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I. INTRODUCTION
As the Internet services become popular, the number
of mobile Internet users has been rapidly increasing with
wide popularity of smart phones. It is reported that the
number of mobile Internet users will exceed the number of
desktop users in near future [1]. The current Internet does
not support the IP mobility because an IP address has
overloaded semantics as both Identifier (ID) and Locator
(LOC). In the network layer, an IP address is used as a
LOC to find a destination host and to forward the data
packets to the host. This IP address is also used as a host
ID to identify host in the transport layer. When a mobile
host moves from one subnet to another, it acquires a new
IP address. In mobile networks, however, the location of
mobile host may continue to change by movement. This
means that the static allocation of LOC (i.e., an IP
address) to a host may become problematic in mobile
environments. In the meantime, the host ID needs to be
kept persistently without change to maintain on-going
sessions against movement of a host. Accordingly, ID and
LOC need to be separated to support IP mobility [2].
To deal with this problem, the Internet Engineering
Task Force (IETF) and the other segments of Internet
community have recently been discussing the ID-LOC
split concept using the separate namespaces for host ID
and locator, which could be helpful for IP mobility
support, multi-homing support, routing scalability, and
security enhancement.
Recently, Mobile IP (MIP) [3, 4] and Proxy Mobile
IPv6 (PMIP) [5] have been developed for IP mobility
support. These protocols also use the ID-LOC separation
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The Mobility Management (MM) is one of the crucial requirements for future mobile networks. The current MM
schemes, such as Mobile IP and Proxy Mobile IP, are based on a centralized mobility anchor for mobility control and
data delivery. However, it is reported that such a Centralized MM (CMM) approach tends to give a couple of
drawbacks, which include non-optimal data route, injection of unwanted data traffics into core networks, and increased
cost of network engineering. Recently, some proposals on Distributed MM (DMM) architectures have been discussed
so as to overcome limitations of the centralized MM approach, which can be divided into Partially Distributed MM (P-
DMM) and Fully Distributed MM (F-DMM). In this paper, we conduct a comparative study on the three MM
approaches in terms of total delay and traffic overhead. From numerical results, we see that F-DMM and P-DMM can
give better performance than CMM in terms of control/data traffic overhead. However, in terms of total delay, it seems
that CMM is preferred to P-DMM and F-DMM in the mesh-like networks, whereas P-DMM and F-DMM is preferred
to CMM in the tree-like networks.
Keywords: Mobility management, Centralized, Distributed, Numerical analysis, Comparison
논문번호: TR14-072, 논문접수일자:2014.08.19, 논문수정일자:2015.04.15, 논문게재확정일자:2015.06.02
Moneeb Gohar: Yeungnam UniversitySeok-Joo Koh(Corresponding Author): Kyungpook National University
A Comparative Analysis of Centralized and Distributed
Mobility Management in IP-Based Mobile Networks
Moneeb Gohar ·Seok-Joo Koh
concept for mobility support. That is, Home Address
(HoA) is used as ID, whereas Care-of Address (CoA) is
employed as LOC to represent the current location of
mobile node. However, these protocols are based on a
centralized Mobility Management (MM) approach, in
which Home Agent (HA) or Local Mobility Anchor
(LMA) is used as a centralized mobility anchor by which
all control and data packets are processed. Such a
centralized anchor allows a mobile host to be reachable,
when it is away from its home domain, by ensuring the
forwarding of data packets destined to or sent from the
mobile host. However, the centralized MM scheme tends
to be vulnerable to several problems. First, the centralized
mobility anchor tends to induce unwanted control/data
traffics into core networks, which may give a big burden
to network operators due to large operational costs. In
addition, a single point of failure of central node may
induce severe degradation of overall system performance
and also the increased cost of network engineering.
The IETF has recently discussed the distributed
mobility management to overcome limitations of this
Centralized MM (CMM) approach [6], [7], which can be
divided into the Partially Distributed MM (P-DMM) and
the Fully Distributed MM (F-DMM). In P-DMM, only
data plane is distributed, as shown in Host Identity
protocol (HIP) [8], Locator Identifier Separation Protocol -
Alternative Topology (LISP-ALT) [9-11], and Identifier
Locator Network Protocol (ILNP) [12]. In F-DMM, both
data plane and control plane are distributed, as shown in the
examples of LISP-DMC [13], DMM-LIS [14], and LISP-
DHT [15]. The CMM schemes may incur non-optimal data
routes and performance degradations, whereas the DMM
schemes can provide optimal data routes and high
performance, since the route optimization will be intrinsically
supported, and unnecessary traffics can be reduced when the
two hosts communicate directly with each other, not relying
on a centralized anchor. This will also be helpful to reduce
the handover delay. In this paper, we will conduct a
comparative study of the centralized and distributed MM
architectures for IP mobility support.
