Re: I-D Action: draft-ietf-dmm-requirements-07.txt

Sri,

Thanks for the comments. We are replying under different sections in separate emails. More emails will follow.
-----------------------------------------------
We have revised Section 3 in version 08. Our responses are in-line. Please check.

3.  Centralized versus distributed mobility management

   Mobility management functions may be implemented at different layers
   of the protocol stack.  At the IP (network) layer, mobility
   management can be client-based or network-based.

   An IP-layer mobility management protocol is typically based on the
   principle of distinguishing between session identifier and routing
   address and maintaining a mapping between the two.  In Mobile IP, the
   home address serves as the session identifier whereas the care-of-
   address (CoA) takes the role of the routing address.  The binding
   between these two is maintained at the home agent (mobility anchor).
   If packets addressed to the home address of a mobile node can be
   continuously delivered to the node, then all sessions using that home
   address are unaffected even though the routing address (CoA) changes.

   The next two subsections explain centralized and distributed mobility
   management functions in the network.

3.1.  Centralized mobility management

   In centralized mobility management, the mapping information between
   the session identifier and the locator IP address of a mobile node
   (MN) is kept at a single mobility anchor.  At the same time, packets
   destined to the MN are routed via this anchor.  In other words, such
   mobility management systems are centralized in both the control plane
   and the data plane (mobile node IP traffic).

   Many existing mobility management deployments make use of centralized
   mobility anchoring in a hierarchical network architecture, as shown
   in Figure 1.  Examples of such centralized mobility anchors are the
   home agent (HA) and local mobility anchor (LMA) in Mobile IPv6
   [RFC6275] and Proxy Mobile IPv6 [RFC5213], respectively.  Current
   cellular networks such as the Third Generation Partnership Project
   (3GPP) GPRS networks, CDMA networks, and 3GPP Evolved Packet System
   (EPS) networks employ centralized mobility management too.  In
   particular, the Gateway GPRS Support Node (GGSN), Serving GPRS
   Support Node (SGSN) and Radio Network Controller (RNC) in the 3GPP
   GPRS hierarchical network, and the Packet Data Network Gateway (P-GW)
   and Serving Gateway (S-GW) in the 3GPP EPS network all act as anchors
   in a hierarchy.


         3G GPRS                 3GPP EPS                MIP/PMIP
         +------+                +------+                +------+
         | GGSN |                | P-GW |                |HA/LMA|
         +------+                +------+                +------+
            /\                      /\                      /\
           /  \                    /  \                    /  \
          /    \                  /    \                  /    \
         /      \                /      \                /      \
        /        \              /        \              /        \
       /          \            /          \            /          \
      /            \          /            \          /            \
  +------+      +------+  +------+      +------+  +------+      +------+
  | SGSN |      | SGSN |  | S-GW |      | S-GW |  |MN/MAG|      |MN/MAG|
  +------+      +------+  +------+      +------+  +------+      +------+
     /\            /\
    /  \          /  \
   /    \        /    \
+---+  +---+  +---+  +---+
|RNC|  |RNC|  |RNC|  |RNC|
+---+  +---+  +---+  +---+

   Figure 1.  Centralized mobility management.

3.2.  Distributed mobility management

   Mobility management functions may also be distributed to multiple
   networks as shown in Figure 2, so that a mobile node in any of these
   networks may be served by a nearby mobility function (MF).


                    +------+  +------+  +------+  +------+
                    |  MF  |  |  MF  |  |  MF  |  |  MF  |
                    +------+  +------+  +------+  +------+
                                           |
                                         +----+
                                         | MN |
                                         +----+

   Figure 2.  Distributed mobility management.

   Mobility management may be partially or fully distributed
   [I-D.yokota-dmm-scenario].  In the former case only the data plane is
   distributed, implicitly assuming separation of data and control
   planes as described in [I-D.wakikawa-netext-pmip-cp-up-separtion].
   Fully distributed mobility management implies that both the data
   plane and the control plane are distributed.  While mobility
   management can be distributed, it is not necessary for other
   functions such as subscription management, subscription database, and
   network access authentication to be similarly distributed.

   A distributed mobility management scheme for a flat mobile network of
   access nodes is proposed in [Paper-Distributed.Dynamic.Mobility].
   Its benefits over centralized mobility management are shown through
   simulations in [Paper-Distributed.Centralized.Mobility].  Moreover,
   the (re)use and extension of existing protocols in the design of both
   fully distributed mobility management [Paper-Migrating.Home.Agents]
   [Paper-Distributed.Mobility.SAE] and partially distributed mobility
   management [Paper-Distributed.Mobility.PMIP] [Paper-
   Distributed.Mobility.MIP] have been reported in the literature.
   Therefore, before designing new mobility management protocols for a
   future distributed architecture, it is recommended to first consider
   whether existing mobility management protocols can be extended.


The following have contributed to the revisions in draft 08: Pierrick, Dapeng, and Jouni


From: [email protected]<mailto:[email protected]> [mailto:[email protected]] On Behalf Of Sri Gundavelli (sgundave)
Sent: Sunday, August 25, 2013 10:04 PM
To: [email protected]<mailto:[email protected]>
Subject: Re: [DMM] I-D Action: draft-ietf-dmm-requirements-07.txt

Please see inline for some comments.

