INTAREA S. Kanugovi
Internet-Draft S. Vasudevan
Intended status: Standards Track Nokia
Expires: January 4, 2018 J. Zhu
Intel
F. Baboescu
Broadcom
S. Peng
Huawei
S. Seo
Korea Telecom
J. Mueller
AT&T
July 3, 2017

Control Plane Protocols and Procedures for Multiple Access Management Services
draft-zhu-intarea-mams-control-protocol-02

Abstract

Today, a device can be simultaneously connected to multiple communication networks based on different technology implementations and network architectures like WiFi, LTE, DSL. In such multi-connectivity scenario, it is desirable to combine multiple access networks or select the best one to improve quality of experience for a user and improve overall network utilization and efficiency. This document presents the control plane protocols, as well as describes control plane procedures for configuring the user plane in a multi access management services (MAMS) framework that can be used to flexibly select the combination of uplink and downlink access and core network paths, and user plane treatment for improving network efficiency and enhanced application quality of experience.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on January 4, 2018.

Copyright Notice

Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.


Table of Contents

1. Conventions used in this document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

2. Introduction

Multi Access Management Service (MAMS) [I-D.kanugovi-intarea-mams-protocol] is a framework to select and configure network paths when multiple connections can serve a client device. It allows the path selection and configuration to adapt to dynamic network conditions. It is based on principles of user plane interworking that enables the solution to be deployed as an overlay without impacting the underlying networks.

This document presents the control plane protocols for the MAMS framework. It co-exists and complements user plane protocols (e.g. MPTCP [RFC6824], MPTCP Proxy [I-D.boucadair-mptcp-plain-mode], [I-D.wei-mptcp-proxy-mechanism], GRE [I-D.zhu-intarea-mams-user-protocol]) by providing a way to negotiate and configure them based on client and network capabilities. It allows exchange of network state information and leverages network intelligence to optimize the performance of such protocols.

3. Terminology

"Anchor Connection": Refers to the network path from the N-MADP to the Application Server that corresponds to a specific IP anchor that has assigned an IP address to the client.

"Delivery Connection”: Refers to the network path from the N-MADP to the client.

"Network Connection Manager" (NCM), "Client Connection Manager" (CCM), "Network Multi Access Data Proxy" (N-MADP), and "Client Multi Access Data Proxy" (C-MADP) in this document are to be interpreted as described in [I-D.kanugovi-intarea-mams-protocol].

4. MAMS Control-Plane Protocol

The MAMS architecture [I-D.kanugovi-intarea-mams-protocol] introduces the following functional elements,



    +------------------------------------------+
    |    Multi Access (MX) Control Message     |
    |                                          |
    +------------------------------------------+
    |                WebSocket                 |
    |                                          |
    +------------------------------------------+
    |               TCP/TLS                    |
    |                                          |
    +------------------------------------------+
		

Figure 1: TCP-based MAMS Control Plane Protocol Stack

Figure 1 shows the default MAMS control plane protocol stack. WebSocket is used for transporting management and control messages between NCM and CCM.

5. MAMS User Plane Protocol


   +-----------------------------------------------------+
   |      User Payload (e.g. IP PDU)                     |
   +-----------------------------------------------------+
                               
+-----------------------------------------------------------+
|  +-----------------------------------------------------+  |
|  | Multi Access (MX) Convergence Sublayer              |  |
|  +-----------------------------------------------------+  |
|  +-----------------------------------------------------+  |
|  | MX Adaptation   | MX Adaptation  | MX Adaptation    |  |
|  | Sublayer        | Sublayer       | Sublayer         |  |
|  | (optional)      | (optional)     | (optional)       |  |
|  +----------------++--------------+-+------------------+  |
|  | Access #1 IP   | Access #2 IP  | Access #3 IP       |  |
|  +-----------------------------------------------------+  |
|                             MAMS User Plane Protocol Stack|
+-----------------------------------------------------------+


		

Figure 2: MAMS User Plane Protocol Stack

Figure 2 shows the MAMS user plane protocol stack.

It consists of the following two Sublayers:

6. MAMS Control Plane Procedures

6.1. Overview

CCM and NCM exchange signaling messages to configure the user plane functions, C-MADP and N-MADP, at the client and network respectively. The means for CCM to obtain the NCM credentials (FQDN or IP Address) for sending the initial discovery messages are out of the scope of MAMS document, e.g. using methods like provisioning, DNS query. Once the discovery process is successful, the (initial) NCM can update and assign additional NCM addresses for sending subsequent control plane messages.


