[SIPForum-discussion] Relation b/w SIP and IMS

aditya kumar adityaakumar at hotmail.com
Tue Nov 27 08:30:31 UTC 2007

Really your explanation is awesome and appreciate for sharing your valuable thoughts.

From: neill.wilkinson at quortex.comTo: adityaakumar at hotmail.com; discussion at sipforum.orgSubject: RE: [SIPForum-discussion] Relation b/w SIP and IMSDate: Sun, 25 Nov 2007 20:25:13 +0000

OK – IMS is an evolution of the softswitch model and has evolved from the UMTS standards.
The scenario you refer to below is what would occur in a Release 4/5 Network.
Let me expand – as I think you are probably aware of the stages of architecture from “standard” GSM what is now called release 2 and with GPRS added on called release 2.5 or also known as release 99. All these are the ETSI/3GPP standards releases. Beyond 2.5 we move in to release 3, then 4, then 5. Through releases 3-5 we start to decompose the normal switching functions of the of the Radio Network Controllers, MSCs, HLRs etc. into a softswitch architecture and introduce the Soft-MSC or MSC server and Media/Signalling Gateways to replace the circuit-switched core (CS Domain) and put either ATM or IP in its place.
Once release 6 of the standards is reached, we decompose this further, to fully introduce IMS. IMS is first introduced in release 5.
So to expand further on your example if you have Media Gateways and MCGP/MEGACO in the architecture then the call is originating in a release 4 network. Release 4 networks connect to the IP world via the GPRS (GGSN), and to the TDM world via the Media Gateways. The media gateways controlled by some for of Media Gateway Control Protocol. The MSCs Servers are also acting as Protocol Interworking functions to translate between SIGTRAN, MEGACO, BICC, SIP etc. This allows us to utilise the existing SS7 protocols inherent in the earlier mobile networks whilst interworking to the newer SIP protocols of the IP world.
So why do I go to such lengths to point all this out? Two things:

up to release 5 we’re dealing with an Interworking scenario where we still have some “old-world” equipment and interworking to GSM devices, and the PSTN. The idea up to Release 5 is that the core of the Mobile network can be transformed to and IP core (although ATM is still allowed and prevalent in a number of operators networks), whilst giving the external impression of still being a circuit switched core (CS Domain).
IMS relies on the whole of the environment being IP based. Signalling from the mobile device (UE in UMTS terms) is SIP, no interworking is required from SIP-to-SIP connections directly from Mobile devices to say softphones. The network is simpler and requires less interworking and translation, since MGCP/MEGACO is gone and BICC is gone. It allows connections and roaming across Network boundaries to be pure IP all the way without the need for media gateways between Networks. The Circuit Switched core (CS Domain) is gone an only the GPRS function remains in the mobile elements at release 5 onwards.
Value added services are enabled in IMS through the Application Server. The Application Servers in turn provide a secure “sandbox if you will” for 3rd Party developers to communicate to the IMS subscribers and add applications. Adding applications in this way through APIs was impossible in the “old” mobile world (up to release 5). With IMS the ability to construct and add value-added services is much easier and should enable carriers to open up their networks to 3rd parties for new and exciting applications, without having to rely on the manufacturers features.
Hope that all makes sense and is of use.
Anyone else on the discussion group want to add/correct my thoughts?
Aeonvista Ltd

From: aditya kumar [mailto:adityaakumar at hotmail.com] Sent: 23 November 2007 09:26To: neillw at quortex.com; discussion at sipforum.orgSubject: RE: [SIPForum-discussion] Relation b/w SIP and IMS
Thanks Neil..for giving a clear cut idea on IMS and SIP.Could you please share your thoughts on the following scenario:1.One Call is from mobile to IP phone.[As per my knowledge by using MGCP/MEGACO, we can successful establish the call b/w these 2 different N/Ws]Then what's the need of IMS architecture,if we need then How it plays the value added services?--Adi > From: neillw at quortex.com> Subject: Re: [SIPForum-discussion] Relation b/w SIP and IMS> To: adityaakumar at hotmail.com; discussion at sipforum.org> Date: Thu, 22 Nov 2007 16:03:30 +0000> > IMS is a whole platform/Architecture Framework. The > session control protocol (signalling protocol) is SIP with > a number of extensions.> > The IMS architecture uses the inherent features that SIP > brings and combines those with the features of Mobile > networks and adds the ability to construct external > applications through SIP Application Servers and the > PARLAY/OSA APIs.> > > Neill...;o)> On Thu, 22 Nov 2007 15:00:55 +0000> aditya kumar <adityaakumar at hotmail.com> wr> >Hi guys,> > > >1.If IMS is working on SIP protocol then what’s the > >disadvantage/doesn’t support the features by SIP, so that > >we have to go for IMS?> >2.How IMS brings a great flexibility in our near feature?> > > >Please guide me.> > > >Thanks,> >Adi> >_________________________________________________________________> >Tried the new MSN Messenger? It’s cool! Download now.> >http://messenger.msn.com/Download/Default.aspx?mkt=en-in> 

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