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Versions: (draft-zhu-intarea-mams-control-protocol) 00

INTAREA                                                      S. Kanugovi
Internet-Draft                                                     Nokia
Intended status: Informational                               F. Baboescu
Expires: July 2, 2018                                           Broadcom
                                                                  J. Zhu
                                                                   Intel
                                                              J. Mueller
                                                                    AT&T
                                                                  S. Seo
                                                           Korea Telecom
                                                       December 29, 2017


                  Multiple Access Management Services
                draft-kanugovi-intarea-mams-framework-00

Abstract

   In multiconnectivity scenarios the end-user devices can
   simultaneously connect to multiple networks based on different access
   technologies and network architectures like WiFi, LTE, DSL.  Both the
   quality of experience of the users and the overall network
   utilization and efficiency may be improved through a smart selection
   and combination of access and core network paths that can dynamically
   adapt to changing network conditions.  This document presents the
   problem statement and proposes solution principles.  It specifies the
   requirements and architecture for the multi-access management
   services framework that can be used to 1) flexibly select the best
   combination of access and core network paths for uplink and downlink,
   as well as 2) determining the user plane treatment and traffic
   distribution over the selected links ensuring better network
   efficiency and enhanced application performance.

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 https://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."




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   This Internet-Draft will expire on July 2, 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
   (https://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.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Access technology agnostic interworking . . . . . . . . .   6
     4.2.  Support common transport deployments  . . . . . . . . . .   6
     4.3.  Independent Access path selection for Uplink and Downlink   6
     4.4.  Core selection independent of uplink and downlink access    6
     4.5.  Adaptive network path selection . . . . . . . . . . . . .   7
     4.6.  Multipath support and Aggregation of access link
           capacities  . . . . . . . . . . . . . . . . . . . . . . .   7
     4.7.  Scalable mechanism based on user plane interworking . . .   7
     4.8.  Separate Control and Data plane functions . . . . . . . .   7
     4.9.  Lossless Path (Connection) Switching  . . . . . . . . . .   8
     4.10. Concatenation and Fragmentation to adapt to MTU
           differences . . . . . . . . . . . . . . . . . . . . . . .   8
     4.11. Configuring network middleboxes based on negotiated
           protocols . . . . . . . . . . . . . . . . . . . . . . . .   8
     4.12. Policy based Optimal path selection . . . . . . . . . . .   8
     4.13. Access Technology Agnostic Control signaling  . . . . . .   8
     4.14. Service discovery and reachability  . . . . . . . . . . .   9
   5.  Solution Principles . . . . . . . . . . . . . . . . . . . . .   9
   6.  MAMS Reference Architecture . . . . . . . . . . . . . . . . .   9
   7.  MAMS Protocol Architecture  . . . . . . . . . . . . . . . . .  12
     7.1.  MAMS Control-Plane Protocol . . . . . . . . . . . . . . .  12
     7.2.  MAMS User Plane Protocol  . . . . . . . . . . . . . . . .  13
   8.  MAMS Control Plane Procedures . . . . . . . . . . . . . . . .  15
     8.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .  15
     8.2.  Common fields in MAMS Control Messages  . . . . . . . . .  17



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     8.3.  Common procedures for MAMS Control Messages . . . . . . .  17
       8.3.1.  Message Timeout . . . . . . . . . . . . . . . . . . .  17
       8.3.2.  Keep Alive Procedure  . . . . . . . . . . . . . . . .  17
     8.4.  Discovery & Capability Exchange . . . . . . . . . . . . .  18
     8.5.  User Plane Configuration  . . . . . . . . . . . . . . . .  22
     8.6.  MAMS Path Quality Estimation  . . . . . . . . . . . . . .  26
     8.7.  MAMS Traffic Steering . . . . . . . . . . . . . . . . . .  27
     8.8.  MAMS Network ID Indication  . . . . . . . . . . . . . . .  28
     8.9.  MAMS Client Measurement Configuration and Reporting . . .  29
     8.10. MAMS Session Termination Procedure  . . . . . . . . . . .  31
   9.  Generic MAMS Signaling Flow . . . . . . . . . . . . . . . . .  32
   10. Applying MAMS Control Procedures with MPTCP Proxy as User
       Plane . . . . . . . . . . . . . . . . . . . . . . . . . . . .  34
   11. Applying MAMS Control Procedures for Network Assisted Traffic
       Steering when there is no convergence layer . . . . . . . . .  39
   12. Co-existence of MX Adaptation and MX Convergence Layers . . .  41
   13. Security Considerations . . . . . . . . . . . . . . . . . . .  41
     13.1.  MAMS Control plane security  . . . . . . . . . . . . . .  41
     13.2.  MAMS User plane security . . . . . . . . . . . . . . . .  42
   14. Implementation considerations . . . . . . . . . . . . . . . .  42
   15. Applicability to Multi Access Edge Computing  . . . . . . . .  42
   16. Contributing Authors  . . . . . . . . . . . . . . . . . . . .  43
   17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  43
   18. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  43
   19. References  . . . . . . . . . . . . . . . . . . . . . . . . .  43
     19.1.  Normative References . . . . . . . . . . . . . . . . . .  43
     19.2.  Informative References . . . . . . . . . . . . . . . . .  43
   Appendix A.  MAMS Control Plane Optimization over Secure
                Connections  . . . . . . . . . . . . . . . . . . . .  45
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  45

1.  Introduction

   Multi Access Management Services (MAMS) is a programmable framework
   that provides mechanisms for flexible selection of network paths in a
   multi-access communication environment, based on application needs.
   It leverages network intelligence and policies to dynamically adapt
   traffic distribution across selected paths and user plane treatment
   to changing network/link conditions.  The network path selection and
   configuration messages are carried as user plane data between the
   functional elements in the network and the end-user device, and thus
   without any impact to the control plane signaling schemes of the
   individual access network.  For example, in a multi-access network
   with LTE and WiFi technologies, existing LTE and existing WiFi
   signaling procedures will be used to setup the LTE and WiFi
   connections, respectively, and MAMS specific control plane messages
   are carried as LTE or WiFi user plane data.  The proposed MAMS
   framework offers the capabilities of smart selection and flexible



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   combination of access paths and core network paths, as well as the
   user plane treatment when the traffic is distributed across the
   selected paths.  Thus, it is a broad programmable framework providing
   functions beyond just sharing network policies, e.g.  ANDSF that
   provides policies/rules for assisting 3GPP devices to discover and
   select available access networks.  Further, it allows choosing and
   configuring user plane treatment for the traffic over the multiple
   paths, depending on needs of the application.

