Internet DRAFT - draft-bertz-alto-mobilitynets

draft-bertz-alto-mobilitynets







ALTO WG                                                         L. Bertz
Internet-Draft                                                    Sprint
Intended status: Informational                          October 19, 2015
Expires: April 16, 2016


                    Mobility Network Models in ALTO
                    draft-bertz-alto-mobilitynets-00

Abstract

   Application Layer Traffic Optimization can become complex in networks
   supporting IP mobility.  This document discusses a general model
   approach for such networks and a method to minimize ALTO client
   queries.

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   This Internet-Draft will expire on April 16, 2016.

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   Copyright (c) 2015 IETF Trust and the persons identified as the
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   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  General Approach  . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Attachment Point and Address Pool Representation  . . . .   4
     2.2.  Dynamic and Static Relationship Representation  . . . . .   5
     2.3.  Other Considerations in Mobility  . . . . . . . . . . . .   6
   3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  CDN Request Router  . . . . . . . . . . . . . . . . . . .   7
     3.2.  Dynamic Mobility Management (DMM) Forwarding Policy
           Configuration (FPC) . . . . . . . . . . . . . . . . . . .   7
   4.  Possible ALTO Extensions  . . . . . . . . . . . . . . . . . .   7
   5.  Informative References  . . . . . . . . . . . . . . . . . . .   8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Networks have devices that vary in terms of mobility.  IP mobility
   can provide both session continuity (maintaining the IP endpoint
   while the device moves from a point of network attachment to others)
   and reachability (maintaining the IP address for an extended period
   of time).

   [ONDEMANDMOBILITY] provides a mechanism for devices to select the
   type of mobility session desired.  It breaks down IP mobility into
   three different types by address:

   o  Fixed IP Address - Provides IP session continuity and IP address
      reachability

   o  Sustained IP Address - Provides only IP address continuity

   o  Nomadic IP Address - Provides neither IP session continuity nor IP
      address reachability

   There are multiple points of attachment where each is typically noted
   by a single endpoint address, e.g. a E-UTRAN Global Cell Identifier
   (EGCID).  The mobility client communicates through the point of
   attachment to a mobility gateway such as a Mobile Access Gateway
   (MAG) for Proxy Mobile IP (PMIP) or a Serving Gateway (SGW) in 3GPP
   networks.  These devices provide the session continuity.  They
   forward traffic through a tunnel, e.g.  GTP or GRE, to an anchor
   function, e.g.  Local Mobility Anchor (LMA) for PMIP or PDN-Gateway
   (PGW) for 3GPP mobility networks.  Such anchor functions provide
   address reachability.

   Figure 1 shows an example of PMIP and 3GPP mobility elements in a
   network.



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   Device--+
           |             +==========+  +==========+   +==============+
         +==========+  | | +======+ |  | +======+ |   | +==========+ |
         | Point of |--|-|-|      |-|--|-| LMA1 |-|-+-| | Service1 | |
         | Attach A |  | | | MAG1 | |  | +======+ | | | +==========+ |
         +==========+  | | |      | |  |          | | |              |
                       | | +======+ |  |          | | |              |
                       | |          |  |          | | |    _----_    |
                       | | +=====+  |  |          | | |  _(      )_  |
          +==========+ +-|-| MME |  |  |          | +-|-( Internet )-|-
          | Point of | | | +=====+  |  |          | | |  (_      _)  |
          | Attach B |-+ |    |     |  |          | | |    '----'    |
          +==========+ | | +======+ |  | +=====+  | | |              |
            (eNodeB)   +-|-| SGW1 |-|--|-| PGW |--|-+ |              |
                         | +======+ |  | +=====+  | | | +==========+ |
                         |          |  |          | +-|-| Service2 | |
                         +==========+  +==========+   | +==========+ |
                            Tier 1       Tier 2       +==============+
                                                           Tier 3

               Figure 1: PMIP / 3GPP Mobile Network Example

   Representation of such networks in ALTO is further complicated by the
   fact that Anchor Functions assign individual IP address from pools of
   addresses in the home network.  Such pools appear as routes and
   associated with PIDs that are typically associated with a network
   map.  Attachment points, being a single value, are typically
   represented as ALTO Endpoints but mobile points of attachment use
   type formats not currently supported in ALTO.