The rest of this paper is organized as follows. In
Section II, we review the candidate schemes for
centralized and distributed MM architectures. Section III
analyzes the performance of the candidate schemes in
terms of the total delay and the data/control traffic
overhead. Section IV discusses the numerical results and
qualitative comparisons for those candidate architectures.
Section V concludes this paper.
II. CANDIDATEARCHITECTURES FORMOBILITY MANAGEMENT
1. Overview of Mobility ManagementArchitectures
The candidate mobility schemes, considered in this
paper, are all based on the ID-LOC separation concept,
and thus they need an ID-LOC mapping agent. However,
in the viewpoint of how to provide mobility support, those
schemes can be classified into CMM and DMM, and
DMM is further divided into Partial DMM (P-DMM) and
Full DMM (F-DMM). Before going into the detailed
description, let us compare the candidate MM schemes in
the architectural perspective, as described in Table 1.
In the mobility perspective, MIP [3], [4] and PMIP [5]
can be viewed as a centralized MM architecture, in which
all control and data traffics are processed by a centralized
agent, such as HA and LMA. Data packets are first
delivered to the centralized node, and then the centralized
node will forward the data packets to the corresponding
host. In the ID-LOC mapping control, the centralized
mapping agents, HA and LMA, are used for ID-LOC
A Comparative Analysis of Centralized and Distributed Mobility Management in IP-Based Mobile Networks 657
Table 1. Comparison of mobility management architectures
Architectures
Relevant Protocols
ID-LOC Mapping Agent
Plane Separation(Data-Control)
Data Delivery Model
Mapping Control Model
CMM
MIP [3],[4], PMIP [5]
HA (MIP), LMA(PMIP)
Integrated
Data-First(Centralized)
Centralized
P-DMM
HIP [8]LISP-ALT [9]~[11],
ILNP [12]
RVS (HIP), MS (LISP-ALT), D-DNS (ILNP)
Separated
Query-First(Distributed)
Centralized
F-DMM
LISP-DMC [13], DMM-LIS [14], LISP-DHT [15]
TR/MS (LISP-DMC, DMM-LIS, LISP-DHT)
Separated
Query-First(Distributed)
Distributed
performed based on a central server. Figure 1 depicts the
basic operations for map update (or registration) and data
delivery in CMM, in which it is assumed that the control
operations for map update is performed by a network
router, rather than by a host.
In the figure there are the three hosts, denoted by two
Mobile Nodes (MNs) and a Correspondent Node (CN).
When each host is attached to its nearest Access Router
(AR) in Step 1, its ID and LOC will be registered or
updated to the central server by using a Map Update
message (Step 2). Now, we assume that CN wants to send
a data packet to MN1. The data packet of CN will first be
delivered to AR3 (Step 3). AR3 forwards the data packet
to the central server, since it has no information of LOC of
MN1 (Step 4). On reception of this data packet, the
central server will look up its ID-LOC mapping table
which has been updated in the map update operation, so as
to find the LOC of MN1. Now, the data packet is
delivered to AR1 of MN1, further to MN1 (Step 5).
Typical examples of CMM include the currently well-
known mobility protocols, such as MIP and PMIP. In
MIP and PMIP, the central server of CMM corresponds to
the Home Agent (HA) of MIP or the Local Mobility
Anchor (LMA) of PMIP. In MIP, the Binding Update
message corresponds to Map Update message. In PMIP,
LMA is used as the control server (or mapping system),
and Mobile Access Gateway (MAG) corresponds to an
AR in CMM. In terms of control messages, the PBU
message of PMIP can be regarded as Map Update message
mapping management.
HIP [8], LISP-ALT [9]~[11] and ILNP [12] can be
regarded as a partially distributed MM approach, in which
the data plane is separated from the control plane. For
distributed ID-LOC mapping management, some
dedicated mapping agents are used: Rendezvous Server
(RVS) in HIP, Map Server (MS) in LISP, and Dynamic
Domain Name System (D-DNS) in ILNP. All mobility
control traffics are processed by these mapping control
entities. The mapping query operations will be performed
with the mapping agents to find the location of mobile
hosts, before transmission of data packets. It is noted that
LISP will be MM protocol.
In the meantime, LISP-DMC [13], DMM-LIS [14],
and LISP-DHT [15] can be classified as the fully
distributed MM approach, in which both control plane and
data plane are separated. That is, a centralized mapping
agent is not used. Instead, the mapping query operations
will be performed to obtain the location of mobile hosts by
applying a hash function or by multicasting of a map query
message. Each of the candidate MM schemes for F-DMM
has its distinctive features, but the overall MM mechanisms
are based on the fully distributed approach for all of the
associated schemes. The details of each candidate scheme
will be discussed in the subsequent sections.
