Mobility Analysis for all-ip Networks

Transcription

1 Mobility Analysis for all-ip Networks Ramy Farha Department of Electrical and Computer Engineering University of Toronto Toronto, Ontario, Canada Alberto Leon-Garcia Department of Electrical and Computer Engineering University of Toronto Toronto, Ontario, Canada Abstract This paper discusses and compares different approaches to handle mobility in all-ip networks, at both the application and network layers. First, three key parameters of mobility schemes are quantified: handoff delay, registration/binding cost, and packet delivery cost. Next, these schemes are compared based on criteria such as the need for encapsulation, changes in endsystems and/or infrastructure, scalability, and reliability. Finally, a mobility model is used to perform extensive simulations in order to compare the different all-ip mobility approaches. Application Network Fig. 1. SIP H.323 Mobile IP SIP-MS MIPv4 MIPv4 Optimizations MIP-LR Classification of Mobility Protocols I. INTRODUCTION The last decade has witnessed an explosive development of wireless devices and of various wireless access networks. With the increasing popularity of the Internet, efforts to develop a wireless Internet infrastructure are underway. The goal is to provide an end-to-end IP platform supporting real-time and non-real-time multimedia services over wireless networks. The present day first/second generation (1G or 2G) circuitswitched cellular networks will ultimately evolve toward an all-ip wireless network, leading to what is referred to as the third or even fourth generation (3G or 4G) wireless networks. The most exciting opportunities appear in the convergence of the IP and wireless technologies by allowing seamless access to the Internet for mobile users communicating through handlheld devices. While seamless mobility and connection handoff support are the key strength of a wireless network, IP protocols were designed primarily for a fixed routing infrastructure and do not transparently support mobile access. The problem of augmenting IP s basic destination addressbased routing to support changes in the network connectivity of a Mobile Node (MN) has been addressed by various mobility solutions. This paper analyzes the major attempts in that direction, their advantages and their shortcomings. II. MOBILITY TYPES AND APPROACHES All-IP mobility can be categorized into four main types: Terminal: Terminal mobility is defined as the ability of a Mobile Node (MN) to move between IP subnets, while continuing to be reachable for incoming requests and maintaining sessions across subnet changes. Session: Session mobility is defined as the ability of a user to maintain a session when changing terminals. Personal: Personal mobility is defined as the ability of a user to address another user located at several terminals by the same logical address, or to address one terminal by several logical addresses. Service: Service mobility is defined as the ability of users to maintain access to their services even when moving and changing devices or service providers. Terminal mobility is classified into two main categories: Micro-Mobility is the movement of a MN within or across different Base Stations (also referred to as Access Points) in a subnet within an Administrative Domain. Usually, the IP address of the MN remains the same. These schemes will not be considered in this paper. Interested readers are referred to [1] for more information. Macro-Mobility is the movement of a MN across different subnets within an Administrative Domain, or across different subnets belonging to different Administrative Domains. Usually, the IP address of the MN changes. Existing all-ip mobility protocols are usually limited to a single layer, hence are transparent to the other layers. Proposals to support mobility have been advanced for several layers, namely subnetwork, network, transport, and application. Figure 1 shows a classification of the most popular approaches at the network and application layers. In the remainder of this paper, we will analyze these approaches. We will refer interested readers to our ongoing work [2], where we survey the different all-ip micro- and macro- mobility schemes. The analysis that follows will be divided into two parts. In the first, we will perform an analytical analysis of these schemes, attempting to quantify the handoff delay, the registration/binding cost, and the packet delivery cost. In the second, we will compare the different approaches based on several criteria of importance for efficient all-ip mobility. III. QUANTITATIVE ANALYSIS In order to conduct an analytical analysis of the main mobility mechanisms, a generic model needs to be defined IEEE Communications Society / WCNC /05/$ IEEE