   In many networks the assets assigned may be dedicated.  For example,
   the assets in Tier 1 of Figure 1 may have assets in Tier 2 statically
   assigned to them.  Such 'direct' relationships would be present in
   the ALTO Endpoint Property Service (EPS).  For example, the endpoint
   of MAG1 would have a property of

   "lma" : "lma1" (or IP address of LMA1)

   The points of attachment could have similar static assignments in the
   EPS.

   Such representation is difficult and even quite complicated when the
   property value is a large array.

   Other relationships may be more dynamic and decisions are best made
   by looking at metrics in a Costmap or Endpoint Costmap.





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   In summary, networks supporting various levels of IP mobility have
   multiple representation challenges in ALTO:

   o  The Points of Attachment are typically an endpoint type not
      currently supported in ALTO.

   o  Anchor Functions allocate addresses from pools that are typically
      represented as PIDs in a network map while the anchor function
      itself is an endpoint.

   o  Relationships can be dynamic or static for the same type of query.
      This results in using EPS to determine static relationships and
      EPCS/CS to acquire dynamic relationships (possibly repeatedly)
      just to complete a single ALTO based decision.

2.  General Approach

2.1.  Attachment Point and Address Pool Representation

   Due their importance, network attachment point representations are
   represented as PIDs in network maps with no routes.  PID properties
   [PIDPROPS] could be used to associate the non-ALTO supported endpoint
   type as a property of the Point of Attachment.

   If all of the endpoints associated with an Attachment Point are
   contained by another PID it is possible to represent all endpoints in
   a PID.  However, any change could result in a PID conflict which is
   not allowed.  This approach was not used here.

   Address Pools are represented as PIDs.  Two pools may belong to the
   same PID if they are assigned to the same element or aggregated into
   a PID that contains the pools.

   Figure 2 shows the modified mapping.  The eNodeB now appears as an
   endpoint (element) associated to Point of Attach B.
















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    +==========+   +============+   +==========+   +==============+
    | Point of |   | +======+   |   | +======+ |   | +==========+ |
    | Attach A |---|-|      |---|---|-| LMA1 |-|-+-| | Server1  | |
    +==========+   | | MAG1 |   |   | +======+ | | | +==========+ |
                 +-|-|      |   |   |          | | |              |
                 | | +======+   |   |          | | |              |
                 | |            |   |          | | |    _----_    |
                 | | +=====+    |   |          | | |  _(      )_  |
    +==========+ +-|-| MME |    |   |          | +-|-( Internet )-|--
    | Point of | | | +=====+    |   |          | | |  (_      _)  |
    | Attach B |-+ |    |       |   |          | | |    '----'    |
    +==========+ | | +======+   |   | +=====+  | | |              |
                 +-|-| SGW1 |---|---|-| PGW |--|-+ |              |
                 | | +======+   |   | +=====+  | | | +==========+ |
                 | |            |   |          | +-|-| Server2  | |
                 | | +========+ |   +==========+   | +==========+ |
                 +-|-| eNodeB | |     Tier 2       +==============+
                   | +========+ |                      Tier 3
                   +============+
                        Tier 1

                     Figure 2: Mobile Network Mapping

   Address Pools from the PGW and LMA1 appear in PIDs and may appear in
   the same PID if both the PGW and LMA1 are part of the same PID.

2.2.  Dynamic and Static Relationship Representation

   In order to reduce the number of ALTO services required for Client
   queries the Static Relationships are mapped to Dynamic relationship
   based metrics.

   The following logic is applied.

   1.  If a direct relationship exists between a PID and an endpoint the
       ALTO server should generate a PID to represent the endpoint.  The
       PID must only contain the endpoint as its single entry.  There
       server will generate a costmap value between the newly generated
       and existing PIDs.

   2.  If the relationship is direct and between two endpoints a EPCS
       value should generated.

   The values used should be the maximum/minimum for a metric in order
   to achieve the desired result of always returning the endpoint in the
   direct relationship (or the PID it represents).





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2.3.  Other Considerations in Mobility

   Quite often more than one characteristic is used in selecting
   mobility gateways and anchor functions.  Figure 3 below shows an
   example where the address types defined in [ONDEMANDMOBILITY] will
   dictate the LMA chosen.