+-----+                +-----+
| CCM |                | NCM |
+--+--+                +--+--+
   |    Discovery and     |
   |    Capability        |
   |    Exchange          |
   <---------------------->
   |                      |
   |    User Plane        |
   |    Protocols         |
   |    Setup             |
   <---------------------->
   |    Path Quality      |
   |    Estimation        |
   <---------------------->
   | Network capabilities |
   | e.g. RNIS[ETSIRNIS]  |
   <----------------------+
   |                      |
   | Network policies     |
   <----------------------+
   +                      +



		

Figure 3: MAMS Control Plane Procedures

CCM discovers and exchanges capabilities with the NCM. NCM provides the credentials of the N-MADP end-point and negotiates the parameters for user plane with the CCM. CCM configures C-MADP to setup the user plane path (e.g. MPTCP/UDP Proxy Connection) with the N-MADP based on the credentials (e.g. (MPTCP/UDP) Proxy IP address and port, Associated Core Network Path), and the parameters exchanged with the NCM. The key procedures are described in details in the following sub-sections.

6.2. Common fields in MAMS Control Messages

Each MAMS control message consists of the following common fields:

6.3. Common procedures for MAMS Control Messages

This section describes the common procedures for MAMS Control Messages.

6.3.1. Message Timeout

MAMS Control plane peer (NCM or CCM) waits for a duration of MAMS_TIMEOUT ms, after sending a MAMS control message, before timing out when expecting a response. The sender of the message will retransmit the message for MAMS_RETRY times before declaring failure. A failure implies that the MAMS peer is dead. CCM may initiate the MAMS discovery procedure for re-establishment of the MAMS session.

6.3.2. Keep Alive Procedure

MAMS Control plane peers execute the keep alive procedures to ensure that peers are reachable and to recover from dead-peer scenarios. Each MAMS control plane end-point maintains a MAMS_KEEP_ALIVE timer that is set for duration MAMS_KEEP_ALIVE_TIMEOUT. MAMS_KEEP_ALIVE timer is reset whenever the peer receives a MAMS Control message. When MAMS_KEEP_ALIVE timer expires, MAMS KEEP ALIVE REQ message is sent. On reception of a MAMS KEEP ALIVE REQ message, the receiver responds with a MAMS KEEP ALIVE RSP message. If the sender does not receive a MAMS Control message in response to MAMS_RETRY number of retries of MAMS KEEP ALIVE REQ message, the MAMS peer declares that the peer is dead. CCM may initiate MAMS Discovery procedure for re-establishment of the MAMS session.

CCM shall additionally send MX KEEP ALIVE REQ message immediately to NCM whenever it detects a handover from one base station/access point to another. During this time the user equipment shall stop using MAMS user plane functionality in uplink direction till it receives a MX KEEP ALIVE RSP from NCM.

MX KEEP ALIVE REQ includes following information:

6.4. Discovery & Capability Exchange


     CCM						  NCM
      |							   |
      +------- MX Discovery Message ---------------------->|
      |                                         +-----------------+
      |						|Learn CCM        |
      |                                         | IP address      |
      |						|& port	          |
      |						+-----------------+
      |                                                    |
      |<--------------------------------MX System INFO-----|
      |                                                    |
      |---------------------------------MX Capability REQ->|
      |<----- MX Capability RSP----------------------------|
      |---------------------------------MX Capability ACK->|
      |                                                    |
      +                                                    +
		

Figure 4: MAMS Control Procedure for Discovery & Capability Exchange

Figure 4 shows the MAMS discovery and capability exchange procedure consisting of the following key steps:

Step 1 (Discovery): CCM periodically sends out the MX Discovery Message to a pre-defined (NCM) IP Address/port until MX System INFO message is received in acknowledgement.

MX Discovery Message includes the following information:

MX System INFO includes the following information:

Step 2 (Capability Exchange): On receiving MX System Info message CCM learns the IP Address and port to start the step 2 of the control plane connection, and sends out the MX Capability REQ message, including the following Parameters:

In response, NCM creates a unique identity for the CCM session, and sends out the MX Capability RSP message, including the following information:

Unique Session Identifier: Unique session identifier for the CCM which has setup the connection. In case the session for the UE already exists then the existing unique session identifier is sent back.

In response to MX Capability RSP message, the CCM sends confirmation (or reject) in the MX Capability ACK message. MX Capability ACK includes the following parameters

If MX_REJECT is received by the NCM, the current MAMS session will be terminated.