   The document presents the requirements, solution principles,
   functional architecture, and protocols for realizing the MAMS
   framework.  MAMS mechanisms are not dependent on any specific access
   network type or user plane protocols like TCP, UDP, GRE, MPTCP etc.
   It co-exists and complements the existing protocols by providing a
   way to negotiate and configure these protocols based on client and
   network capabilities to match the multi-access scenario.  Further it
   allows exchanges of network state information and leveraging network
   intelligence to optimize the performance of such protocols.

   An important goal for MAMS is to ensure that it either requires
   minimum dependency or (better) no dependency on the actual access
   technologies of the participating links, beyond the fact that MAMS
   functional elements form an IP-overlay across the multiple paths.
   This allows the scheme to be future proof by allowing independent
   technology evolution of the existing access and core networks as well
   as, seamless integration of new access technologies.

2.  Terminology

   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].

   "Client": The end-user device supporting connections with multiple
   access nodes, possibly over different access technologies.

   "Multiconnectivity Client": A client with multiple network
   connections.

   "Access network": The segment in the network that delivers user data
   packets to the client via an access link like WiFi airlink, LTE
   airlink, or DSL.

   "Core": The functional element that anchors the client IP address
   used for communication with applications via the network.

   "Network Connection manager"(NCM): A functional entity in the network
   that handles MAMS control messages from the client and configures



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   distribution of data packets over the multiple available access and
   core network paths, and user plane treatment of the traffic flows.

   "Client Connection Manager" (CCM): A functional entity in the client
   that exchanges MAMS Signaling with the Network Connection Manager and
   configures the multiple network paths at the client for transport of
   user data.

   "Network Multi Access Data Proxy" (N-MADP): This functional entity in
   the network handles the user data traffic forwarding across multiple
   network paths.  N-MADP is responsible for MAMS related user-plane
   functionalities in the network.

   "Client Multi Access Data Proxy" (C-MADP): This functional entity in
   the client handles the user data traffic forwarding across multiple
   network paths.  C-MADP is responsible for MAMS related user-plane
   functionalities in the client.

   "Anchor Connection": Refers to the network path from the N-MADP to
   the user plane gateway (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.

3.  Problem Statement

   Typically, an end-user device has access to multiple communication
   networks based on different technologies, say LTE, WiFi, DSL,
   MuLTEfire, for accessing application services.  Different
   technologies exhibit benefits and limitations in different scenarios.
   For example, WiFi provides high throughput for end users when under
   good coverage, but the throughput degrades significantly as the user
   moves closer to the edge of WiFi coverage (typically in the range of
   few tens of meters) or with large user population (due to contention
   based WiFi access scheme).  In LTE networks, the capacity is often
   constrained by the limited availability of licensed spectrum.
   However, the quality of the service is predictable even in multi-user
   scenarios due to controlled scheduling and licensed spectrum usage.

   Additionally, the use of a particular access network path is often
   coupled with the use of its associated core network and the services
   that are offered by it.  For example, in an enterprise that has
   deployed both WiFi and LTE networks, the enterprise services, like
   printers, Corporate Audio and Video conferencing, are accessible only
   via WiFi access connected to the enterprise hosted (WiFi) core,
   whereas the LTE access can be used to get operator core anchored
   services including access to public Internet.



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   Thus, application performance in different scenarios becomes
   dependent on the choice of the access networks (e.g.  WiFi, LTE,
   etc.) because of the coupling of the access and the core network
   paths.  Therefore, to achieve the best possible application
   performance in a wide range of scenarios, a framework is needed that
   allows the selection and flexible combination of access and core
   network paths for uplink and downlink data delivery.

   For example, to ensure best performance for enterprise applications
   at all times, in uncongested scenarios, when the user is under good
   WiFi coverage, it would be beneficial to use WiFi access in both
   uplink and downlink for connecting to enterprise applications.
   However in congested scenarios or when the user is getting close to
   the edge of its WiFi coverage, the use of WiFi in uplink by multiple
   users can lead to degraded capacity and increased delays due to
   contention.  In this case, it would be beneficial to at least use the
   LTE access for increased uplink coverage while WiFi may still
   continue to be used for downlink

4.  Requirements

   The requirements set out in this section are for the definition of
   behavior of the MAMS mechanism and the related functional elements.

4.1.  Access technology agnostic interworking

   The access nodes may use different technology types like LTE, WiFi,
   etc.  The framework, however, MUST agnostic to the type of underlying
   technology used at the access network.

4.2.  Support common transport deployments

   The network path selection and user data distribution MUST work
   transparently across various transport deployments that include e2e
   IPsec, VPNs, and middleboxes like NATs and proxies.

4.3.  Independent Access path selection for Uplink and Downlink

   Client should be able to transmit on the uplink and, receive on the
   downlink, using one or more accesses.  The selection of the access
   paths for uplink and downlink SHOULD happen independent of each
   other.

4.4.  Core selection independent of uplink and downlink access

   A client SHOULD flexibly select the Core, independent of the access
   paths used to reach the Core, depending on the application needs,
   local policies and the result of MAMS control plane negotiation.



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4.5.  Adaptive network path selection

   The framework MUST have the ability to determine the quality of each
   of the network paths, e.g. access link delay and capacity.  The
   network path quality information needs to be considered in the logic
   for selection of the combination of network paths to be used for
   transporting user data.  The path selection algorithm can use network
   path quality information, in addition to other considerations like
   network policies, for optimizing network usage and enhancing QoE
   delivered to the user.

4.6.  Multipath support and Aggregation of access link capacities

   The framework MUST support distribution and aggregation of user data
   across multiple network paths at the IP layer.  The client SHOULD be
   able to leverage the combined capacity of the multiple network
   connections by enabling simultaneous transport of user data over
   multiple network paths.  If required, packet re-ordering needs to be
   done at the receiver.  The framework MUST allow flexibility to choose
   the flow steering and aggregation protocols based on capabilities
   supported by the client and the network data plane entities.  The
   multi-connection aggregation solution MUST support existing transport
   and network layer protocols like TCP, UDP, GRE.  The framework MUST
   allow use and configuration of existing aggregation protocols such as
   Multi-Path TCP(MPTCP) and SCTP.

