Routers/back to back/V.35/Bandwidth

Discussion in 'Cisco' started by Baruah, Mar 3, 2006.

  1. Baruah

    Baruah Guest

    Hi,
    I would like have some advice regarding connecting 2 routers back
    to back using V.35 interface. How much bandwidth I can attain in this
    manner ? Is it possible to get beyond 2Mbps !! and is it ok if I use
    this configuration in a production environment ?

    Can someone please give a few pointers regarding the
    issue ?

    Thanks in advance.

    BB
    Baruah, Mar 3, 2006
    #1
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  2. Baruah

    Guest

    , Mar 3, 2006
    #2
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  3. Baruah

    Charlie Root Guest

    <> wrote in message
    news:...
    > It looks like you can go up to 4 Mbps with V.35 though that is more
    > than the recommended maximum.
    >
    > Take a look at
    >
    > http://www.cisco.com/univercd/cc/td/doc/product/core/cis7000/7000_him/7000prep.htm#xtocid2904339
    >


    According to this page recommended maximum is only 48Kbps, which is really
    low. I suspect this is an old document (for Cisco 7000 platform). I've been
    using V.35 interfaces for 2Mbps connections routinely for past 10 years
    without problems. Also the newer documents do mention speeds that are much
    higher than those humble few Kbps:

    http://www.cisco.com/en/US/customer...s274/products_tech_note09186a00800b0858.shtml

    So back to original question - one can get up to 8Mbps over V.35 connection,
    but it depends on the hardware configuration.

    Kind regards,
    iLya
    Charlie Root, Mar 3, 2006
    #3
  4. Baruah

    Guest

    Charlie Root wrote:
    > According to this page recommended maximum is only 48Kbps, which is really
    > low. I suspect this is an old document (for Cisco 7000 platform). I've been
    > using V.35 interfaces for 2Mbps connections routinely for past 10 years
    > without problems. Also the newer documents do mention speeds that are much
    > higher than those humble few Kbps:


    I suspect that the recommendation they speak of is not Cisco's, but
    the CCITT's. The V.35 spec actually calls out only one speed of use:
    48K. But as you say, well beyond that is no problem (and very
    common) for V.35. In general, for differential signals like V.35 and
    RS-422, the shorter the distance and lower capacitance of the cable,
    the faster you can go.

    So the OP won't run into an electrical limitation. That leaves the
    question of what the serial port can handle, which is also not
    likely to be a issue.

    Steve

    ------------------------------------------------------------------------
    Steve Schefter phone: +1 705 725 9999 x26
    The Software Group Limited fax: +1 705 725 9666
    642 Welham Road,
    Barrie, Ontario CANADA L4N 9A1 Web: www.wanware.com
    , Mar 3, 2006
    #4
  5. Baruah

    Baruah Guest

    Thank you all for you comments. So, in summary we can use back to back
    configuration and depanding upon the distance and lower capacitance of
    the cable, and the hardware capability of the routers. I guess its not
    of a issue if one of the router is of NOT cisco make.

    -BB
    Baruah, Mar 3, 2006
    #5
  6. Baruah

    Peter Guest

    Hi Steve,

    > Charlie Root wrote:
    > > According to this page recommended maximum is only 48Kbps, which is really
    > > low. I suspect this is an old document (for Cisco 7000 platform). I've been
    > > using V.35 interfaces for 2Mbps connections routinely for past 10 years
    > > without problems. Also the newer documents do mention speeds that are much
    > > higher than those humble few Kbps:

    >
    > I suspect that the recommendation they speak of is not Cisco's, but
    > the CCITT's. The V.35 spec actually calls out only one speed of use:
    > 48K. But as you say, well beyond that is no problem (and very
    > common) for V.35. In general, for differential signals like V.35 and
    > RS-422, the shorter the distance and lower capacitance of the cable,
    > the faster you can go.
    >
    > So the OP won't run into an electrical limitation. That leaves the
    > question of what the serial port can handle, which is also not
    > likely to be a issue.


    This brings up memories of 2 unrelated (but similar) situations that I
    ran into with V.35 in 1996. We had been using V.35 at 2Mb for many
    years, and in one situation we ran into an issue with a new V.35
    connection between an IBM 3746 and Cisc 4700 Router (the 4700 was
    providing clocking) . If I remember correctly, the Cisco 4700 Docs of
    the time suggested that ~35ft was the maximum distance recommended,
    whereas the IBM Docs suggested that 50ft was fine (using IBM cable of
    course). We tried several local "tricks" to get this working over 45ft
    of cable but had regular errors (at a fairly low rate) at the 4700
    end. Eventually we were able to shorten the cable to about 36ft and it
    all ran clean.

    However this got us interested because we had never seen any issues
    with 2Mb at 50ft, and theoretically, you probably could run 100Mb over
    V.35, provided the cable length was short enough. Our research turned
    up a little known fact that the particular model of serial port card
    (I cannot remember what exact 4700 Serial card it was, except it had 6
    ports on it) we were using in the 4700 had a "known cable length
    limitation", and that testing with a different Serial card the 4700
    worked fine at 2Mb over 50ft.

    So there are the published specs and each manufacturers implementation
    of those specs.........;-)

    Cheers.................pk.


    --
    Peter from Auckland.
    Peter, Mar 3, 2006
    #6
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