AS5200 Fractional calls & IP transit on T1/PRI port

Discussion in 'Cisco' started by Jeff, Nov 22, 2004.

  1. Jeff

    Jeff Guest

    In short, my question: Can a T1/PRI port on a Cisco AS5200 be
    configured to accept inbound calls on several of the channels and use
    the rest of a fractionalized T1 circuit for an IP interface?


    In long, the explanation of why I would ask:

    I have a modem pool co-located at a CLEC's facility and setup to bring
    calls in from all over the state to a common huntgroup. We are trying
    to add local numbers for some rural exchanges that are served by a
    different ILEC. The CLEC has obtained an agreement from the ILEC in
    question to permit calls to come into their switch which is located in
    the same building as my modem rack. However, the ILEC is being a pain
    in the neck about this and insists that the calls must terminate to
    equipment physically located within the boundaries of any one of their
    own exchanges, or else they will bill the CLEC by the minute for
    having received the calls over the CLEC's own facilities.

    The proposed "solution" is to establish a point to point T1 circuit
    between the building that houses my modem rack and the CLEC's phone
    switch, and some office space owned by a friend of mine that happens
    to be located in one of the exchanges that are served by this ILEC.
    Calls from all over the state will come into the CLEC's switch. If the
    call comes from the other ILECs then they will terminate it to an
    inexpensive PRI circuit in the same building on my rack in the other
    room. If the the call comes in from this headache of an ILEC, then the
    CLEC will push it back out over this point to point T1 circuit and
    terminate it at this friend's office space 80 miles away. A call from
    across the street would take a 160 mile round trip at 0 cents per
    minute, verses an 80 mile one-way trip at several cents a minute. The
    only logic I can find in this is to rip me off on the local loop
    charges for another unnecessary T1 circuit or two.

    Unfortunately I currently do not have anything in the building that we
    intend to terminate these calls to. No bandwidth, no equipment, no
    nothing. I intend to build a wireless network to bring bandwidth to
    the building from a neighboring community. However, this will take a
    couple of repeater sites that I do not have arangements for yet. In
    the meantime the suggestion would be to install another T1 circuit
    through this rip-off of a local phone company just to get IP bandwidth
    to feed my access server after the calls are answered. I don't want to
    give another dime to this company than I have to, so I'd really like
    to avoid getting a second T1 from them when the first one is obviously
    pointless as it is.

    I think my usage will be relatively low at least for the first few
    months while I'm still building this wireless network. I am wandering
    if in the meantime I could get by with fractionalizing the T1 that
    runs between the CLEC's building and the office space in this ILEC's
    stupid exchange, and using the same T1 both for incomming calls and
    for upstream bandwidth.

    I'd like to do this on a budget. Since I originally had expected to be
    able to terminate all these calls on my existing rack, I hadn't
    planned for a major equipment expense or this rediculus 'point to
    pointless' T1 circuit. I have some Cisco AS5200's laying around, and
    am thinking about using them for this project at least until there
    gets to be some reasonable amount of usage in the area. I have never
    tried to configure an AS5200 for a fractional T1 line before. Is it
    possible to have the AS5200 answer incomming calls on half of the
    channels and use the other half of the T1 for an IP interface? I have
    always used the serial ports for IP transit, and have never tried to
    use the T1/PRI ports for anything but answering calls before.

    Thanks in advance for your help.
     
    Jeff, Nov 22, 2004
    #1
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  2. On 21 Nov 2004 22:29:51 -0800, (Jeff) wrote:

    ~ In short, my question: Can a T1/PRI port on a Cisco AS5200 be
    ~ configured to accept inbound calls on several of the channels and use
    ~ the rest of a fractionalized T1 circuit for an IP interface?

    In short, yes.

    ~ In long, the explanation of why I would ask:

    In long, I have to admit that I didn't entirely follow your tale of
    woe ... but let's just assume that you have an AS5200 somewhere with
    one T1 coming into it - and that you want to use 12*64=768k of that
    T1 as a "leased line" to provide Internet backhaul and the other
    12*64 of that to provide dialin modem access. So, yes, you can do
    this.

    Let's assume that you want to use the low 12 DS0s for the backhaul
    (which is your only option if you want to do ISDN for the dialin,
    since we only support a T1 D channel in the last timeslot),
    so configure this:

    controller t1 0
    framing b8zs
    linecode esf
    channel-group 0 timeslots 1-12 speed 64

    This will give you an interface Serial0:0 corresponding
    to your 768k frac T1 pipe.

    For the dialin modem lines ... if you want to do ISDN, then:

    controller t1 0
    pri-group timeslots 13-24

    This gives you an ISDN D channel interface on
    Serial0:23 to handle incoming calls on
    Serial0:12 .. Serial0:22 (note that we number
    serial interfaces starting at 0 but timeslots
    starting at 1 just to keep everyone confused.)

