In the CUPS architecture, SAEGW-C selects a user plane by using an algorithm that selects the least connected user plane. It also selects the user plane from a flat list of user planes.

This feature enables the operator to select a user plane from a specific UP group associated with an APN or APN Profile.

In S-GW, UP groups are associated with an Access Point Name (APN) profile. An APN profile groups a set of APN-specific parameters that are applicable to one or more APNs. A single APN profile can be associated with multiple operator policies.

Cisco CUPS solution supports static UP selection. This is based on static selection of active and available SAEGW-U. The static UP selection uses the UP Group concept. UP group is a group of UP SAEGW-Us. Each APN is then associated with one UP group. APN is served by the UP groups associated with it. UPs are selected using an algorithm that selects the least connected UP available in that particular group.

UP Group

A UP can be part of only one UP group. In a UP Group, all UPs must be of the same capacity and capability. Different type of UPs must be part of different UP groups.

CUPS supports the following types of UP groups:

• Specific UP Group—It is a set of explicitly configured UPs. The specific group gives the flexibility to group certain specific types of UPs together. This helps in reserving specific set of UPs for a specific purpose. There can be multiple specific groups that can be configured.

• Default UP Group—This is a default group that groups all UPs that are registered and are not explicitly configured as part of any specific UP group. The default group has advantage of registering UPs in a zero touch manner without configuring a UP on the CP explicitly. This type of group is suited for collocated CUPS cases where all UPs with the same capacity and capability are in the same data center. The default group optimizes the UP configuration on CP.

An APN can be associated with UP group. If no group is associated with an APN, then default UP group is used to serve that APN. Similarly, for selecting UP for Pure-S calls, UP group can be associated to an APN profile. If there is no APN Profile/Operator-Policy defined or no group is associated with APN Profile, then SAEGW-C uses the "default" UP group for selection.

An operator can reserve certain UPs for certain applications. For example, IMS, Internet, and IOT can have different UP groups.

With this feature:

• SAEGW-C always has one user plane group with the name "default".

• SAEGW-C supports a maximum number of 100 user planes.

• The user planes can be organized in different groups.

• Currently, 100 user-plane-groups can be configured, and a single group can have a maximum number of 100 user planes.

• One user plane can be part of only one user plane group.

• Multiple user planes can be configured in specific user-plane-groups and default group.

• The user planes associated with SAEGW-C but not defined in any user plane group are added in the default group.

• An operator can associate a User Plane Group to APN and APN Profile.

• If there is no User Plane group associated to an APN for Pure-P and Collapsed calls, SAEGW-C uses the default group to select user plane for that session.

• If there is no user plane group associated to APN Profile or no APN Profile is defined, then SAEGW-C uses the "default" user plane group for Pure-S calls.

• For multi-PDN call with same APN, the same user plane is selected. For multi-PDN call with different APN, a different user plane from a different user plane group is selected.

• User Plane group associated with APN is also used while sending IP Pool chunks to User Plane. IP Pool associated with APN is broken down to chunks and are available for distribution to all UPs from group associated with APN.

• For user-plane-groups that are not associated with any APN, SAEGW-C does not send any IP pool chunks to UPs belonging to these groups. This is also applicable to the default group.

• Sessions with static IP address (IPv4 or IPv6) are supported. The user plane selection of static session is fixed as per chunk allocation to user plane from user plane group associated to an APN.

• If the same static IP address range is used across multiple APNs, it is recommended to use the same user plane group in those APNs.

This section provides information about configurations available in support of this feature.

Prerequisites:

• Same IP context should be present at Control-Plane as well as in User-Plane.

• IP context name which is specified in APN configuration should be same at Control-Plane and User-Plane.

This feature supports the following CLI commands:

• show sx peers

  • Group Name Column in the output of this command displays the name of the user-plane-group under which the peer is configured at Control Plane.

  • Peer, which is not part of any group, will be added under "default" user-plane-group

  • For a user-plane-group that is not associated with any "apn", SAEGW-C will not send any IP pools to user planes from this group. Hence, in the output of this command, for the Group Name that is not associated with "apn", the IP Pool status will be "N – Not Applicable". Also, for user planes in this group, when show sx peers is executed on UP, it displays Peer ID as "0".

• show ip user-plane

• show ip pool-chunks up-id up_id user-plane-group name up_group_name

In a Multi-access Edge Computing (MEC) architecture, selecting an edge User Plane (UP) provides low latency and maximum bandwidth efficiency. The location information of the user equipment (UE) is used to select an UP.

For selecting an edge UP, the following levels of granularity are considered:

• E-UTRAN Cell Global Identifier (ECGI) or Cell Global Identification (CGI) offers the lowest level of granularity.

• Tracking Area Identifier (TAI) or Routing Area Identity (RAI) or Service Area Identifier (SAI) offers the next level of granularity.

