entifier of processing units at O-DU. BandSector_ID - The band and sector ID supported by O-RU. CC_ID - The carrier components ID supported by the O-RU. RU_Port_ID - The spatial streams or beams ID used by the O-RU. Sequence_ID - The message sequence ID. E_Bit - The last message indicator pertaining to the section. Subsequence_ID - The subsequence ID. Figure 4.5.10 shows the O-RAN message payload common header and section fields. We describe the two blocks separately below. Payload common header fields: dataDirection - The indicator of data direction (gNB Tx/Rx). Section Type : any 0 (msb) 7 (1sb) bytes ecpri Version ecpriReserved ecpriConcat Octet 1 enation ecpriMessage Octet 2 ecpriPayload Octet 3 ecpriRtcid / ecpriPcid Octet 5 ecpriSeqid Octet 7 Figure 4.5.8 eCPRI header table. (Source: Reproduced by permission of © O-RAN). Section Type : any o (msb) 7 (1sb) bytes RoEsubType Octet 1 RoEflowld Octet 2 RoElength Octet 3 RoEorderInfo Octet 5 Figure 4.5.9 IEEE1914.3 header table. (Source: Reproduced by permission of © O-RAN). 4.5 Lower-Layer Split Section Type 1 : DL/UL control rnsgs 0 (msb) 7 (1sb) bytes Octet 1 dataDirection payloadVersion filterindex Octet 9 frameld Octet 10 subframeld slotld Octet 11 slotld startSymbolid Octet 12 inumberOfsections Octet 13 sectionType = 1 Octet 14 sudCompHdr Octet 15 reserved Octet 16 sectionld Octet 17 sectionld symlnc startPrbc Octet 18 startPrbc Octet 19 numPrbc Octet 20 reMask[11:4] Octet 21 reMask[3:0] numSymbol Octet 22 beamId[14:8] Octet 23 beamld[7:0] Octet 24 section extensions as indicated by "ef" Octet 25 sectionld Octet N sectionld Symlnc startPrbc startPrbc numPrbc N + 3 reMask[11:4] reMask[3:0] numSymbol N + 5 beamld[14:8] N + 6 beamId[7:0] N + 7 section extensions as indicated by "ef" Octet M Figure 4.5.10 Control plane section type 1 message format. (Source: Reproduced by permission of © O-RAN). payloadVersion - The payload version field. Value = "1" (first version for payload format). filterIndex - The filter index. frameId - The frame identifier. subframeId -