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Thread: Why does ADSL use PPPoe?

  1. #1

    Post Why does ADSL use PPPoe?

    Why does ADSL need to use PPPoe to connect to the internet while Cable does not need to use it?

  2. #2
    Kip Patterson
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    Post

    One major reason is to eliminate any association between you and a specific IP address. This prevents you from running a server effectively, but it also provides the ISP with a great deal of protection against the consequences of customer's abuses. Open mail servers, hacked machines, etc, create major problems for ISPs.

  3. #3

    Post

    Cable ISPs have capped the upload speed to prevent users running server. Why don't they use PPPoe, which will eliminats abuse, in Cable?

    <font face="Verdana, Arial" size="2">Originally posted by Kip Patterson:
    One major reason is to eliminate any association between you and a specific IP address. This prevents you from running a server effectively, but it also provides the ISP with a great deal of protection against the consequences of customer's abuses. Open mail servers, hacked machines, etc, create major problems for ISPs.</font>

  4. #4
    wee96
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    Post

    Some RR areas actually do, its not exactly pppoe, but its simliar.

  5. #5
    Kip Patterson
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    Well, Dennis asks a good question, not sure about the answer.

    ADSL modems are modems, whereas cable modems are really bridges. Not sure how PPPoE would work in that situation.

    All of Road Runner did have a login system when it started, and required the use of the proxy. They did not deal out IP's as ADSL does, however.

  6. #6
    wee96
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    Post

    Ahh yea thats what I was thinking of, being in an @home enviroment I forgot all about it.

  7. #7
    dannjr
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    Most ADSL ISP allow you to run a server I just got done digging through the AUP of my ISP and there is nothing that say's otherwise.
    The thing with running a server of your own is that you just end up hurting yourself by doing it the bandwidth just doesn't warrent it. I run a small FTP myself but limit it to the size of the files that can be sent and recieved. You really don't need to have one with the other services on the web. Like driveway.com
    PPPoE Point to Point Protocol over Ethernet.
    PPPoA Point to Point Protocol over ATM.
    Both Utilizing bridged routers over a fixed ATM circuit.
    The PPPoE software runs to the Authenication server as a sort of VPN(virtual private network) where they assign you a IP then go up on the web. weather or not you go up on the web at the ISP or go up like I do at the first Cisco router.
    In other words. I go through 5 routers to get authenticated but when I go up on the web its through a single local server/router.
    The IP that I'm assigned is direct.
    I hope this helps a little more...

    ------------------
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  8. #8
    rmrucker
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    Question

    Kip- isn't it also a way to ration out IP addresses? With cable, I am always on -- so I am always utilizing an IP address.

    With PPPoE, when your not on, your not utilizing an address. So the provider can serve more people with less address numbers. I think this makes sense.

    I also read somewhere that cable will be getting PPPoE in the near future -- but I don't recall where, so who knows!

  9. #9
    rpeAMP
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    <font face="Verdana, Arial" size="2">Originally posted by rmrucker:
    Kip- isn't it also a way to ration out IP addresses? With cable, I am always on -- so I am always utilizing an IP address.

    With PPPoE, when your not on, your not utilizing an address. So the provider can serve more people with less address numbers. I think this makes sense.

    I also read somewhere that cable will be getting PPPoE in the near future -- but I don't recall where, so who knows!
    </font>
    Yeah I hear that many ADSL providers use PPPoE so that they can oversubscribe their service a bit.


  10. #10
    Kip Patterson
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    MRucker: Yes, it does cut down on the number of IP addresses required, and I've heard this comment before, but I did not include it as a reason because I could never figure out a real benefit to using fewer IP's. Granted, they are running out in IP4, but you can still get them and they cost nothing.

    Do you have an idea why it would be useful to limit them? I may be missing something there.

    rpeAMP: Please say some more about what you mean by over-subscribing as it relates to IP's.

    Thanks,

    Kip Patterson

  11. #11

    Post

    In some foreign countries, other than U.S.A., ISPs charge ADSL by the connection time. It makes sense to use PPPoe to let the users have the choice to connect or not to connect. But, in the case of ADSL in U.S.A., most ISPs are offering unlimited always-on service. It makes no sense to use PPPoe.