If CCM can no longer continue with the current capabilities, it should send an MX SESSION TERMINATE message to terminate the MAMS session. In response, the NCM should send a MX SESSION TERMINATE ACK to confirm the termination.

6.5. User Plane Configuration


CCM	  	                                      NCM
 |					              |
 |------MX Reconfiguration REQ (setup)--------------->|
 |<------------------------+MX Reconfiguration RSP+---|
 |                                        +-----------+----------------+
 |	                                  | NCM prepares N+MADP for    |
 |	                                  | User Plane|Setup           |
 |	                                  +----------------------------+
 |<----------------------------- MX UP Setup Config---|
 |-----| MX UP Setup CNF+---------------------------->|
+-------------------+                                 |
|Link "X" is up/down|				      |
+-------------------+				      |
 |-----MX Reconfiguration REQ (update/release)------->|
 |<------------------------+MX Reconfiguration RSP+---|


		

Figure 5: MAMS Control Procedure for User Plane Configuration

Figure 5 shows the user plane configuration procedure consisting of the following key steps:

Reconfiguration: when the client detects that the link is up/down or the IP address changes (e.g. via APIs provided by the client OS), CCM sends out a MX Reconfiguration REQ Message to setup / release / update the connection, and the message SHOULD include the following information

If (Reconfiguration Action is setup or update), then include the following parameters

At the beginning of a connection setup, CCM informs the NCM of the connection status using the MX Reconfiguration REQ message with Reconfiguration Action type set to "setup". NCM acknowledges the connection setup status and exchanges parameters with the CCM for user plane setup, described as follows.

User Plane Protocols Setup: Based on the negotiated capabilities, NCM sets up the user plane (Adaptation Layer and Convergence Layer) protocols at the N-MADP, and informs the CCM of the user plane protocols to setup at the client (C-MADP) and the parameters for C-MADP to connect to N-MADP.

Each MADP instance is responsible for one anchor connection. The MX UP Setup Config consists of the following parameters:

e.g. When LTE and Wi-Fi are the two user plane accesses, NCM conveys to CCM that IPsec needs to be setup as the MX Adaptation Layer over the Wi-Fi Access, using the following parameters - IPsec end-point IP address, Pre-Shared Key., No Adaptation Layer is needed or Client NAT may be used over the LTE Access as it is considered secure with no NAT. The MX Convergence Method is configured as MPTCP Proxy along with parameters for connection to the MPTCP Proxy, namely IP Address and Port of the MPTCP Proxy for TCP Applications.

Once the user plane protocols are configured, CCM informs the NCM of the status via the MX UP Setup CNF message. The MX UP Setup CNF consists of the following parameters:

6.6. MAMS Path Quality Estimation

Path quality estimations can be done either passively or actively. Traffic measurements in the network could be performed passively by comparing the real-time data throughput of the device with the capacity available in the network. The utilization of a cell/eNB attached to a device could be used as an indicator for path quality estimations without creating an extra traffic overhead. Active measurements by the device are alternatives to measure path quality estimations.


CCM						    NCM
|						     |
|<--------------+ MX Path Estimation Configuration+--|
|-----+ MX Path Estimation Results+----------------->|
|                                                    |



		

Figure 6: MAMS Control Plane Procedure for Path Quality Estimation

NCM sends following the configuration parameters in the MX Path Estimation Configuration message to the CCM

CCM configures the C-MADP for probe reception based on these parameters and for collection of the statistics according to the following configuration.

The user plane probing is divided into two phases - Initialization phase and Active phase.

In Initialization phase, NCM configures N-MADP to send an MX Idle Probe REQ message. CCM collects the Idle probe statistics from C-MADP and sends the MX Path Estimation Results Message to NCM per the Initialization Probe Results configuration.

In Active phase, NCM configures N-MADP to send an MX Active Probe REQ message.. C-MADP calculates the metrics as specified by the Active Probe Results Configuration. CCM collects the Active probe statistics from C-MADP and sends the MX Path Estimation Results Message to NCM per the Active Probe Results configuration.

