[SIPForum-discussion] Basic SIP Questions

[Fortunato Lacson]

Thanks Vivek and all those who replied earlier. In the new network design,
we are going to give-up the ISDN-PRI trunks which comes to us in a DS3. The
nice thing about this is that when a circuit is down, it goes red. When a
DID from the Telco is down (switch issue), you see a circuit without any
call.

Moving to SIP trunks, we will lose the TDM circuits. We will get one or two
GigEthernet Public Internet connection. We will have our own MSX. Our Telco
vendors will route calls to our DIDs via SIP to us. Since all these DIDs
will be coming in to us in one big pipe, it will be harder to monitor which
is working and which doesn't, unless somebody complains. One option, like
suggested, is have an auto-dialer constantly testing the DIDs.

For those who have implemented something like this already. I was wondering
what kind of security is implemented to secure the SIP and RTP packets from
the Telco SIP trunk provider to your edge router.

Have a great night.

Fortunato Lacson



On Sun, Aug 24, 2008 at 8:55 AM, Vivek Batra <vivek7683 at gmail.com> wrote:

> Fortunato,
> Comments Inline in RED.
>
> --Vivek Batra
>
> On Sun, Aug 17, 2008 at 9:58 PM, Fortunato Lacson <junlacson at gmail.com>wrote:
>
>>
>> Good day all. Like I mentioned before, I am very new in embracing SIP. My
>> concern is the network portion of the project to ensure our bandwidth will
>> be able to accommodate all the expected calls. I am doing rough calculations
>> myself.
>>
>> My first question is so basic but I couldn't seem to find a straight
>> answer to solidify what I understand from what I read. For a point to point
>> SIP call to a SIP PABX, an RTP + RTCP session is established. This is
>> calculated @ g.711 around 84Kbps on the WAN link. This RTP + RTCP session is
>> only one way, and that another one will be established in the reverse
>> direction. This means 2 X 84Kbps bandwidth out of my WAN link? So my 1 GigE
>> WAN link can roughly accommodate (not considering other factors like
>> tunneling, IPSec, etc); 1 Gig / (2 X84 Kbps) = simultaneous calls?
>>
>
> This is precisely true. However, you can increase the number of calls by
> using codec's viz G.729 etc.
>
>>
>>
>> Second question is, how can I monitor my SIP network in real time,
>> specifically my DIDs, to ensure that they are not down on the Telco vendor
>> end? Our business relies heavily on hundreds of DIDs, and in my current TDM
>> setup, when a PRI is down I see it instantly.
>>
>
> How do you currently monitor the ISDN when it is down in your ISDN PBX?
> How are you planning to interface SIP with ISDN? I mean, which gateway??
>
>>
>>
>> Regards to all.
>>
>>
>> Fortunato
>>
>>
>>
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