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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

656

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


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,


Figure 3. Overview of Fully Distributed Mobility Management (F-DMM)


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


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


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.


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


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-


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


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


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.


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).

[References][1] Morgan Stanley Report, Internet trends,

http://www.morganstanley.com/, 2013.[2] J. Saltzer, On the naming and binding of network

destinations, IETF RFC 1498, Aug. 1993.[3] C. Perkins, et al., IP Mobility Support for IPv4, IETF

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:

Current Practices and Gap Analysis, IETF RFC 7429, Jan. 2015.

[8] P. Jokela, et al., Host Identity Protocol, IETF RFC 5201,Apr. 2008.

[9] D. Farinacci, et al., Locator/ID Separation Protocol, IETF RFC 6830, Jan. 2013.

[10] V. Fuller, et al., Locator/ID Separation Protocol - Alternative Topology (LISP+ALT), IETF RFC 6836, Jan. 2013.

[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.

[13] M. Gohar, et al., ''Network-based Distributed Mobility Control in Localized Mobile LISP Networks,''IEEE Communications Letters, Vol. 16, Jan. 2012, pp. 104-107.

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Networks,'' Wireless Personal Communications, Vol. 72. No. 1, Sep. 2013, pp. 565-579.

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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]


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]

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