2 CN Fig. 2. Parameter D p D tx C p P p C tx P tx P tx tun P tun b e AR g c home network HA j i MN: Mobile Node CN: Correspondent Node HA: Home Agent d AR: Access Router h f AR a MN foreign network Generic Model for the Analysis of all-ip Mobility Approaches TABLE I VARIABLES USED FOR QUANTITATIVE ANALYSIS Meaning Processing Delay at a node Transmission Delay across a hop Cost of processing registration/binding at a node Cost of processing data packet at a node Cost of registration/binding transmission across a hop Cost of data packet transmission across a hop Cost of tunneled data packet transmission across a hop Cost of tunneling de-tunneling data packet at a node first. This model will be used throughout this paper. Figure 2 shows the generic architecture which will be used in the rest of this paper. The Mobile Node (MN) and Corresponding Node (CN) are in the middle of an ongoing session when the handoff occurs. The Home Agent (HA) is present in the home network of the MN, and the Access Router (AR) is present at the edge of both the MN s and CN s networks. Both play different roles depending on the mobility scheme considered. For instance, in Mobile IPv4, the AR will be the Foreign Agent (FA). The letters (a to j) on each link denote the shortest hop distance between the two entities that this link connects. In the first part of our analysis, we will quantify the following parameters: 1) Handoff Delay: Quantifies the handoff delay. This delay has two main components: a) Mobility detection and b) Registration/binding delay. 2) Registration/binding Cost: Quantifies the registration/binding updates overhead in the network. 3) Packet Delivery Cost: Quantifies the cost of delivering a packet in the network. We neglect the handoff delay due to security issues and to the mobility detection mechanism. Table I shows the different variables used to quantify the aforementioned parameters. In Table II, we quantify these parameters for each mobility scheme. Note that for some schemes, the handoff delay is factored by a parameter α 1. This denotes the fact that disruption only occurs in one of the two possible situations: MN transmitting or MN receiving, but not in both. A. MIPv4 In this scheme [3], the AR in the foreign network denotes the Foreign Agent (FA). When a MN changes its subnet, it obtains a temporary Care-of-Address (CoA) from the FA. Then, it informs the HA of the obtained CoA, so the HA binds the permanent IP address (called Home Address) of the MN to its CoA. All packets addressed to the MN from a CN are routed to the home network, intercepted by the HA, and forwarded to the FA by tunneling. Mobile IPv4 comes in two variants, depending on the form of its CoA. In the first, the MN uses the FA s address as its CoA and the FA registers this foreign CoA (FA-CoA) with the HA. Hence, the packets are tunneled from the HA to the FA, where the FA decapsulates and forwards the original packets directly to the MN. In the second, the MN obtains a CoA for itself, for instance through DHCP [4], and registers this co-located CoA (CCoA) either directly with the HA or via the FA. Tunneling packets from the HA are decapsulated by the MN itself. B. MIPv4 Optimizations 1) Route Optimization: To deal with the triangular routing problem, Mobile IPv4 with Route Optimization (RO) [5] has been proposed. In this scheme, the AR in the foreign network denotes the Foreign Agent (FA). A CN must understand mobility binding updates and should be able to tunnel packets to a CoA, while the MN must send binding updates to the CN to update it on the MN s location, and the CN can tunnel packets to the CoA without going through the HA. If there is no binding cache entry in a CN for a given MN, packets still need to go through the HA as is the case in basic Mobile IPv4. We will assume that binding updates are always available. 2) Regional Registration: To deal with the delays in the registration of MNs with their HA, the long service disruption, and the packet losses, Mobile IPv4 with Regional Registration (RR) [6] has been proposed. In this scheme, the AR in the foreign network denotes the Gateway Foreign Agent (GFA). The MN is assigned a global CoA belonging to the GFA. As long as the mobile stays within the domain of the same GFA, only local location updates up to the GFA are necessary. When changing GFA, the MN must perform a normal registration to its home network. Let P local denote the probability that the MN only needs local updates, and P normal denote the probability that the MN needs registration to the home network. 3) Reverse Tunneling: To deal with the problem of firewalls dropping IP packets, Mobile IPv4 with Reverse Tunneling [7] has been proposed. In this scheme, the AR in the foreign network denotes the firewall (FW). This extension establishes a reverse tunnel from the FW in the foreign network to the HA. A sent packet is then decapsulated at the HA, and delivered to the CN with the MN s Home Address as its IP source address. C. Mobile IPv6 is the corresponding framework of Mobile IPv4 but for IPv6. In this scheme, no ARs are needed. When a MN changes its subnet, it obtain a temporary CoA for itself, for instance through IPv6 address autoconfiguration IEEE Communications Society / WCNC /05/$ IEEE

