DIY ADSL connection?

As a matter of interest, what qualification puts you in the category of those "who know what they're talking about", as opposed to the manufacturer and ISP?

Reply to
Timothy Murphy
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There's no point whatsoever in having conversations along these lines, since on the Internet no-one knows you're a dog. I could say whatever I like and you've no way of knowing that what I say is true.

But I make a very comfortable living by knowing what I'm talking about in computing and associated fields.

Reply to
Huge

(...)

What that's telling you is that your modem/router is implementing NAT, otherwise there's no way you'd be talking to the rest of the world. You're not talking to the modem on 192.168.1.0/24, you're talking to the router part of the modem/router box.

NAT with no incoming connections allowed means you don't need much firewalling, but most of the boxes provide this too.

If you're running a server accessible to the outside world, with the relevant hole in the firewall, you ought to be able to do your own logging of attempted entries to that port etc. And attempts to connect to other ports from the outside world will simply fail silently - TBH I don't really care about those. A portscan on an IP address is trivial, and the fact that somebody has done one isn't interesting. When they start probing the open port, that is more interesting, and you can do something with that, since it's forwarded to your computer.

Reply to
Clive George

I'd rather hope the manufacturer knows exactly what they're making. However their marketing department may choose to use a different name when describing it to consumers in order to sell more stuff.

Reply to
Clive George

well it is a modem, but its not just a modem

Typically a basic NAT router is a modem, a bridge, a router, a NAT engyne, a stateful firewall machine, a DHCP server a proxy DNS server and..a web server . To name just a few. Its probably alos a log server and may have an snmp server in it too. Oh and a wireless bridge.

Only a USB connected modem with none of those is strictly JUST a modem.

And I am not sure if those don't do ATM bridging as well.

Reply to
The Natural Philosopher

For once, I agree with you.

Reply to
The Natural Philosopher

Cant answer for huge, but in my case 30 years in IT and 15 in internetworking.

Reply to
The Natural Philosopher

According to Wikipedia, "A modem is a device or program that enables a computer to transmit data over, for example, telephone or cable lines."

You obviously have a different definition. What is it; and do you have some authority to back your definition?

Reply to
Timothy Murphy

Are you asserting that income is a measure of expertise? If so, perhaps you could tell us your income.

Reply to
Timothy Murphy

The Modem is the bit that turns the stream of digital bits into analogue signals. Short for Modulator/ Demodulator, but we all knew that, didn;t we? Broadband "Modems" as supplied by ISPs in the UK normally have a router and a NAT function built in.

The suppliers still call them modems, AFAIK, while the likes of PC World call them routers if they've got Wifi or ethernet connections on them. Home Hub is another meaningless name used by marketing departments....

Reply to
John Williamson

No, I have the same definition.

The box you are describing as a modem has some additional features as well. It understands IP and ethernet, allows various computers to talk to each other over those, and via IP + NAT to the outside world. It'll probably provide DHCP for the computers if you want. It's a lot more sophisticated than a modem, and this is why I'm calling it a modem/router, and it's also why if you look at those links I gave you there's modems and modem/routers in separate sections.

A modem doesn't understand need to understand IP. Remember that device described as an ethernet modem I pointed to? How does that communicate to the computer - which protocol is used to transmit the data intended for the outside world over the cable between the two? What protocol does your computer (server) use to talk to your modem/router? If you plugged your computer into the ethernet modem I mentioned, what would its IP address be? We already know the answer for when it's plugged into your modem/router.

Reply to
Clive George

Simplistically:

Routers look at the packets of data and make decisions about what to do with them based on rules and what they find.

Switches associate the MAC address connected to each port with IP address's (I think!) and only send packets arriving on any other port to the relevant port.

Hubs send all the data received on any port out on all the other ports.

You also need to know that only ports have IP address's not devices. A given device can have more than one port and thus more than one IP address. So my ADSL to ethernet modem has a WAN IP address (as seen by the internet) and an LAN IP address.

Reply to
Dave Liquorice

And of course we'll stay away from situations where multiple ports have the same IP address, ports have multiple IP addresses, and both :-)

(I was very pleased the day I inserted a software firewall into a network by adding a VM with it on, converting the network port to a tagged one, configuring the switch it was plugged into to have a private VLAN for the far side of the firewall, moving all the devices I wanted to firewall to the new VLAN and so on. All done from 250 miles away, no playing with wires at all :-) (yes, I know this is probably bread-and-butter for any networking person, but it's not my area so I was pleased))

Reply to
Clive George

Perhaps you could f*ck off and die?

Reply to
Huge

I've no idea, please tell me.

Again, please tell me.

Incidentally, I haven't seen an ADSL modem in the last 5 years that wasn't accessible over the web at address 192.168.1.1 or 192.168.1.254 (occasionally a port also had to be specified).

Reply to
Timothy Murphy

Umm ... where are the analogue signals in a lets say router that you'd use for a ADSL Broadband service in the UK;?..

Reply to
tony sayer

PPPoE, like it says in the blurb. If you know what you're talking about, it's fairly obvious from the description why it's different to the devices most of us use.

86.whatever - the address given to you by your ISP. The computer is directly connected to the internet - no firewall, no NAT.

Doesn't the fact that you don't know this, despite claiming that it works in exactly the same way as your current kit, worry you or indicate that you might not know quite so much as you think you do?

When you say over the web, presumably given the addresses you mean HTTP on your local network, rather than the public internet "the web" more commonly refers to. And in that case, every device you describe as an ADSL modem is in fact an ADSL modem/router.

When ADSL first came out, ISPs would provide ADSL modems which connected by USB to a single computer. There are various problems with this : first is it's only one device at once - all the various playstations etc that a typical family has these days would be stuck. Second is security

- it relies on the computer having a decent firewall, and most people can't manage such a thing. Third, they were generally shit, and you needed special drivers. Nowadays most ISPs provide ADSL modem/routers with wifi, which solves all these problems.

If you wish to carry on calling an ADSL modem/router an ADSL modem, you're allowed to. You'll be wrong, in the same way as people who talk about PIN numbers are wrong, but the general public won't care. It's only the people who actually know what they're talking about who will care, and who really cares about people who know stuff?

Reply to
Clive George

On the connection from the router to the exchange. The "last mile" from the exchange is mostly analogue on domestic BT lines. The new optical fibre extends the digital bit to the street box. Certainly the bit from the street box to your premises is.

ADSL uses a combination of bandsplitting and multiple modulated HF carrier signals. The Microfilter is a fairly simple analogue filter which splits the HF and AF signals. The AF goes to the handset, while everything goes to the ADSL modem, which rejects the AF signals internally.

Wikipedia explains the details:-

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Reply to
John Williamson

To clarify and add to the confusion;)..

Here's an ADSL to Ethernet modem

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Modem and router

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a few other things thrown in for good measure;)

Sometime they are sort of phone exchanges as well;!..

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sometimes almost something completely different;)..

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Reply to
tony sayer

Note the ;? ..

Had this very conversation the other month with Two BT exchange engineer types.. one argued that it was a digital system the other argued that it was not.. I presume the actual modulation scheme in use would determine that..

Haven't got time to look it up at the moment but if anyone has 10 mins spare!..

Reply to
tony sayer

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