Page 304 - 5G Basics - Core Network Aspects

1 Core network aspects

8.3 MPT-enhanced MPC-FE requirements

In a multi-path transmission control initiated by the network, MPT-enhanced MPC-FE is responsible for
making adjustment policy decisions by obtaining and analysing access network performance parameters and
the capability of the corresponding end. The policy decision will be pushed to MPT-enhanced SCF to make
the related MPT decisions periodically. The MPT-enhanced functions of the MPC-FE are as follows:
1) obtain the information of each access network's performance parameters (e.g., network
throughput, response time, network bandwidth capacity and PLR) and determine the capability of
the corresponding end (MPT-enhanced MUE, or not);
2) analyse the entire network status based on the information obtained above;

3) make MPT policy decisions based on the overall network performance;
4) push the overall network performance parameters to the related MPT-enhanced SCF periodically.

8.4 MPT-enhanced SCF requirements
In a multi-path transmission initiated by the network, the multi-path transmission proxy functions extended
in SCF can transparently provide multi-path transmission capabilities to multi-path unaware hosts.
Depending on the multi-path transmission capabilities of the sending end and the receiving end, MPT-
enhanced SCF can act as a sender proxy or a receiver proxy to:
1) intercept the service request message for proxy initialization;
2) interact with the MPT-enhanced MPC for proxy decision;
3) act as a sender proxy to provide multi-path transmission capability in place of the sender;
4) act as a receiver proxy to provide multi-path transmission capability in place of the receiver;

5) accept the overall network performance parameters from the MPT-enhanced MPC periodically as a
multi-path transmission proxy.

9 Information flow

9.1 Path selection mechanism
In a multi-path transmission, services with high bandwidth requirements can be routed over multiple paths
simultaneously to increase the network utilization by balancing the traffic load over the networks, which
removes the restriction of a single network not satisfying high bandwidth services. However, if only a single
path can satisfy the service requirements, it is unnecessary to split the service into several paths, and the
most appropriate path should be selected.
The path or paths selection is required to take the service requirements, the paths' performance and the
paths' energy consumption into consideration, and the most appropriate path is required to be selected as
described in [b-IETF RFC 6897] or [b-IETF RFC 4960]. In order to select the most appropriate path or paths,
the status of each available path is required to be assessed and analysed.
To ensure the reliable, in-order delivery of a separated service, a connection level receive buffer is required
to be maintained at the receiving end. A sequence of numbers to indicate connection level is necessary for
traffic aggregation, and a sequence of numbers for sub-transmission flow is necessary for reliable delivery in
order to identify the retransmission traffic of a specific path.
Path selection can be executed by the MPT-enhanced MUE or the network proxy entity (i.e., MPT-enhanced
SCF which supports multi-path transmission proxy functions). The high-level information flow is described
separately as follows.

9.1.1 Path selection mechanism initiated by MPT-enhanced MUE
Suppose that MUE_A is an MPT-enhanced MUE with two interfaces and is accessing the 3G (IF (1)) and WLAN
(IF (2)) access networks simultaneously. Consider the example scenario where MPT-enhanced MUE_A
initializes an FTP service request to establish the control connection with an FTP server through the 3G

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