I'm struggling to find comprehensive (or at least convincingly accurate)\ninformation on what I'm sure must be a FAQ:\n\n- What are the "good" values for SNR/attenuation for\ndifferent line speeds, and more importantly:\n- what are the symptoms of borderline low SNR?\n- what are the symptoms of borderline high\nattenuation?\n- what (in each case) if the upstream figures\nare good and downstream bad?\n- Vice versa?\n\n- Regarding CRC errors:\n- what causes them?\n- what is a "good reading? (Obviously 0 is good\nbut at what figure should I worry about them?)\n- what impact do they have?\n\n- What impact does hardware play in making up for\nborderline figures? Eg:\n- having a crap filter?\n- having crap cable?\n- having a crap modem?\n- having too much or crap telephone equipment\nhung on the same telephone line?\n\n- What does environmental conditions (eg weather)\naffect:\n- the SNR and attenuation readings?\n- the impact of bad values?\n\nTo put the whole question another way: I want to have a reasonable idea if I\nvisit a customer with ADSL issues, when I look at the information the router\ncan tell me, what I should do. In which cases will changing the hardware\nhelp (and in those cases what should I be changing).