3 and neighbor discovery, hence following the CCoA model of Mobile IPv4. There are more than enough addresses in the IPv6 space that there is no need for a FA in order to save IP addresses by tunneling packets to one point of attachment in the foreign network. Route Optimization (RO) is now built in as a fundamental part of the protocol. Binding updates are sent to the CNs by the MN rather than the HA. Some improvements of were proposed such as Hierarchical [8], but are similar to the same improvements proposed for Mobile IPv4, hence were discarded here due to space constraints. D. MIP-LR In this scheme [9], the ARs denote the home location register (HLR) and the visitor location register (VLR). Each subnet may contain a node that functions as a VLR and/or a node that functions as a HLR. When a MN moves to a foreign network, it obtains a CoA from the pool of addresses that the VLR has. The MN registers with the foreign VLR using the CoA it has obtained, which in turn relays the registration to the MN s HLR. A CN wishing to send a packet to the MN issues a query to the HLR, which returns the MN s CoA as well as the remaining registration lifetime. The CN then directly sends the packet to the MN s CoA. The CN caches a binding for the MN s CoA and uses this binding for subsequent packets destined to the MN. The CN must refresh its binding cache by querying the HLR again before the MN s remaining registration lifetime expires. E. Reverse Address Translation () The approach [10] adds new entities to the home network: a registration server and a device. The rest of the network infrastructure remains unchanged. In particular there are no mobility specific entities in the foreign network required. The approach applies the Network Address Translation (NAT) paradigm. In this scheme, no ARs are needed, but the HA now denotes the registration server and the device which we assume are co-located. Suppose a CN wishes to send a packet to the MN and directs it to the MN s home address. In the home network, the device intercepts the packet and performs a network address translation. Therefore, it replaces the destination address with the MN s temporary CoA and the source address with the address of the device. Then the packet is sent directly to the MN without tunneling. In the reverse direction, the MN sends a packet directly to the CN. F. SIP-MS In this scheme [11], no ARs are needed, but the HA now denotes the SIP Redirect Server (RS). When the MN moves during a session, it must send a new INVITE to the CN using the same Call Identifier as the initial call. It must put the new IP address in the Contact field of the SIP INVITE message. This tells the CN where to send future SIP messages. Finally, the MN updates its registration information with the SIP RS in the Home Network. G. Host Mobility Management Protocol () In this scheme [12], no ARs are needed, but the HA again denotes the SIP Redirect Server (RS). utilizes as well as extends SIP-MS to support both real-time and non-real-time multimedia applications on mobile terminals. spoofs constant endpoints for mobile TCP connections and supports mobile TCP applications in a SIP environment without any changes to the TCP. The MN should have an agent (referred to as SIP EYE [13]) that keeps the list of ongoing TCP connections as well as their identifiers. H. H.323 In this scheme [14], the HA denotes the Gatekeepers (GK), and the AR in the foreign network denotes the Visitor Location Function (VLF). As the MN enters a new domain, it first discovers its new GK (from GK Address Advertisement for instance), then sends a GRQ message to its HLF including all the user s identities. After successful authentication, the new VLF will send a GCF message to indicate that it will accept registration. The MN then registers with its new domain, and updates its HLF about its new location. IV. COMPAIVE ANALYSIS In the second part of our analysis, we will use the following criteria for comparison: 1) Encapsulation: Whether encapsulation is needed when moving between administrative domains. 2) End-System Changes: Whether the operating system of the communicating nodes needs to be modified to support the proposed solution. 3) Infrastructure Changes: Whether the infrastructure (routers, access points...) needs to be modified to support the proposed solution. 4) Triangular Routing: Whether the triangular routing problem exists (i.e., packets routed to the home network before being forwarded to the foreign network). 5) Scalability: Whether the proposed solution is scalable, i.e. whether it is simple to support more devices. 6) Reliability: Whether the proposed solution is considered reliable, i.e. the operation of the system does not depend on a single device. A solution is deemed reliable if redundancy can be easily introduced, and if the extent of disruption caused by a single failure is contained. 7) Transport Layer Protocols Supported: Lists which of the main transport layer protocols (TCP, UDP, SCTP) can maintain connectivity despite mobility. Table III compares the different schemes using the aforementioned criteria 1. We assume that changes such as SIP stack installation, H.323 stack installation, and Mobile IP stack installation are not changes to the end system, since they are basic mobility solutions proposed, hence are not considered additions. However, adding something like a SIP EYE agent or tunneling capabilities at CNs and/or MNs is considered a change in the end system. As well, for the changes to the 1 Numbers correspond to the criteria listed at the beginning of Section IV IEEE Communications Society / WCNC /05/$ IEEE