• TAI-SAI-RAI-ECGI offers fixed priority of TAI, SAI, RAI and ECGI in which the ULI type is matched when more than one ULI type is received.

This section describes the sequence of operation.

1. For P-GW, GGSN, or SAEGW, Fully Qualified Domain Names (FQDN) in UP, which contains fqdn-postfix and FQDN type (EGCI/CGI or TAI/RAI/SAI) are configured at APN level.

2. During an S6b interface protocol-based authorization, the fqdn-postfix value in the authorization response is used (applicable for P-GW, GGSN, or SAEGW service only).

3. The DNS (S-NAPTR) query is sent to the DNS server.

   Note	DNS (S-NAPTR) is generated based on the type (E-CGI | RAI-TAI-SAI | TAI-SAI-RAI-ECGI) configured in user plane FQDN at APN level for GGSN.

4. The response that is received from the DNS server is matched for service x-3gpp-upf:x-sxb for P-GW/GGSN/SAEGW (Collapsed) and x-3gpp-upf:x-sxa for S-GW.

5. The matching DNS (S-NAPTR) response is processed recursively for UP IPs.

   • If enabled, the processed IPs are shortlisted for LCI-based UP selection.

   • If not enabled, the processed IPs are shortlisted for session count based UP selection (with or without LCI).

6. If none of the UP IPs present in the response match with the associated Sx peers, then it leads to a session creation failure.

7. For S-GW dynamic UP selection, the DNS client context must be the same as sgw-service context.

8. If there is a successful DNS response for S-GW dynamic UP selection, UPs are selected from the DNS dynamic list of UP addresses. If there is DNS failure (DNS response is empty without any UP address or DNS time-out), the UP selection falls back to the statically configured APN profile based user-plane-groups functionality.

   Note

   Pure S-GW multi-PDNs work with independent DNS-based UP selection. S-GW relocation use cases work with independent DNS-based UP selection during a handover. If user-plane-group is configured under APN-profile, dynamic UP selection takes preference. After the DNS (NAPTR) query is sent, there is a delat of few seconds (equivalent to tx + rx ) to receive the response. If the DNS server is not reachable, session establishment might be delayed upto a maximum of 30 seconds before it uses the legacy method to select an UP.

The following sections describe various scenarios that are associated with the Dynamic UP Selection feature.

This section describes how to configure the Dynamic User Plane Selection feature.

This section describes the supported commands for the Dynamic UP Selection feature.

show apn name apn_name

This command displays DNS related information for Pure-P and collapsed calls.

The output of this command can be used to check the following values:

• FQDN of APN

• Type of FQDN

show sgw-service name sgw_service_name

This command displays DNS related information for Pure-S calls.

The output of this command can be used to check the following values:

• FQDN of APN

• Type of FQDN

show saegw-service statistics

Use the show saegw-service statistics CLI command to collect the statistics information.

The following is a sample partial output of the show saegw-service statistics all and show saegw-service statistics name SAEGW21 CLI commands:

Dynamic Uplane Selection Statistics:
   Attempted              :             x
   Successful             :             x
   Failure                :             x
   Peer not Found         :             x
   Negative DNS response  :             x
   DNS timed out          :             x
   Unsolicited UP Selection Response:   x
   DNS Query Response post DNS timeout: x

The following is a sample partial output of the show saegw-service statistics all function sgw CLI command:

Dynamic Uplane Selection Statistics:
  Attempted:                             7
  Successful                             4
  Failure:                               3
    Mismatch DNS response:               1
    Negative DNS response:               1
    DNS timed out:                       1
    Unsolicited UP Selection Response:   1
    DNS Query Response post DNS timeout: 1

Use this schema to collect the following bulk statistics pertaining to the Dynamic User Plane Selection feature:

• saegw-dyn-up-attempt

• saegw-dyn-up-attempt

• saegw-dyn-up-success

• saegw-dyn-up-success

• saegw-dyn-up-failure

• saegw-dyn-up-failure

• saegw-dyn-up-peer-not-found

• saegw-dyn-up-peer-not-found

• saegw-dyn-up-dns-timeout

• saegw-dyn-up-dns-timeout

• saegw-dyn-up-neg-resp

• saegw-dyn-up-neg-resp

Remote CUPS allows a progressive configuration rollout on an operator network. You can deploy and activate a pilot or canary version N+1 on a given CP or UPs pool, while the version N configuration is still active on the other CP or UP pool until the operator decides to roll out this N+1 configuration to all the CP or UP pools after the monitoring period.

Use cases for this feature are as follows:

• ECS or ADC configuration update rollout: The ability to test the configuration using one CP or UP pilot, while the other CP or UP uses the old configuration.

• New APN configuration update: Ability to test new APN configuration using a set of CP or UP pilot, while another component uses the old configuration.

• Add or remove the IP pool configuration update.

