Home Networking Explanation of DOCSIS 3.0/3.1/4.0, Why Upload Speeds Are Generally Lower |
- Explanation of DOCSIS 3.0/3.1/4.0, Why Upload Speeds Are Generally Lower
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| Explanation of DOCSIS 3.0/3.1/4.0, Why Upload Speeds Are Generally Lower Posted: 01 Apr 2022 05:59 PM PDT Hey Guys, This is in response to the thread asking why internet upload speeds are generally slower than download speeds, and it was suggested that I start this as a new post rather than as a reply that gets buried, so here it is. I'm a network engineer for a large ISP, and my main focus is DOCSIS, so I'm rather qualified to post this and answer questions. Here goes: There are a lot of reasons that upload speeds are generally much lower on cable internet, so this will be a deep dive. I'll start with the physical layout, then get into the nitty gritty. I'm sorry, but this will get pretty technical. Traditional DOCSIS 3.0 and 3.1 HFC (Hybrid Fiber Coax) nodes tend to have the following physical layout: Fiber to node, which has four coax legs (branches). Each leg may have 50 to 400 homes connected, depending on how good or how crappy the ISP is. The more homes, the less bandwidth and the worse experience. The node can push signal a fair distance down a line to a modem or TV (downstream power), but the modems don't have a ton of transmit power to send data back (upstream), so amplifiers are needed on the lines to boost the upstream data from the modems to the node. Amps can have one to three outputs, so the layout can branch out like, well, branches on a tree. The more amps, the more homes a node can serve, but that creates more points of failure and more noise. Most good ISPs try to have fewer homes per node, so that they don't need to 'cascade' more than one or two amps deep on any leg of any node. Crappy ISPs tend to go 8 to 10 amps deep, and 20 up to amps deep do exist (and are absolutely terrible). Keep these amps in mind, they become important later on. The new generation is generally called 'node +0' or 'fiber deep,' but the general concept is to replace the coax trunk of the tree and the largest branches with fiber, all the way up to where the last amps are, and to replace those amps with nodes (so no amps are needed at all). You end up with very short coax runs, and if there is a bad coax line/connector/fitting it affects a much smaller number of customers (and can still be repaired even faster, since it's easier to track down and locate the problem). The smaller number of customers per node means there's more bandwidth available for each customer, but that doesn't mean symmetrical speeds yet. Cable internet and TV are RF delivered services, and the DOCSIS specs have been pretty specific about what frequencies are used for what. Yes, the DOCSIS 3.0, 3.1 and now 4.0 specs promise some pretty cool speeds, but you never see them in the real world because RF noise (generally in the 5MHz to 110MHz range), Cable TV (which has to exist on the same physical cabling and share spectrum), and old modems that people refuse to upgrade/replace get in the way. I will refer to the following screenshot quite a bit in the next few paragraphs. Frequency is along the bottom (x) axis. The top screenshot is of a live downstream reading, middle is of the upstream of a node configured for D3.0 upstream carriers, and the bottom screenshot is the upstream of a node configured for D3.0 and D3.1 upstream carriers. https://i.imgur.com/U1AaaHg.png DOCSIS and cable TV exist on coax lines on RF frequencies from 5MHz to 1GHz, with specific ranges having specific purposes (please see the screenshots for visuals of these frequency layouts). Think of it like radio stations existing at specific frequencies. DOCSIS 3.0 defined 5MHz to 65MHz for upstream (modem transmitting back to node, generally with one or more amps in line, boosting that all the way to the node), and 85MHz to 1GHz for downstream (cable TV and downstream data). Most ISPs (including the one I work for) put cable TV channels starting at about 120MHz up to about 480MHz, and then groups of downstream (D3.0) data channels from about 480MHz to 585MHz. (These frequency ranges can vary a little node to node and city to city, for the record, but generally follow the same rough layout.) That worked great until DOCSIS 3.1 came along and said that we can use 5MHz to 204MHz for upstream, and created 192MHz wide 'OFDM' channels for downstream data. Yay! Backwards compatible with old modems, but every amp would have to be replaced with one that supports up to 204MHz (which is doable). But let's see where we can fit everything in the spectrum. We have 200MHz for upstream data, about 360MHz for cable TV, 100MHz for old D3.0 modems that people won't get rid of, 192MHz for the new downstream OFDM channels. Factor in some 'guard bands' (blank spaces) between each group, and we're at about 900MHz of total width, so it's a tight fit but we should be able to fit that all in and stay under 1GHz, right? Not quite. Remember those amps? Yeah, pretty much every cable plant will pick up ingress in the FM spectrum (~80-105MHz), so we have to totally