So it is -- trunking, be it sigtran, SIP-T, SIP-I is in fact one of the largest volume VoIP applications outthere. The key motivation is in fact the IP transport, even though my personal choice is SIP-T on top of it as well.
-jiri Alex Balashov wrote: > Adrian Georgescu wrote: > >> Why should SIP-T still exist? Is it cheaper than having a gateway? What >> is the practical use case for investing in such technology? >> >> I am eager to learn > > We've used it extensively in work with CLECs that operate TDM switches > such as the Metaswitch, Lucent LCS/Telica, etc. > > When a carrier operates more than one switch, SS7 interconnection > between them is generally required so, for the same basic reasons an > internal iBGP mesh or partial mesh (confederation) between two border > routers is required for IP. One switch must be aware of numbers routed > or ported into the other switch, and so on. > > The reason for its existence is that if both network elements support > SIP-T, it allows you to replace an SS7 IMT (inter-machine trunk) with an > IP-based mechanism for this interconnection. This allows you to move > the traffic over a data network and get all the benefits that this > brings; economies of scale through decreased facilities, > oversubscription, etc. The main benefit is the elimination of TDM trunk > exhaust; SS7 IMTs are physically bundles (trunk groups/TCICs) of DS0s, > usually consisting of one or more T1s, and sometimes DS3s or more. That > means that when a large volume of calls is running between the two > switches, you could burn up all your SS7 trunks. Running the calls as > SIP-T allows you to use something like a gigabit network core to make > that problem go away somewhat -- a key benefit of VoIP in most other > scenarios with which you are familiar with. > > At the same time, the switches still need ISUP attributes carried in SS7 > IAMs and ACMs for billing, because that's just the information they > operate on internally. SIP-T provides an IP-based way to encapsulate > that information. > > SIGTRAN (essentially, SS7-over-IP) is another way to do this. However, > SIP-T is lightweight and easier to deploy. It also allows you to use > existing SIP network elements (proxies, session border controllers, > etc.) to route and manage the traffic. For example, if you were using > OpenSIPS + ACC + FreeRADIUS as a CDR catcher, you could run the "SS7" > calls between two switches and log the appropriate information as custom > attributes. There are no good open-source implementations for SIGTRAN - > nothing as turn-key as Kamailio or OpenSIPS. SIP is high-level and much > easier to deal with and manipulate using a far wider range of tools. > > SIP-T is also becoming an attractive external interconnect option. > _______________________________________________ Users mailing list [email protected] http://lists.opensips.org/cgi-bin/mailman/listinfo/users
