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Cable vs. DSL, Explained
Alan Shutko writes "Simson Garfinkel has a great article on Salon which explains the relative merits and disadvantages of cable modems and DSL. This should quiet the cable/DSL wars seen occasionally. " Very good overview of the difference between cable and DSL, cutting through the hype of the various companies.
Just for informational purposes im quickly going to run thru the major methods of getting a DSL connection. I imagine the same applies for cable.
:)
:P)
When you power up your DSL modem the first thing that happens after the power on test is it attempts to sync with a line card in the captive office. Depending on what kind of system you are on this could be at anywhere from 100kbps to 9Mbps and down. Typically up tends to be significantly less then down (usually in the 320kbps to 1.5Mbit range) but it does not have to be.
There are several encapsulation methods used to get packets over the DSL wire all of them revolving around ATM.
The end to end connection typically looks something like this:
PC --Ethernet-> Modem --DSL-> LineCard --ATM-> ATM Switch/Router --Whatever-> Internet
From there it your data can bounce around the net
being re-encapsulated until it eventually becomes ethernet again.
Typical encapsulation methods over DSL are:
RFC 1483 Ethernet over ATM (most common)
RFC 1577 Classical IP over ATM
RFC 2364 PPP over ATM
1483 encapsulation involves setting up a bridge group on your router. A bridge group is essentially a software hub that sucks in packets from multiple connections and forwards them along to wherever they need to go.
If you have a setup like this, when you look in your arp cache you should only ever see the (fictional) MAC address of your bridge group.
(and your modems MAC assuming its not a dumb bridge either)
1577 isnt used much in the real world as it requires more effort to setup and maintain.
2364 is becoming more prevalant, especially a nasty variant called PPP over Ethernet which is like a combo of PPP over ATM and 1483 bridging.
Just so you can see all the work thats going on
here are the quick protocol stacks for the data encapsulation methods before the data ever hits the phone wire. (pretty complicated
1483: TCP/IP->802.3->RFC 1483->AAL5/ATM->ADSL
1577: TCP/IP->AAL5/ATM->ADSL
2364: TCP/IP->PPP->RFC 2364->AAL5/ATM->ADSL
PPP over Ethernet: TCP/IP->PPPOE->802.3->RFC 1483->AAL5/ATM->ADSL
Anyhow, hope this was useful.
Oh yes, one last note about speeds. While most DSL available today sits in the 1Mbit range or so
within a year or so high speed DSL will start to roll out offering equal or better bandwidth compared to cable (i.e up to full 10Mbit down and 1.5Mbit+ up)
Enjoy the competition, its good for you the end user.
-N
Recently, USWEST decided to change all it's DSL customer accounts to a new PPP-DSL based connection. This means you would have to enter a username and password in your router (aka dsl-modem). There are certain disadvantages to this new services.
.. and all the fun).
:)
When your router is in PPP-DSL mode, the DHCP server assigns an IP directly to the router. From there you have to use NAT to pierce open ports for your own NIC. People most effected by this would be gamers and those who wish to use advanced forms of internet communcation (voice/video chat, file sharing and so on).
USWEST ISP web site claims that they are giving a full internet service. But this is not so. I have been able to open ports 22, 80 and 21 for my various serices. But, everytime they change your ip. You have to telnet into your router and change the NAT tables. This gets worse if you reboot your router (since the nat is deleted off). After 2 weeks of this, I changed over to startnet, here in Tucson, which didnt put restrictions such as this (but did firewall off lower ports).
So, if your getting DSL through USWEST, dont pick them as your ISP. Check the other ISP's in your area that offer DSL with USWEST as their backbone. And ask them if they are providing PPP-DSL or Bridged mode DSL. (in which case the IP is given directly to your NIC
Most users who get DSL are powerusers and demand more from their DSL service. I was alarmed by these restrictions that USWEST was putting for DSL users. Also it went to the point that I had to use a normal modem to play quake
--
If the history of technology is any guide, however, it's unlikely that the battle between cable modems and DSL will be won on technical merits...Ultimately, this battle will be won and lost on mundane issues like price and quality of service.
Truer words have never been written.
Broadband is beginning to take off and speaking as someone who makes his living from using the resources on the internet, it's about time!