2. Centralized Mobility Management (CMM)
In CMM, both data delivery and control function are
658 Telecommunications Review·Vol. 25 No. 4·2015. 8
Figure 1. Overview of Centralized Mobility Management (CMM)
CN (Step 5). Now, the data packet can be delivered from
CN to MN1 (Step 6).
The recently proposed protocols for ID-LOC
separation, such as HIP [8], LISP-ALT [9-11], and ILNP
[12], can be classified as P-DMM. In HIP, the Rendezvous
Server (RVS) is used as the control server, and HIP I1 and
R1 messages correspond to the Map Query and Map
Query ACK messages, respectively. In LISP-ALT, the
Map Server (MS) is used as the control server, and LISP
Tunnel Router corresponds to AR of P-DMM. The Map
Register, Map Request, and Map Reply messages of LISP
can be regarded as the Map Update, Map Query, and Map
Query ACK messages of P-DMM. On the other hand, in
case of ILNP, the Dynamic Domain Name System (D-
DNS) is used as the control server which requires an
extension of the legacy DNS.
Now, we describe the HIP, LISP-ALT and ILNP
schemes on the basis of Figure 2. In HIP, a locator and a
host identifier are separated, in which a 128-bit Host
Identity Tag (HIT) is used as a host ID, and an IP address
of the host is used as a LOC. That is, HIT is the node
identifier, and IP address is used for packet routing in the
network. It is noted that HIP depends on a centralized
RVS for LOC binding update in the global scale, which
may create a lot of unnecessary signaling and control
messages in mobile networks. This makes the HIP
approach very inconvenient. To deal with this problem,
the work in [16] proposed an enhanced scheme for HIP.
The main idea is similar to HIP. However, it deploys a
A Comparative Analysis of Centralized and Distributed Mobility Management in IP-Based Mobile Networks 659
of CMM. Based on Figure 1, we are going to describe the
operations of MIP and PMIP. In MIP, when MN1 is
attached to AR1, it performs the map update operation
with HA. Then, CN tries to communicate with MN1.
Now, CN transmits a data packet to MN1 via HA. In
PMIP, when MN1 is attached to AR1 (MAG), AR1 will
perform the map update operation with LMA. Now, CN
can send data packets to MN1 via LMA.
3. Partially Distributed MM (P-DMM)
In P-DMM, both data delivery and control function are
separated, and an optimal data path is obtained from the
control server by using the 'map query' function, before
data transmission. That is, the data delivery function is
distributed by using an optimal route, whereas the control
function can still be regarded as a centralized scheme.
The name of P-DMM comes from this observation.
Figure 2 illustrates the basic operations for map update,
map query, and data delivery in P-DMM.
In the figure, when each host is attached to its nearest
AR (Step 1), its ID and LOC are registered with the
control server by using a Map Update message (Step 2).
When CN sends a data packet to MN1 (Step 3), AR3 of
CN sends a Map Query message to the control server (step
4). On reception of this message, the central server will
look up its ID-LOC mapping table so as to find the LOC
of MN1. Finally, the server responds with a Map Query
ACK message (containing the LOC of MN1) to AR3 of
Figure 2. Overview of Partially Distributed Mobility Management (P-DMM)
which may incur significant overhead of control messages
at MS. To deal with this problem, the work in [18]
proposed an enhanced scheme of LISP-MN. The main
idea is the same with LISP-MN, but it deploys a Local
Map Server (LMS) at the gateway of mobile network so as
to provide a localized mobility control. In Figure 2, when
MN1 is attached to AR1, then it will perform the map
update operation with LMS (control server). LMS will
also perform the map update operation with the global
MS. For data delivery, CN will first send a Map Query
message to LMS. The LMS will respond with Map Query
ACK message to CN. Now, CN can send the data packet
to MN1.
ILNP [12] is another scheme for ID-LOC separation,
which is based on the address re-writing, in which a 128-
bit IPv6 address will be divided into the upper 64 bits for
LOC and the lower 64 bits for ID. For mobility support, a
Dynamic DNS (D-DNS) server is used for mapping
between ID and LOC of hosts. In Figure 2, when MN1 is
connected to AR1, then it will perform the map update
operation with D-DNS (control server). In the data
delivery operation, CN will first send a Map Query
message to D-DNS. D-DNS then responds with a Map
Query ACK message to CN. Now, CN can send data
packets to MN1 through an optimized route.