avoid that. The more homes on a node, the more amps, the more noise, and the more that noise gets amplified. Even if we shuffle things around, we run into equipment incapability issues (cable boxes, old modems, etc), and ingress/noise in the spectrum that's newly allocated for upstream. Even if the coax lines outside are well maintained, there are just too many homes with crappy wiring and/or loose coax fittings on modems and cable boxes to make it work reliably. It works in the lab (especially without cable TV), but not in the real world. The solution? Node splits, and to dodge the FM 80-105MHz range on the upstream. Push fiber all the way up to the amps, put in nodes, as I mentioned earlier in my description of the new layout. This is really the only way to make DOCSIS 3.1 work reliably, and it's very expensive. The ISP I work for is doing these at a pretty crazy rate, but there are tens of thousands of miles of cable to replace with fiber, and it's all either up in the air or buried underground. Our current US layout for our 'node +0' / 'fiber deep' is three DOCSIS 3.0 US channels and one D3.1 OFDMA channel, all between 5MHz and 80MHz so we can dodge FM. We still have our cable TV channels from 120MHz to 480MHz, but we've launched an IPTV product and are in the process of swapping every traditional cable box for an IPTV box so it's all multicast data, which will open up the 120MHz to 480MHz spectrum for more US and DS data channels. If we can get rid of all of the old D2.0 and D3.0 modems we can ditch the legacy US and DS channels currently reserved for those, and swap them out for the much faster OFDMA (US) and OFDM (DS) channels. Only then can we start to look at multi-gigabit upload and download speeds over DOCSIS, as long as we have under 100 homes per node. We also stopped building coax networks a few years back, have been doing EPON FTTH on all new areas, and have been replacing HFC with EPON as fast as we can. EPON is another story for another day, but I will say that we're currently selling (and delivering) up to 5 gig symmetrical for residential customers, the gear that we're using is easily capable of 10 gig, and the fiber itself is ready for 20 gig and 40 gig with equipment upgrades on either end. No RF noise to worry about, and it's stupidly rock solid. Feel free to ask questions, comment, etc! Edit: I will also go on record here and say that any ISP who has monthly data caps is just being cheap/lazy and doesn't want to upgrade their network to keep up with the real world. Contracts on residential accounts are also BS, and exist solely to prevent them from having to compete with other ISPs on price and on delivering good service. The ISP I work for doesn't have either of these shady/crappy practices and we do great. We deliver good service for at a good price and our customers are 'fiercely loyal' because of it according to a friend of mine who is a sales rep for a competing ISP. [link] [comments] | ||
| Unknown device automatically connects after hard reset. Can’t figure out what it is Posted: 02 Apr 2022 04:33 AM PDT HELP Unknown device automatically joining Wifi Devices after hard reset Please someone help me, I'm a noob and I'm going paranoid over the possibility of having a hacker / sniffer lately. I use Google fiber, there is the fiber jack in my closet and I have a Network Box connected to the wall - Fiber Jack. Even if I change password, SSID, and have all my wifi devices turned off, shortly after turning the Wifi Network on, there will be an unknown Wifi Device with a TOTALLY different MAC address than the one the network box shows. Even after all wireless devices are off. It doesn't matter how complex the password is. Is it possible that the network box creates an extra MAC address for an unknown Wifi device? The address returns ZERO results online about vendor or anything, it starts with e2:b8:43 and it will briefly show a ipv6 starting with either fe80 or 2605 then vanish, then only showing an ipv4 address. It's always the same MAC address, not randomized. The device will not show ir connect if I'm just using the network box with Ethernet. Thank you and sorry if it's a stupid question [link] [comments] | ||
| Is 50/20 Mbps enough for video zoom meeting calls? Posted: 01 Apr 2022 08:59 PM PDT My mother says her co workers are experiencing blurry screen sharing and video calling specifically with her. There are three people in the house, I play online video games/youtube/discord, that's about it. My father mostly watches netflix/facebook. My pc is the only one connected through ethernet while all the other devices are wireless. My mothers laptop from which she does zoom meetings on is only like 10m away from the modem. Do I need to upgrade my speed, modem (modem is about 4 years old) or does she just need to be connected via ethernet. Please help thanks! [link] [comments] | ||
| Posted: 02 Apr 2022 04:29 AM PDT Hi, what are good fibreless alternatives in the UK? Our new home doesn't have any fibre to it all, something to do with it not being serviceable. The fastest speed is quoted as 17mbps. We run X1 Series X, 1 series s , sky tv and mobiles. Would this speed be good enough to play online? Thanks. [link] [comments] | ||