                           +====================+
            +==========+   | +======+  +======+ |
            | Point of |---|-|      |--| LMA1 | |
     Device-| Attach A |   | | MAG1 |  +======+ |
            +==========+   | |      |           |
                           | |      |           |
            +==========+   | |      |           |
            | Point of |---|-|      |           |
            | Attach B |   | |      |           |
            +==========+   | |      |-----------|--+
                           | |      |           |  |
            +==========+   | |      |           |  |
            | Point of |---|-|      |           |  |
            | Attach C |   | +======+           |  | +======+
            +==========+   +====================+  +-|      |
                                                     | LMA3 |
                           +====================+  +-|      |
            +==========+   | +======+           |  | +======+
            | Point of |---|-|      |-----------|--+
            | Attach D |   | | MAG2 |           |
            +==========+   | |      |           |
                           | |      |           |
            +==========+   | |      |  +======+ |
            | Point of |---|-|      |--| LMA2 | |
            | Attach E |   | +======+  +======+ |
            +==========+   +====================+

                      Figure 3: Multiple LMA Options

   If a Fixed IP Address is required then LMA3 is the preferred choice.
   If the device requires a Sustained Address and is traveling at slow
   speed, which is often referred to as a device's speed state, then
   LMA1 is sufficient.  If the speed state is high, e.g. the device may
   be in a moving vehicle, then LMA3 may be a better selection.

   Two options exist when considering how an ALTO client could select a
   proper LMA:

   1.  The LMAs could be pre-filtered using the EPS.





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   2.  The ALTO server can represent criteria such as speed state as
       another metric and use multi-metric search methods.

3.  Examples

3.1.  CDN Request Router

   Content Delivery Network (CDN) Request Routers (RRs) take an external
   IP address provided by an upstream CDN over a CDNI interface.  Using
   ALTO a RR can determine the correct CDN Node.  Following example
   Figure 2 a RR can determine if Server1 or Server2 is most appropriate
   for devices served by the LGW or LMA.

   For devices that are directly attached to the network, e.g. a fixed
   (wired) device, the RR can query for the best Server for the Point of
   Attachment.

3.2.  Dynamic Mobility Management (DMM) Forwarding Policy Configuration
      (FPC)

   DMM FPC [DMMFPC] provides the ability for a control plane element
   (FPC Client) to use FPC dataplane nodes for forwarding.
   Communication between the Client and nodes is accomplished by an FPC
   Agent which may not be co-located with the dataplane node and may, in
   fact, represent multiple dataplane nodes.

   The Client must select the best Dataplane Node and then its
   corresponding agent.

   It can accomplish this by:

   1.  Querying EPS for all endpoints with FPC Dataplane nodes and,
       during the query, their FPC Agent information.  There are number
       of ways to accomplish this.  Ideally, EPS can be extended to
       select any nodes, e.g. ipv4:* or ipv6:* in the query, along with
       the corresponding properties.

   2.  Query ECPS for the best Dataplane node that serves the mobility
       client.

   3.  Once selected, contact the FPC agent.

4.  Possible ALTO Extensions

   This document does not propose significant ALTO extensions as much as
   how data can be mapped or computed in various ALTO services in order
   to minimize the queries a client must make.




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   The only proposed extension is to permit a wildcard or empty value in
   the ALTO EPS query to permit an open ended query.  Such a service
   would deviate from the current EPS definition to only return
   endpoints that contain the value as opposed to return all endpoints
   including those with empty structures.

5.  Informative References

   [DMMFPC]   Liebsch, M., Matsushima, S., Gundavelli, S. and Moses, D. 
              "Protocol for Forwarding Policy Configuration (FPC) in  
              DMM", 2015.

   [ONDEMANDMOBILITY]
              Yegin, A., Kweon, K., Lee, J., Park, J., and Moses, D. 
              "On Demand Mobility Management", 2015.

   [PIDPROPS]
              Roome, W., "Extensible Property Maps for the ALTO
              Protocol", 2015.

Author's Address

   Lyle Bertz
   Sprint
   6220 Sprint Parkway
   Overland Park  KS 66251
   USA

   Email: lyleb551144@gmail.com
























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