Local RVS (LRVS) at the gateway of mobile network to
provide a localized mobility control. In Figure2, when
MN1 is connected to an access router 1 (AR1), it
configures its LOC. Then, MN1 performs the map update
operation with a Localized RVS (LRVS).The LRVS also
performs the binding update operation with the global
RVS. In data delivery, as indicated in Figure 2, CN sends
a data packet to MN1. To do this, CN will initiate the HIP
4-way handshaking operations with MN1 for connection
setup. The first I1 packet is sent to LRVS, and LRVS will
forward the I1 packet to MN1. After receiving the I1
packet, MN1 responds with a R1 message to CN. The
other two messages, I2 and R2, are exchanged between
CN and MN for completion of security association. Now,
CN can send the data packets directly to MN1.
On the other hand, LISP has recently been made in the
IETF, which splits the current IP address space into
Endpoint IDentifier (EID) and Routing LOCator (RLOC).
To support the LISP mobility, the LISP is extended to the
LISP-MN architecture in [17], in which it is assumed that
each mobile node implements the light-weight tunnel
router functionality in mobile networks. In this
architecture, a Map Server (MS) is used as an anchor point
for MNs. That is, a MN will maintain the map cache and
directly communicate with MS. It is noted that LISP-MN
depends on a central MS for mapping control operations,
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Figure 3. Overview of Fully Distributed Mobility Management (F-DMM)
A Comparative Analysis of Centralized and Distributed Mobility Management in IP-Based Mobile Networks 661
4. Fully Distributed MM (F-DMM)
In F-DMM, the control server is not used, differently
from P-DMM. Instead, both data delivery and control
function are performed by ARs in the distributed way.
Figure 3 illustrates the operations for map update, map
query, and data delivery in F-DMM.
As shown in the figure, each AR performs the
mapping control function, instead of the control server.
The ID-LOC mapping management is performed based on
a Distributed Hash Table (DHT) or hash function. That is,
the AR that is responsible for ID-LOC mapping
management for a certain host will be determined by
applying a DHT or hash function to the ID of the
concerned host. In this way, the overhead of mapping
management will be distributed onto a lot of ARs in the
network, not relying on a single control server. From the
example of Figure 3, we can see that the ID-LOC mapping
information of MN1 is managed by AR4, MN2 is
allocated to AR1, and CN is assigned to AR2.
When a host is attached to AR (Step 1), the attached
AR will determine which AR in the network shall be
responsible for ID-LOC mapping management for the
concerned host. Then, the attached AR sends a Map
Update message to the determined AR (Step 2). When CN
sends a data packet to MN1 (Step 3), AR3 of CN will look
up its DHT table or perform its hash function so as to find
which AR in the network has the ID-LOC mapping
information of MN1. After that, AR3 of CN sends a Map
Query message to AR4 that has the associated mapping
information (Step 4). In turn, AR4 will respond with a
Map Query ACK message to AR3 (Step 5). Now, the data
packet can be delivered from CN to MN1 over an
optimized path (Step 6).
Several works on distributed ID-LOC management have
so far been made. Most of them are based on the DHT, and
each scheme uses a distinctive DHT or hash function.
Typical examples of the F-DMM architecture include LISP-
DMC [13], DMM-LIS [14], and LISP-DHT [15].
In LISP-DMC, AR/TR performs the processing of
both data and control messages, but the binding update
operation is not performed. That is, the central server, such
as MS, is not used. Instead, the binding query operations
are performed to get the LOC of the concerned host by
multicast. The Map Request message of LISP-DMC
corresponds to the Map Query message of F-DMM. In
DMM-LIS, a network is divided into a lot of domains.
Each domain contains a Mapping Server (MS) and several
TRs. The MS will maintain the mapping information
between global EID and Autonomous System Number
(ASN) of each domain. Each MS also maintains the
mapping between ASN and TR. Each TR constitutes one-
hop DHT ring. The Map Register and Map Request
messages of DMM-LIS correspond to the Map Update and
(a) Mesh Topology
Figure 4. Network topologies for analysis
(b) Tree Topology
662 Telecommunications Review·Vol. 25 No. 4·2015. 8
connected each other. We also define the parameters used
for analysis in Table 2.
In the table, we denote Tx-y(S) by the transmission
delay of a message with size S sent from x to y via 'wired 'link. Then, Tx-y(S) is expressed as Tx-y(S)=[(S/Bw)+Lw+Tq]. The transmission delay over the
wireless link is neglected, since it is a common for all of
the candidate schemes.
In the analysis, the Total Delay (TD) consists of the
Binding Update Delay (BUD), the Binding Query Delay
(BQD) and Data Delivery Delay (DDD). That is,
TD=BUD+BQD+DDD.
2. Analysis of Total Delays (TD)
2.1. CMM
In CMM, when MN is attached to a new AR, the AR
will perform the binding update operation with the control
server (MA). The MA updates its database. If all ARs are
inter-connected in the mesh topology, the distance
between two ARs or the distance between AR and MA is
only one-hop link. In the tree topology, the distance
between AR and MA is more than one-hop link.
