...but how about mobility? The SGSN isn't an anchor point. It may change at any moment, when the mobile does an SGSN handover to another Routing Area. The new SGSN doesn't have a clue about what mcast groups the mobile has joined somewhere else.
The old SGSN might inform the new one about the groups, but that is architecturally messy. So far GPRS is pretty agnostic about what protocol the mobile uses - IPv4, IPv6, X.25(!), or even PPP. Integrating IPv6 mcast functions would violate the idea. It would also mean that the SGSN has an IP interface that the mobile can see. That violates the stratified model. The feature would still need to be standardised as an extra parameter in GTP-C. Not all SGSNs in a network come from the same vendor. 3GPP does have an unwritten prohibition: disallow non-standard features that would lock an operator to a single vendor. -- Lassi > -----Original Message----- > From: ext Dr. Subrata Goswami [mailto:[EMAIL PROTECTED]] > Sent: Tuesday, May 28, 2002 8:19 PM > To: [EMAIL PROTECTED] > Subject: RE: MLD comments on cellular host drafts - seeking feedback > > > Hesham, SGSN "sees" the mobile's traffic - as it passes through it. > SGSN being an L2 device for IP, it is capable of doing L2 > switching (if > the 3gpp spec does not prohibit and the vendor innovates). The > following is the protocol stack for the SGSN (user plane, from the TS > 23.060 you referred, btw the 3GPP web-site needs better navigation). > > ------------- --------------- > |SNDCP GTP-U| |GTP-U GTP-U | > |LLC UDP | |UDP/IP UDP/IP| > |BSSGP IP | |AAL5 L2 | > |FR L2 | |ATM L1 | > |L1 L1 | --------------- > ------------ > GPRS-SGSN UMTS-SGSN > > From the above, it is possible to make GPRS-SGSN to mcast as it > detunnels the IP packets. > > In case of UMTS, the same functionality can be in the UTRAN. > > Subrata > > > -----Original Message----- > From: Hesham Soliman (ERA) [mailto:[EMAIL PROTECTED]] > Sent: Tuesday, May 28, 2002 4:44 AM > To: 'Dr. Subrata Goswami'; [EMAIL PROTECTED]; > [EMAIL PROTECTED] > Subject: RE: MLD comments on cellular host drafts - seeking feedback > > > > Sorry, that isn't the correct model. > > > > Then it is the correct model, if you read my email it was > > mentioned that > > SGSN is an L2 device. Also as one SGSN supports multiple > > mobiles - it needs > > to know somehow which mobiles are part of an mcast group > > and that can be > > done by MLD. > > => No. The model is not correct as we tried to > explain. The SGSN does not 'see' the mobile's > traffic and does not do any 'L2 switching'. > So your conclusion is not correct. > > For more information, please refer to 3GPP > specs: TS 23.060 (any revision will explain > this issue clearly). > > Hesham > > > > -------------------------------------------------------------------- > IETF IPng Working Group Mailing List > IPng Home Page: http://playground.sun.com/ipng > FTP archive: ftp://playground.sun.com/pub/ipng > Direct all administrative requests to [EMAIL PROTECTED] > -------------------------------------------------------------------- > -------------------------------------------------------------------- IETF IPng Working Group Mailing List IPng Home Page: http://playground.sun.com/ipng FTP archive: ftp://playground.sun.com/pub/ipng Direct all administrative requests to [EMAIL PROTECTED] --------------------------------------------------------------------