4.7.  Scalable mechanism based on user plane interworking

   The framework MUST leverage commonly available routing and tunneling
   capabilities to provide user plane interworking functionality.  The
   addition of functional elements in the user plane path between the
   client and the network MUST not impact the access technology specific
   procedures.  This makes solution easy to deploy and scale when
   different networks are added and removed.

4.8.  Separate Control and Data plane functions

   The client MUST use the control plane protocol to negotiate with the
   network, the choice of access and core network paths for both uplink
   and downlink, as well as the user plane protocol treatment.  The
   control plane MUST configure the actual user plane data distribution
   function per this negotiation.  A common control protocol SHOULD
   allow creation of multiple user plane function instance with
   potentially different user plane (e.g. tunneling) protocol types.
   This enables maintaining a clear separation between the control and
   data plane functions, allowing the framework to be scalable and
   extensible, e.g. using SDN based architecture and implementations.




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4.9.  Lossless Path (Connection) Switching

   When switching data traffic from one path (connection) to another,
   packets may be lost or delivered out-of-order, which will have
   negative impacts on the performance of higher layer protocols, e.g.
   TCP.  The framework SHOULD provide necessary mechanisms to ensure in-
   order delivery at the receiver, e.g. during path switching.  The
   framework MUST not cause any packet loss beyond that of access
   network mobility functions may cause.

4.10.  Concatenation and Fragmentation to adapt to MTU differences

   Different network paths may have different security and middlebox
   (e.g NAT) configurations, which will lead to use of different
   tunneling protocols for transport of data between the network user
   plane function and the client.  As a result, different effective
   payload sizes (e.g. due to variable encapsulation header overheads)
   per network path are possible.  Hence, MAMS framework SHOULD support
   fragmentation of a single IP packet payload across MTU sized IP
   packets to avoid IP fragmentation when aggregating packets from
   different paths.  Further, concatenation of multiple IP packets into
   a single IP packet to improve efficiency in packing the MTU size
   should also be supported.

4.11.  Configuring network middleboxes based on negotiated protocols

   The framework SHOULD enable identification of the optimal parameters
   that may be used for configuring the middle-boxes, like radio link
   dormancy timers, binding expiry times and supported MTUs, for
   efficient operation of the user plane protocols, based on parameters
   negotiated between the client and the network, e.g.  Configuring
   longer binding expiry time in NATs when UDP transport is used in
   contrast to the scenario where TCP is configured at the transport
   layer.

4.12.  Policy based Optimal path selection

   The framework MUST support consideration of policies at the client,
   in addition to guidance from the network, for network path selection
   addressing different application requirements.

4.13.  Access Technology Agnostic Control signaling

   The control plane signaling MUST NOT be dependent on the underlying
   access technology procedures, e.g. be carried transparently as user
   plane.  It should support delivery of control plane signaling over
   the existing Internet protocols, e.g.  TCP or UDP.




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4.14.  Service discovery and reachability

   There can be multiple instances of the control and user plane
   functional elements of the framework, either collocated or hosted on
   separate network elements, and reachable via any of the available
   user plane paths.  The client MUST have flexibility to choose the
   appropriate control plane instance in the network and use the control
   plane signaling to choose the desired user plane functional element
   instances.  The choice can be based on considerations like, but not
   limited to, quality of link through which the network function is
   reachable, client preferences, pre-configuration etc.

5.  Solution Principles

   This document proposes the Multiple Access Management Services(MAMS)
   framework for dynamic selection and flexible combination of access
   and core network paths independently for the uplink and downlink, as
   well as the user plane treatment for the traffic spread across the
   selected links.  MAMS framework consists of clearly separated control
   and user plane functions in the network and the client.  The control
   plane protocol allows configuration of the user plane protocols and
   desired network paths for transport of application traffic.  The
   control plane messages are carried as user plane data over any of the
   available network paths between the peer control plane functional
   elements in the client and the network .  The selection of paths and
   user plane treatment of the traffic, is based on negotiation of
   capabilities (of device and network) and network link quality between
   the user plane functional elements at the end-user device/client and
   the network.  The framework enables leveraging network intelligence
   to setup and dynamically configure the best network path combination
   based on device and network capabilities, application needs and
   knowledge of the network state.

6.  MAMS Reference Architecture

















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        +--------------------------------------------------------+
        |           +---------------+       +---------------+    |
        |           !               !       !               !    |
        |           !Core(IP anchor)! +---+ !Core(IP anchor)!    |
        |           !network 1      !       !(network 'n'   !    |
        |           !               !       !               !    |
        |           +---------------+       +---------------+    |
        |                           \             /              |
        |                     Anchor \   +---+ Anchor            |
        |                     Connection 1     Connection 'n'    |
        |                              \       /                 |
        |              +---------------+\+---+/+------+          |
        |              | |-----+      +----------+    |          |
        |            +----|NCM !      |  N-MADP  |    |          |
        |            | | |-----+      +----------+    |          |
        |            | +------------------------------+          |
        |            |                /           \              |
        |    Control Plane     Delivery  +----+Delivery          |
        |    Path (over any    Connection 1    Connection 'n'    |
        |    access user plane)    /                 \           |
        |            |            /                   \          |
        |         +------------------+        +---------------+  |
        |         |  |  Access       | +---+  | Access        |  |
        |         |  |  n/w 1        |        |  n/w 'n'      |  |
        |         +------------------+        +---------/-----+  |
        +-----------------------------\----------------/---------+
                     |                 \              /
                     |           +---- -\------------/-+
                     |           | +---+ \ |------+ /  |
                     +------------+CCM |  \|C-MADP|/   |
                                 | +---+   +------+    |
                                 |        Client       |
                                 +---------------------+


                   Figure 1: MAMS Reference Architecture

   Figure 1 illustrates MAMS architecture for the scenario of a client
   served by multiple (n) networks.  It introduces the following
   functional elements,

   o  Network Connection Manager (NCM) and Client Connection Manager
      (CCM) in the control plane, and
   o  Network Multi Access Data Proxy (N-MADP) and Client Multi Access
      Data Proxy (C-MADP) handling the user plane.

   NCM: It is the functional element in the network that handles the
   MAMS control plane procedures.  It configures the network (N-MADP)



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   and client (C-MADP) user plane functions like negotiating the client
   on the use of available access network paths, protocols and rules for
   processing the user plane traffic, as well as link monitoring
   procedures.  The control plane messages between the NCM and CCM are
   transported as an overlay, without any impact to the underlying
   access networks.