Regards
Sri





3.  Centralized versus distributed mobility management



   Mobility management functions may be implemented at different layers

   of the protocol stack.  At the IP (network) layer, they may reside in

   the network or in the mobile node.  In particular, a network-based

   solution resides in the network only.  It therefore enables mobility

   for existing hosts and network applications which are already in

   deployment but lack mobility support.



[Sri] Above text is bit confusing to me, specially the last sentence. Mobility management can be based on client-based, or network-based.



Accept and revised in version 08



   At the IP layer, a mobility management protocol supporting session

   continuity is typically based on the principle of distinguishing

   between identifier and routing address and maintaining a mapping

   between the two.

[Sri] Replace, "Session continuity" with "IP mobility" or "IP address continuity".



Delete session continuity, but also keep the discussion general and not specific to MIP.



In Mobile IP, the home address serves as an

   identifier of the device whereas the care-of-address (CoA) takes the

   role of the routing address.  The binding between these two is

   maintained at the home agent (mobility anchor).  If packets can be

   continuously delivered to a mobile node at its home address, then all

   sessions using that home address are unaffected even though the

   routing address (CoA) changes.



[Sri] We should leave it at, "IP address mobility".



Revised this section but tried to keep it general and not specific to MIP.



   The next two subsections explain centralized and distributed mobility

   management functions in the network.



3.1.  Centralized mobility management



   In centralized mobility management, the mapping information between

   the persistent node identifier and the locator IP address of a mobile

   node (MN) is kept at a single mobility anchor.  At the same time,

   packets destined to the MN are routed via this anchor.

[Sri] Can we use the MIP terminology, home address/Care-of address terminology, as supposed to LISP terminology ?



Revised this section but tried to keep this section general and not specific to MIP

  In other

   words, such mobility management systems are centralized in both the

   control plane and the data plane (mobile node IP traffic).



   Many existing mobility management deployments make use of centralized

   mobility anchoring in a hierarchical network architecture, as shown

   in Figure 1.  Examples of such centralized mobility anchors are the

   home agent (HA) and local mobility anchor (LMA) in Mobile IPv6

   [RFC6275] and Proxy Mobile IPv6 [RFC5213], respectively.  Current

   cellular networks such as the Third Generation Partnership Project

   (3GPP) GPRS networks, CDMA networks, and 3GPP Evolved Packet System

   (EPS) networks employ centralized mobility management too.  In

   particular, the Gateway GPRS Support Node (GGSN), Serving GPRS

   Support Node (SGSN) and Radio Network Controller (RNC) in the 3GPP

   GPRS hierarchical network, and the Packet Data Network Gateway (P-GW)

   and Serving Gateway (S-GW) in the 3GPP EPS network all act as anchors

   in a hierarchy.

























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Internet-Draft                  DMM-Reqs                     August 2013





         3G GPRS                 3GPP EPS                MIP/PMIP

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

         | GGSN |                | P-GW |                |HA/LMA|

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

            /\                      /\                      /\

           /  \                    /  \                    /  \

          /    \                  /    \                  /    \

         /      \                /      \                /      \

        /        \              /        \              /        \

       /          \            /          \            /          \

      /            \          /            \          /            \

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

  | SGSN |      | SGSN |  | S-GW |      | S-GW |  |MN/MAG|      |MN/MAG|

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

     /\            /\

    /  \          /  \

   /    \        /    \

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

|RNC|  |RNC|  |RNC|  |RNC|

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



   Figure 1.  Centralized mobility management.



3.2.  Distributed mobility management



   Mobility management functions may also be distributed to multiple

   networks as shown in Figure 2, so that a mobile node in any of these

   networks may be served by a nearby mobility function (MF).





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

                    |  MF  |  |  MF  |  |  MF  |  |  MF  |

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

                                           |

                                         +----+

                                         | MN |

                                         +----+



   Figure 2.  Distributed mobility management.





   Mobility management may be partially or fully distributed.  In the

   former case only the data plane is distributed.  Fully distributed

   mobility management implies that both the data plane and the control

   plane are distributed.  Such concepts of data and control plane

   separation are not yet described in the IETF developed mobility

   protocols so far but are described in detail in [I-D.yokota-dmm-

   scenario].  While mobility management can be distributed, it is not

   necessary for other functions such as subscription management,







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   subscription database, and network access authentication to be

   similarly distributed.



[Sri] The case of centralized CP and distributed DP is covered in IETF docs,

http://datatracker.ietf.org/doc/draft-wakikawa-netext-pmip-cp-up-separation/

This is a variant of the DMM models.



Already quoted the yokota reference but added this reference anyway.



   A distributed mobility management scheme for flat IP-based mobile

   network architecture consisting of access nodes is proposed in

   [Paper-Distributed.Dynamic.Mobility].  Its benefits over centralized

   mobility management are shown through simulations in [Paper-

   Distributed.Centralized.Mobility].  Moreover, the (re)use and

   extension of existing protocols in the design of both fully

   distributed mobility management [Paper-Migrating.Home.Agents] [Paper-

   Distributed.Mobility.SAE] and partially distributed mobility

   management [Paper-Distributed.Mobility.PMIP] [Paper-

   Distributed.Mobility.MIP] have been reported in the literature.

   Therefore, before designing new mobility management protocols for a

   future flat IP architecture, it is recommended to first consider

   whether existing mobility management protocols can be extended to

   serve a flat IP architecture.



[Sri] Lot of unnecessary text in this document. Not sure, we need all of this text.



Added the term "flat mobile network" and revised in version 08

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