[rohc] Support of ROHC Piggyback Feedback in LTE

[Karthik Balaguru <[e-mail]>]

Hi,

Need clarifications on ROHC Piggyback feedback support in LTE.

LTE standrad states that PDCP Control Packet (Feedback) shall not be 
ciphered (Reference - 3GPP TS 36.323 V8.5.0, Section 5.5.4 ) and PDCP data 

packets shall be ciphered by configured algorithm (Reference - Section 
5.2.1, 5.2.2 ) . 
In case of Piggyback feedback packet, DataPacket will be attatched at the 
end of feedback packet.  (RFC 3095 - Page no 43,44 & Section 5.2.2)
1. In LTE PDCP, If the Data Packet should be ciphered for these piggyback 
packets , then how will the Peer entity generate COUNT input for ciphering 
algorithm as PDCP-SN is not available ?
2. In LTE PDCP, Can the data Packet be sent without ciphering in Piggyback 
Feedback packets ?

Further reference w.r.t RFC 3095 - Page no 44
d) To allow piggybacking, 5), it is possible to deduce the length of 
feedback information by examining the first few octets of the
    feedback.  This allows the decompressor to pass piggybacked feedback 
information to the associated same-side compressor
    without understanding its format.  The length information decouples 
the decompressor from the compressor in the sense that
    the decompressor can process the compressed header immediately without 
waiting for the compressor to hand it back after parsing
    the feedback information.

Kindly clarify regarding the support of RoHC piggyback Feedback in LTE ?

Thx in advans,
Karthik Balaguru

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