Liaison statement
LS on Improved end-to-end QoS Enhancements for MTSI

1. Overall Description:

SA4 have been studying the resource allocation at session setup and have found
that lack of bandwidth information elements and lack of end-to-end alignment
can result in different settings of QoS parameters in 3GPP networks, primarily
of the Maximum Bandwidth (MBR) and Guaranteed Bandwidth (GBR) parameters.

For MBR=GBR bearers, the b=AS bandwidth can be used to achieve sufficient
alignment between networks. However, for MBR>GBR bearers there is not always
sufficient information in the SDP that can reliably be used to determine GBR.
For speech one can sometimes use the codec information, for example the AMR and
AMR-WB mode-set parameter. For video there is only the maximum bitrate, which
is used to configure MBR, but there is no codec information that can be used to
configure GBR.

This means that local procedures often need to be used to set GBR, which can
result in over-allocation and/or under-allocation in one or several networks.

To ensure targeted service quality, SA4 have considered several possible
solutions to add more bandwidth information elements to SDP. An advantage to
adding this to SDP is that all networks in the path would have the same
information and, if used properly, this information could be achieved to reach
end-to-end alignment across networks.

The details on the problem analysis and the potential solutions are documented
in a technical report, which can be found in
http://www.3gpp.org/ftp/Specs/archive/26_series/26.924/26924-d00.zip.

SA4 are planning to continue with a specification phase based on the most
promising potential solutions. The intention is to define a new SDP attribute
in 3GPP TS 26.114, which can be used to negotiate additional bandwidth
properties. This work will be done in coordination with other relevant 3GPP
groups.

SA4 would like IETF MMUSIC to consider this work and to provide feedback on
whether MMUSIC would like to be involved in the coordination of the future work.

2. Actions:
To IETF MMUSIC group.
ACTION:         TSG-SA4 asks IETF MMUSIC to review TR 26.924 and provide
feedback (where needed). TSG-SA4 would also like to know if IETF MMUSIC would
like to be included in the coordination of the future work.

3. Date of Next TSG-SA4 Meetings:
TSG-SA4 Meeting #87     25th – 29th January 2016        Sophia Antipolis,
France. TSG-SA4 Meeting #88     18th – 22nd April 2016  TBD, US.