[OpenSIPS-Users] OpenSip SIP, SIP-I e SIP-T

[Jiri Kuthan]

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.
>