6.7. MAMS Traffic Steering


CCM						  NCM
 |						   |
 |                                +------------------------------+
 |				  |Steer user traffic to Path "X"|               
 |				  +------------------------------+
 |<------------------MX Traffic Steering (TS) REQ--|
 |----- MX Traffic Steering (TS) RSP ------------->|
				

Figure 7: MAMS Traffic Steering Procedure

NCM sends out a MX Traffic Steering (TS) REQ message to steer data traffic. It is also possible to send data traffic over multiple connections simultaneously, i.e. aggregation. The message includes the following information:

In response, CCM sends out a MX Traffic Steering (TS) RSP message, including the following information:

6.8. MAMS Network ID Indication


    CCM                                               NCM
     |                                                 |
     |                            +---------------------------------+
     |                            |NCM determines preferred Networks|
     |                            +---------------------------------+
     |<------------------MX SSID Indication------------|
				

Figure 8: MAMS Network ID Indication Procedure

NCM indicates the preferred network list to the CCM to guide client on networks that it should connect to. To indicate preferred Wi-Fi Networks, the NCM sends the list of WLAN networks, represented by SSID/BSSID/HESSID, available in the MX SSID Indication.

6.9. MAMS Client Measurement Configuration and Reporting



    CCM                                               NCM
     |                                                 |
     |<------------------MX MEAS CONFIG----------------|
     |                                                 |
    +---------------------------------+                |
    |Client Ready to send measurements|                |
    +---------------------------------+                |
     |                                                 |
     |----- MX MEAS REPORT---------------------------->|

Figure 9: MAMS Client Measurement Configuration and Reporting Procedure

NCM configures the CCM with the different parameters (e.g. radio link information), with the associated thresholds to be reported by the client. The MX MEAS CONFIG message contains the following parameters. For each Delivery Connection, include the following:

The MX MEAS REPORT message contains the following parameters

6.10. MAMS Session Termination Procedure


CCM                                 NCM
 |                                   |
 |+----MX Session Terminate--------->|
 |                                   |
 |                                   |
 |<---MX Session Terminate Ack-------|
 |                              +---------------+
 |                              Remove Resources
 |                              +---------------+
 |                                   |

Figure 10: MAMS Session Termination Procedure - Client Initiated

	
	   CCM                                     NCM
            |                                       |
            |<----------MX Session Terminate--------|
            |                                       |
            |                                       |
            |                                       |
            +--------MX Session Terminate Ack------->
            |                                       |
            |                                       |
+-----------+-----------+                           |
|    Remove Resources   |                           |
+-----------+-----------+                           |
            |                                       |
           

	   

Figure 11: MAMS Session Termination Procedure - Network Initiated

At any point in MAMS functioning if CCM or NCM is unable to support the MAMS functions anymore, then either of them can initiate a termination procedure by sending MX Session Terminate to the peer, the peer shall acknowledge the termination by sending MX Session Terminate ACK message. After the session is disconnected the CCM shall start a new procedure with MX Discover Message. MX Session Terminate message shall contain Unique Session Identifier and reason for termination in Request. Possible reasons for termination can be:

7. Applying MAMS Control Procedures with MPTCP Proxy as User Plane

If NCM determines that N-MADP is to be instantiated with MPTCP as the MX Convergence Protocol, it exchanges the MPTCP capability support in discovery and capability exchange procedures. NCM then exchanges the credentials of the N-MADP instance, setup as MPTCP Proxy, along with related parameters to the CCM. CCM configures C-MADP with these parameters to connect with the N-MADP, MPTCP proxy (e.g. [I-D.wei-mptcp-proxy-mechanism], [I-D.boucadair-mptcp-plain-mode]) instance, on the available network path (Access).

+------+   +---------+   +---------+   +---------+   +---------+   +------+
|      |   |         |   |         |   |         |   |         |   |      |
|CCM   |   |  C-MADP |   |Wi-Fi N/W|   | LTE N/W |   |  NCM    |   |N-MADP|
+------+   +---------+   +---------+   +---------+   +---------+   +------+
 +------------------------------------------------------------------------+
 |                  1. LTE Session Setup and IP Add. Allocation           |
 -------------------------------------------+-------------+-------------+-+
  |2. MAMS Discovery Message (MAMS Version) |             |             |
  +-----------------------------------------+------------->             |
  | 3. MX SYSTEM INFO (Serving NCM IP/Port Address)       |             |
  <-------------+-------------+-------------+-------------+             |
  |             |             |             |             |             |
  |4. MX CAPABILITY REQ(Supported Anchor/Delivery Links ( Wi-Fi, LTE )  |
  +-----------------------------------------------------+->             |
  |5. MX CAPABILITY RSP(Convergence/Adaptation Parameters)|             |
  <-----------------------------------------+-------------+             |
  | 6. MX CAPABILITY ACK(ACCEPT)            |             |             |
  +-------------+-------------+--------------------------->             |
  |             |             |             |             |             |
  |7. MX MEAS CONFIG (WLAN/LTE Measurement Thresholds/Period)           |
  <-------------------------------------------------------+             |
  |8. MX MEAS REPORT ( LTE RSRP, UL/DL TPUT )             |             |
  +-----------------------------------------+------------->             |
  |9. MAMS SSID IND(List of SSIDs)          |             |             |
  <-------------+-------------+---------------------------+             |
  |             |             |             |             |             |
  |10. MX RECONFIGURATION REQ (LTE IP)      |             |             |
  +------------------------------------------------------->             |
  |11. MX RECONFONFIGURATION RSP            |             |             |
  <-----------------------------------------+-------------+             |
  |12. MX UP SETUP REQ (MPTCP Proxy IP/Port, Aggregation) |             |
  <---------------------------+-------------+-------------+             |
  |13. MX UP SETUP RSP        |             |             |             |
  +-------------+-------------+-------------+------------->             +
  |             | 14. MPTCP Connection with designated MPTCP Proxy over LTE
  |             +-------------+-------------+-------------+------------->
  |             |             |             |             |             |
  +             +             +             +             +             +

