Generalities about X.25

Discussion in 'Cisco' started by Angelot, Nov 2, 2003.

  1. Angelot

    Angelot Guest

    Bonjour,

    Is it possible to carry X.25 to the PSTN on a twisted pair ?
    In this case is it the X.21 protocol that is used ? I have some trouble to
    represent the physical layer.

    Thanks for the reply.
    Michel
    Angelot, Nov 2, 2003
    #1
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  2. Angelot

    Scooby Guest

    X.25 has nothing to do with the physical layer. Just like Frame-Relay,
    HDLC, PPP don't either. You can run them over a standard T1. So, the
    answer is yes, you can have it over a copper pair - don't think they are
    twisted though. The real question is who would want to anymore?

    Oh yea....

    __________
    / \
    ! Here lies... !
    ! !
    ! X.25 !
    ! !
    ------------------
    ! R I P !
    ------------------


    "Angelot" <> wrote in message
    news:bo1jn2$2pj$...
    > Bonjour,
    >
    > Is it possible to carry X.25 to the PSTN on a twisted pair ?
    > In this case is it the X.21 protocol that is used ? I have some trouble to
    > represent the physical layer.
    >
    > Thanks for the reply.
    > Michel
    >
    >
    Scooby, Nov 2, 2003
    #2
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  3. Angelot

    Steinar Haug Guest

    ["Scooby"]

    | X.25 has nothing to do with the physical layer. Just like Frame-Relay,
    | HDLC, PPP don't either. You can run them over a standard T1. So, the
    | answer is yes, you can have it over a copper pair - don't think they are
    | twisted though. The real question is who would want to anymore?

    X.25 is still used out there. Not in huge amounts, but it's used. As an
    example, in Norway there is a fair number of ATMs (no, that's *not*
    Asynchronous Transfer Mode this time) connected to the bank with X.25.

    Steinar Haug, Nethelp consulting,
    Steinar Haug, Nov 2, 2003
    #3
  4. Bonjour,

    Thanks Scooby and Steinar.

    (1) So, Scooby, if we have X.25 over a standard T1 or E1, we have the
    protocol stack like this :

    X.25 layer 3 > LapB > fractional T1 or E1.

    Is it correct for you ?


    (2) Do you know Steinar the standard for having X.25 over ATM ? I think it's
    not RFC1483 that describes multiprotocol encaspsulation over AAL5. This RFC
    is for routed and bridged protocoles, and not packet switching.


    (3) If the view (1) is correct, we can have probably an IP router connect to
    a PAD with that stack :

    IP > encapsulation X.25 layer 3 (RFC1386) > LapB > fractionnal T1 or E1.

    What's your advice ? Thanks

    Angelot
    Michel.Hostettler, Nov 2, 2003
    #4
  5. Angelot

    Scooby Guest

    1) Right on

    2) Don't know. I'm not an ATM guy and it has been years since I've touched
    X.25. Honestly, ATM is built for speed with latency in mind and is
    expensive, X.25 is not fast by any stretch of the imagination. With X.25,
    throughput is not the major concern, but latency is. So, to run X.25 on ATM
    would be a huge mistake if you ask me.

    3) Yes. Time was that you'd hook your router to the PAD with a serial v.35
    cable (or similar). It looks like most PAD's you buy now will have a built
    in bridge/router and 10BT connection - if it is for what I think it would
    be. If not, you can still hook your router up with a v.35 cable.

    My advice? Get Frame Relay ;-P Okay, my advice if you want to use x.25? A
    quick search on Cisco finds that they have LAPB support for x.25. My guess
    is that you can just get a router with internal T1 CSU/DSU (or what ever
    connection type you like) and configure x.25 on it. That is how it works
    now for Frame-Relay so, that makes sense. As far as ATM, I would guess that
    your ATM card would allow the x.25 protocol, but you'd have to have the
    service provider running it.

    http://www.cisco.com/en/US/products/sw/iosswrel/ps1818/products_configuratio
    n_guide_chapter09186a0080087858.html



    "Michel.Hostettler" <> wrote in message
    news:bo2lvj$5qj$...
    > Bonjour,
    >
    > Thanks Scooby and Steinar.
    >
    > (1) So, Scooby, if we have X.25 over a standard T1 or E1, we have the
    > protocol stack like this :
    >
    > X.25 layer 3 > LapB > fractional T1 or E1.
    >
    > Is it correct for you ?
    >
    >
    > (2) Do you know Steinar the standard for having X.25 over ATM ? I think

    it's
    > not RFC1483 that describes multiprotocol encaspsulation over AAL5. This

    RFC
    > is for routed and bridged protocoles, and not packet switching.
    >
    >
    > (3) If the view (1) is correct, we can have probably an IP router connect

    to
    > a PAD with that stack :
    >
    > IP > encapsulation X.25 layer 3 (RFC1386) > LapB > fractionnal T1 or E1.
    >
    > What's your advice ? Thanks
    >
    > Angelot
    >
    >
    Scooby, Nov 2, 2003
    #5
  6. Angelot

    Angelot Guest

    Angelot, Nov 2, 2003
    #6
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