Actually, the first thing you'd need to do is identify the actual symptom. For example, if you're only experiencing a problem with a specific application, such as a game, you should begin with ping, PingPlotter, tracert, etc. This would quickly indicate a potential problem somewhere remote on the network(s).
However, if you're experiencing a problem with overall connectivity...all your applications share the same router and modem...then you should begin with the signal specs of your equipment.
The problem with signal specs is a lot of subscribers don't know the acceptable ranges of measurement. There are a lot of sites recommending these ranges but only Cox can provide this information...because it's their network. You could argue the specs from another site but it'd be a moot point.
I think Cox wants these ranges of specs to be a secret. If never read a moderator's assessment of an out-of-spec signal. It's always we'll send a tech to your house.
I don't think Cox wants them to be secret as much as they don't see the value in publishing the information to non-technical end users so they don't bother publishing them. I can also see why the moderators don't want to make a diagnosis since they could then be held to that diagnosis which might later turn out to be wrong. That's why we users have to discuss these topics amongst ourselves.
Signal strength is really a secondary indicator anyway. If you downstream signal levels are -14 but you have 0 uncorrectable packets, then it's all good. By the same token, if your downstream signals are +3 and you have 10 million uncorrectables, you still have a big problem. Basically, downstream signals can show you if you might have a giant problem if they're below -15 or above 15. Beyond that, SNR and uncorrectable packets are more important.
Same goes for upstream power. If your upstream signals are "too low" but you have all 4 (or 5) channels bonded with no T3 errors then it's fine. But if your upstream is +56 and you only have 1 channel, that's a definite problem.
I know everyone wants a step by step guide that always provides a definite answer but that doesn't really exist. Unfortunately we have to learn some details of how the cable modem system works in order to troubleshoot our own problems. IMHO, all cable networks are extremely fragile and require constant maintenance, so the last thing any cable provider wants is for end users to be finding problems and asking for repair. But if you want a good reliable cable connection that's what you have to do.
The values aren't actual measurements but a log-scale representation to, probably, save space. For example, it's easier to notate -5 as opposed to 0.31622776602 dBmV.
Wouldn't it be nice if Cox could compare our values to a truth table based on our equipment and plan? A 3-light traffic signal within the software of the modem comes to mind:
Green = Within Specs
Yellow = Operational
Red = Out-of-Specs
More gooderly, a 5-light model:
Green = Ideal
Pale Green = Within Specs
Yellow = Operational
Pale Red = Out-of-Specs
Red = No Connectivity
Does Cox measure upstream SNR?
As I understand it, the level 1 techs get that type of red/yellow/green indication when they check the modem. That's why they will sometimes say the modem is "unhealthy". But I don't think the red/yellow/green takes things like uncorrectable codewords or T3 timeouts into account.
Cox can see upstream SNR but we can't. It would be nice if we could see it because that would help us to troubleshoot a lot of our own issues.
