Page 321 - 5G Basics - Core Network Aspects

Core network aspects 1

6.2.1 FSC capability discovery/negotiation requirement

A mechanism is defined for the MUE and the network to discover whether the network and the MUE
respectively support FSC and to decide whether FSC is applied for multi-connection. The MUE and the access
control functional entity (AC-FE) shall always be aware of which access Internet protocol (IP) flows are used
in multi-connection.
During initial multi-connection establishment over the first connection, the MUE triggers a FSC request. The
intermediate network nodes indicate to the AC-FE whether they support FSC for the corresponding request.
If an MPC-FE is deployed, the AC-FE communicates to the MPC-FE indicating whether or not the MUE and
the network support FSC. The MPC-FE then takes the decision of whether or not FSC may apply to the multi-
connection and communicates this decision to the AC-FE.
If the network supports FSC and is willing to accept FSC for the multi-connection, the AC-FE confirms the FSC
support in an "FSC accepted" indication sent back to the MUE in the multi-connection establishment accept
message.
6.2.2 Routing rules

It is recommended that a routing rule contains the following parameters:
– Routing filter
– Routing access information
– Routing rule priority

– Routing rule identifier
A routing filter consists of IP header parameter values and/or ranges used to identify one or more IP flows.
The routing access information identifies the access type where the IP flow shall be routed.

For the purpose of matching user traffic against routing rules, filters are applied in the order designated by
the routing rule priority.

The routing rule identifier uniquely identifies a routing rule for one connection. The routing rule identifier is
allocated by the entity creating the routing rule; i.e., by the MUE in MUE-initiated FSC mode and by the AC-
FE in network-initiated FSC mode.

6.2.3 Delivery of routing rules
Routing rules are exchanged between the MUE and the AC-FE via control plane signalling.

For the MUE-initiated FSC procedure, the routing rules are provided by the MUE to the network. The MUE
does not apply new routing rules until the AC-FE has acknowledged them.
For the network-initiated FSC procedure, the MPC-FE makes the decision on when and which flows should
be moved to which connections. The MPC-FE learns about the multiple accesses supporting a
multi-connection via event triggers from the AC-FE.

7 Flow-based service continuity mechanisms

7.1 Overview

Both, the MUE-initiated FSC mode and the network-initiated mode are supported. The FSC mode applicable
to multi-connection is determined during connection establishment. Routing rule installation is possible at
any time during the lifetime of the multi-connection sessions. The routing rules can even be installed if there
is no IP flow currently matching the routing filter in the routing rule.
The AC-FE performs IP flow routing for downlink traffic. The MUE performs IP flow routing for uplink traffic.

During the multi-connection sessions and when the policies determine that the IP flows should be moved
and the target access is available for the MUE, it is possible to move individual IP flows from one access
network to another.

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