8.54 RAB Context
29.2743GPP3GPP Evolved Packet System (EPS)Evolved General Packet Radio Service (GPRS) Tunnelling Protocol for Control plane (GTPv2-C)Release 18Stage 3TS
The RAB Context shall be coded as is depicted in Figure 8.54-1.
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Bits |
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Octets |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
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1 |
Type = 124 (decimal) |
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2 to 3 |
Length = 9 |
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4 |
Spare |
Instance |
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5 |
ULPSI |
DLPSI |
ULGSI |
DLGSI |
NSAPI |
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6 to 7 |
DL GTP-U Sequence Number |
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8 to 9 |
UL GTP-U Sequence Number |
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10 to 11 |
DL PDCP Sequence Number |
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12 to 13 |
UL PDCP Sequence Number |
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Figure 8.54-1: RAB Context
The RAB Context IE may be repeated within a message with exactly the same Type and Instance to represent a list.
The RAB context information element contains sequence number status for one RAB in RNC, which corresponds to one PDP context. The RAB contexts are transferred between the RNCs via the SGSNs at inter SGSN hard handover.
NSAPI identifies the PDP context and the associated RAB for which the RAB context IE is intended.
The following bits within Octet 5 shall indicate:
– Bit 8 – ULPSI (UL PDCP Sequence Number Indication): This bit shall be set to "1" if the UL PDCP Sequence Number is not received from the source RNC and the UL PDCP Sequence Number field shall be set to "0";
– Bit 7 – DLPSI (UL PDCP Sequence Number Indication): This bit shall be set to "1" if the DL PDCP Sequence Number is not received from the source RNC and the DL PDCP Sequence Number field shall be set to "0";
– Bit 6 – ULGSI (UL GTP-U Sequence Number Indication): This bit shall be set to "1" if the UL GTP-U Sequence Number is not received from the source RNC and the UL GTP-U Sequence Number field shall be set to "0";
– Bit 5 – DLGSI (DL GTP-U Sequence Number Indication): This bit shall be set to "1" if the DL GTP-U Sequence Number is not received from the source RNC and the DL GTP-U Sequence Number field shall be set to "0".DL GTP-U Sequence Number is the number for the next downlink GTP-U T-PDU to be sent to the UE.
UL GTP-U Sequence Number is the number for the next uplink GTP-U T-PDU to be tunnelled to the SGW.
DL PDCP Sequence Number is the number for the next downlink PDCP-PDU to be sent to the UE.
UL PDCP Sequence Number is the number for the next uplink PDCP-PDU to be received from the UE.