Architecture

The following illustration provides an overview of Nexthop Forwarding feature.

Nexthop Forwarding

You can configure Nexthop 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 Nexthop IP address at the UPF through Charging-Action.

Note

When Nexthop 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

Nexthop supplied only in DNN

IPv4

209.165.201.18

Not configured

Not configured

Nexthop Address is selected from DNN: IPv4: 209.165.201.18 IPv6: 8001::10

IPv6

8001::10

Not applicable

Nexthop supplied only in IP pool

IPv4

Not configured

209.165.201.19

Not configured

Nexthop Address is selected from IP Pool: IPv4: 209.165.201.19

IPv6

Not configured

Not applicable

IPv4 and IPv6 configured in DNN, and IPv4 in IP pool

IPv4

209.165.201.18

209.165.201.19

Not configured

Nexthop Address is selected from DNN: IPv4: 209.165.201.18 IPv6: 9001::3

IPv6

9001::3

Not applicable

IPv6 configured in DNN, and IPv4 in IP pool

IPv4

Not configured

209.165.201.19

Not configured

Nexthop IPv4 is selected from IP pool: 209.165.201.19

Nexthop IPv6 selected from DNN : 8001::10

IPv6

8001::10

Not applicable

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

Nexthop Address is selected from UPF (CA): 209.165.201.20

IPv6

8001::10

Not applicable

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

Nexthop Address is selected from UPF(CA) : 9001::10

IPv6

8001::10

Not applicable

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 Nexthop 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