   CCM: It is the peer functional element in the client for handling
   MAMS control plane procedures.  It manages multiple network
   connections at the client.  It is responsible for exchange of MAMS
   signaling messages with the NCM for supporting functions like UL and
   DL user network path configuration for transporting user data
   packets, link probing and reporting to support adaptive network path
   selection by NCM.  In the downlink, for the user data received by the
   client, it configures C-MADP such that application data packet
   received over any of the accesses to reach the appropriate
   application on the client.  In the uplink, for the data transmitted
   by the client, it configures the C-MADP to determine the best access
   links to be used for uplink data based on a combination of local
   policy and network policy delivered by the NCM.

   N-MADP: It is the functional element in the network that handles the
   user data traffic forwarding across multiple network paths, as well
   as other user-plane functionalities like encapsulation,
   fragmentation, concatenation, reordering, retransmission, etc.  It is
   the distribution node that routes the uplink user plane traffic to
   the appropriate anchor connection towards the core network, and the
   downlink user traffic to the client over the appropriate delivery
   connection(s).  In the downlink, the NCM configures the use of
   delivery connections, and user plane protocols at the N-MADP for
   transporting user data traffic.  The N-MADP should implement ECMP
   support for the down link traffic.  Or alternatively, it may be
   connected to a router with ECMP functionality.  The load balancing
   algorithm at the N-MADP is configured by the NCM, based on static
   and/or dynamic network policies like assigning access and core paths
   for specific user data traffic type, data volume based percentage
   distribution, and link availability and feedback information from
   exchange of MAMS signaling with the CCM at the Client.. N-MADP can be
   configured with appropriate user plane protocols to support both per-
   flow and per-packet traffic distribution across the delivery
   connections.  In the uplink, N-MADP selects the appropriate anchor
   connection over which to forward the user data traffic, received from
   the client (via the delivery connections).  The forwarding rules in
   the uplink at the N-MADP are configured by the NCM based on
   application requirements, e.g.  Enterprise hosted Application flows
   via Wi-Fi Anchor, Mobile Operator hosted applications via the
   Cellular Core.




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   C-MADP: It is the functional element in the client that handles the
   MAMS user plane data procedures.  C-MADP is configured by CCM based
   on signaling exchange with NCM and local policies at the client.  The
   CCM configures the selection of delivery connections and the user
   plane protocols to be used for uplink user data traffic based on the
   signaling exchanged with NCM.  The C-MADP entity handles user plane
   data forwarding across multiple delivery connections and associated
   user-plane functions like encapsulation, fragmentation,
   concatenation, reordering, retransmissions, etc.

   The NCM and N-MADP can be either collocated or instantiated on
   different network nodes.  NCM can setup multiple N-MADP instances in
   the network.  NCM controls the selection of N-MADP instance by the
   client and the rules for distribution of user traffic across the
   N-MADP instances., This is beneficial in multple deployment
   scenarios, like the following examples.

   o  Different N-MADP instances to handle different sets of clients for
      load balancing across clients
   o  Address deployment topologies e.g.  N-MADP hosted at the user
      plane node at the access edge or in the core network, while the
      NCM hosted at the access edge node)
   o  Address access network technology architecture.  For exanple,
      N-MADP instance at core network node to manage traffic
      distribution across LTE and DSL networks, and N-MADP instance at
      access network node to manage traffic distribution across LTE and
      Wi-Fi traffic.
   o  A single client can be configured to use multiple N-MADP
      instances.  This is beneficial in addressing different application
      requirements.  For example, separate N-MADP instances to handle
      TCP and UDP transport based traffic.

   Thus, MAMS architecture flexibly addresses multiple network
   deployments.

7.  MAMS Protocol Architecture

   This section describes the protocol structure for the MAMS User and
   Control plane functional elements.

7.1.  MAMS Control-Plane Protocol

   Figure 2 shows the default MAMS control plane protocol stack.
   WebSocket is used for transporting management and control messages
   between NCM and CCM.






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                 +------------------------------------------+

                 |    Multi Access (MX) Control Message     |

                 |                                          |

                 +------------------------------------------+

                 |                WebSocket                 |

                 |                                          |

                 +------------------------------------------+

                 |               TCP/TLS                    |

                 |                                          |

                 +------------------------------------------+




           Figure 2: TCP-based MAMS Control Plane Protocol Stack

7.2.  MAMS User Plane Protocol

   Figure 3 shows the MAMS user plane protocol stack.























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          +-----------------------------------------------------+

          |      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 3: MAMS User Plane Protocol Stack

   It consists of the following two Sublayers:

   o  Multi-Access (MX) Convergence Sublayer: The MAMS framework
      configures the Convergence sublayer to perform multi-access
      specific tasks in the user plane.  This layer performs functions



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      like access (path) selection, multi-link (path) aggregation,
      splitting/reordering, lossless switching, fragmentation,
      concatenation, etc.  MX Convergence layer can be implemented using
      existing user plane protocols like MPTCP or by adapting
      encapsulating header/trailer schemes (e.g Trailer Based MX
      Convergence as specified in [I-D.zhu-intarea-mams-user-protocol]).
   o  Multi-Access (MX) Adaptation Sublayer: The MAMS framework
      configures the Adaptation Sublayer to address transport network
      related aspects like reachability and security in the user plane.
      This layer performs functions to handle tunnelling, network layer
      security, and NAT.  MX Adaptation can be implemented using IPsec,
      DTLS or Client NAT (Source NAT at Client with inverse mapping at
      N-MADP [I-D.zhu-intarea-mams-user-protocol]).  The MX Adaptation
      Layer is optional and can be independently configured for each of
      the Access Links.  E.g.  In a deployment with LTE (assumed secure)
      and Wi-Fi (assumed not secure), the MX Adaptation Sublayer can be
      omitted for the LTE link but MX Adaptation Sublayer is configured
      as IPsec for securing the Wi-Fi link.  Further details on the MAMS
      user plane are described in [I-D.zhu-intarea-mams-user-protocol].

8.  MAMS Control Plane Procedures

8.1.  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.  As an example, the client can obtain the NCM
   credentials 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 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.  Further, NCM and CCM exchange link status information to adapt
   traffic steering and user plane treatment with dynamic network
   conditions.  The key procedures are described in details in the
   following sub-sections.