Figure 12: MAMS-assisted MPTCP Proxy as User Plane - Initial Setup with LTE leg

Figure 8 shows the call flow describing MAMS control procedures applied to configure user plane and dynamic optimal path selection in a scenario with MPTCP Proxy as the convergence protocol in the user plane.

Following are the salient steps described in the call flow. The client connects to the LTE network and obtains an IP address (assume LTE is the first connection), and initiates the NCM discovery procedures and exchange capabilities, including the support for MPTCP as the convergence protocol at both the network and the client.

The CCM informs the LTE connection parameters to the NCM. NCM provides the parameters like MPTCP Proxy IP address/Port for configuring the convergence layer. This is useful if N-MADP is reachable via different IP address or/and port, from different access networks. The current MPTCP signaling can't identify or differentiate the MPTCP proxy IP address and port among multiple access networks. Since LTE is the only connection, the user plane traffic flows over the single TCP subflow over the LTE connection. Optionally, NCM can provide assistance to the device on the neighboring/preferred Wi-Fi networks that it can associate with.


+------+   +---------+   +---------+   +---------+   +---------+   +------+
|      |   |         |   |         |   |         |   |         |   |      |
|CCM   |   |  C-MADP |   |Wi-Fi N/W|   | LTE N/W |   |  NCM    |   |N-MADP|
+------+   +---------+   +---------+   +---------+   +---------+   +------+
 +------------------------------------------------------------------------+
 |   Traffic over LTE in UL and DL over MPTCP Connection                  |
 +------------------------------------------------------------------------+
 +------------------------------------------------------------------------+
 |   Wi-Fi Connection Establishment and IP Address Allocation             |
 +---------------------------------------------------------------------+--+
 |15. MX RECONFIGURATION REQ (Wi-Fi IP)    |             |             |
 +------------------------------------------------------->             |
 |16. MX RECONFONFIGURATION RSP            |             |             |
 <-----------------------------------------+-------------+             |
 |17. MX UP SETUP REQ (MPTCP Proxy IP/Port, Aggregation) |             |
 <---------------------------+-------------+-------------+             |
 |18. MX UP SETUP RSP        |             |             |             |
 +-------------+-------------+-------------+------------->             |
 |             | 19. IPsec Tunnel Establishment over WLAN path         |
 |             <-----------------------------------------|------------->
 | 20. MX MEAS REPORT (WLAN RSSI, LTE RSRP. UL/DL TPUT)  |+-------------+
 +-------------+-------------+-------------+------------->+Wait for     | 
 |             |             |             |             |+good reports |
 |             |             |             |             |+-------------+
 |   21. MX TRAFFIC STEERING REQ (UL/DL Access, TFTs)    | +------------+
 <-----------------------------------------+-------------+ |Allow Use of|
 |   22. MX TRAFFIC STEERING RSP (...)     |             | |Wi-Fi link  |
 +-------------+-------------+---------------------------> +-----------++
 |             |             |             |             |             |
 |            Add TCP subflow to the MPTCP connection over the WiFi link
 |             |<----------------------------------------------------->|
+-----------------------------------------------------------------------+
||              Aggregated Wi-Fi and LTE capacity for UL and DL        ||
+-----------------------------------------------------------------------+
 |                                                                     |
 |                                                                     |