For most rational people the value of downloading Netscape in 5 or 10 minutes will be secondary to the relationship your broadband carrier establishes with you as a customer. How do they respond to problems? How flexible are they with with regard to how you use your broadband? Are they knowledgable about the product?
Most of these questions will be answered based on where you live and what your previous relationships are with these broadband carriers. Have you been satisfied with your current cable service? Is your telcomm responsive to your phone line problems.
I have had serious problems with my cable company (Cablevision). From their unresponsiveness to someone illegally billing their services to my account (had to get my my congressman on them) to their inability to offer a la carte programming (in process of going to satellite programming). As a result, I decided to go with DSL. I couldn't be happier with the service. I am paying $10 a month more than comparable cable service and haven't had one problem. I've found my provider (Bell Atlantic) to be very helpful and responsive.
This obviously isn't rocket science. The companies that build relationships with their customers will retain them. Even in the face of a supposedly superior product. While the article was topical and timely, I think the penultimate paragraph could have been fleshed out a bit to emphasize this more clearly.
Hates people who have stupid little sigs
All a cracker needs to do is to keep checking these IP addresses. As soon as it gets a response from one of them, you're toast.
99 little bugs in the code, 99 bugs in the code,
fix one bug, compile it again...
I'm a leaf on the wind. Watch how I soar.
I work for an DSL provider in Wisconsin. I see these arguments all the time. I rarely try to argue anymore.
The reason for this is because when you see a cable vs DSL argument on the irc, in newsgroups, or even in person, the people arguing are almost always arguing about the cable modem service in THEIR AREA vs DSL service in THEIR AREA. It's never an argument about the technology, always about the providers. They always talk about bandwidth on adsl or sdsl being less, but this is probably a function of the provider throttling it down. Everyone talks about security on cable, but this is all relative as adsl or sdsl can be just as lax if not implemented properly. It's almost an apples and oranges argument.
This Salon article is no different. He is comparing PacBell dsl (which sucks) to MediaOne's cable service. This is not representative of the technologies involved and frankly makes me a little upset.
Hopefully someone (maybe me) can find a good link to post that compares technologies, not services.
Or maybe someone who really is involved with cable technology can write a article here on cable technology, and I or someone else would be happy to reply with a similar paper on DSL technologies.
-=Ex-manager of Wrestlers=-
I hate it when someone talks about choice creating customer confusion. Why does everyone say that? Show me one example where choice brings customer confusion? Is the customer confused when they have 4 dozen different types of cereal to choose from? Are they confused when they have a choice of 40 resteraunts to eat at?
Choice is *always* good. Choice creates innovation. It creates cheaper prices. It creates diversity in product. Customers are greatly benefitted by choice.
Customers won't be "confused" because each solution is good enough. The are benefits to using either one. So they'll be hyped both and then buy the one that looks the best to them. No problems...
-Brent--
The description why cable modems are cool (page 2) applies equally well to DSL. In fact, take the first few paragraphs, replace cable with DSL and you have a perfectly good and valid piece of writing.
To say that a DSL line is shared with the phone service is a lame excuse. The phone line bandwidth is so tiny compared to the total frequency range of the line DSL uses, that it's not even an issue, certainly nothing even close to the amount of sharing going on on cable lines.
In the same paragraph saying that cable is the king of bandwidth and that the writer gets 7 mb/s is the statement that the modem is limited to 600 kb/s. So which is it?
And then the dismissal of the issue of line sharing (page 3). If you get 600kb/s on a cable modem, and that's enough to satisy you, then DSL will do fine as well. I routinely get 600kb/s on DSL and I'm near the bottom of the serviceability scale for DSL.
Then you have the upload speeds. How can standard cable service even compete with the ul caps?
And prices for DSL are coming down fast these days, at least over here (Calgary, Canada). You can get a 768kb/s line for some $50/month (Canadian!, that's like 5 cents US), which almost matches cable service prices.
I will admit, that from reading warious posts around /. and other forums, DSL service (as in people service) sucks; this gives a lot of advantage to cable service. But the article is not a well balanced article on cable vs DSL; rather it's cable vs 'something I've never really tried just heard about and I hate it and I think cable is oh so cool' article.
