8.2.43 Fully qualified PDN Connection Set Identifier (FQ-CSID)
29.2443GPPInterface between the Control Plane and the User Plane nodesRelease 17TS
A fully qualified PDN Connection Set Identifier (FQ-CSID) identifies a set of PDN connections belonging to an arbitrary number of UEs on a SGW-C, PGW-C, SGW-U and PGW-U, or a set of PDU sessions belonging to an arbitrary number of UEs on a SMF or UPF. The FQ-CSID is supported on the Sxa, Sxb and N4 interfaces.
The size of CSID is two octets. The FQ-CSID is coded as follows:
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Bits |
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Octets |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
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|
1 to 2 |
Type = 65 (decimal) |
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3 to 4 |
Length = n |
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|
5 |
FQ-CSID Node-ID Type |
Number of CSIDs= m |
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6 to p |
Node-Address |
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(p+1) to (p+2) |
First PDN Connection Set Identifier (CSID) |
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(p+3) to (p+4) |
Second PDN Connection Set Identifier (CSID) |
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|
… |
… |
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q to q+1 |
m-th PDN Connection Set Identifier (CSID) |
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q+2 |
Spare |
Node Type |
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(q+3) to (n+4) |
These octet(s) is/are present only if explicitly specified |
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Figure 8.2.43-1: FQ-CSID
Where FQ-CSID Node-ID Type values are:
0 indicates that Node-Address is a global unicast IPv4 address and p = 9.
1 indicates that Node-Address is a global unicast IPv6 address and p = 21.
2 indicates that Node-Address is a 4 octets long field with a 32 bit value stored in network order, and p= 9. The coding of the field is specified below:
– Most significant 20 bits are the binary encoded value of (MCC * 1000 + MNC).
– Least significant 12 bits is a 12 bit integer assigned by an operator to an MME, SGW-C, SGW-U, PGW-C, PGW-U, ePDG, TWAN , SMF or UPF.
Other values of Node-Address Type are reserved.
Values of Number of CSID greater than 1 shall only be employed in the PFCP Session Deletion Request. The value 0 shall be used in a PFCP Session Modification Request, with the FQ-CSID Node-ID Type and Node-Address fields set to all zeros, and with the Node Type indicating one node type, to remove an FQ-CSID previously provisioned for the PFCP session for the related node type.
NOTE: The CP function can remove all the FQ-CSIDs for all node types provisioned in the UP function for a given PFCP session by sending a PFCP Session Modification Request with one FQ-CSID IE with a null length.
The node that creates the FQ-CSID (i.e. SGW-C for SGW-C FQ-CSID, PGW-C or SMF for PGW-C/SMF FQ‑CSID and PGW-U or SGW-U or UPF for PGW-U/SGW-U/UPF FQ‑CSID) needs to ensure that the Node-ID is globally unique and the CSID value is unique within that node.
The Node Type field in bits 1 to 4 of octet (q+2) shall be encoded as defined in Table 8.2.43-2. Bits 5 to 8 of octet (q+2) shall be set to zero by the sender and ignored by the receiver.
Table 8.2.43-2: Node Type
|
Node Type |
Value (Decimal) |
|
MME |
0 |
|
SGW-C |
1 |
|
PGW-C/SMF |
2 |
|
ePDG |
3 |
|
TWAN |
4 |
|
PGW-U/SGW-U/UPF |
5 |
|
Spare, for future use. |
6-15 |