Figure 13: MAMS-assisted MPTCP Proxy as User Plane - Add Wi-Fi leg

Figure 9 describes the steps, when the client establishes a Wi-Fi connection. CCM informs the NCM of the Wi-Fi connection along with parameters like the Wi-Fi IP address, SSID. NCM determines that the Wi-Fi connection needs to be secured configures the Adaptation Layer to be IPsec and provides the required parameters to the CCM. In addition, NCM provides the information to configure the convergence layer, (e.g. MPTCP Proxy IP Address), and provides the Traffic Steering Request to indicate that client should use only the LTE access. NCM may do this, for example, on determination from the measurements that the Wi-Fi link is not consistently good enough. As the Wi-Fi link conditions improve, NCM sends a Traffic Steering Request to use Wi-Fi access as well. This triggers the client to establish the TCP subflow over the Wi-Fi link with the MPTCP proxy


+------+   +---------+   +---------+   +---------+   +---------+   +------+
|      |   |         |   |         |   |         |   |         |   |      |
|CCM   |   |  C+MADP |   |Wi+Fi N/W|   | LTE N/W |   |  NCM    |   |N+MADP|
+------+   +---------+   +---------+   +---------+   +---------+   +------+
 +------------------------------------------------------------------------+
 |   Traffic over LTE and Wi Fi in UL And DL over MPTCP                   |
 +-------------+-------------+-------------+-------------+------------+---+
 |             |             |             |             |            |
 | 23. MX MEAS REPORT (WLAN RSSI, LTE RSRP ,UL/DL TPUT)  |+-----------+---+
 +-------------+-------------+-------------+------------>|| Reports of bad|
 |             |             |             |             |+ Wi-Fi UL tput|
 |             +             +             +             ++---------------+
 |   24. MX TRAFFIC STEERING REQ (UL/DL Access, TFTs)    | +-------------+
 |<-----------------------------------------+------------+ |Disallow  use|
 |   25. MX TRAFFIC STEERING RSP (...)     |             | |of Wi-Fi UL  |
 |-------------+-------------+-------------------------->| +----------+--+
 |             |             |             |             |            |
++-------------+-------------+-------------+-------------+------------+-+
|  UL data to use TCP subflow over LTE link only,                       |
|  Aggregated Wi-Fi+LTE capacity for DL                                 |
++-------------+-------------+-------------+-------------+-------------++
 |             |             |             |             |            |
 +             +             +             +             +            +


Figure 14: MAMS-assisted MPTCP Proxy as User Plane - Wi-Fi UL degrades

Figure 10 describes the steps, when the client reports that Wi-Fi link conditions degrade in UL. MAMS control plane is used to continuously monitor the access link conditions on Wi-Fi and LTE connections. The NCM may at some point determine increase in UL traffic on Wi-Fi, and trigger the client to only LTE in the UL via Traffic Steering Request to improve UL performance.


+------+   +---------+   +---------+   +---------+   +---------+   +------+
|      |   |         |   |         |   |         |   |         |   |      |
|CCM   |   |  C+MADP |   |Wi+Fi N/W|   | LTE N/W |   |  NCM    |   |N+MADP|
+------+   +---------+   +---------+   +---------+   +---------+   +------+
+-----------------------------------------------------------------------+
|  UL data to use TCP subflow over LTE link only,                       |
|  Aggregated Wi+Fi+LTE capacity for DL                                 |
++-------------+-------------+-------------+-------------+------------+-+
 |             |             |             |             |            |
 |             +             +             +             |            |
 | 23. MX MEAS REPORT (WLAN RSSI, LTE RSRP, UL/DL TPUT)  +------------+---+
 +-------------+-------------+-------------+------------>|| Reports of bad+
 |             |             |             |             || Wi+Fi UL/DL tput
 |             +             +             +             +----------------+
 |   24. MX TRAFFIC STEERING REQ (UL/DL Access, TFTs)    | +-------------+
 +<----------------------------------------+-------------+ |Disallow  use|
 |   25. MX TRAFFIC STEERING RSP (...)     |             | |of Wi+Fi     |
 +-----------------------------------------+------------>+ +-------------+
 |             |Delete TCP subflow from MPTCP conn. over Wi-Fi link   |
 |             +<---------------------------------------------------->|
+-----------------------------------------------------------------------+
|| Traffic over LTE link only for DL and UL              |            | |
|| (until Client reports better Wi-Fi link conditions)   |            | |
+-----------------------------------------------------------------------+
 |             |             |             |             |            |
 +             +             +             +             +            +

Figure 15: MAMS-assisted MPTCP Proxy as User Plane - Part 4

Figure 11 describes the steps, when the client reports that Wi-Fi link conditions degrade in both UL and DL. As the Wi-Fi link conditions deteriorate further, the NCM may determine to send Traffic Steering Request guiding the client to stop using Wi-Fi, and to use only LTE access in both UL and DL. This condition may be maintained until NCM determines, based on reported measurements that Wi-Fi link has become usable.

