Period Cat5e cabling

[MdB]

When you log onto a website / server, your password obviously needs to be checked to ensure it is correct. This means the password needs to be stored on the server which is fine until it gets hacked and then the bad guys have your password. To get around this, the password is stored encrypted on the server using a one way encryption. This means it is easy to convert the password into the encrypted version but basically impossible to go the other way around. When you log on, the password you send is encrypted and then compared with the stored encrypted version. If they are the same then you are allowed in.

Now lets say you are the bad guy and have managed to get hold of the encrypted passwords and want to find out what the original password is. Working the encryption backwards is impossible so you are left with brute force methods where you encrypt each possible password and compare with the list you have stolen. With 6 characters of upper / lower alpha numeric, there are 5.7x10^10 possible combinations which will take months / years to calculate. However, various people have done this and stored the results which are available online. This data is known as rainbow tables. All the bad guy needs to do is look up the encrypted passwords he has found and the table will tell him the original password instantly without having to do any work.

Obviously this is a problem and this is where salt comes in. Salt is an additional set of random bytes which are added to each password before they are encrypted. The salt is stored with the encrypted password and will also be available to the bad guy when he steals the password file. He therefore knows what random bytes to add to the password before encryption but now he has to calculate all 5.7x10^10 possibilities for each password he wants to crack and can't use rainbow tables to do this.

Now 5.7x10^10 calculations is a lot but isn't impossible so if somebody wants your password enough and cracks the server then they can get it.

To make it harder, you need to make your password longer and more complex.

8 digits helps but many people use all lower case with no numbers or other characters ;,.><!"£$%^&*) etc giving 2x10^11 options.
upper and lower increases it to 5x10^13.
upper, lower and numerical increases it to 2x10^14
upper, lower, numerical and other increases it to 1.5x10^15

Personally, I use 12 digits passwords made up from upper, lower, numerical and other which gives 6x10^22 possibilities with a different password for every site. Unfortunately, this is rather hard to remember so I use lastpass.com to remember them all apart from bank ones.

 

[worms]

You use salt when storing computer passwords. The addition of salt makes it harder to use rainbow tables to recover encrypted passwords when your server gets hacked.

(and I haven't made any of the above up!)

:shock:

OK, someone's got to be daft enough to ask so it might as well be me - Salt? Passwords? Please explain, preferably in English!

http://en.wikipedia.org/wiki/Salt_(cryptography)

So I think I was right - its an in joke. :roll:

 

[Flyfisher]

I found the image online to illustrate my own little joke and it was coincidental that it contained its own geeky joke - I assume it was deliberate. Full marks to MdB for spotting it and providing the explanation. All a bit esoteric, admittedly, but it does give some insight into the complexity behind the IT systems we all take for granted these days and is a good example of the value of mathematical reasearch and how it affects our everyday lives - even if we don't entirely understand the details (which I certainly don't).

 

[LadyArowana]

. All a bit esoteric, admittedly, but it does give some insight into the complexity behind the IT systems we all take for granted these days and is a good example of the value of mathematical reasearch and how it affects our everyday lives - even if we don't entirely understand the details (which I certainly don't).

You mean there are no magic pixies in the boxes ?

 

[Flyfisher]

But of course . . . they just weave their magic using mathmatics. :wink:

 

[MdB]

and it was coincidental that it contained its own geeky joke - I assume it was deliberate.

Doubtful - far more likely somebody couldn't be bothered to clear up after lunch...

Full marks to MdB for spotting it and providing the explanation.

You can blame worms for pointing it out...

 

[Feltwell]

Thanks MdB for the explanation. I really should sort my passwords out, I'm a bit lax

 

[CliffordPope]

My experience of these cables, for what it's worth:

1) They are very fragile, and do not take kindly to any kind of disturbance. I ran one under a foam rubber carpet underlay. After a few months the friction from people walking on it had split the outer cable and caused the wires inside to twist. This stopped it working. The wires have to remain twisted in specific pairs, and I was unable to twist them back together satisfactorily, even though there was no physical break
2) There are heavy duty cables, with tougher plastic sleeving, suitable eg outdoors. But they are much more expensive.

3) My attempt at doing a DIY fitting on the end was a failure. I found it impossible to prevent the pairs untwisting. Even when I thought I had solved that problem, it still wouldn't work.

4) Proximity to power cables doesn't matter. Our offices have miles of special trunking running round all the walls, stuffed with Cat5, mains and telephone cables. There are lots of unused sockets, all permanently connected, and no problems with dead-ends.

 

[Flyfisher]

Sorry to read about those bad experiences, however, walking on any sort of cable is not a good idea, unless it is armoured!

I've used 'outdoor' data cable with no problems - the main difference is a UV-resistant outer sheath.

Untwisting an inch or so of the cable pairs for termination should not cause the cabling to fail completely, so I wonder if there was something else causing this?

Unused outlets are not a problem if the cables are arranged in a 'star' configuration. Basically, there should only ever be a single run of cable with an RJ45 connector at each end.

I agree that the risks of running data cables in the same trunking as mains cables is often exaggerated and it depends mainly on the nature of the connected mains devices. In a domestic or office environment there are unlikely to be devices that would cause problems, but that may not be the case in an industrial environment, so the general rule is to try to avoid it where possible. It's one of those 'good practice' things.

