Upstream: This means away from you and towards the internet and your internet service provider. Your cable modem is connected to a coaxial cable that leaves your house. Think of wherever that goes as upstream. Downstream: The opposite of upstream. This means information coming down from the internet to your modem. SNR: Signal to Noise Ratio. Quite simply, this is a number that represents how much signal there is on the line versus noise. Signal is what you want: encoded, understandable information from the internet. Noise is bad and can come from electromagnetic interference (from other electronic devices and radio signals) and thermal noise. Knowing what those two things are isn’t too important right now. Just know that you want a better signal and less noise. Frequency: When you tune your radio or change your TV channel, you are telling the device to listen at a different frequency. Channels are also used to send information destined for the internet over the cable network in pretty much the same way that TVs do. Headend/CMTS: Where your cable modem and the modem of other people in your town/city connect to. This is a piece of equipment operated by your ISP that manages all the cable modems and connects them to the internet. From here, network engineers can check the health of your modem as well as reboot it remotely and push configuration changes to it. FEC: Forward error correction. Data doesn’t always transmit through cables perfectly, there are often some errors in the bits (1s and 0s). For instance, a 0 might be flipped to a 1 or vice versa. In order to correct those errors, some extra data has to be attached to every codeword that goes out (a codeword is just a fixed chunk of data). If it can fix the error, then everyone’s happy. However, sometimes codewords have too many incorrect bits and the error correction algorithm (called Reed-Solomon, if you’re interested) can’t fix it. If more than 1% of your codewords are uncorrectable, you will start to encounter some issues (especially with VoIP). [1] X Research source
If you have more than one Internet connection, to get this local IP address, make sure that you are connected to that particular connection before typing in the address into your browser. For only some issues, even if your modem is connected to your computer, you can still check your server settings despite the inability to check any other page. However, a more complicated setup may require a visit from a technician.
For some Linksys modems (especially wireless modems), you can stick pretty much anything in the username box (even gibberish) and place your current network password into the password box.
Acquire Downstream Channel: This should say “Locked”, “OK” or similar. This means your modem found the frequency with which to receive information from the internet. There should always be at least 1 channel acquired with a DOCSIS 1. 1 or 2. 0 modem. If you have a DOCSIS 3. 0 modem, you should be acquiring up to the maximum your modem supports (8 or 16). Connectivity State: This should be OK or Operational. Configuration File: This should show the name of your configuration file. If not, just see if it says “OK” or similar. This file is downloaded from your ISP and tells the modem how it should behave. Security: This should always say “Enabled” or “BPI+” in all cases.
Downstream power levels should be between -10 dBmV and 10 dBmV. Ideally, it should be as close to zero as possible. Many line technicians aim for the even more stringent +/-5 dBmV range. As long as it’s within these ranges, they should be okay. Many modems are even rated to +/- 15 dBmV. Too low means your signal is weak, and too high means the signal is strong - possibly too strong (and will need to be corrected with an attenuator or splitter). Upstream power levels should be between 40 - 50 dBmV. Think of this measurement as how loud your modem has to scream to be heard by the CMTS. If you are transmitting less than 40 dBmV, your upstream SNR will degrade (If you’re whispering and the CMTS is shouting at the same time, they’ll have trouble hearing). If it’s higher than about 50 dBmV, your cable modem may intermittently go offline or have a high number of uncorrectable codeword errors. One of the most common causes of upstream power problems is splitters. If possible, your cable modem for your internet should be on the first splitter attached to the line that comes in from your house. Further splitters will degrade the signal quality — TVs can handle it, but you will see more noticeable problems with the internet.
No Ranging Response received - T3 time-out: The cable modem’s knocking at the door, trying to find your ISP. Alas no one’s home or it can’t hear them if they are. This is usually indicative of an upstream noise problem, so check your upstream power level to see if it’s too high (perhaps > 55). If so, call your ISP for help. SYNC Timing Synchronization failure - Failed to acquire FEC framing: FEC means forward error correction. Possible causes include too much noise, low signal, or a bad cable modem. Resetting the cable modem due to docsDevResetNow: Normally a reboot issued by your ISP, due to a firmware update, provisioning your modem, or other upstream maintenance. It’s not usually something to worry about. If it happens frequently, you should ask your ISP what’s going on — there might be an outage in your area they’re trying to fix.