| Is it counterproductive to activate QoS with a 500mbps symmetrical connection? Posted: 02 Apr 2022 03:43 AM PDT I am doing configuration tests with my Netgear RAX43 router to optimize the network as much as possible for remote work. Obviously the speed is much more than enough for the use we have at home, two people working remotely with frequent meetings, so the goal is to reduce as much as possible the latency in video calls to have the smoothest possible experience and avoid micro-cuts and drops in audio and video quality. Everything I have read regarding the use of QoS has been very diverse and even contradictory, so it is not clear to me if that extra layer of processing in the router can produce an improvement, not notice anything or even worsen the latency in the devices. What has been your experience with this feature? [link] [comments] | ||
| Posted: 01 Apr 2022 07:17 PM PDT
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| Posted: 02 Apr 2022 02:30 AM PDT Hi guys, hope someone can help with this. I got a set of 3 TP Link Deco M5's yesterday and they were all working fine with good speeds. I woke up this morning and the Deco in my bedroom is flashing red, and no matter how many times I've tried rebooting it still stays red. The main Deco is downstairs in my living room plugged into the router and in access point mode, and there is a Deco device upstairs about 12 feet from the one in my bedroom that's not working. What I can't understand is that it was working fine yesterday so I don't think it would be too far away. Any help appreciated [link] [comments] | ||
| Is there some in-wall cabinet I could use here? More details in comments... Posted: 01 Apr 2022 10:54 AM PDT
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| Posted: 01 Apr 2022 09:01 PM PDT hey all, i'm building a backyard office. I'm running an ethernet cable from my house to the office. I want the office to have a few wall ports for connectivity (based on being able to move desk to different areas, etc) and an outside IP security camera and WAP. I looked at the Leviton SMC in-wall solution which seems perfect. However, it states it should not be mounted to an external wall. Well, being an 8' x 12' shed i do not have any interior walls. What are my options here? What would you guys do? I'm not opposed to just having a switch on my desk or something, wall mounted perhaps that just terminates all these connections. I'm just not too enthused about having a bundle of 5-6 cables coming out of the wall or an exposed patch panel somewhere.... Thanks! [link] [comments] | ||
| Pfsense as router with Tp-Link Omada wireless AP? Posted: 01 Apr 2022 06:35 PM PDT I am having one of those issues where I feel like everything I have set up is correct, but it is not working as intended... you know those weeks right? I would appreciate some advice or new ideas I currently have a virtual instance of pfsense set up as my home router/firewall. I went out and bought a Tp-link Omada jetstream switch and wireless AP (EAP 225 v3). I create a wireless hotspot and it works great with native vlan, works like normal. But whenever I create a new hotspot and set it to a VLAN, nothing works. On the switch, the ports are set to "All" profile. On the router I have created a VLAN with the same VLAN id as I assigned in the wireless AP. I enabled the interface, I created a DHCP range for that vlan, i enabled that dhcp service. I went into the native vlan and allowed all traffic. I went into the vlan firewall rules and allowed all traffic. After over a week of trying things Im out of ideas. I feel like everything is correct, with no luck though... Would love to hear some thoughts or suggestions [link] [comments] | ||
| Wireless over a bit of a distance Posted: 01 Apr 2022 10:11 PM PDT First time needing to dig into wireless extensions and I'm wondering if anyone could help/point me to some resources. https://www.amazon.com/dp/B08C4QCWC5?psc=1&ref=ppx_yo2_dt_b_product_details I live in a boat and the local yacht club is right on the other float from me. When I'm nearby them I get 160MB on my phone but with the above extension on my boat I only get 7Mb (I got 40 when I first set it up) and it's in an out. Should I go higher up the mast VS the extra 7 feet down the boat? I can only really make changes on my side for now but that could change later. [link] [comments] | ||
| Just ran CAT6 through my home - anything concerning here? Posted: 01 Apr 2022 10:04 PM PDT Attaching netstat -s from my PC. I'm mostly looking for any evidence of bad runs. I'm not noticing any performance issues or anything, but this is the first time I've ever run cable and I want to know if anything looks to be a concern. Received Address Errors and UDP receive errors are mildly concerning to me, but I'm not sure that either directly point to layer 1 issues since Received Address Errors appear to relate to invalid IPs and UDP receive errors seem like they could just be a quirk of the way the UDP protocol functions. If this is insufficient, is there a better way I can verify my CAT6 is in good shape?
