Hi,
Country "A" has a plan on implementing three things (mostly
regulatory)
a. Mandatory interconnectivity between phone companies.
b. Cheaper International calls to user.
c. Easy MNP implementation.
1. All the phone companies will be connected to Interconnection
Exchanges. These Interconnection Exchanges should offer services like
MNP, ENUM-assisted routing etc. These Interconnection Exchanges will
have to connect to International (VoIP) gateways. You might consult
the total layout at the end of this document. What can be the
interfaces between these two layers? Currently all the Phone companies
have bilateral E1 connections with each of them.
2. Most of the Phone companies are using (some have plans for
upgrading) Softswitches except for the incumbent operator. These phone
companies are either owned by big telecom players and small operators
have started operating afresh. Both have their kind of economic
reasons for deploying Softswitches. The incumbent PSTN operator has
TDM switches like some other countries.
3. As there are no Interconnection Exchanges and proper International
Gateways (VoIP) are in place in Country A, so, you can start designing
with a clean slate by putting things like softswitches, session
initiation protocol (SIP) application servers, media servers, and SIP-
capable endpoints from the International (VoIP) Gateways to
Interconnection Exchange layer! Only problem you might encounter with
integrating older incumbent PSTN's TDM exchanges.
4. As we are planning a total IP infrastructure in both International
Gateway and Interconnection Exchange layers (do not exist), we might
use SIGTRAN that will interface between our incumbent's PSTN - via a
Signaling Gateway and MGCs to connect to all IP Interconnection
Exchanges. This signaling gateway will eventually convert ISUP over
MTP to ISUP over SIGTRAN. The MGC installed here then receives ISUP
messaging; recreate the equivalent SIP for the Interconnection
Exchanges. Do these PSTNs need standalone signal transfer points
(STPs) when 3GPP IMS architecture introduces the IMS call session
control function (CSCF)?
4a. With my knowledge, the Interconnection Exchanges and International
VoIP Gateway can be connected over the Ethernet with gigabit
interface. If the incumbent operator does not upgrade their TDM based
networks, they can always be connected with Interconnection Exchanges
with TDM over IP as a temporary solution. Emulation of TDM circuits
over the IP networks can be carried out using pseudowires (PWs). TDM
over IP protocol operates over IP networks, including UDP over IPv4 or
IPv6, MPLS, L2TPv3 over IP, or pure Ethernet. But how do I track
number of calls (session handling) if those are encrypted? Should
regulator intervene not to allow encryption on principle?
5. We know that the Signaling networks are the best source of CDRs,
not the switches. All networks want to protect their part of the
revenue, what happened when incumbent sees these IP networks may incur
loss to their revenue what have been done so far without hassle with
TDM networks. The questions can be similar to these:
5a. What happens when the Phone companies are allowed to use NGN
signaling over IP to connect to Interconnection Exchanges and then to
VoIP gateways? How the revenue is protected? What if the phone
companies bypass the billing entities installed in these two layers
and connect to another VoIP gateway?
5b. Will phone companies be able to create VPN through these two
layers to connect to their choice of VoIP gateways? Using SS7 over TCP/
IP; like using M2UA and M3UA for MTP2 and MTP3 respectively, SUA for
SCCP and SCTP with TCP might allow routing to their choice of
destination.
5c. Some solution providers (mostly, revenue assurance groups) are
advocating for installing TDM interfaces between all the layers (i.e.
Phone companies, Interconnection Exchanges and International VoIP
gateways) to protect the revenue. It might incur more overhead cost
when TDM interfaces gone obsolete. How does NGN signaling provide
better visibility to what is coming into and leaving each of their
networks? What kind of OSS will track all available UDP/TCP ports to
prevent no VPN is being used?
6. For MNP, ITU defines Signaling Relay Function (SRF) - a trigger
less solution and intelligent network (IN) triggering - a triggered
solution but the later impresses me most. What about using IN
triggering when these Interconnection Exchanges will have IN
functionality? For NP, as I read; ISUP-based trigger less solution
needs to be used. Will it be possible to implement MNP without ISUP
triggering from Interconnection Exchanges? How to get ready for MNP
without installing extra solution in Interconnection Exchanges?
I know you might criticize the idea of using extra layers, but it has
its advantage too. Newer services will be added to this
Interconnection layer without hassle.
Should you need to consult the design part of it, the link follows:
http://sigtranss7.googlepages.com/diagram.jpg
Thanks in advance for the replies.
--
Raqueeb Hassan
***
Communication has always been a human need.
We believe it is also a human right. ----- ITU
