TSG-C

Title: CSNA-Lite L2 Ack issue____________________________________________________________________________________________________________________

Source:Rajeev Ranjan (Motorola) rajeev.ranjan@motorola.com

_____________________________________________________________________________________________________________________

Abstract:

This contribution Discuss CSNA-Lite L2 Ack issue ____________________________________________________________________________________________________________________

Recommendation: Discuss and Adopt

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Background

• CSNA-Lite protocol architecture “C22-20090615-035R1 Updated Tunneling Protocol for 1x CSFB for approval.pdf” was approved in concept during Jun-09 New-Port Beach meeting–CSNA-Lite tunneling protocol (between UE and IWS) supports:

Message header (Header version, Optional L2 acknowledgement, 1x Protocol Revision, and Logical Channel Indication)

–1XLAC Protocol (between UE and IWS) also supports: Optional L2 acknowledgement

1xLAC PDU

CSNA-Lite

Lower Layer

S102-A21

Lower Layer

S102-A21

Lower Layer (Other Access Technology)

1xLAC PDU

CSNA-Lite

Lower Layer (Other Access Technology)

UE MME IWS

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Issues• There is no need to use LAC L2 Ack and CSNA-Lite L2 Ack

simultaneously.• Optionality of L2-Ack in both protocols necessitates that one of them

should be turned off. This requires additional configuration between UE and IWS and leads to complex negotiations.

• LAC L2-Ack is already in use for most 1X networks, turning it off over CSNA-Lite and turning it on again over 1x Network during CSFB will lead to extra complexity.

• If few Networks choose LAC L2 Ack and other networks choose CSNA-Lite L2-Ack then this would cause interoperability issues during roaming or will lead to additional complex negotiations.

• Few companies feel that 400ms timeout for LAC L2 Ack may not be sufficient and there may be a need of CSNA-Lite L2 Ack, but this assumption may not be true because LTE air–interface is much faster than 1X air interface and Motorola experience has shown that 400ms time out will still hold good over CSNA-Lite tunnel.–Motorola’s estimate of LTE Service Request (an analogous LTE

procedure) indicates this procedure will complete well under 400 ms so Motorola believes LAC L2 Ack timer value is more than adequate

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Recommendations

–To avoid unnecessary complexity CSNA-Lite L2 Acknowledgement should permanently be turned off for 1XCSFB solution.