    Note that an 11B+D PRI is rather unusual and
    your CLEC's switch may not support it ... so
    a more typical way to get calls into the top
    12 timeslots would be CAS, ideally what we call
    "e&m-fgb" and what they probably call "e&m wink start":

    controller t1 0
    ds0-group 1 timeslots 13-24 type e&m-fgb

    Good luck,

    Aaron

    ---

    ~ I have a modem pool co-located at a CLEC's facility and setup to bring
    ~ calls in from all over the state to a common huntgroup. We are trying
    ~ to add local numbers for some rural exchanges that are served by a
    ~ different ILEC. The CLEC has obtained an agreement from the ILEC in
    ~ question to permit calls to come into their switch which is located in
    ~ the same building as my modem rack. However, the ILEC is being a pain
    ~ in the neck about this and insists that the calls must terminate to
    ~ equipment physically located within the boundaries of any one of their
    ~ own exchanges, or else they will bill the CLEC by the minute for
    ~ having received the calls over the CLEC's own facilities.
    ~
    ~ The proposed "solution" is to establish a point to point T1 circuit
    ~ between the building that houses my modem rack and the CLEC's phone
    ~ switch, and some office space owned by a friend of mine that happens
    ~ to be located in one of the exchanges that are served by this ILEC.
    ~ Calls from all over the state will come into the CLEC's switch. If the
    ~ call comes from the other ILECs then they will terminate it to an
    ~ inexpensive PRI circuit in the same building on my rack in the other
    ~ room. If the the call comes in from this headache of an ILEC, then the
    ~ CLEC will push it back out over this point to point T1 circuit and
    ~ terminate it at this friend's office space 80 miles away. A call from
    ~ across the street would take a 160 mile round trip at 0 cents per
    ~ minute, verses an 80 mile one-way trip at several cents a minute. The
    ~ only logic I can find in this is to rip me off on the local loop
    ~ charges for another unnecessary T1 circuit or two.
    ~
    ~ Unfortunately I currently do not have anything in the building that we
    ~ intend to terminate these calls to. No bandwidth, no equipment, no
    ~ nothing. I intend to build a wireless network to bring bandwidth to
    ~ the building from a neighboring community. However, this will take a
    ~ couple of repeater sites that I do not have arangements for yet. In
    ~ the meantime the suggestion would be to install another T1 circuit
    ~ through this rip-off of a local phone company just to get IP bandwidth
    ~ to feed my access server after the calls are answered. I don't want to
    ~ give another dime to this company than I have to, so I'd really like
    ~ to avoid getting a second T1 from them when the first one is obviously
    ~ pointless as it is.
    ~
    ~ I think my usage will be relatively low at least for the first few
    ~ months while I'm still building this wireless network. I am wandering
    ~ if in the meantime I could get by with fractionalizing the T1 that
    ~ runs between the CLEC's building and the office space in this ILEC's
    ~ stupid exchange, and using the same T1 both for incomming calls and
    ~ for upstream bandwidth.
    ~
    ~ I'd like to do this on a budget. Since I originally had expected to be
    ~ able to terminate all these calls on my existing rack, I hadn't
    ~ planned for a major equipment expense or this rediculus 'point to
    ~ pointless' T1 circuit. I have some Cisco AS5200's laying around, and
    ~ am thinking about using them for this project at least until there
    ~ gets to be some reasonable amount of usage in the area. I have never
    ~ tried to configure an AS5200 for a fractional T1 line before. Is it
    ~ possible to have the AS5200 answer incomming calls on half of the
    ~ channels and use the other half of the T1 for an IP interface? I have
    ~ always used the serial ports for IP transit, and have never tried to
    ~ use the T1/PRI ports for anything but answering calls before.
    ~
    ~ Thanks in advance for your help.
     
    Aaron Leonard, Nov 22, 2004
    #2
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  3. Jeff

    Jeff Guest

    "Aaron Leonard" <> wrote in message news:...
    > On 21 Nov 2004 22:29:51 -0800, (Jeff) wrote:
    >
    > ~ In short, my question: Can a T1/PRI port on a Cisco AS5200 be
    > ~ configured to accept inbound calls on several of the channels and use
    > ~ the rest of a fractionalized T1 circuit for an IP interface?
    >
    > In short, yes.
    >
    > ~ In long, the explanation of why I would ask:
    >
    > In long, I have to admit that I didn't entirely follow your tale of
    > woe ...

    {snip}


    Aaron, thank you so much for your response! I really appreciate it.
    You have given me the information I need much more quickly than I
    would have been able to look it up, since I haven't used these 5200's
    in a while and I've just been too busy lately to tinker around with
    all of this stuff.

    As for not being able to follow my telco fiasco, believe me you are
    not the only one! What it all comes down to is that certain phone
    companies charge each other by the minute for some sort of recpricical
    compensation fee for completing each other's calls. As long as the
    balance of inbound verses outbound traffic between the CLEC and the
    ILEC is about equal (as would be expected for conventional voice
    traffic), then there wouldn't be any significant access charges. But
    because I'd only be taking inbound calls this would create an
    imbalance of traffic resulting in the CLEC having to pay the
    compensation fees to the ILEC for each minute I use. That of course
    would only increase as my usage increases and I add more circuits and
    equipment.

    What just gets me is that the ILEC charges the CLEC for calls bound
    for the CLEC, only to have the CLEC turn around and bill the ILEC the
    very same fee in reverse for the very same calls going back to the
    ILEC's network to terminate on one of their T1 loops. Simply because
    the two legs of the call are in opposite directions they can cancel
    out these rediculus compensation charges, despite the fact that every
    call would be using two channels on their trunk lines instead of one.
    Of course, if the stupid ILEC would just give me a reasonable price
    quote for what I want in the first place I wouldn't have had to deal
    with the CLEC at all and we could have just all of this locally
    without the calls routing to some place 80 miles away and back. But,
    they created this mess and not suprisingly I get to pay for it.
    Sheesh!


    Anyway, thanks again for your help.

    -Jeff
     
    Jeff, Nov 23, 2004
    #3
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