    The only advantage I can think of is that PPPoe gives the user the CHOICE not to connect to the internet. This is like some kind of fire-wall.

    [This message has been edited by Dennis (edited 01-10-2001).]

  12. #12
    Kip Patterson
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    From the user's prospective, PPPoE makes no sense whatsoever, agreed.

    I didn't know that they were charging by the hour overseas. Thanks for the iinfo

    Kip Patterson

  13. #13
    Regular Member Thorazine's Avatar
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    Lightbulb

    uh, ADSL "modems" are not modems (modulator/demulator).

    Cable normally uses a bridge at the end user's machine. There may be cable routers but I'm not real familar with end user cable equipment so I'm not sure if a cable router exists.

    However, I am very familar with xDSL and how it works. ADSL end user equipment is either a bridge or a router. This will depend on which provider you decide to contract with. From a end users stand point they are functionally the same.

    The reason is two fold why PPPoE is used for ADSL and most cable providers do not use PPPoE. First, it's a very nice way to see who comes and goes from very big networks. And second as Kip said, it also is a nice way to prevent users from running ftp, web sites, mail servers and stuff like that from their home.

    It's just a real nice way to keep track and audit your network.


  14. #14
    gmcd33
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    Post

    Exactly! ADSL modems are not modems, thier usually bridges, sometimes routers.

  15. #15
    rmrucker
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    Post

    OK, so now I have heard that cable modems are not modems -- they are bridges. And I have heard that ADSL modems are not modems -- they are bridges. Is it one, the other, both, or neither?

    But cable companies definitely call the device on the end of my cable a "modem" -- for whatever that is worth.

    And my cable company says my "DOCSIS" cable "modem" -- eh, bridge -- does the EXACT same thing! My DOCSIS setup is designed so I cannot run "ftp, web sites, mail servers and stuff like that."

    Believe me -- I don't have ANY answers! In fact, I am more confused now than ever!! Why did cable go one way and DSL go another?

    ~~~~~~~~~~~~~~~~

    Kip, I just remember reading that PPPoE was a way for providers to be able to extend their IP addresses so that they could serve more users with less IP addresses. It makes sense to me.

    If IP addresses are running out (in IPv4), then they become a hot commodity. If a company can better utilize what it already owns, this is a smart business move.

    I don't remember WHERE I read this -- so whose propaganda was it anyway?? I don't know, but on the surface it makes sense.

    [This message has been edited by rmrucker (edited 01-11-2001).]

  16. #16
    glc1
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    <font face="Verdana, Arial" size="2">Originally posted by rmrucker:
    OK, so now I have heard that cable modems are not modems -- they are bridges.</font>
    Correct.

    <font face="Verdana, Arial" size="2">Originally posted by rmrucker:
    And I have heard that ADSL modems are not modems -- they are bridges.</font>
    Correct. Some are routers though, usually for business connections.

    <font face="Verdana, Arial" size="2">Originally posted by rmrucker:
    But cable companies definitely call the device on the end of my cable a "modem" -- for whatever that is worth.</font>
    For marketing reasons. The general public is very familiar w/the term "modem".

    <font face="Verdana, Arial" size="2">Originally posted by rmrucker:
    Why did cable go one way and DSL go another?</font>
    Two completely different technologies.

    <font face="Verdana, Arial" size="2">Originally posted by rmrucker:
    Kip, I just remember reading that PPPoE was a way for providers to be able to extend their IP addresses so that they could serve more users with less IP addresses. It makes sense to me.</font>
    W/PPPoE, ISPs don't have to spend as much money on IPs b/c only customers who logon are assigned an IP.

    <font face="Verdana, Arial" size="2">Originally posted by rmrucker:
    If IP addresses are running out (in IPv4), then they become a hot commodity.</font>
    We have several years to go before there is a true IP shortage.

    [This message has been edited by glc1 (edited 01-11-2001).]

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