dac cables go but happens to be a little bit longer and of course the cable in between being fiber means it's pretty thin cable to run and of course power consumption is low on all these they have the wattage listed uh transmission distance back to that and overall cost now emi immunity electromagnetic interference refers to disturbance generated by an external source that will affect electrical circuit this is something you deal with a lot the active optical cable contains optical which means yeah no big problems with emi you can run it across something like let's say you have some type of the high voltage coming in a room on the other side and we're in between where you want these two cables to be and running a fiber optic cable across here whether it be a standard fiber optic or you're running one of these aocs you're going to eliminate the problems that you have with that and they have a few more examples i'll be leaving links all this and you know here's your top of rack switch and where you may want these and the servers and the different cables that you'll have in between now i wanted to include these in here because these are some of the newer ones is the 25g connectors now one thing about them they're the same physical plug of sfp so sfp one gig sfp plus 10 gig sfp 28 25 gig okay i didn't name it but right here 25 gig is sfp 28 physically the same here something cool that they've done here is the dual rate transceiver solution to the 1025 upgrade path i thought this was kind of cool and it keeps with some of the backwards compatibility let's actually show it in action rather than just read stuff that says it works let's actually show you how it works what we have here are two different unifi switches this is just a 10g switch this is the unifi aggregation switch that offers 25g connectivity and what we did here was plug in and the 25 gig port which is actually unplugged right now so i'll plug that back in so that's playing with it there we go it should light up here in a second but in order to get this to work we took and you can see here we have a 25 gig connector plugged into a 10 gig port the way the compatibility works this does include with some of the fiber modules that they have produced the 25 gig sfp 28 cables and fiber modules are both backwards compatible with sfp plus ports but you do have to force negotiate them down for example right now this is showing connected at 10 gig because we overrode the settings and turned off auto detection and said force it to 10. if we go to 25 it fails and if we set it on auto i'm 99 sure that's going to fail and give it a second provision it's going to think for a second and blink i think it blinks back if we're trying to negotiate it doesn't yeah and yep it's failing kind of get the idea but when you negotiate them yeah we'll turn them back on to negotiate back down you are able to keep that compatibility so if we go here profile override turn off auto negotiation force it down to 10 gig that works and we did the same thing we just plugged one of the fiber modules in so if you actually see that the fiber module which is in this port right here this one nope that's the yeah there we go we have an sfp 28 plugged in there and it'll negotiate down so the negotiation down does work and we have it in here as well you can see that these are both marked to be the uh sfp-28 sfp-28 and this is what's important to consider you can take if you have ports that are sfp and you can use an sfp plus cable now you can't do the opposite you can't take an sfp cable and plug it into an sfp plus port will physically plug in but it won't negotiate up so you want to get the sfp plus cables or sfp 28 cables like they have here from fs.com that i'm holding because these you can force to a down speed but you can't force them up now this is good if you are dealing with some interoperability of old legacy systems and for example this has 28 ports on it that are sfp plus 10 gig ports but what if we have all these 10 gig switches a couple of them are only one gig but they still are fiber connected to a far end of a building somewhere that means you would be able to negotiate down the speed and be able to keep those in there until you got around to upgrading them and then the way they work with the ones here from fs.com are these modules that are sfp-28s are able to negotiate down to 10. once again if you start building out the head end of your network first but you still have some further away devices that are still at 10 gig you can negotiate these 28 sfp 28s down to 20 from 25 gig over down to that that 28 and 25 gig is keep messing me up here i don't know why they needed it why they just call them sfp 25. wouldn't that be easier i didn't make the naming schemes up but you can see they negotiate fast when you force negotiate them and that's something in general it's not like when you're dealing with the standard you know cat6 on up cables you will sometimes have to set the negotiated speeds when you're using some of the deck but the way it works with the cards the way it works with here it's that lower latency application more cost effective less power consumption and more budget friendly overall so that's one of the reasons these are popular and they come in a variety of different sizes so you can usually find one free application but of course they're not quite as short as normal patch cables and there's not patch panels for these so if you're trying to make me really nice looking you know mount everything in there and make it look really pretty back and forth it's a little bit harder with the back cable so that is kind of a disadvantage of them but i mean some velcro you can do do some cable management it's not going to be as pretty as the patch cables but it's still going to be a great application a great way to use these so hopefully that educated you a little bit on some of these things i'll be leaving links to these articles where you can dive deeper in there including a video i did before based on this research from arista labs here and talking about copper is faster than fiber there's actually some other details if you want to dive deep again i've done a video on this before and it always opens up a lot of debates but they do talk about some of the different multi-mode fibers and yes if you're wondering and i will leave with this who may have seen the orange fibers sitting here if you are curious at their speed limits to connecting the fiber to yeah i might do a different video altogether on fiber but just look up the om ratings on fiber and you can find that pretty readily and learn that yes there are speed limits to the fiber connections as well but that'll be a separate video i'll do later i just want to get this one out of the way before i did some of this 25 gig projects that i'm working on so if i have reviewed this switch in the future which will be soon the link will be down below if i haven't reviewed it yet that link will be missing but yes this is the unifi aggregation switch that we've been doing testing with so that's a future video coming future now but if you've watched this in the future that link may be down below so all depends on when you're watching this all right tom lawrence here and you can find me over in the forums where we can dive deeper into this and leave your arguments and debates below and uh looking forward to hear from you thanks and thank you for making it to the end of this video if you enjoyed this content please give it a thumbs up if you'd like to see more content from this channel hit the subscribe button and the bell icon to hire a shared project head over to lawrences.com and click on the hires button right at the top to help this channel out in other ways there is a join button here for youtube and a patreon page where your support is greatly appreciated for deals discounts and offers check out our affiliate links in the descriptions of all of our videos including a link to our shirt store where we have a wide variety of shirts and new designs come out well randomly so check back frequently and finally our forums forums.lawrencesystems.com is where you can have a more in-depth discussion about this video and other tech topics covered on this channel thank you again and we look forward to hearing from you in the meantime check out some of our other videos you

Channel: Lawrence Systems

Views: 38,805

Keywords: LawrenceSystems, sfp transceiver, cable management, sfp28, sfp28 switch, sfp28 rj45, sfp28 adapter, sfp28 dac cable, sfp28 sr optic 25gbe 85c, sfp28 sr optic, dac vs aoc, dac vs aoc cables, dac vs aoc latency

Id: o8jL1lxdN4M

Length: 13min 35sec (815 seconds)

Published: Fri Aug 06 2021