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| Changing network password for a wifi+cable decoder connected to main router Posted: 01 Apr 2022 09:51 PM PDT Hi, all. Where I live, our landlord has the main modem for our internet service, and we all connect to wifi-transmitting devices that in turn are themselves connected to the main router via ethernet cable; these devices are provided by the ISP (they also provide cable tv) and have their own ESSID and passphrase. Since the main router has local IPv4 Is this possible? Please do refrain from "solutions" such as "get your own internet service" and the like; this is where I live, this is what I can afford for now. I just want to make my wifi AP a bit more secure. Thanks! [link] [comments] | ||
| Posted: 01 Apr 2022 09:26 PM PDT A few things I've noticed cause problems.
Will cause lag for everybody connected to the network both via cable and wireless. There seem to be more things that cause lag but I can not seem to know what. I have QoS enabled, which should in theory fix this, but it doesn't seem to. I would like to provide more information but I am not sure what else I can give. These problems did not happen on the previous router that was replaced due to it no longer functioning correctly. [link] [comments] | ||
| Someone unscrewed my coax cable? (TL;Dr) at end Posted: 01 Apr 2022 09:01 PM PDT So, long story. My fiancé and I bought our house from a friend. We didn't get a lot of info about the neighborhood, but knew it wasn't a great one. The house is off of a major highway, and we have a lot of foot traffic by the property. We have Spectrum internet. They're affordable, provide good internet and pretty good customer service aside from the junk mail I get. Our internet box with all of our connections is connected to our electrical box in our backyard. There was no lock or anything securing the box. One night, I was home alone while my fiancé was at work and our cameras went down. The cameras are wifi synched, so I got a notification immediately. I checked the modem and router, got no signal, and decided to go check the outdoor box. There were wasps in the box (like normal), but they were lethargic and wet. I then called Spectrum. They replaced my modem and nothing changed. Finally, a tech came out. The tech brought a friend, just in case, because their database said we didn't have a live coax cable. Turns out a connection WITHIN our internet box was unscrewed fully and just hanging. The entire line had been disconnected and stayed that way. They looked around for any other signs of tampering, but didn't find any. They installed a two-way splitter on the wire so if it happened again, we'd know, but it would also be slower than just a quick unscrew. The techs said this would not have happened by accident, and was either a Spectrum tech with sticky fingers (which I doubt, because no tech would be behind our house, our property line is pretty visible, and 9:30p is a bit late for ANY tech) or deliberately done by a neighbor. Has this happened to anyone else? If so, what did you do to circumvent it? I am thinking about putting up a camera watching our back yard where the box is, but finding a non-wifi wireless outdoor camera that isn't super pricey is pretty hard. We already have an interior camera and ring doorbell, but the ring doorbell didn't pick anything up that night. Should I have called the police? TL;DR: Someone yanked our coax cable from within our box. Tech said it was deliberate. Has this happened to you? [link] [comments] | ||
| Posted: 01 Apr 2022 08:54 PM PDT The spectrum cable modem is connected to google wifi router. I know I can connect to the cable modem if the computer is directly connected to the modem. Can I login to the modem with the computer connected to the router? [link] [comments] | ||
| small wifi 5 or 6 wireless router with 4-5 LAN switches Posted: 01 Apr 2022 08:42 PM PDT Hi can u recommend me with such a router please? I have a room with a dead wifi zone with 4 devices I would like to connect directly to the internet with a LAN cable. I'd like to use my mobile devices wirelessly in the room as well . The connection will be from the main router in my living room via a long Ethernet cable, connected to this small router what will give out wireless connection. My other gaming and audio devices can then connect directly via LaN to this router as well. [link] [comments] | ||
| Posted: 01 Apr 2022 08:38 PM PDT
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| Can I use 2 ethernet cables on my PC? One for internet, one for file transfers Posted: 01 Apr 2022 11:42 AM PDT So I have 2 PCs, I'd be doing a lot of file transfers between those. The problem is:
My plan is, I buy two 10gbps ethernet adapters (skip 10gbps switch) and use those for transferring files while the ethernet ports on my PC's mobo would be for internet. Is this possible? I'm using Windows 10. [link] [comments] | ||
| 220V PDU - Ground to earth? (Safety help) Posted: 01 Apr 2022 06:55 PM PDT I have one 220v metered PDU on a metal shelving rack and I'm looking to purchase two more 220v PDUs. I was looking at the manual for the PDU and it's stating that it must be grounded to earth and has warnings about 'High Leakage Current'. I looked at my first PDU has a grounding point on it however I didn't hook that up and it's been operating for about a year without issue. That said I don't want to be unsafe. Is that label because it's designed to mount directly to a rackmount frame (I won't be doing that) or is that a necessity even if it's not? Any input especially from people who build these out professionally would be appreciated. [link] [comments] | ||
| Asus Router (AC86U) dropping LAN packets under load Posted: 01 Apr 2022 05:49 PM PDT
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| Posted: 01 Apr 2022 05:06 PM PDT
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