Accordingly, the Binding Update Delay (BUD) of CMM
for each topology can be represented as follows.
CMM_BUDMesh=2×TAR-MA(Sc)
CMM_BUDTree=2×β×TAR-MA(Sc)
The binding query delay of CMM is 0, because the
binding query operation is not performed. Thus, the
Binding Query Delay (BQD) of CMM can be represented
Map Query messages of F-DMM. On the other hand,
LISP-DHT is a mapping distribution system based on
DHT, which is designed to take full advantage of the DHT
architecture so as to build an efficient and secure ID-LOC
mapping system.
Based on Figure 3, we describe the operations of
LISP-DMC schemes. In LISP-DMC, when MN1 is
attached to AR1, then AR1 will store its ID-LOC in its
binding cache. AR1 will not perform the map update
operation. Now, CN sends a data packet to AR3. Then,
AR3 will send a Map Query message to all ARs by
multicast. Only the corresponding AR, where MN is
staying, will respond with a Map Query ACK message to
AR3. Now, AR3 will forward the data packets to MN1
through an optimized route.
III. PERFORMANCE ANALYSIS
In this section, we analyze the traffic overhead at the
central node and the total delay for binding update,
binding query and data delivery.
1. Network Models for Analysis
For analysis, we consider the two network topologies:
mesh and tree, as illustrated in Figure 4. In the mesh
topology, all Access Routers (ARs) are directly connected
to each other. Only a single AR will perform the
functionality of Mobility Agent (MA) for CMM and P-
DMM. In F-DMM, each AR will perform the functionality
of MA.
For CMM and P-DMM, the centralized MA is located
at the root node in the tree topology. On the other hand, in
F-DMM, MAs are located at leaf nodes in a balanced
binary tree. We assume that the leaf nodes in the tree are
Table 2. Parameter used for a numerical nalysis
Parameter
Sc
Sd
Bw
Lw
βσTq
NHost
NAR
Description
Size of control packets (bytes)
Size of data packets (bytes)
Wired link bandwidth (Mbps)
Wired link delay (ms)
Hop count between node AR and MA in the tree topology
Hop count between node AR and AR in the tree topology
Average queuing delay at each node (ms)
Number of host per AR
Number of ARs per domain
PDMM_BQDMesh=2×TAR-MA(Sc)
PDMM_BQDTree=2×β×TAR-MA(Sc)
In data delivery, the data traffic will be delivered
through an optimized route. So, the data delivery delay of
P-DMM can be represented as follows.
PDMM_DDDMesh=2×TAR-AR(Sd)
PDMM_DDDTree=2×σ×TAR-AR(Sd)
So, we obtain the total delay of P-DMM as follows:
PDMM_TDMesh=PDMM_BUDMesh+PDMM_BQDMesh
+PDMM_DDDMesh
PDMM_TDTree=PDMM_BUDTree+PDMM_BQDTree
+PDMM_DDDTree
2.3. F-DMM
In F-DMM, when MN is attached to a new AR, the
AR will perform the binding update operation with the
distributed MA. Each MA has a rich finger table on all
MAs. The Map Update and Map Query messages are
transmitted through an optimal path. The probability for
F-DMM is ((NAR-2)/NAR). Accordingly, the Binding
Update Delay (BUD) of F-DMM can be represented as
follows.
FDMM_BUDMesh=((NAR-2)/NAR)×(2×TAR-AR(Sc))
FDMM_BUDTree=((NAR-2)/NAR)
×(2×σ×TAR-AR(Sc))
In F-DMM, the binding query delay from CN to MN
can be calculated as follows. First, AR performs the map
query operation with a distributed AR/MA so as to find
the LOC of MN. Then, MA will look up for the LOC of
A Comparative Analysis of Centralized and Distributed Mobility Management in IP-Based Mobile Networks 663
as follows.
CMMBQDMesh=CMMBQDTree
=0
In data delivery, a data packet is first delivered to MA,
and MA will forward the data packet to the concerned
host. So, the data delivery delay of CMM is as follows.
CMM_DDDMesh=2×TAR-MA(Sd)
CMM_DDDTree=2×β×TAR-MA(Sd)
So, we get the total delay of CMM as follows:
CMM_TDMesh=CMM_BUDMesh+CMM_BQDMesh
+CMM_DDDMesh
CMM_TDTree=CMM_BUDTree+CMM_BQDTree
+CMM_DDDTree
2.2. P-DMM
In P-DMM, when MN is attached to a new AR, the
AR will perform the binding update operation with MA.
The MA updates its database. Accordingly, the Binding
Update Delay (BUD) of P-DMM is represented as
follows.
PDMM_BUDMesh=2×TAR-MA(Sc)
PDMM_BUDTree=2×β×TAR-MA(Sc)
The binding query delay of P-DMM from CN to MN
can be calculated as follows. First, AR performs the map
query operation with MA to find the LOC of MN. Then,
MA will look for the LOC of MN in its database. After
lookup, the MA responds to AR with a Map Query ACK
message. Thus, the binding query delay of P-DMM can
be represented as follows.
CMM_TOMesh=CMM_TOTree=Sc×NHost×NAR+Sd
×NHost×NAR
3.2. P-DMM
In P-DMM, we calculate the traffic overhead by the
number of mapping control to be processed by MA. For
mapping update, all hosts in the network will send the
Map Update messages to MA. Thus, the Map Update
message of Sc×NHost×NAR shall be processed by MA.
For data transmission, each host sends Map Query
messages to MA. Thus, the Map Query messages of Sc×NHost×NAR shall be processed by MA. Accordingly, we
get the traffic overhead of P-DMM for each topology is as
follows.
PDMM_TOMesh=PDMM_TOTree
=2×(Sc×NHost×NAR)
3.3. F-DMM
In F-DMM, we calculate the traffic overhead by the
number of mapping control to be processed by AR/MA. It
is assumed that mobile hosts are equally distributed in the
network. For mapping update, all hosts in the network
will send the Map Update messages to its own AR. Each
AR/MA will process the binding update messages of Sc×(NHost/NAR). After that, the AR/MA will perform a hash
function to determine the designated AR/MA for the
concerned host. If the hashed value of the host is the other
AR/MA, then the AR will forward a Map Update message
to the designated AR/MA of host. Thus, the Map Update
message of Sc×(NHost-NHost/NAR) shall be processed.
For data delivery, each host sends a Map Query messages
to AR/MA. Each AR/MA will process the map query
messages of Sc×(NHost/NAR). After that, AR/MA will
perform the hash function to determine the designated
AR/MA of host. Then, AR will forward the Map Query
message to the designated AR/MA of host. Thus, the Map
Query messages of Sc×(NHost-NHost/NAR) shall be
processed by MA/AR. The data packets of Sd×(NHost/NAR) shall also be processed by AR/MA. Let us
assume that the probability for F-DMM is (NAR-2)/NAR.
Accordingly, we get the traffic overhead of F-DMM for
each topology is as follows.
MN in its database. After lookup, the designated AR/MA
responds to AR/MA with a Map Query ACK message. We
assume that mobile hosts are equally distributed in the
network with the probability of (NAR-2)/NAR. Thus, the
binding query delay of F-DMM can be represented as
follows.
FDMM_BQDMesh=((NAR-2)/NAR)×(2×TAR-AR(Sc))
FDMM_BQDTree=((NAR-2)/NAR)×(2×σ×TAR-AR(Sc))
In data delivery, the data traffic will be through an
optimized route. So, the data delivery delay of F-DMM
can be represented as follows.
FDMM_DDDMesh=2×TAR-AR(Sd)
FDMM_DDDTree=2×σ×TAR-AR(Sd)
So, we obtain the total delay of F-DMM as follows:
FDMM_TDMesh=FDMM_BUDMesh+FDMM_BQDMesh
+FDMM_DDDMesh
FDMM_TDTree=FDMM_BUDTree+FDMM_BQDTree
+FDMM_DDDTree
3. Analysis of Traffic Overhead (TO)
3.1. CMM
In CMM, we calculate the traffic overhead by the
number of mapping control and data traffic to be
processed at MA. It is assumed that mobile hosts are
equally distributed in the network. For mapping update,
all hosts in the network will send the Map Update
messages to MA. Thus, the Map Update message of Sc×NHost×NAR shall be processed by MA. For data
transmission, the data packets Sd×NHost×NAR shall also
be processed at MA. Accordingly, we get the traffic
overhead of CMM for each topology is as follows.
664 Telecommunications Review·Vol. 25 No. 4·2015. 8
FDMM_TOMesh=FDMM_TOTree
=((NAR-2)/NAR)×{2×(Sc×(NHost
-NHost/NAR))+2×Sc×(NHost/NAR)
+Sd×(NHost/NAR)}
IV. RESULTS AND DISCUSSION
Based on the analysis given so far, we now compare
the performances of the proposed schemes. For numerical
analysis, the default values of parameters are configured
as given in Table 3 by referring to [18], [19]. Among
these parameters, we note that β, Tq, Lw, NHost, and NARmay depend on the network conditions of mobile
networks. Thus, we will compare the performance of
candidate schemes by varying those parameter values.
1. Total Delays (TD)
1.1. Mesh Topology
Figure 5 and Figure 6 compare the total delays for
different average queuing delay at each node (Tq) and
wired link delay (Lw). It is shown in the figures that the
total delay linearly increases, as Tq and Lw get larger, for
the three candidate schemes. We can see that P-DMM and
F-DMM give slightly worse performance than CMM.
This is because P-DMM and F-DMM perform the binding
update and query operations. In the meantime, it is shown
that CMM gives the best performance among the
candidate schemes, since the binding query operation is
not performed in CMM.
1.2. Tree Topology
Figure 7 compares the total delay for different hop
count between AR and MA (β). In the figure, we can see
A Comparative Analysis of Centralized and Distributed Mobility Management in IP-Based Mobile Networks 665
Figure 5. Impact of Tq on total delay in mesh topology
Default
15
2 ms
5 ms
30
500
Minimum
1
1
1
2
100
Maximum
15
28
28
30
1000
Parameters
βLw
Tq
NAR
NHost
σSd
Sc
Bwl
Bw
Table 3. Parameter values used for analysis
√NAR
1024 bytes
200 bytes
11 Mbps
100 Mbps
that P-DMM and CMM give better performance than F-
DMM, until the hop count reaches 5. However, if the hop
count is greater than 5, the proposed F-DMM scheme
provides smaller delays than CMM and P-DMM, and the
performance gaps between the candidate schemes get
larger, as β increases. This is because the F-DMM does
not use the centralized MA for binding update and query
operation, and the data delivery and query operations are
performed in the distributed way. In the figure it is shown
that P-DMM gives better performance than CMM. This is
because P-DMM uses an optimal path for data delivery.
Figure 8 and Figure 9 illustrate the impact of average
queuing delay at each node (Tq) and wired link delay (Lw)
on total delays. We can see that the total delay linearly
increases, as Tq and Lw get larger, for the three candidate
schemes. We can see that CMM gives worse performance
than P-DMM and F-DMM. This is because CMM
performs the binding update operations with a centralized
MA, while there is no query operation, and the data
packets are directly delivered to the centralized MA. On
the other hand, it is shown in the figure that F-DMM gives
the best performance among the candidate schemes. This
is because the F-DMM does not use the centralized MA,
and the data delivery and query operations are performed
in the distributed way.
Figure 10 shows the impact of the number of ARs in
the domain on total delay. From the figure, the total delay
slightly increases, as NAR gets larger for the P-DMM and
F-DMM schemes. This implies that the distributed
schemes are much preferred in mobile network with a
maximum number of ARs in the domain. Overall, F-
DMM and P-DMM provide much smaller total delays than
CMM. This is because the data delivery operation is
performed through an optimal path. On the other hand, F-
666 Telecommunications Review·Vol. 25 No. 4·2015. 8
Figure 6. Impact of Lw on total delay in mesh topology
Figure 7. Impact of β on total delay in tree topology
DMM gives the best performance among the candidate
schemes.
2. Traffic Overhead (TO)
Figure 11 and Figure 12 compare the number of
control/data messages to be processed by MA or AR/MA
for different NHost and NAR. In Figure 11, we can see that
the F-DMM and P-DMM schemes provide smaller traffic
overhead than CMM. This is because all of the mapping
control and data messages shall be processed by MA in
CMM. On the other hand P-DMM gives worse
performance than F-DMM. This is because that all of the
mapping control messages are processed by MA. It is
shown in the figure that F-DMM gives the best
performance among the candidate schemes. This is
because all the control traffics are distributed onto the
AR/MAs in the network. The gaps of performance
between centralized and distributed schemes get larger, as
the number of hosts in the network increases. In Figure
12, we can see that the traffic overhead of F-DMM is not
affected by the number of ARs in the domain. This is
because all of the mapping control traffics are processed
by the AR/MAs in the network.
3. Discussion
In addition to the numerical analysis and results until
A Comparative Analysis of Centralized and Distributed Mobility Management in IP-Based Mobile Networks 667
Figure 8. Impact of Tq on total delay in tree topology
Figure 9. Impact of Lw on total delay in tree topology
now, we discuss the qualitative comparison of CMM and
DMM. Table 4 summarizes the pros and cons of CMM
and DMM by functionality.
CMM schemes maintain the data path between a
central network entity and the host. A single data path is
maintained per host. The tunnel management is easy to
deploy and broadly used. However, those tunnels tend to
induce data overhead due to encapsulations and data
processing. Tunnels header compression may also add
further processing. This induced overhead may impact on
core network links as well as access networks. In the
centralized schemes, the central entities need to maintain
per-user tunneling contexts, which may cause scalability
issues. The aggregated traffic is huge, and the mobile data
traffic explosion may occur. The data path centralization
tends to induce the single point of failure and bottleneck
issues.
On the other hand, in DMM schemes, only the
necessary and temporary tunnels are used between access
nodes. If a mobile node does not move, its data traffic can
be simply routed without additional overhead. The tunnel
endpoints are located at the access level, thus the rest of
the network is not affected. This can reduce the
processing overhead for encapsulation and de-capsulation.
However, each access node may need to be maintained in
per-user context. An active host may have parallel data
flows that are anchored at different access nodes. The
user contexts and tunnel maintenance are distributed
668 Telecommunications Review·Vol. 25 No. 4·2015. 8
Figure 10. Impact of NAR on total delay in tree topology
Figure 11. Impact of NHost on traffic overhead
among access nodes, which is helpful to avoid the single
point of failure and bottleneck issues. When the flows of a
moving host are anchored on different access nodes, they
require several parallel updates. Delays and packet loss
may be affected by the distance between access nodes.
V. CONCLUSIONS
In this paper, we have conducted a comparative study
for the candidate MM architectures: Centralized MM
(CMM), Partially Distributed MM (P-DMM), and Fully
Distributed MM (F-DMM) for IP mobility support in
future mobile networks.
By performance analysis, the three candidate schemes
are compared in terms of total delay and traffic overhead.
From numerical results, we see that F-DMM and P-DMM
can gives better performance than CMM in the mesh-like
and tree-like networks in terms of traffic overhead.
However, from the perspective of total delay, CMM may
be preferred to P-DMM and F-DMM in the mesh
topology, whereas P-DMM and F-DMM are preferred to
CMM in the tree topology.
A Comparative Analysis of Centralized and Distributed Mobility Management in IP-Based Mobile Networks 669
Figure 12. Impact of NAR on traffic overhead
Table 4. Qualitative analysis of CMM and DMM schemes
DMM
No tunnel is required when the active is motionless
Avoid unnecessary overhead
Temporary tunnel endpoints distributed at access node level
Avoid single point of failures
Multiple inter-access node tunnels per host situation
Avoid scalability issues
Contexts replication (e.g. for a host with flows on different anchors)
CMM
Single path per host
Permanent tunnel per active host
Overhead in processing
Easy to deploy
Huge aggregated traffic in network
Bottlenecks/single point of failure
Easy to administrate
Dimensioning of central mobility agents, scalability
Pros
Cons
Pros
Cons
Pros
Cons
Functionality
Encapsulation
Tunnel management
User context
AcknowledgmentThis research was partly supported by the Basic
Science Research Program of NRF(2010-0020926).
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RFC 3344, Aug. 2002.[4] D. Johnson, et al., Mobility Support in IPv6, IETF RFC
3775, Jun. 2004.[5] S. Gundavelli, et al., Proxy Mobile IPv6, IETF RFC
5213, Aug. 2008.[6] H. Chan, et al., Requirements for Distributed Mobility
Management, IETF RFC 7333, Aug. 2014.[7] D. Liu, et al., Distributed Mobility Management:
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[8] P. Jokela, et al., Host Identity Protocol, IETF RFC 5201,Apr. 2008.
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[11] V. Fuller, et al., LISP Map Server Interface, IETF RFC 6833, Jan. 2013.
[12] RJ Atkinson, et al., Identifier-Locator Network Protocol (ILNP) Architecture Description, IETF RFC 6740, Nov. 2012.
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670 Telecommunications Review·Vol. 25 No. 4·2015. 8
Moneeb Gohar
He received B.S. degree in Computer Science from
University of Peshawar, Pakistan, and M.S. degree in
Technology Management from Institute of Management
Sciences, Pakistan, in 2006 and 2009, respectively. He
also received Ph. D degree from the School of Computer
Science and Engineering in the Kyungpook National
University, Korea, in 2012. From September 2012 to
September 2014, he worked as a Post-Doctoral researcher
for Software Technology Research Center (STRC) in
Kyungpook National University, Korea. He has been as an
International Research Professor with the Department of
Information and Communication Engineering in the
Yeungnam University since September 2014. His current
research interests include Network Layer Protocols,
Wireless Communication, Mobile Multicasting, Wireless
Sensors Networks, TRILL, and Internet Mobility.
E-mail: [email protected]
A Comparative Analysis of Centralized and Distributed Mobility Management in IP-Based Mobile Networks 671
Seok-Joo Koh
He received the B.S. and M.S. degrees in Management
Science from KAIST in 1992 and 1994, respectively. He
also received Ph.D. degree in Industrial Engineering from
KAIST in 1998. From August 1998 to February 2004, he
worked for Protocol Engineering Center in ETRI. He has
been as a professor with the school of Computer Science
and Engineering in the Kyungpook National University
since March 2004. His current research interests include
mobility management in the future Internet, IP mobility,
multicasting, LED-based visible lights communication,
IoT and SCTP. He has so far participated in the
international standardization as an editor in ITU-T SG13
and ISO/IEC JTC1/SC6.
E-mail: [email protected]