 

[AMc]

I see the horse has bolted here but still.

I installed a network in my house as part of the renovation. I ran 4 cables to 4 plates in 8 rooms all terminated at a patch panel in the utility.
I ran an phone extension to a BT socket by the patch panel from the master socket (using cat6 capable cable). Cat5 or 6 cable is so much better than the cable BT use to get the the house then I doubt the extra run will seriously compromise the performance should I move my router there - for now it sits by the master socket and has all 4 LAN connections routed to the patch panel.
The room faceplates were installed by a professional but money had run out when I needed to do the patch panel so I bought a very cheap LAN continuity tester, punch down tool and RJ45 plug crimper from eBay (£10 all in). The patch panels were Belkin 3 x 12 ports at £10.50 each which are "professionally" mounted on bits of wood screwed to the wall

I used cat6 equipment because you can send HDMI video signals point to point over 2xcat5 or 2xcat6 cables and the maximum range is better using the faster cable. The difference in cost wasn't that significant. I was buring some of my cabling in the walls and floor so saw no reason to skimp on the cable as the labour - and floor - were the expensive bit.

I haven't had the system certified for cat6 and I doubt it would pass but large file transfers max the 100/10 network cards in the PCs I own so gigabit or more is beyond my needs for now. Some of the "professional" terminations turned out to need a bit of repunching to get all cables connected.

 

[Flyfisher]

Some of the "professional" terminations turned out to need a bit of repunching to get all cables connected.

Not entirely unknown but such bad connections would have been easily discovered and rectified during the final testing, which is very easy with a cheap LAN tester (if you don't want to buy the full certification test kit). Because the professionals only did half the job they wouldn't have been able to easily test the room sockets.

 

[AMc]

My <£5 LAN tester showed the problems instantly. I was a bit surprised as the terminations were very neat but a couple had just missed being punched all the way down. It took longer to unscrew the faceplates than to fix the connections.

 

[Feltwell]

Merry Christmas one and all.

In the true spirit of PPUK, it's taken months to finish to finish this job off. All the cables were in up to a point - I just couldn't face taking our bedroom apart to get the floor up to do the final run to the BT master socket. However, Mrs F provided the final push - she signed us up (without my knowing) for faster fibre broadband, which meant that the Feltwell family PC, happily sitting downstairs and previously linked via an extension phone socket to the BT master Socket, suddenly had to be relocated to where the master socket is - which is in our bedroom :roll:

BT engineer confirmed that the phone extension wiring wasn't up to the job with the new broadband. After 2 months I got fed up of falling over the PC every morning, and finally got around to running proper Cat5e cable downstairs so it could go back to it's former home. All now in and working fine, thanks go to those who gave the techie answers to this thread way back in February.

 

[Owain]

Frm the title I was expecting something like

 

[Feltwell]

Nah - that's period Cat 6 that is.

 

[worms]

It is timely that this thread has come back up, as I was about to go looking for it!

I need to finally get around to sorting our phone and Internet connections - at present it is functional but far from ideal as there is a dead Internet zone in one corner of the house and none of the phone extension sockets have worked since we installed the wireless modem a few years back.

I guess the starting point is to try and locate the BT master socket? And then work out the best location for the wireless router? Do I do this by walking the router around on a long cable and looking for signal strength on the laptop in all the furthest corners of the house? Then cable from the master to the chosen router location, then Ethernet cable from router location to tv/x-box :roll: location?

And any ideas why the extensions won't work with the adsl filter plugged in to the phone socket (which I assume is the master as it was the only one that the router would speak to)?

 

[MdB]

And any ideas why the extensions won't work with the adsl filter plugged in to the phone socket (which I assume is the master as it was the only one that the router would speak to)?

Probably because you have a filter on your master socket which is also filtering all the extensions.

The filter has two sockets, the phone socket and the ADSL socket. The phone socket is the part that actually has a filter and will block the ADSL signal - the ADSL socket is straight through and doesn't do anything apart from change the socket type. You therefore need to ensure that the incoming phone line doesn't go through any phone side sections of the filter before reaching your ADSL modem.

As for getting a good signal the other side of the house, I would (and use myself) a powerline adapter. http://www.solwise.co.uk/net-powerline-av-index.htm You can either plug your computer directly into it at the other end or add a wireless node.

 

[worms]

Probably because you have a filter on your master socket which is also filtering all the extensions.

Ok, that sounds probable and I'll need to look into that. I've no clue where the extensions come off the main line, there are old gpo era boxes in various places that may or may not be still wired in to the system. The filter is just one of these ones that you insert into the standard phone socket :

Even with a similar one fitted to the other extension we get no dialling tone. However, the two useable extensions were both ones that I fitted ten years ago, so I may have done something wrong at that point that was Ok for phone but has mucked it up for ADSL. I think I need to start from scratch and actually understand it!

As for getting a good signal the other side of the house, I would (and use myself) a powerline adapter. http://www.solwise.co.uk/net-powerline-av-index.htm You can either plug your computer directly into it at the other end or add a wireless node.

Looks like one of these would be useful, thanks!

 

[MdB]

Draw out your phone socket / connection layout if you can work it out and post here.

Your master socket should look something like this:

Note the low screw position.

If it looks like any of these then let us know as different things apply.