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                      +-----+                +-----+

                      | CCM |                | NCM |

                      +--+--+                +--+--+

                         |    Discovery and     |

                         |    Capability        |

                         |    Exchange          |

                         <---------------------->

                         |                      |

                         |    User Plane        |

                         |    Protocols         |

                         |    Setup             |

                         <---------------------->

                         |    Path Quality      |

                         |    Estimation        |

                         <---------------------->

                         | Network capabilities |

                         | e.g. RNIS[ETSIRNIS]  |

                         <----------------------+

                         |                      |

                         | Network policies     |

                         <----------------------+

                         +                      +








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                  Figure 4: MAMS Control Plane Procedures

8.2.  Common fields in MAMS Control Messages

   Each MAMS control message consists of the following common fields:

   o  Version: indicates the version of MAMS control protocol.
   o  Message Type: indicates the type of the message, e.g.  MX
      Discovery, MX Capability REQ/RSP etc.
   o  Sequence Number: auto-incremented integer to uniquely identify a
      transaction of message exchange, e.g.  MX Capability REQ/RSP.

8.3.  Common procedures for MAMS Control Messages

   This section describes the common procedures for MAMS Control
   Messages.

8.3.1.  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, and the sender reverts
   back to native non-multi access/single path mode.  CCM may initiate
   the MAMS discovery procedure for re-establishment of the MAMS
   session.

8.3.2.  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.



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   MX KEEP ALIVE REQ includes following information:

   o  Reason: Can be 'Timeout' or 'Handover'.  Reason 'Handover' shall
      be used by CCM only on detection of handover.
   o  Unique Session Identifier: As defined in Section 8.4.
   o  Connection Id: This field shall be mandatorily be included if the
      reason is 'Handover'.
   o  Delivery Node Identity (ECGI in case of LTE and WiFi AP Id or MAC
      address in case of WiFi).  This field shall be mandatorily be
      included if the reason is 'Handover'.

8.4.  Discovery & Capability Exchange

   Figure 5 shows the MAMS discovery and capability exchange procedure
   consisting of the following key steps:




































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         CCM                                                  NCM

          |                                                    |

          +------- MX Discovery Message ---------------------->|

          |                                         +-----------------+

          |                                         |Learn CCM        |
          |                                         | IP address      |

          |                                         |& port           |

          |                                         +-----------------+

          |                                                    |

          |<--------------------------------MX System INFO-----|

          |                                                    |

          |---------------------------------MX Capability REQ->|

          |<----- MX Capability RSP----------------------------|

          |---------------------------------MX Capability ACK->|
          |                                                    |

          +                                                    +




   Figure 5: MAMS Control Procedure for Discovery & Capability Exchange

   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:

   o  MAMS Version

   MX System INFO includes the following information:

   o  Number of Anchor Connections

      For each Anchor Connection, it includes the following parameters:



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      *  Connection ID: Unique identifier for the Anchor Connection
      *  Connection Type (e.g., 0: Wi-Fi; 1: 5G NR; 2: MulteFire; 3:
         LTE)
      *  NCM Endpoint Address (For Control Plane Messages over this
         connection)

         +  IP Address or FQDN (Fully Qualified Domain Name)
         +  Port Number

   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:

   o  MX Feature Activation List: Indicates if the corresponding feature
      is supported or not, e.g. lossless switching, fragmentation,
      concatenation, Uplink aggregation, Downlink aggregation,
      Measurement, probing, etc.
   o  Number of Anchor Connections (Core Networks)

      For each Anchor Connection, it includes the following parameters:

      *  Connection ID
      *  Connection Type (e.g., 0: Wi-Fi; 1: 5G NR; 2: MulteFire; 3:
         LTE)
   o  Number of Delivery Connections (Access Links)

      For each Delivery Connection, it includes the following
      parameters:

      *  Connection ID
      *  Connection Type (e.g., 0: Wi-Fi; 1: 5G NR; 2: MulteFire; 3:
         LTE)
   o  MX Convergence Method Support List

      *  Trailer-based MX Convergence
      *  MPTCP Proxy
      *  GRE Aggregation Proxy
   o  MX Adaptation Method Support List

      *  UDP Tunnel without DTLS
      *  UDP Tunnel with DTLS
      *  IPsec Tunnel [RFC3948]
      *  Client NAT

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



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   o  MX Feature Activation List: Indicates if the corresponding feature
      is enabled or not, e.g. lossless switching, fragmentation,
      concatenation, Uplink aggregation, Downlink aggregation,
      Measurement, probing, etc.
   o  Number of Anchor Connections (Core Networks)

      For each Anchor Connection, it includes the following parameters:

      *  Connection ID
      *  Connection Type (e.g., 0: Wi-Fi; 1: 5G NR; 2: MulteFire; 3:
         LTE)
   o  Number of Delivery Connections (Access Links)

      For each Delivery Connection, it includes the following
      parameters:

      *  Connection ID
      *  Connection Type (e.g., 0: Wi-Fi; 1: 5G NR; 2: Multi-Fire; 3:
         LTE)
   o  MX Convergence Method Support List

      *  Trailer-based MX Convergence
      *  MPTCP Proxy
      *  GRE Aggregation Proxy
   o  MX Adaptation Method Support List

      *  UDP Tunnel without DTLS
      *  UDP Tunnel with DTLS
      *  IPsec Tunnel [RFC3948]
      *  Client NAT

   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.

   o  NCM Id: Unique Identity of the NCM in the operator network.
   o  Session Id: Unique identity assigned to the CCM instance by this
      NCM instance.

   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

   o  Unique Session Identifier: Same identifier as provided in MX
      Capability RSP.
   o  Acknowledgement: An indication if the client has accepted or
      rejected the capability phase.



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      *  MX ACCEPT: CCM Accepts the Capability set proposed by the NCM.
      *  MX REJECT: CCM Rejects the Capability set proposed by the NCM.

   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.

8.5.  User Plane Configuration

   Figure 6 shows the user plane configuration procedure consisting of
   the following key steps:




































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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 6: MAMS Control Procedure for User Plane Configuration

   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

   o  Unique Session Identifier: Identity of the CCM identity at NCM,
      created by NCM during the capability exchange phase.




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   o  Reconfiguration Action: indicate the reconfiguration action
      (0:release; 1: setup; 2: update).
   o  Connection ID: identify the connection for reconfiguration

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

   o  IP address of the connection
   o  SSID (if Connection Type = WiFi)
   o  MTU of the connection: MTU of the delivery path that is calculated
      at the UE for use by NCM to configure fragmentation and
      concatenation procedures[I-D.zhu-intarea-mams-user-protocol] at
      N-MADP.
   o  Delivery Node Identity: Identity of the node to which the client
      is attached.  ECGI in case of LTE and WiFi AP Id or MAC address in
      case of WiFi.

