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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

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>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

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.