4 Scheme Handover Delay Registration Cost Packet Delivery Cost MIPv4-FA 2D P,F A + D P,HA +2(a + d)d tx, 2C P,F A + C P,HA +2(a + d)c tx, CN to MN: if MN is roaming if MN is roaming P tun,ha + P tun,f A + dp tx tun +(a + e)p tx, D P,HA +2aD tx, C P,HA +2aC tx, if MN is roaming if MN is in home network if MN is in home network (a + e)p tx, if MN is in home network MIPv4-CoA D P,HA +2fD tx, C P,HA +2fC tx, CN to MN: if MN is roaming if MN is roaming P tun,ha + P tun,mn + fp tx tun + ep tx, D P,HA +2aD tx, C P,HA +2aC tx, if MN is roaming if MN is in home network if MN is in home network (a + e)p tx, if MN is in home network MIP-RO-FA 2D P,F A + D P,CN +2(a + h)d tx 2C P,F A + C P,CN +2(a + h)c tx CN to MN: P tun,cn + P tun,mn + P P,F A +(a + h)p tx tun MIP-RO-CoA D P,CN +2iD tx C P,CN +2iC tx CN to MN: P tun,cn + P tun,mn + ip tx tun MIP-RR P local (D P,GF A +2aD tx) P local (C P,GF A +2aC tx) CN to MN: +P normal (2D P,GF A +P normal (2C P,GF A P tun,ha + P tun,gf A + dp tx tun +(a + e)p tx tun +D P,HA +2(a + d)d tx) +C P,HA +2(a + d)c tx) MIP-RT 2D P,F W + D P,HA +2(a + d)d tx, 2C P,F W + C P,HA +2(a + d)c tx, P tun,ha + P tun,f W + dp tx tun +(a + e)p tx, if MN is roaming if MN is roaming if MN is roaming D P,HA +2aD tx, C P,HA +2aC tx, (a + e)p tx, if MN is in home network if MN is in home network if MN is in home network α[d P,HA + D P,CN +2(f + i)d tx] C P,HA + C P,CN +2(f + i)c tx ip tx MIP-LR 2D P,V LR + D P,HLR +2(a + j)d tx 2C P,V LR + C P,HLR +2(a + j)c tx P P,HLR +(2b + i)p tx α[d P, +2fD tx] C P, +2fC tx CN to MN: P ch, +(e + f)p tx SIP-MS α[d P,CN + D P,RS +2(i + f)d tx] C P,CN + C P,RS +2(i + f)c tx When updates are fresh: ip tx When updates are not fresh: CN to MN: (e + f)p tx α[d P,CN + D P,RS +2(i + f)d tx] C P,CN + C P,RS +2(i + f)c tx When updates are fresh: ip tx tun, if TCP ip tx, if UDP When updates are not fresh: (e + f)p tx tun, if TCP (e + f)p tx, if UDP H.323 2D P,GK +2D P,V LF 2C P,GK +2C P,V LF CN to MN: (a + d + e)p tx +D P,HLF +(2f +4d)D tx +C P,HLF +(2f +4d)C tx TABLE II QUANTITATIVE ANALYSIS OF MOBILITY SCHEMES infrastructure, we will assume changes to firewalls, routers among others, as modifications to the infrastructure. As well, when considering scalability and reliability, we look at factors such as the possibility to load balance and duplicate. IP-in-IP encapsulation is needed for MIPv4 and all its variants. TCP-in-IP encapsulation is needed for to allow a TCP connection to be handed off. No encapsulation is needed in case a UDP connection is handed off. Note that is basically a NAT-like function, so the IP address is changed rather than encapsulated. End-system changes are needed for MIP-RO and MIP-LR due to the fact that encapsulation is performed by the CN, and for due to the addition of the SIP EYE agent to the existing SIP protocol stack. Infrastructure changes are needed for MIP-RT due to the changes in the firewalls, for due to the need for HAs to play the role of NATs, for due to the need for SIP servers to be aware of SIP EYE agents, and for H.323 due to the need for the HLF/VLF. Triangular routing is needed for all MIPv4 s variants, except MIP-RO, which was mainly designed to avoid the costly routing to the home network. also needs triangular routing as the HA plays the role of NAT for both CN-MN and MN-CN transmissions. To analyze scalability, we focus on the ability of the mobility solution s infrastructure to handle a large number of users, without potential bottlenecks. MIPv4 and its variants have poor scalability, mainly because of the need to address the HA for all transmissions. In addition, the scarcity of IPv4 addresses can be a problem. s scalability is good because the IP addresses are plentiful, and the transmissions occur directly between MN and CN in both directions, hence the home network bottleneck is avoided. MIP-LR s scalability is poor due to the need for HLR and VLR queries and the possible resulting delays. has scalability problems because the HA performs the IP address changes on all packets exchanged in any direction, hence the need to re-compute the IP header checksum. SIP-MS and are scalable because IEEE Communications Society / WCNC /05/$ IEEE

