Multiple T-1's from different carriers

Discussion in 'Cisco' started by PaulJCohen2007@gmail.com, Jun 4, 2007.

  1. Guest

    I have a client that is in a building that has managed telephone
    services. The building has a call manager and 10 T-1's for call
    traffic. Currently, 6 T-1's are being used for outbound and 4 T-1's
    are being used for inbound traffic. The 6/4 T-1's are from different
    providers (i.e. the 6 outbound are from one company and the 4 inbound
    from another provider).

    The questions I have are as follows:

    1. Why would you want to separate inbound and outbound traffic like
    that?

    2. Can't you use either of the T-1's for both inbound and outbound
    traffic?

    3. What would happen if all of the inbound (or outbound T-1's for that
    matter) went down? Can the other T-1's take over as a failsafe? What
    is required for that?

    4. If a failure does occur how do the DID's know where to go? Aren't
    the DID's down since the T-1 is down?

    5. What can be done to insure uptime and create a failsafe so that
    phone service does not go down inbound or outbound?

    Thank you all in advance.

    Paul
    , Jun 4, 2007
    #1
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  2. Scooby Guest

    <> wrote in message
    news:...
    >I have a client that is in a building that has managed telephone
    > services. The building has a call manager and 10 T-1's for call
    > traffic. Currently, 6 T-1's are being used for outbound and 4 T-1's
    > are being used for inbound traffic. The 6/4 T-1's are from different
    > providers (i.e. the 6 outbound are from one company and the 4 inbound
    > from another provider).
    >
    > The questions I have are as follows:
    >
    > 1. Why would you want to separate inbound and outbound traffic like
    > that?
    >
    > 2. Can't you use either of the T-1's for both inbound and outbound
    > traffic?
    >
    > 3. What would happen if all of the inbound (or outbound T-1's for that
    > matter) went down? Can the other T-1's take over as a failsafe? What
    > is required for that?
    >
    > 4. If a failure does occur how do the DID's know where to go? Aren't
    > the DID's down since the T-1 is down?
    >
    > 5. What can be done to insure uptime and create a failsafe so that
    > phone service does not go down inbound or outbound?
    >
    > Thank you all in advance.
    >
    > Paul


    Paul,

    First, it appears that by saying T1, you mean PRI. Yes, a PRI is a T1, but
    there is a technical difference when comparing with a data T1, as the PRI
    will include voice services. So, given that assumption, I'll do my best to
    answer your questions. I'm used to a smaller number of PRI's and gateways
    for a location, but still have the concepts down.

    1. This would be done to keep one type of call from overwhelming the other.
    For example, you could be be overwhelmed with incoming calls (denial of
    service or some other issue) and this would prevent you from making outgoing
    calls. By separating them, you insure that each has a certain amount of
    time slots available.

    2. Potentially. This is easier if all lines are from the same carrier.
    Outgoing is fairly simple to share the extra lines, but incoming is a little
    more difficult, since the range of DID's would be different. One carrier
    would not know to reroute all calls to another carrier on failure. You
    could have them manually forward the calls for all incoming DID's, but for a
    network of this size, that would probably be a nightmare. And, then you'd
    have to have them turn off forwarding once service is restored. Also, keep
    in mind for the outgoing calls that some carriers will not allow you to send
    an outgoing Calling Number that does not match the DID's you are assigned,
    at least without a special assembly for doing so.

    3. Bummer !!!! This could happen if there is a cable cut. However, I would
    hope that if you are receiving this number of lines, that you have requested
    services from different CO's and different paths to minimize the chances of
    this. I addressed the failover in number 2.

    4. Yep, the DID's go down with the lines (group of lines from the telco, not
    any individual PRI). So, if ALL incoming PRI's are down, then the DID's are
    down. But, hopefully, with good planning, you won't lose all at any given
    time and you can make do with the minimal number. You should over provision
    to the amount that is critical to your business.

    5. Over provisioning is a start as mentioned in #4. But, also, redundancy
    as mentioned in #3. Lastly, you can actually have the PRI's come into
    completely different facilities. This way, even if there is a major cable
    cut, you probably won't lose everything.

    There are ways to build redundancy into your phone network, but they often
    come with a cost. It comes down to how critical it is to your network and
    what your budget is. It is hard to say without the bigger picture if this
    is a good design, or not. I do hope that they have a second call manager,
    though - that would be a must for this design.

    Hope that helps,

    Jim
    Scooby, Jun 4, 2007
    #2
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  3. writes:
    >I have a client that is in a building that has managed telephone
    >services. The building has a call manager and 10 T-1's for call
    >traffic. Currently, 6 T-1's are being used for outbound and 4 T-1's
    >are being used for inbound traffic. The 6/4 T-1's are from different
    >providers (i.e. the 6 outbound are from one company and the 4 inbound
    >from another provider).


    >The questions I have are as follows:


    >1. Why would you want to separate inbound and outbound traffic like
    >that?


    Could be a bunch of reasons. It could be a low-cost method of
    redundancy, if one carrier goes down, at least you have the other
    functionality, etc. Could be cost savings to be able to make outbound
    over another carrier that charges more for inbound DIDs than the first one.

    >2. Can't you use either of the T-1's for both inbound and outbound
    >traffic?


    Depends on the carrier and the type of circuits. For instance, many
    old-school ILECs on a CAS T1 doing DIDs can only do inbound calls on
    the CAS channels set asside for DIDs. They don't support outbound
    calls on the CID channels.

    >3. What would happen if all of the inbound (or outbound T-1's for that
    >matter) went down? Can the other T-1's take over as a failsafe? What
    >is required for that?


    Not really split across carriers like that. You can buy that level of
    service from a single carrier, but its going to cost money. But when
    its split across carriers, they aren't going to allow dynamic updates
    to the call-routing databases.

    >4. If a failure does occur how do the DID's know where to go? Aren't
    >the DID's down since the T-1 is down?


    Yes, unless you get some high-end call-routable services from a single
    bigger carrier. Ie. call-centers for the big companies can route their
    DIDs from one call-center to another on a schedule, or a web-page
    control of where the DIDs route.

    >5. What can be done to insure uptime and create a failsafe so that
    >phone service does not go down inbound or outbound?


    Ask your carrier what they can do, and how much it'll cost.
    Doug McIntyre, Jun 4, 2007
    #3
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