The following process flow describes about the Content Filtering enhancement to insert Device ID in EDNS0 records:

The enterprise policy ID (CF_POLICY_ID) from PCRF helps to create the Device ID. The SMF sends the device ID to the UPF. Adding the Device ID to the DNS packet helps in creating the EDNS0 packet. The format of EDNS0 packets is specified by RFC2671. The following are few specifics:

• Following is the structure for the fixed part of an OPT RR:

  Field Name   Field Type     Description
  ------------------------------------------------------
  NAME         domain name    empty (root domain)
  TYPE           u_int16_t          OPT
  CLASS          u_int16_t          sender's UDP payload size
  TTL            u_int32_t          extended RCODE and flags
  RDLEN          u_int16_t          describes RDATA
  RDATA          octet stream       {attribute, value} pairs
  

• Following is the variable part of an OPT RR encoded in its RDATA:

        +0 (MSB)                            +1 (LSB)
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
    0: |                       OPTION-CODE                             |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
    2: |                       OPTION-LENGTH                           |
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
    4: |                                                               |
       /                       OPTION-DATA                             /
       /                                                               /
       +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
  

  • OPTION-CODE: Assigned by IANA

  • OPTION-LENGTH: Size (in octets) of OPTION-DATA

  • OPTION-DATA- Varies per OPTION-CODE

Example: If received policy-id from PCF/PCRF is “1234” and static prefix configured on UPF is “5678”.

64-bits Device-ID will be “0000162e000004d2”.

• 0000162e -- 5678 (Decimal)

• 000004d2 -- 1234 (Decimal)

RDATA 69 42 00 0f 4f 70 65 6e 44 4e 53 00 00 16 2e 00 00 04 d2

• 6942 -- option-code

• 000f -- option-length

• 4f70656e444e53 -- OpenDNS (String)

• 0000162e -- 5678 (MSB)

• 000004d2 -- 1234 (LSB)

The new CLI is configured within trigger action to readdress the DNS traffic to the Umbrella DNS. This CLI uses the existing readdress server list configuration from the ACS service. Readdressing of packets based on the destination IP address of the packets enables redirecting gateway traffic to configured server/port in the readdressed server list.

Following are the behavior and restrictions applicable for this feature:

• Trigger Condition is evaluated at flow creation time. Any change in trigger condition in between the flow doesn’t affect the existing flow but affects the new flows.

• Any change to trigger action is applicable on the same flow.

• Neither CF nor EDNS is enforced when the CF Policy ID range is defined but Service-schema is not defined, or the Trigger condition pertaining to EDNS is not configured.

• If no CF Policy ID is received from Gx, range check is not performed, and content filtering works as defined in rule base.

• Cases where the ‘security-profile’ CLI is not associated with the ‘EDNS format’ CLI in Trigger Action, the device-id in the outgoing EDNS packet is sent with only 32-bit CF Policy ID.

• DNS queries with type other than A, AAAA, CNAME, NS, PTR, SRV, TXT, NULL are not to be EDNS converted.

• CF Policy ID change over Gx in between inflow are not applicable for the current flows. The current flows continue to insert the CF Policy ID present at the time of flow creation.

Following are the limitations for this feature:

• The feature doesn’t support the EDNS response packet reformat.

• The UPF must be able to include the IMSI MSISDN tag value in the EDNS0 queries. This feature doesn’t support the encrypted IMSI in EDNS0 packet. This feature also doesn’t support the following configuration on the EDNS fields currently.

  configure 
     active-charging-service  service_name  
        edns 
           fields  fields_name 
              tag default device-id 
              tag 101 imsi encrypt 
              tag 102 pgw-address    
              end 

Following is the sample configuration for configuring the EDNS packets:

configure
active-charging service ACS
content-filtering range 10 to 100
ruledef dns-port
udp either-port = 53
tcp either-port = 53
multi-line-or all-lines
rule-application routing
#exit
 readdress-server-list re_adr_list_ta
  server 209.165.202.141
  server 2001::14
  server 209.165.202.142
  server 2001::15
#exit
rulebase starent
route priority 20 ruledef dns-port analyzer dns
#exit
edns
security-profile sec_profile cf-policy-id-static-prefix 123456
fields test_fields
tag 26946 cf-policy-id
#exit
format test_format
fields test_fields encode
#exit
#exit
trigger-action TA1
edns format test_format security-profile sec_profile
flow action readdress server-list re_adr_list_ta hierarchy
#exit
trigger-condition TC1
external-content-filtering
app-proto = dns
#exit
service-scheme SS1
trigger flow-create
priority 1 trigger-condition TC1 trigger-action TA1
#exit
subs-class SC1  
rulebase = starent
multi-line-or all-lines
#exit
subscriber-base SB1
priority 1 subs-class SC1 bind service-scheme SS1
exit
end

Following are the show commands and outputs that are modified in support of the enhance content filtering support to Insert device ID in EDNS0 records.

• show user-plane-service inline-services info

  CF Range: Enabled	<<<<
    Start Value:  1	<<<<
    End Value:    1000	<<<

• show user-plane-service statistics analyzer name dns : output is modified to include the “EDNS Response Received” in both “EDNS Over UDP” and “EDNS Over TCP” sections.

• show subscribers user-plane-only full callid : output is modified to include the following parameters in the EDNS statistics per subscriber.

  • DNS-to-EDNS Uplink Pkts

  • DNS-to-EDNS Uplink Bytes

  • EDNS Response Received

• show user-plane-service edns all

  Fields:
      Fields Name: fields_1
      tag 26946 cf-policy-id
  
      Fields Name: fields_2
      tag 2001 imsi
      tag 2002 msisdn
      tag 26946 cf-policy-id
  
      Format:
      Format Name: format_1
      fields fields_1 encode
  
      Format Name: format_2
      fields fields_2 encode
  
      Security-profile Name: high
      CF Prefix Policy ID: 1234

Use the following show commands to view the Trigger Action statistics:

• show user-plane-service statistics trigger-action all

• show user-plane-service statistics trigger-action name trigger_action_name

• show user-plane-service trigger-condition all

  Trigger-Condition: TC1
         External-content-filtering : Enabled
         App-proto : dns
         Multi-line-OR All lines : Disabled
  

• show user-plane-service trigger-action all

  Trigger-Action: TA1
         HTTP Response Based TRM      : none
         HTTP Response Based Charging : none
         Throttle Suppress            : Disabled
         Flow Recovery                : Disabled
         Traffic Optimization         : Disabled
         Step Up GBR                  : Disabled
         Step Down GBR                : Disabled
         TCP Acceleration             : Disabled
         TCP Acceleration Threshold   : Disabled
         Service-Chain                : none
         UP-Service-Chain             : none
         EDNS-Encode                  : Enabled
         Flow-IP-Readdressing         : Enabled

The following bulk statistics are available in support of the Device ID in EDNS0 Records feature: