Network Working Group D. Liu
Internet-Draft Z. Cao
Intended status: Informational China Mobile
Expires: September 9, 2010 March 8, 2010
Distributed mobility management Problem Statement
draft-liu-distributed-mobility-01
Abstract
Current mobility solutions normally introduce an anchor point in the
network, eg HA in MIPv6, LMA in PMIPv6, GGSN in 3GPP. The anchor
point is used to maintain the mapping between the stable IP address
(eg Home address in MIPv6) and the current routable IP address (eg
CoA in MIPv6). In the hierarchical architecture, since the anchor
point normally locates in the top of the hierarchical architecture,
there will no scalability issue. But in the more flat architecture,
the anchor point will be much lower compared with hierarchical
architecture; this will introduce some issues if traditionally
mobility protocol is used.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 4
3. Overview of mobility problems in flat architecture . . . . . . 5
4. Considerations of distributed mobility solutions . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 10
8. Normative References . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
As the mobile network is evolving towards the more flat architecture,
traditional mobility protocol is not suitable for this architecture.
For example, in the LIPA/SIPTO architecture which is discussed in
3GPP, the gateway function is located near the base station. In this
architecture, if the anchor point locates in the gateway, the
frequently handover between base station may cause more signaling
overhead compared with hierarchical architecture.
The triangle routing issue will become more severe in flat
architecture, since there will be many UE under one gateway roaming
to other gateways. In this condition, the visiting gateway will need
to establish the mobility tunnel back the original access gateway of
the UE.
Due to the triangle routing issue, the traffic could not break out
locally.
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2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL","SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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3. Overview of mobility problems in flat architecture
+----------------------------------------+
| Mobility tunnel |
+-------+ +-------+ +-------+ +-------+
|L-GW | |L-GW | |L-GW | |L-GW |
|MAG/LMA| |MAG/LMA| |MAG/LMA| |MAG/LMA|
+-------+ +-------+ +-------+ +-------+
\
\ +-----+
| UE |
+-----+
Figure 1 Flat network architecture
1) Signaling overhead
As figure 1 illustrated, in the flat network architecture, the
mobility anchor point may locates near the base station if
traditional mobility protocol is used. The UE's handover between
base stations may cause frequently handover between anchor points.
2) Triangle routing
The triangle routing problem will become more severe in the flat
architecture if traditional mobility protocol is used. The mobility
tunnel needs to be connection back to the anchor point where the UE
is first access to the network and get the IP address allocation.
For example, if a user opens his mobile phone to see a video
streaming program at office and then take a subway to get home. When
the user gets back to home, the mobility tunnel still need to connect
back to the anchor point where locates near his office. This will
lead all the traffic goes back to the gateway near his office to
access the Internet instead of locally break out from the base
station which near his home.
Local break out
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As the speed of wireless Internet access is increasing rapidly, if
all the Internet traffic need to go through the core network, it will
give much pressure to the mobile operator's core network and may
decline the user experience due to the latency cause by the long
route to the destination. It is preferred that the Internet access
traffic could break out locally, it means that the Internet traffic
beak out from a gateway which locates near the base station. To
ensure the local break, the gateway should have the IP address
allocation function. It is also preferred that the network should
provide mobility in the local break out scenario, so the gateway
should be the anchor point of mobility. It is preferred that when UE
roams to other base station the traffic could break out locally and
also maintain the session continuity. That will be a challenge if
use traditional mobility protocols.
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4. Considerations of distributed mobility solutions
Based on the above analysis, there may be a need for developing new
mobility solutions for the flat architecture, the solution may be
called distributed mobility solutions since the mobility anchor
function is distributed compared with the centralized mobility anchor
point of traditional mobility protocol.
The distributed mobility solutions should make less change to the
existing network entity. It is preferred that there is no change
requirement to the UE and transparent to the application layer. The
details of distributed mobility solution requirements will be further
identified.
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5. Security Considerations
TBD
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6. IANA Considerations
None
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7. Contributors
Bo Zhou
China Mobile
zhouboyj@chinamobile.com
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8. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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Authors' Addresses
Dapeng Liu
China Mobile
Unit2, 28 Xuanwumenxi Ave,Xuanwu District
Beijing 100053
China
Email: liudapeng@chinamobile.com
Zhen Cao
China Mobile
Unit2, 28 Xuanwumenxi Ave,Xuanwu District
Beijing 100053
China
Email: caozhen@chinamobile.com
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