8. Applying MAMS Control Procedures for Network Assisted Traffic Steering when there is no convergence layer

Figure Y shows the call flow describing MAMS control procedures applied for dynamic optimal path selection in a scenario convergence and Adaptation layer protocols are not ommitted. This scenario indicates the applicability of a MAMS Control Plane only solution.

In the capability exchange messages, NCM and CCM negotiate that Convergence and Adaptation layer protocols are not needed (or supported). CCM informs the NCM of the availability of the LTE and Wi-Fi links. NCM determines the access links, Wi-Fi or LTE to be used dynamically based on the reported link quality measurements.


+------+   +---------+   +---------+   +---------+   +---------+   +------+
|      |   |         |   |         |   |         |   |         |   |      |
|CCM   |   |  C+MADP |   |Wi+Fi N/W|   | LTE N/W |   |  NCM    |   |N+MADP|
+------+   +---------+   +---------+   +---------+   +---------+   +------+
 +------------------------------------------------------------------------+
 |                1. LTE Session Setup and IP Add. Allocation             |
 +------------------------------------------+-------------+-------------+-+
  |2. MAMS Discovery Message (MAMS Version) |             |             |
  +-----------------------------------------+------------>|             |
  | 3. MX SYSTEM INFO (Serving NCM IP/Port Address)       |             |
  <-------------+-------------+-------------+-------------+             |
  |             +             +             +             +             |
  |4. MX CAPABILITY REQ(Supported Anchor/Delivery Links ( Wi-Fi, LTE )  |
  +------------------------------------------------------>|             |
  |5. MX CAPABILITY RSP(No Convergence/Adpatation parameters)           |
  |<-----------------------------------------+------------+             |
  | 6. MX CAPABILITY ACK(ACCEPT)            |             |             |
  +-------------+-------------+-------------------------->|             |
  |             +             +             +             +             |
  |7. MX MEAS CONFIG (WLAN/LTE Measurement Thresholds/Period)           |
  |<------------------------------------------------------|             |
  |8. MX MEAS REPORT ( LTE RSRP, UL/DL TPUT )             |             |
  |-----------------------------------------+------------>|             |
  |9. MAMS SSID IND(List of SSIDs)          |             |             |
  |<------------------------------------------------------|             |
+-----------------------------------------------------------------------++
|             10. Wi|Fi connection setup and IP Address allocation       |
+-+-------------+-------------+-------------+-------------+-------------++
  |             +             +             |             |             |
  |10. MX RECONFIGURATION REQ (LTE IP, Wi-Fi IP)          |             |
  +-----------------------------------------+------------>|             |
  |11. MX RECONFONFIGURATION RSP            |             |             |
  <------------------------------------------------------+|             |
+-----------------------------------------------------------------------++
|    Initial Condition, Data over LTE link only, WLAN link is poor       |
+---------------------------------------------------------+-------------++
  |12. MX MEAS REPORT (WLAN RSSI, LTE RSRP, UL/DL TPUT)   |+-------------+
  |------------------------------------------------------>||Wi-Fi Link   |
  |             |             |             |             ||conditions   |
  |             |             |             |             ||reported good|    
  |             |             |             |             |+-------------+   
  |             |             |             |             |             |
  |13. MX TRAFFIC STEERING REQ (UL/DL Access, TFTs)       |+--------------+
  |<-------------+-------------+-------------+------------||Steer traffic |
  |14. MX TRAFFIC STEERING RSP (...)        |             ||to use Wi-Fi  |
  |<-------------+-------------+-------------+------------||link          |
  |             |             |             |             |+--------------+
+-----------------------------------------------------------------------++
|    Use Wi-Fi link for Data                                             |
+---------------------------------------------------------+-------------++
  |             |             |             |             |             |
  +             +             +             +             +             +


Figure 16: MAMS-assisted MPTCP Proxy as User Plane - Part 3

9. Co-existence of MX Adaptation and MX Convergence Layers

MAMS u-plane protocols support multiple combinations and instances of user plane protocols to be used in the MX Adaptation and the Convergence layer.

