8.62 Fully qualified PDN Connection Set Identifier (FQ-CSID)
29.2743GPP3GPP Evolved Packet System (EPS)Evolved General Packet Radio Service (GPRS) Tunnelling Protocol for Control plane (GTPv2-C)Release 18Stage 3TS
A fully qualified PDN Connection Set Identifier (FQ-CSID) identifies a set of PDN connections belonging to an arbitrary number of UEs on a MME, SGW, TWAN, ePDG or PGW. The FQ-CSID is used on S5, S8, S2a, S2b and S11 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 |
Type = 132 (decimal) |
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2 to 3 |
Length = n |
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4 |
Spare |
Instance |
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|
5 |
Node-ID Type |
Number of CSIDs= m |
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6 to p |
Node-ID |
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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) to (n+4) |
These octet(s) is/are present only if explicitly specified |
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Figure 8.62-1: FQ-CSID
Where Node-ID Type values are:
0 indicates that Node-ID is a global unicast IPv4 address and p = 9.
1 indicates that Node-ID is a global unicast IPv6 address and p = 21.
2 indicates that Node-ID 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, TWAN, ePDG or PGW. Other values of Node-ID Type are reserved.
Values of Number of CSID other than 1 are only employed in the Delete PDN Connection Set Request.
The node that creates the FQ-CSID, (i.e. MME for MME FQ-CSID, SGW for SGW FQ-CSID, TWAN for TWAN FQ-CSID, ePDG for ePDG FQ-CSID and PGW for PGW FQ‑CSID), is responsible for making sure the Node-ID is globally unique and the CSID value is unique within that node.
When a FQ-CSID is stored by a receiving node, it is stored on a PDN basis even for messages impacting only one bearer (i.e. Create Bearer Request). See 3GPP TS 23.007 [17] for further details on the CSID and what specific requirements are placed on the PGW, TWAN, ePDG, SGW and MME.