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Ok for starters we have Time Warner which happens to be the worst provider ever. We have two PCs(windows 7) and two Laptops(windows 8). We are paying for 100mbps our laptops on wifi average around 25mbps, the office computer (right next to the router) has a 3ft Ethernet cable connecting it to the router gets around 70mbps.

The other PC is in the garage about 40ft away its connetion comes from an ETech Commercial Electric command center in the attic. This computer averages 0.9mbps and most days doesn't have it at all.

Time Warner says the length of Cat5e is the reason for our poor connection. Should it really be making this huge a difference in our speed?

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The best way to verify if the cable company is delivering the speed they promise is to connect directly to the modem with an ethernet cable and do a speed test. If that's good, then any slower speeds on your network are the fault of some component in your internal network setup. The cable company isn't responsible for what happens after the internet reaches your modem. –  nhinkle Mar 10 at 6:37
    
Cat5e can go 330ft without signal degradation. In my experience, the method of securing the cable does more damage than the length. You should bypass any inside wiring and connect directly to the NID. ISPs are only responsible for wiring on the street up to the NID, anything in your residence is your responsibility, even if it precedes the modem. Some ISPs will give warranty on cable they ran for a short period of time (usually 30 days), but ultimately it is yours to test and fix. So first connect the modem to where it comes in off the street and test for speed there. –  MaQleod Mar 10 at 6:57
    
Also if you look at the contract/TOS, they guarantee "up to" a certain speed, they never guarantee a specific speed. If 70mbps is the best they can do to your residence, that is what you're stuck with, they likely won't fix it. See help.twcable.com/RSSA_English.pdf section 5c: "We do not guarantee that you will obtain the Maximum Throughput Rate" –  MaQleod Mar 10 at 7:01
    
There are two ways for the cable to affect speed: 1) The connected devices on each end use a high-speed protocol and for some reason one of them decides the cable is incapable of such high speed. 2) The cable causes data errors and hence frequent retries. But the cable must be over 300 feet long, poorly installed, or improperly connected for either of these problems to occur. –  Daniel R Hicks Mar 10 at 11:19
    
But in the above scenario it's unlikely that Time-Warner is at fault. Unless they're intentionally throttling the garage PC (because they think it's being used as a server), there is probably something wrong with your connection between that PC and the router. Note that it could be a misconfiguration such that the PC is being handed the wrong DNS or routing info by the router (or is ignoring what the router passes it). –  Daniel R Hicks Mar 10 at 11:25

2 Answers 2

Unless the cable is over 90m you usually do not see any change unless the cable is damaged or is encountering interference from electrical wires, etc.

Try a ping test and see if there's any packet loss, also take note of RTT. It should be low, mine is less than 1ms, but I'm on a gigabit network.

"ETech Commercial Electric command center" dunno what that is but if you can rule it out, do so. Patch the ethernet cable strait from your router to the computer. You can buy ethernet couplers at most electronic shops.

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Does the lenght of Cat5e cable effect the network speed?

It can do but it would have to be either faulty, seriously long 100m+ (cat 5) and in a position where it is affected by interference. I suspect the issue is interference somewhere... We can try and prove it.

Move your garage to PC into the same room as the router, connect it to the router and with a different cable (one that you know works well). If the speed is good, the PC is fine.

Now, use your 40' cable with your garage PC (but still in the room with the router). This will indicate if the issue is actually the cable or not.

If they're OK, then I think you may need to connect the 40' cable to your laptop and try it at various distances (testing your speed as you move from your router room to the garage) until you reach your garage, hopefully during this time you'll see where the issue is and then you can work out why.

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