For example, one instance of the MX Convergence Layer can be MPTCP Proxy and another instance can be Trailer based. The MX Adaptation for each can be either UDP tunnel or IPsec. IPSec may be set up when network pathneeds to be secured, e.g. to protect the TCP subflow traversing the network path between the client and MPTCP proxy.

Each of the instances of MAMS user plane, i.e. combination of MX Convergence and MX Adaptation layer protocols, can coexist simultaneously and independently handle different traffic types.

10. Security Considerations

10.1. MAMS Control plane security

For deployment scenarios, where the client is configured (e.g. by the network operator) to use a specific network for exchanging control plane messages and assume the network path to be secure, MAMS control messages will rely on security provided by the underlying transport network.

For deployment scenarios where the security of the network path cannot be assumed, NCM and CCM implementations MUST support the "https" URI scheme [RFC2818] and Transport Layer Security (TLS) [RFC5246] to secure control plane message exchange between the NCM and CCM.

For deployment scenarios where client authentication is desired, HTTP Digest Authentication MUST be supported. TLS Client Authentication is the preferred mechanism if it is available.

10.2. MAMS User plane security

User data in MAMS framework relies on the security of the underlying network transport paths. When this cannot be assumed, NCM configures use of protocols, like IPsec [RFC4301] [RFC3948] in the MX Adaptation Layer, for security.

11. Contributing Authors

The editors gratefully acknowledge the following additional contributors in alphabetical order: A Krishna Pramod/Nokia, Hannu Flinck/Nokia, Hema Pentakota/Nokia, Nurit Sprecher/Nokia

12. References

12.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, December 2005.

12.2. Informative References

[ETSIRNIS] "Mobile Edge Computing (MEC) Radio Network Information API"
[I-D.boucadair-mptcp-plain-mode] Boucadair, M., Jacquenet, C., Bonaventure, O., Behaghel, D., stefano.secci@lip6.fr, s., Henderickx, W., Skog, R., Vinapamula, S., Seo, S., Cloetens, W., Meyer, U., Contreras, L. and B. Peirens, "Extensions for Network-Assisted MPTCP Deployment Models", Internet-Draft draft-boucadair-mptcp-plain-mode-10, March 2017.
[I-D.kanugovi-intarea-mams-protocol] Kanugovi, S., Vasudevan, S., Baboescu, F., Zhu, J., Peng, S., Mueller, J. and S. Seo, "Multiple Access Management Services", Internet-Draft draft-kanugovi-intarea-mams-protocol-04, March 2017.
[I-D.wei-mptcp-proxy-mechanism] Wei, X., Xiong, C. and E. Ed, "MPTCP proxy mechanisms", Internet-Draft draft-wei-mptcp-proxy-mechanism-02, June 2015.
[I-D.zhu-intarea-mams-user-protocol] Zhu, J., Seo, S., Kanugovi, S. and S. Peng, "User-Plane Protocols for Multiple Access Management Service", Internet-Draft draft-zhu-intarea-mams-user-protocol-02, June 2017.
[IEEE] "IEEE Standard for Information technology: Telecommunications and information exchange between systems Local and metropolitan area networks:Specific requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications."
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L. and M. Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC 3948, DOI 10.17487/RFC3948, January 2005.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, January 2012.
[RFC6824] Ford, A., Raiciu, C., Handley, M. and O. Bonaventure, "TCP Extensions for Multipath Operation with Multiple Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P. and T. Kivinen, "Internet Key Exchange Protocol Version 2 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 2014.

Appendix A. MAMS Control Plane Optimization over Secure Connections

If the connection between CCM and NCM over which the MAMS control plane messages are transported is assumed to be secure, UDP is used as the transport for management & control messages between NCM and UCM (see Figure 9).



+-----------------------------------------------------+
|        Multi-Access (MX) Control Message            |
|-----------------------------------------------------| 
|              	 UDP	      	     	              |
|-----------------------------------------------------|
		

Figure 17: UDP-based MAMS Control plane Protocol Stack

Authors' Addresses

Satish Kanugovi Nokia EMail: satish.k@nokia.com
Subramanian Vasudevan Nokia EMail: vasu.vasudevan@nokia.com
Jing Zhu Intel EMail: jing.z.zhu@intel.com
Florin Baboescu Broadcom EMail: florin.baboescu@broadcom.com
Shuping Peng Huawei EMail: pengshuping@huawei.com
SungHoon Seo Korea Telecom EMail: sh.seo@kt.com
Julius Mueller AT&T EMail: jm169k@att.com