Architecture
The following illustration provides an overview of Next hop forwarding feature.

You can configure Next hop IP address at the SMF under DNN profile or IPAM profile. During PDU Establishment, the SMF relays the IPv4/IPv6 address over the N4 interface in the NEXT HOP IP private IE in a PFCP Session Establishment Request.
You can also configure the Next hop IP address at the UPF through Charging-Action.
Note | When Next hop address is provided by both SMF and UPF Charging-Action, the UPF Charging-Action Nexthop address takes precedence. |
Configuration Priority
S. No. |
Configuration |
Priority |
---|---|---|
1. |
UPF (Charging Action) |
1 |
2. |
DNN profile |
2 |
3. |
IP Pool |
3 |
Configuration Use Cases
Case |
IP Type |
DNN |
IP Pool |
UPF (Charging Action) |
Nexthop IP Selection |
---|---|---|---|---|---|
Next hop supplied only in DNN |
IPv4 |
209.165.201.18 |
Not configured |
Not configured |
Next hop Address is selected from DNN: IPv4: 209.165.201.18 IPv6: 8001::10 |
IPv6 |
8001::10 |
Not configured |
|||
Next hop supplied only in IP pool |
IPv4 |
Not configured |
209.165.201.19 |
Not configured |
Next hop Address is selected from IP Pool: IPv4: 209.165.201.19 IPv6: 8001::10 |
IPv6 |
Not configured |
8001::10 |
|||
IPv4 and IPv6 configured in DNN and IP pool |
IPv4 |
209.165.201.18 |
209.165.201.19 |
Not configured |
Next hop Address is selected from DNN: IPv4: 209.165.201.18 IPv6: 9001::3 |
IPv6 |
9001::3 |
8001::10 |
|||
IPv6 configured in DNN and IPv4 in IP pool |
IPv4 |
Not configured |
209.165.201.19 |
Not configured |
Next hop IPv4 is selected from IP pool: 209.165.201.19 Next hop IPv6 selected from DNN : 8001::10 |
IPv6 |
8001::10 |
Not configured |
|||
IPv6 configured in DNN, IPv4 in IP pool, and IPv4 in UPF Charging Action |
IPv4 |
209.165.201.18 |
209.165.201.19 |
209.165.201.20 |
Next hop Address is selected from UPF (CA): 209.165.201.20 |
IPv6 |
8001::10 |
Not configured |
Not configured |
||
IPv6 configured in DNN, IPv4 in IP pool, and IPv6 in UPF Charging Action |
IPv4 |
209.165.201.18 |
209.165.201.19 |
Not configured |
Next hop Address is selected from UPF(CA) : 9001::10 |
IPv6 |
8001::10 |
Not configured |
9001::10 |
Interface
The following Private IEs are introduced in Sx/N4 Session Establishment message.
2 3 8 |
PFCP _IE_ NEXT HOP |
||||||||||
PFCP_IE_NEXTHOP |
Sx/N4 Session Establish ment Request |
Private IE: UPF: nexthop forward ing support- IPv4 /IPv6 address |
|||||||||
BITS |
|||||||||||
Octets |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
||||
1 to 2 |
Type = 238 (decimal) |
||||||||||
3 to 4 |
Length = n |
||||||||||
5 to 10 |
PFCP_IE_NEXTHOP_ID |
||||||||||
11-14 |
PFCP_IE_NEXTHOP_IP |
||||||||||
2 3 9 |
PFCP _IE_ NEXTHOP _ID |
PFCP_IE_NEXTHOP_ID |
1. Inside Create FAR IE of Sx Session Establish ment Request |
Private IE : UPF: nexthop forward ing support- IPv4 /IPv6 address |
|||||||
BITS |
2. Inside PFCP _IE_ NEXTHOP IE of Sx/N4 Session Establish ment Request |
||||||||||
Octets |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
PFCP _IE_ NEXTHOP of Sx/N4 Session Establish ment Request |
|||
1 to 2 |
Type = 239 (decimal) |
||||||||||
3 to 4 |
Length = 5 |
||||||||||
5 to 10 |
|||||||||||
2 4 0 |
PFCP_IE_ NEXTHOP _IP |
PFCP_IE_NEXTHOP_IP |
||||||||||
Bits |
PFCP_IE_ NEXTHOP of Sx/N4 Session Establish ment Request |
Private IE : UPF: nexthop forwarding support- IPv4/ IPv6 address |
||||||||||
Octets |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
|||||
1 to 2 |
Type = 240 (decimal) |
|||||||||||
3 to 4 |
Length = n |
|||||||||||
5 |
spare |
V4 |
V6 |
|||||||||
m to m+3 |
IPv4 Address |
|||||||||||
p to p+15 |
IPv6 Address |
The following is a sample output of SX_SESSION_ESTABLISHMENT_REQUEST in which the SMF relays the Next hop IP to the UPF.
CREATE FAR:
Type: 3
Value:
FAR ID:
Type: 108
Value: 0x80000002
APPLY ACTION:
Type: 44
Value:
DROP: 0
FORW: 1
BUFF: 0
NOCP: 0
DUPL: 0
FORWARDING PARAMETERS:
Type: 4
Value:
DESTINATION INTERFACE:
Type: 42
Value: CORE (1)
PDN INSTANCE:
Type: 22
Value: intershat
INNER PACKET MARKING:
Type: 220
TOS/TRAFFIC CLASS: 0xB8 0xFC
NextHop ID:
Value: 0x0001
CREATE TRAFFIC ENDPOINT:
Type: 127 Length: 20
Value:
Traffic Endpoint ID:
Type: 131 Length: 1
Value: 0x0004
Hex: 0083 0001 04
Local F-TEID:
Type: 21 Length: 1
Value:
CH: 1
IPv4: 0
IPv6: 0
CHID: 0
Hex: 0015 0001 04
Bearer Info:
Type: 225 Length: 6
QCI: 5
ARP: 84
Charging ID: 5592407
Hex: 00E1 0006 0554 0055 5557
Hex: 007F 0014 0083 0001 0400 1500 0104 00E1
0006 0554 0055 5557
NEXT HOP IP:
Type: 237 Length: 14
Value:
NextHop ID:
Type: 238 Length: 1
Value: 0x0001
Hex: 00EE 0001 01
IP ADDR:
Type: 239 Length: 5
Value:
IPv4: 1
IPv6: 0
IPv4: 209.165.202.150
IPv6:
Hex: 00EF 0005 020F 0F0F 0F
Hex: 00ED 000E 00EE 0001 0100 EF00 0502 0F0F
0F0F