[AVT] Fw: some questions regarding 3GPP UP over RTP
Haining.Liu@mindspeed.com Wed, 28 September 2005 16:58 UTC
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Subject: [AVT] Fw: some questions regarding 3GPP UP over RTP
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Firstly, thanks Dr. Thomas's comments. May I get some more opinions? Best, haining ----- Forwarded by Haining Liu/USA/Mindspeed on 09/28/2005 09:53 AM ----- Haining Liu/USA/Mindspeed wrote on 09/27/2005 11:27:05 PM: > Hello, > > When we implement 3GPP UP over RTP in our products, we've fould some > confusions regarding how to stack UP and RTP together correctly. > Some of our customers have different opinions regarding these > issues. We consulted 3GPP standards, and the answers are simply not > there. Can you guys throw some opinions? Can we somehow standardize > this within IETF? I can certainly contribute on this if necessary... > > Let me first give a brief overview of the problem. > > > Iu/NbUP is a user plane protocol which is designed to convey GSM AMR > traffic or G711 traffic between base stations and the core networks. > Similar to RTP, it has sequence number, payload type indication, > though defined in a different way. Apart from attaching these > information to each encoded frame, it also has specified some other > control functionalities, such as the delivery of requests such as > error indication, time alignment and rate control. The frames > deliever this type of information are categorized as control frames. > Since IP-based infrastructure is gradually replacing the traditional > PSTN or ATM networks, different venders > and ISPs are calling for IuUP/NbUP over RTP/UDP/IP. 3GPP has two > separate standards that specify how to do this, but there are plenty > of grey zones left which are basically left for the vendors or ISPs > to interpret. > Here are some specific issues. As in past practice, UP layer is > directly stacked over RTP layer. As a result, control frames and > data frames are indeed multiplexed into a single RTP packet flow at > the sender. The how should the sequence number be generated if data > frames and control frames are interleaved together? What about time > stamp, RTP statistics, and RTCP stats? > > Some think that as long as there is only one RTP packet flow, time > stamp value and sequence number value should reference a single > space because all packets use a single SSRC value (e.g., if we have > data packets at 0ms and 20ms, and a control packet at 15ms, we have > the following event sequence: data-->control-->data). This certainly > will create some confusion at the receiver, since there might be > some sequence number gaps between neighbouring data packets. Arguing > this, others think control frames should not share the sequence > number space with data frames. But the down side of this approach is > that some RTP implementation will drop the out-of-the-sequence > packets without investigating what is actually inside the payload. > > Basically the confusion here is about how RTP layer should package > heterogenous upper layer content. How should the time stamp value > and the sequence number value be defined here? > > Any comments or pointers are welcome! > > Haining Liu > Mindspeed Technologies Inc. > Newport Beach, CA, USA
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- [AVT] some questions regarding 3GPP UP over RTP Haining.Liu
- RE: [AVT] some questions regarding 3GPP UP over R… Belling, Thomas
- [AVT] Fw: some questions regarding 3GPP UP over R… Haining.Liu