Pilot CP routes the incoming test pilot calls to the pilot UP group.

Pilot CP also routes usual business calls to any UP as per its original deployment. Therefore, this feature supports multiple UP groups under an APN. The first UP group includes the pilot UPs, and the second UP group includes all the other nonpilot UPs. A single UP cannot exist in two UP groups simultaneously. There is a strict 1:1 mapping between UP and the UP group.

This section describes how to configure the Multiple UP Group Support feature.

Configuring the Multiple UP Group Support feature involves the following steps:

Configuring UP Management Policy

To configure the UP management policy, use the following configuration:

configure 
   up-mgmt-policy policy_name 
      user-plane-group group_name 
      end 

NOTES:

• up-mgmt-policy policy_name —Specify the UP management policy as a string of size 1 to 31 characters.

• user-plane-group group_name —Specify the name of the user plane group.

Selecting UP for Pure-P and Collapsed Calls

To configure UP selection on Pure-P and Collapsed call types, use the following configuration:

configure 
   context context_name 
      apn apn_name 
         up-mgmt-policy policy_name 
         end 

Selecting UP for Pure-S Calls

To configure UP selection on a Pure-S call type, use the following configuration:

configure 
   context context_name 
      apn-profile profile_name 
         up-mgmt-policy policy_name 
         end 

NOTES:

• up-mgmt-policy policy_name must be a string of size 1 to 31 characters.

• You can configure either the APN profile level UP-group or UP management policy.

• For an APN profile, you can configure only a single UP management policy.

• Assign a pool name for the IP address allocation.

With this feature, User Plane group can be selected based on Access Point Name (APN). The ability to configure Tracking Area Code (TAC) range, in rule combinations in virtual APN selection, helps in giving more flexible network design for location-based User Plane selection for edge computing and other services.

With 21.25 and later releases, support is added to configure TAC and Routing Area Code (RAC) profile in the Control Plane node. Using this feature, it is now possible to select APN based on discrete values of TAC/RAC profile instead of range.

In non-CUPS architecture, Virtual APN selection is based on the following parameters:

• Subscriber IP

• Access-gw-address

• Bearer-access

• cc-behavior

• cc-profile

• domain

• mcc

• msisdn-range

• pdp-type

• rat-type

• roaming-mode

• serv-gw-plmnid

In CUPS architecture, Virtual APN selection is based on Tracking Area Code range with other options, such as cc-profile or mcc/mnc.

To support this feature:

• A new CLI keyword is introduced to accommodate new parameter.

• During call processing, incoming tracking area code is compared with the configured tracking area code range to determine the Virtual APN.

The Tracking Area Code based Virtual APN selection:

• Supports at least 30 tracking-area-code-range configured for Virtual APN.

• Supports overlapping ranges (subset or superset). Duplicate of tracking-area-code-range is not allowed for different priority.

• Selects a Virtual APN based on CLI configuration and User Plane is selected based on Virtual APN for a new call based on the tracking-area-code for that UE.

• Supports a combination of tracking-area-code-range and cc-profile in same priority.

Virtual APN functionality includes storing all the Virtual APN selection rules per real/Gn APN. Every rule has multiple criteria. Rule is identified by preference number. The list of APNs are stored and within APN a rule is identified using preference number.

New parameter has been introduced to pass Tracking Area Code, received in CSReq (TAI).

This section provides information about CLI commands available in support of this feature.

From 21.25 and later releases, Tracking Area Code profile can be configured in the Control Plane node. Using this feature, it is now possible to select APN based on discrete values of TAC instead of only range.

The following CLI commands are used to configure Tracking Area Code profile with discrete values and range.

configure 
   context context_name 
      tac-profile tac_profile_name 
         tac range X to Y 
         tac value 

NOTES:

• tac-profile tac_profile : Configures APN for Tracking Area Code profile. The tac_profile is any range or discrete integer value ranging from 0 to 65535.

• The number of discrete TAC values supported per CLI command is 16.

Associating TAC Profile with APN

configure 
   context context_name 
      apn apn_name 
         virtual-apn preference preference apn apn_name tac-profile tac_profile 
         end 

From 21.25 and later releases, Routing Area Code profile can be configured in the Control Plane node. Using this feature, it is now possible to select APN based on discrete values of RAC profile instead of range.

The following CLI commands are used to configure Routing Area Code profile with discrete values.

configure 
   context context_name 
      rac-profile rac_profile_name 
         rac range X to Y 
         rac value 

NOTES:

• routing-area-code-profile rac_profile : Configures APN for Routing Area Code profile. The rac_profile is any range or discrete integer value ranging from 0 to 255.

• The number of RAC profile values supported is upto 16.

Associating RAC Profile with APN

configure 
   context context_name 
      apn apn_name 
         virtual-apn preference preference apn apn_name routing-area-code-profile rac_profile 
         end