   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 is used to create (multiple) MADP instance(s) and
   consists of the following parameters:

   o  Number of Anchor Connections (Core Networks)

      For Each Anchor Connection, it includes the following parameters

      *  Anchor Connection ID
      *  Connection Type (e.g., 0: Wi-Fi; 1: 5G NR; 2: MulteFire; 3:
         LTE)
      *  MX Convergence Method

         +  Trailer-based MX Convergence
         +  MPTCP Proxy
         +  GRE Aggregation Proxy
      *  MX Convergence Method Parameters

         +  Convergence Proxy IP Address



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         +  Convergence Proxy Port
      *  Number of Delivery Connections

         For each Delivery Connection, include the following:

         +  Delivery Connection ID
         +  Connection Type (e.g., 0: Wi-Fi; 1: 5G NR; 2: MulteFire; 3:
            LTE)
         +  MX Adaptation Method

            -  UDP Tunnel without DTLS
            -  UDP Tunnel with DTLS
            -  IPSec Tunnel
            -  Client NAT
         +  MX Adaptation Method Parameters

            -  Tunnel Endpoint IP Address
            -  Tunnel Endpoint Port
            -  Shared Secret

   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.

   Similarly, as an example of the MX Convergence Method configuration
   is to indicate the convergence protocol 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:

   o  Unique Session Identifier: Session identifier provided to the
      client in MX Capability RSP.
   o  MX Probe Parameters (included if probing is supported):

      *  UDP Port Number for receiving Probes
   o  Client Adaptation Layer Parameters:

      *  Number of Delivery Connections
      *  For each Delivery Connection, include the following:

         +  Delivery Connection ID




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         +  UDP port number: If UDP based adaptation is in use, the UDP
            port at C-MADP side

8.6.  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.  In special deployments where the
   NCM has interfaces with access nodes, direct interfaces can be used
   to gather path quality information.  For example, 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 an alternative for estimating
   path quality.


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





    Figure 7: MAMS Control Plane Procedure for Path Quality Estimation

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

   o  Connection ID (of Delivery Connection whose path quality needs to
      be estimated)
   o  Init Probe Test Duration (ms)
   o  Init Probe Test Rate (Mbps)
   o  Init Probe Size (Bytes)
   o  Init Probe Ack Required (0 -> No/1 -> Yes)
   o  Active Probe Frequency (ms)
   o  Active Probe Size (Bytes)
   o  Active Probe Test Duration (ms)
   o  Active Probe Ack Required (0 -> No/1 -> Yes)

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





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   o  Unique Session Identifier: Session identifier provided to the
      client in MX Capability RSP.
   o  Init Probe Results Configuration

      *  Lost Probes (%)
      *  Probe Receiving Rate (packets per second)
   o  Active Probe Results Configuration

      *  Average Throughput in the last Probe Duration

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

   o  Initialization phase: A network path that is not included by
      N-MADP for transmission of user data is deemed to be in the
      Initialization phase.  The user data may be transmitted over other
      available network paths.
   o  Active phase: A network path that is included by N-MADP for
      transmission of user data is deemed to be in 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.

8.7.  MAMS Traffic Steering


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


                 Figure 8: 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




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   connections simultaneously, i.e. aggregation.  The message includes
   the following information:

   o  Connection ID of the Anchor Connection
   o  Connection ID List of Delivery Connections for DL traffic
   o  For the number of Specific UL traffic Templates, include the
      following

      *  Traffic Template for identifying the UL traffic
      *  Connection ID List of Delivery connections for UL traffic
         identified by the traffic template
   o  MX Feature Activation List: each parameter indicates if the
      corresponding feature is enabled or not: lossless switching,
      fragmentation, concatenation, Uplink aggregation, Downlink
      aggregation, Measurement, probing

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

   o  Unique Session Identifier: Session identifier provided to the
      client in MX Capability RSP.
   o  MX Feature Activation List: each parameter indicates if the
      corresponding feature is enabled or not: lossless switching,
      fragmentation, concatenation, Uplink aggregation, Downlink
      aggregation, probing

8.8.  MAMS Network ID Indication


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


              Figure 9: 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.








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8.9.  MAMS Client Measurement Configuration and Reporting



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


      Figure 10: 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:

   o  Delivery Connection ID
   o  Connection Type (e.g., 0: Wi-Fi; 1: 5G NR; 2: MulteFire; 3: LTE)
   o  If Connection Type is Wi-Fi

      *  WLAN_RSSI_THRESH: High and Low Thresholds for sending Average
         RSSI of the Wi-Fi Link.
      *  WLAN_RSSI_PERIOD: Periodicity in ms for sending Average RSSI of
         the Wi-Fi Link.
      *  WLAN_LOAD_THRESH: High and Low Thresholds for sending Loading
         of the WLAN system.
      *  WLAN_LOAD_PERIOD: Periodicity in ms for sending Loading of the
         WLAN system.
      *  UL_TPUT_THRESH: High and Low Thresholds for sending Reverse
         Link Throughput on the Wi-Fi link.
      *  UL_TPUT_PERIOD: Periodicity in ms for sending Reverse Link
         Throughput on the Wi-Fi link.
      *  DL_TPUT_THRESH: High and Low Thresholds for sending Forward
         Link Throughput on the Wi-Fi link.
      *  DL_TPUT_PERIOD: Periodicity in ms for sending Forward Link
         Throughput on the Wi-Fi link.
      *  EST_UL_TPUT_THRESH: High and Low Thresholds for sending Reverse
         Link Throughput (EstimatedThroughputOutbound as defined in
         [IEEE]) on the Wi-Fi link.