So lets keep things in perspective; this article does cut through some of the hype about cable, but merely mentions DSL in passing as some other internet technology.
Ugh, it's too early for this...
"Hot lesbian witches! It's fucking genius!"
Security is a problem. When I first installed LinuxPPC on my PowerMac I noticed an awful lot of failed FTP attempts. This was within minutes of me booting up, I didn't have a chance to install patches or anything at this point. I also didn't have anything important on the machine yet. This was probably happening under MacOS as well, but since I didn't have FTP enabled I never saw it.
I sat up and watched the carnage and kept dumping the logs to a safe place. Most attempts would quickly cease but a few kept returning and I noticed them checking out other services that by default were installed. Eventually somebody took down the web server and managed to get in.
I contacted the ISP's of some of the frequent offenders just for kicks. It turns out that the most frequent one was mp3search.lycos.com (they weren't the ones who got in) trying to search through my non-existant cache of mp3s (mp3search.lycos.com searched from some other site, I ended up corresponding with the principle engineer) Somebody had posted their leased address to mp3search.lycos.com, which resulted in lots of disgruntled people not able to download mp3s and eventually a script kiddy got into my machine.
Had I cared I'd have rebooted with all services disabled and quicky patched, I was just watching for education/entertainment purposes. I never did receive a response from owner of the ISP I was hacked in from.
I just got Mediaone Roadrunner installed in a boston suburb, and the performance/reliability has been spectacular so far. My only complaint is the following conversation I had with a salesperson:
Him: Hello, sir. Will you be connecting mediaone from a windows machine
or a mac?
Me: Actually, I was planning on setting up a Linux server and using IP
masquerading.
Him: (pause). Umm, sir...we don't support anything except Windows and
Macintosh.
Me: I know. I'm going to set it up myself.
Him: Would you please hold?
Me: sure.
Him (4 minutes later): Sir, we only support Macintosh, Windows 95, 98, and
NT 4-point-O.
Me: I understand that. I won't be needing support. I'll do the software
installation myself. I'll just need you to wire it up to the modem.
Him: Our technician needs to install the software on a computer while he's
there, though.
Me: Why?
Him: Because that's mediaone policy.
Me: Why?
Him: Sir, please hold again.
Me: ok.
Him (3 minutes this time): Sir, we need to send a technician out there to
wire the system, and provision your computer.
Me: What do you mean "provision the computer"?
Him: The technician needs to do that.
Me: you just told me that...what does it mean?
Him: I don't know. I'm not a technician.
Me (with HEAVY sarcasm): Really? You don't say? Ok...answer me this
question: Why does a technician need to come out, and do an installation
that I'm going to wipe out as soon as he leaves?
Him: because he needs to get the emac address.
Me: What's that?
Him: The address of your computer.
Me: Then it's a hardware thing. You can get it in Linux.
Him: Our technicians don't support Linux.
Me: I know that. I'm going to do the networking.
Him:Sir, the installation, with the fiber optics, is alot more involved
than you think.
Me (giving up): Fine. The machine will be windows 98.
Him: How much RAM do you have?
Me: 64 megs.
Him: Ok, and what's the processor speed?
Me (thinking i'll just put windows on the machine that will eventually be
the Linux server): 90
Him (another pause): uhhh...excuse me? It needs to be a pentium system.
Me: I know that. It's a pentium 90.
Him: We need at least 166 Mhz.
Me: No you don't. I read the system requirements, and it says it
requires a pentium, and a 166 is recommended.
Him: Sir, we can't send anyone out if you have less than a 166.
Me: Fine. It will be an AMD K6-2 400.
Him: It needs to be a pentium, sir.
Me: Don't worry about it, it's the same thing.
Him: Is it a pentium-class processor, sir?
Me: yes
Him: and do you have an ethernet card, sir?
Me: seeing as i am networking the systems myself once the technician
leaves, yes I have the cards.
Him: thank you very much sir. We'll have someone there to do the survey
on Wednesday.
When the guy came to install it, I started the same conversation with him. His response was basically "Do whatever you want, once I'm gone." I said "ok", and got my linux box going. If there are people out there who need help with Roadrunner for Linux, I'd recommend http://www.vortech.net/rrlinux.
Juiced? Or Not?