# what do the crc errors in modem utility mean?



## komodo7d (Jul 25, 2006)

Is there anybody out there that might be able to offer info on this...which is the tail end of many many months of connection issues....the long story is all the hours of troubleshooting and tech support , changed equiptment, cables, repairs and replacement of phone lines, jacks...and on and on and on....the short story to this is ...I want to reformat,(for the 4th time in 3 months)...to again eliminate any problems with my computer....
I'm downloading updates from sony to put on disc and am concerned about having bad downloads of updates from sony or microsoft...
so here it is...
ISP...bellsouth adsl...3000/384 kB...westell 6100 modem.
still having connection issues...slow speeds (400 - 1000kB) , and that annoying error message...page cannot be displayed/ server cannot be found...which happens when I am already on the page and then poof...I get that error message...so started looking at info in modem utility....noticed the transceiver info...SN margin (db)...downstream ranges from 2.0 to 22.0...upstream stable.....so I know I will have synch issues in the lower #'s...also notice there are times I have a few crc errors but also times when crc errors continue to climb...like 3492 in just a couple hours or less...????? and the longer I am online the higher they go....I can have good #'s for SN and still get lots of crc errors.......starting to look like this occurs most frequently on fri, sat and sun....and better on mon evenings...
am I understanding correctly that downstream is btwn modem and dslam and not btwn modem and my computer?
could those crc errors affect the quality of downloads? such as ...downloaded the pc-cillian internet security suite 2006 (free trial)...first 2 times got error message when trying to install that the file was corrupt...3rd time downloaded it installed....
had a similiar problem with windows xp sp2....
or downloading a file from sony support and it has 34 KB less data than it should and when I download again it I get the right amount of data...
any info greatly appreciated....help solve the mystery connection issue....
thanks


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## TerryNet (Mar 23, 2005)

A Cyclic Redundancy Check (I'm dangerously relying on my memory of what CRC means) error means that the packet would have to be resent. So your effective bandwidth is reduced. Does this answer your question about CRC?

I think that the main message in your post is that you have a phone line that is probably not capable of decent dial-up, much less DSL. Correct?

Has your trouble shooting included trying a different DSL filter? Eliminating all, or as much as possible, of the phone wiring in your house/apartment? Has your ISP or phone company actually tested the line--and what do they say?


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## komodo7d (Jul 25, 2006)

thanks for your reply...

if the crc errors cause packets to be resent that would explain some of the issues ...or maybe more...

my phone lines should be able to handle my dsl connection, in theory...

troubleshooting included but not limited to, the following....(lmao)

new telephone interface box
new dsl filter in the interface box
new dedicated dsl line (cat5e) from interface box to new modem jack
all new phone and ethernet cables (2 times)
new modem
another new modem is being shipped today...Versalink...overnight...so I can go back back to having 2 computers online at the same time and better monitor via the modem info and logs when and what is happening to my connection....(it wasn't any of the 3 routers, either)
great that I have been able to document my connection issues, and the phone co/ISP (same thing) has also been able to and that several physical problems with my ISP were eliminated...they have done all this at no charge to me, including no charge for a month of service...so ya know this ain't my imagination...
at one time the connection was great...started getting frequent probs and then it took a nose dive...some issues have been eliminated...still have frequent problems

fyi...3 computers all have same probs...took my laptop out and ran wireless for hours at several of the free wireless places around town...no problems
spy, virus, etc....scanned like about 200 + hours worth with every thing, including hijack this....nothing
also used trace route, pings and stuff
reformat, reformat, reformat....now need to do this more more time...
turned off everthing electrical but the fridge, modem and computer, unplugged phone...SOS...picture me sitting in the dark...no a/c... hunched over the keyboard for hours
and lets not forget going around the house, inside and out with headphones and a am receiver checking for noise....significant in only two places...the last 16" of phone line wires going into the interface box and the electrical breaker boxes outside which the dsl line passes right under
exterior ground wires all connected but could be cleaner

what else is a girl to do?  save the pennies for a cable modem and switch ISP???...that would take forever 

my ISP says the signal to noise margin from the modem utility indicates a noise problem...and I say ok...but from where??? not at my house???? so could it not also indicate a weak dsl signal? and would that indicate a problem betwn me and the dslam or at the dslam?

it's a mystery to me and my ISP...

so I just want to be as certain as possible that I get good downloads to reformat my computers one last time


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## komodo7d (Jul 25, 2006)

and why all the intermittant crc errors?


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## TerryNet (Mar 23, 2005)

"and why all the intermittant crc errors?"

CRC is a way of adding up all the bytes or words in a packet; the sender does so and puts that answer into the packet also. The receiver makes the same calculation and compares. If the numbers are different then one or more bits in the packet must have changed enroute. Noise can easily cause this. It's like one of us listening on a phone with a lot of static--we'd miss some words. (OK, my ears are old enough that they miss words without external help!) So, in short, CRC errors are just another indication of noise on the line.

Seems that you've done everything, and then some, that you could possibly do to solve this. Sounds like your ISP has been reasonably cooperative also. Now they need to dig up the line and find where a mouse or mole has chewed on it. Or where water has seeped into the insulation. Or where tree limbs are blowing against the line. Or where two wires are rubbing on each other.

I once had a problem where my home phone would be dead. I'd call from the office the next day and phone co. said their test shows everything OK. After a few weeks it finally happened on a Saturday but only a partial failure (loud static). I called from the interface box; when they sent a guy out he found two (2) loose connections--one on a pole a block from my house and the other two blocks away.

With all you have done at your end surely the problem is somewhere between the ISP and the telephone interface box. DSL is only good for certain distances, so if you are at the limit point it could be that the signal is just not strong enough.

Good luck with this. I doubt that I can think of anything else to try.


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## komodo7d (Jul 25, 2006)

CRC is a way of adding up all the bytes or words in a packet; the sender does so and puts that answer into the packet also. The receiver makes the same calculation and compares. If the numbers are different then one or more bits in the packet must have changed enroute. Noise can easily cause this. It's like one of us listening on a phone with a lot of static--we'd miss some words. (OK, my ears are old enough that they miss words without external help!) So, in short, CRC errors are just another indication of noise on the line.


great answer....now it makes sense to me...my ears aren't what they used to be, either but I can still see good... as long as I am the right distance from what I'm looking at ....and this paragraph explains pretty well what I have been experiencing and even seeing on the computer screen, especially if you add that some of the data never gets there and some of it gets there later and out of order...."ya gotta see it to believe it"...and when I grabbed the tech guy out of his truck as he was leaving after testing and finding everything fine...his mouth dropped open...then tested the line again and decided I was on a bad port at the CO...small miracle! too bad that didn't solve the whole problem


I also think the problem is between my interface box and my ISP...and this new modem may only help track when the problem occurs...in the meanwhile, I will have to live with it...
knowing I'm at the "end of the dsl line" so to speak,and not knowing how hard my ISP will look for the problem, I will probably need to change to cable internet service...I should live so long to afford to change over...lol

many thanks...you have been a great help...


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