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      *  EST_UL_TPUT_PERIOD: Periodicity in ms for sending Reverse Link
         Throughput (EstimatedThroughputOutbound as defined in [IEEE])
         on the Wi-Fi link.
      *  EST_DL_TPUT_THRESH: High and Low Thresholds for sending Forward
         Link Throughput (EstimatedThroughputInbound as defined in
         [IEEE]) on the Wi-Fi link.
      *  EST_DL_TPUT_PERIOD: Periodicity in ms for sending Forward Link
         Throughput (EstimatedThroughputInbound as defined in [IEEE]) on
         the Wi-Fi link.
   o  If Connection Type is LTE

      *  LTE_RSRP_THRESH: High and Low Thresholds for sending RSRP of
         Serving LTE link.
      *  LTE_RSRP_PERIOD: Periodicity in ms for sending RSRP of Serving
         LTE link.
      *  LTE_RSRQ_THRESH: High and Low Thresholds for sending RSRQ of
         the serving LTE link.
      *  LTE_RSRQ_PERIOD: Periodicity in ms for sending RSRP of Serving
         LTE link.
      *  UL_TPUT_THRESH: High and Low Thresholds for sending Reverse
         Link Throughput on the serving LTE link.
      *  UL_TPUT_PERIOD: Periodicity in ms for sending Reverse Link
         Throughput on the serving LTE link.
      *  DL_TPUT_THRESH: High and Low Thresholds for sending Forward
         Link Throughput on the serving LTE link.
      *  DL_TPUT_PERIOD: Periodicity in ms for sending Forward Link
         Throughput on the serving LTE link.

   The MX MEAS REPORT message contains the following parameters

   o  Unique Session Identifier: Session identifier provided to the
      client in MX Capability RSP.
   o  For each Delivery Connection, include the following:

      *  Delivery Connection ID
      *  Connection Type (e.g., 0: Wi-Fi; 1: 5G NR; 2: MulteFire; 3:
         LTE)
      *  Delivery Node Identity (ECGI in case of LTE and WiFi AP Id or
         MAC address in case of WiFi)
      *  If Connection Type is Wi-Fi

         +  WLAN_RSSI: Average RSSI of the Wi-Fi Link.
         +  WLAN_LOAD: Loading of the WLAN system.
         +  UL_TPUT: Reverse Link Throughput on the Wi-Fi link.
         +  DL_TPUT: Forward Link Throughput on the Wi-Fi link.
         +  EST_UL_TPUT: Estimated Reverse Link Throughput on the Wi-Fi
            link (EstimatedThroughputOutbound as defined in [IEEE]).




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         +  EST_DL_TPUT: Estimated Forward Link Throughput on the Wi-Fi
            link (EstimatedThroughputInbound as defined in [IEEE]).
      *  If Connection Type is LTE

         +  LTE_RSRP: RSRP of Serving LTE link.
         +  LTE_RSRQ: RSRQ of the serving LTE link.
         +  UL_TPUT: Reverse Link Throughput on the serving LTE link.
         +  DL_TPUT: Forward Link Throughput on the serving LTE link.

8.10.  MAMS Session Termination Procedure


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


     Figure 11: MAMS Session Termination Procedure - Client Initiated


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



     Figure 12: 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,



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   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:

   o  Normal Release
   o  No Response from Peer
   o  Internal Error

9.  Generic MAMS Signaling Flow



                            +----------------------------------------+
                            |   MAMS enabled Network of Networks     |
                            | +-----+    +-----+   +-----+    +------+
     +-----------------+    | |     |    |     |   |     |    |     ||
     |     Client      |    | |Netwo|    |Netwo|   |     |    |     ||
     | +-----+ +-----+ |    | |rk 1 |    |rk 2 +   |NCM  |    N-MADP||
     | C-MADP  |CCM  | |    | |(LTE)|    |(WiFi)   |     |    |     ||
     | +-----+ +-----+ |    | +-----+    +-----+   +-----+    +------|
     -+----------------+    +----------------------------------------+
      |   |       |              |          |         |          |
      |   |       |              |          |         |          |
      |   |    1.SETUP CONNECTION|          |         |          |
      |<-----------+------------>|          |         |          |
      |   |       |              +          +         |          |
      |   |       |  2. MAMS Capabilities Exchange    |          |
      |   |       |<-------------+----------+-------->|          |
      |   |       |              |          |         |          |
      |   |       +              |          |         |          |
      |   |    3. SETUP CONNECTION          |         |          |
      |<--+-------------------------------->|         |          |
      | 4c. Config| 4a. NEGOTIATE NETWORK PATHS, FLOW |4b. Config|
      | C-MADP    | PROTOCOL AND PARAMETERS |         |N-MADP    |
      |   |<----->|<-------------+----------+-------->|<-------->|
      |   |       |              +          +         |          |
      |   |       |5. ESTABLISH USER PLANE PATH ACCORDING TO     |
      |   |       | SELECTED FLOW PROTOCOL  |         |          |
      |   |<---------------------+----------+------------------->|
      |   |       |              |          |         |          |
      +   +       +              +          +         +          +


                         Figure 13: MAMS call flow





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   Figure 13 illustrates the MAMS signaling mechanism for negotiation of
   network paths and flow protocols between the client and the network.
   In this example scenario, the client is connected to two networks
   (say LTE and WiFi).

   1.  UE connects to network 1 and gets an IP address assigned by
       network 1.
   2.  CCM communicates with NCM functional element via the network 1
       connection and exchanges capabilities and parameters for MAMS
       operation.  Note: The NCM credentials (e.g.  NCM IP Address) can
       be made known to the UE by pre-provisioning.
   3.  Client sets up connection with network 2 and gets an IP address
       assigned by network 2.
   4.  CCM and NCM negotiate capabilities and parameters for
       establishment of network paths, which are then used to configure
       user plane functions N-MADP at the network and C-MADP at the
       client.

       4a.  CCM and NCM negotiate network paths, flow routing and
       aggregation protocols, and related parameters.

       4b.  NCM communicates with the N-MADP to exchange and configure
       flow aggregation protocols, policies and parameters in alignment
       with those negotiated with the CCM.

       4c.  CCM communicates with the C-MADP to exchange and configure
       flow aggregation protocols, policies and parameters in alignment
       with those negotiated with the NCM.


   5.  C-MADP and N-MADP establish the user plane paths, e.g. using IKE
       [RFC7296] signaling, based on the negotiated flow aggregation
       protocols and parameters specified by NCM.

   CCM and NCM can further exchange messages containing access link
   measurements for link maintenance by the NCM.  NCM evaluates the link
   conditions in the UL and DL across LTE and WiFi, based on link
   measurements reported by CCM and/or link probing techniques and
   determines the UL and DL user data distribution policy.  NCM and CCM
   also negotiate application level policies for categorizing
   applications, e.g.  based on DSCP, Destination IP address, and
   determining which of the available network paths, needs to be used
   for transporting data of that category of applications.  NCM
   configures N-MADP, and CCM configures C-MADP, based on the negotiated
   application policies.  CCM may apply local application policies, in
   addition to the application policy conveyed by the NCM.





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10.  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).

   Figure 14 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.




































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+------+   +---------+   +---------+   +---------+   +---------+   +------+
|      |   |         |   |         |   |         |   |         |   |      |
|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 14: MAMS-assisted MPTCP Proxy as User Plane - Initial Setup
                               with LTE leg

   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.



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   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.









































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+------+   +---------+   +---------+   +---------+   +---------+   +------+
|      |   |         |   |         |   |         |   |         |   |      |
|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 15: MAMS-assisted MPTCP Proxy as User Plane - Add Wi-Fi leg

   Figure 15 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 and 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



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

   Figure 16 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.









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+------+   +---------+   +---------+   +---------+   +---------+   +------+
|      |   |         |   |         |   |         |   |         |   |      |
|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 17: MAMS-assisted MPTCP Proxy as User Plane - Part 4

   Figure 17 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.

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

   Figure 18 shows the call flow describing MAMS control procedures
   applied for dynamic optimal path selection in a scenario convergence
   and Adaptation layer protocols are not omitted.  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



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   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)       |+--------------+



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  |<-------------+-------------+-------------+------------||Steer traffic |
  |14. MX TRAFFIC STEERING RSP (...)        |             ||to use Wi-Fi  |
  |<-------------+-------------+-------------+------------||link          |
  |             |             |             |             |+--------------+
+-----------------------------------------------------------------------++
|    Use Wi-Fi link for Data                                             |
+---------------------------------------------------------+-------------++
  |             |             |             |             |             |
  +             +             +             +             +             +



                 Figure 18: MAMS With No Convergence Layer

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

   MAMS user plane supports multiple instances and combinations of
   protocols to be used at 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 path needs 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.

13.  Security Considerations

13.1.  MAMS Control plane security

   The NCM functional element is hosted on a network node which is
   assumed to be within a secure network, e.g. within the operator's
   network, and is assumed to be protected against hijack attacks.

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

   For deployment scenarios where the security of the network path
   cannot be assumed, NCM and CCM implementations MUST support the "wss"
   URI scheme [RFC6455] and Transport Layer Security (TLS) [RFC5246] to
   secure control plane message exchange between the NCM and CCM.




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   For deployment scenarios where client authentication is desired, the
   WebSocket server can use any client authentication mechanisms
   available to a generic HTTP server, such as cookies, HTTP
   authentication, or TLS authentication.

13.2.  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.

14.  Implementation considerations

   MAMS builds on commonly available functions available on terminal
   devices that can be delivered as a software update over the popular
   end-user device operating systems, enabling rapid deployment and
   addressing the large deployed device base.

15.  Applicability to Multi Access Edge Computing

   Multi Access Edge Computing (MEC), earlier known as Mobile edge
   computing, is an access-edge cloud platform being standardized at
   ETSI, whose initial focus was to improve quality of experience by
   leveraging intelligence at cellular (e.g. 3GPP technologies like LTE)
   access edge, and the scope is now being extended to support access
   technologies beyond 3GPP.  This applicability of the framework
   described in this document to the MEC platform has been evaluated and
   tested in different network configurations.

   The NCM is hosted on the MEC cloud server that is located in the user
   plane path at the edge of multi-technology access networks.  The NCM
   and CCM negotiate the network path combinations based on application
   needs and the necessary user plane protocols to be used across the
   multiple paths.  The network conditions reported by the CCM to the
   NCM is complemented by Radio Analytics application[ETSIRNIS] residing
   at the MEC to configure the uplink and downlink access paths
   according to changing radio and congestion conditions.

   The user plane functional element, N-MADP, can either be collocated
   with the NCM at the MEC cloud server (e.g.  MEC hosted applications),
   or placed at a separate network element like a common user plane
   gateway across the multiple networks.

   Also, even in scenarios where N-MADP is not deployed, NCM can be used
   to augment the traffic steering decisions at the device.





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   The aim of these enhancements is to improve the end-user's quality of
   experience by leveraging the best network path based on application
   needs and network conditions, and building on the advantages of
   significantly reduced latency and the dynamic and real-time exposure
   of radio network information available at the MEC.

16.  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, Shuping
   Peng/Huawei, Vasudevan Subramanian/Nokia.  Vasudevan Subramanian has
   been instrumental in conceptualization and development of solution
   principles for the MAMS framework.  Shuping Peng has been a key
   contributor in refining the framework and control plane protocol
   aspects.

17.  Acknowledgments

   This protocol is the outcome of work by many engineers, not just the
   authors of this document.  In alphabetical order, the contributors to
   the project are: Barbara Orlandi, Bongho Kim,David Lopez-Perez, Doru
   Calin, Jonathan Ling, Lohith Nayak, Michael Scharf.

18.  IANA Considerations

   This draft makes no requests of IANA

19.  References

19.1.  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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/info/rfc4301>.

19.2.  Informative References

   [ETSIRNIS]
              "Mobile Edge Computing (MEC) Radio Network Information
              API", <ETSI GS MEC 012>.





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   [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", draft-boucadair-mptcp-
              plain-mode-10 (work in progress), March 2017.

   [I-D.wei-mptcp-proxy-mechanism]
              Wei, X., Xiong, C., and E. Ed, "MPTCP proxy mechanisms",
              draft-wei-mptcp-proxy-mechanism-02 (work in progress),
              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", draft-
              zhu-intarea-mams-user-protocol-03 (work in progress),
              August 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.", <IEEE
              802.11-2016>.

   [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,
              <https://www.rfc-editor.org/info/rfc3948>.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <https://www.rfc-editor.org/info/rfc6347>.

   [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,
              <https://www.rfc-editor.org/info/rfc6824>.

   [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, <https://www.rfc-editor.org/info/rfc7296>.







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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 19).



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


          Figure 19: UDP-based MAMS Control plane Protocol Stack

Authors' Addresses

   Satish Kanugovi
   Nokia

   Email: satish.k@nokia.com


   Florin Baboescu
   Broadcom

   Email: florin.baboescu@broadcom.com


   Jing Zhu
   Intel

   Email: jing.z.zhu@intel.com


   Julius Mueller
   AT&T

   Email: jm169k@att.com


   SungHoon Seo
   Korea Telecom

   Email: sh.seo@kt.com



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