5 TABLE III COMPARISON BETWEEN DIFFERENT MACRO-MOBILITY APPROACHES Solutions MIPv4-FA Yes No No Yes Poor Low All MIPv4-CoA Yes No No Yes Poor Low All MIP-RO Yes Yes No No Poor Low All MIP-RR Yes No No Yes Poor Low All MIP-RT Yes No Yes Yes Poor Low All No No No No Good High All MIP-LR No Yes No No Poor High All No No Yes Yes Poor Low UDP SIP-MS No No No No Good High UDP Yes Yes Yes No Good High All H.323 No No Yes No Poor Low TCP load balancing can be easily performed between multiple SIP servers in the home network by using the DNS SRV records. To analyze reliability, we focus on the possible redundancy to avoid single points of failure. In MIPv4 s variants, the HA constitutes a single point of failure. Note that FAs can also be problematic when present. depends solely on the HA for operation, hence is vulnerable to any HA-related failure. H.323 depends on GKs, HLF, and VLF for correct operation, hence reliability can be become an issue. is highly reliable because of its authentication mechanisms, the use of local binding updates for MN locations, and the absence of FAs. MIP-LR can be considered reliable because HLF/VLF can be replicated for redundancy, avoiding single points of failure. SIP-MS and benefit from the redundancy of SIP servers and the lack of FAs to be considered reliable. V. SIMULATION RESULTS The different metrics (handover delay, registration cost, packet delivery cost) are dependent on the distances between the MN, the HA, and the CN. Without loss of generality, we will assume that the MN is moving, while both the CN and HA are fixed. The distance between the HA and the CN is therefore fixed. To model the MN s movement, we use the model presented in [15], and later used in [16]. The network is viewed as a rectangular grid of cells, with the MN moving according to the random walk model between adjacent cells after starting initially in the cell at the center of the grid. In a unit of time measure, the MN moves a distance of X cells. The metrics are averaged over the different possible locations of the MN. We combine the registration and packet delivery costs into a new metric called Signaling Overhead Cost (SOC). SOC depends on the mobility rate of the MN (number of registrations needed), and on the number of active sessions the MN is involved in. We will normalize the values for the sake of comparison, such that each registration occurs on average after the delivery of N packets. Note that the total packet delivery cost was obtained by assuming the MN evenly receives and transmits (i.e. α =0.5), and that the traffic is evenly UDP-based and TCP-based when both are supported. Table II gives some insight on what could be expected from the simulations that follow. Simplifying, we assume a and b are negligible compared to the MN-HA (d) and MN-CN (i) distances, i.e. a = b =0, hence g = h = i = j, c = e, and d = f. We can conclude that H.323 s handover delay is given by (2D P,GK +2D P,V LF + D P,HLF +6dD tx ), so is affected the most (factor of 6) when the MN-HA distance increases. MIP-LR s handover delay is given by (2D P,V LR + D P,HLR +2iD tx ), so is affected the most (factor of 2) when the MN-CN distance increases. s handover delay is given by α[d P, +2dD tx ], so is affected the least when the MN-HA and MN-CN distances increase. Similar conclusions can be deduced from the various equations by using the aforementioned assumptions. Figure 3 shows a 3-D graph of the handover delay (HD) for different values of the MN-CN and MN-HA distances. MIPv4-CoA s HD is fixed as the MN-CN distance increases. The performance is better than most schemes as the MN-CN distance increases, but is poor for small MN-CN distances. The HD increases as the MN-HA distance increases, and performs poorly at high MN-HA distances. MIPv4-FA s HD is fixed as the MN-CN distance increases, but slightly worse than that of MIPv4-CoA. The HD increases as the MN-HA distance increases, and performs very poorly at high MN-HA distances. MIP-RO s HD is fixed as the MN-HA distance increases. Even though the performance is poor at small MN-HA distances, the performance becomes better than most other schemes as the MN-HA distance increases. The HD increases when the MN-CN distance increases, and performs very poorly at high MN-CN distances. MIP-RR s HD is fixed as the MN-CN distance increases, and performs better than most schemes proposed. The HD increases with increasing MN-HA distances, and while it starts well for small MN-HA distances, the performance degrades as the MN-HA distance increases. MIP-RT s HD is fixed as the MN-CN distance increases. This performance is poor though at small MN-CN distances. The HD increases as the MN-HA distance increases, and performs very poorly at high MN-HA distances. s HD increases with both MN-CN and MN-HA distances. However, is affected more when the MN- CN distance increases. Its performance is only better than that of MIP-LR and MIP-RO. MIP-LR s HD is fixed for increasing MN-HA distances, and increases as the MN-CN distance increases. MIPLR s performance degrades and becomes the worst of all schemes as the MN-CN distance increases. s HD performs best for low MN-HA distances, and for all MN- CN distances, but increases as the MN-HA distance increases. H.323 s HD increases as the MN-HA distance increases for a fixed MN-CN distance. H.323 s HD is the worst of all, except for situations where the MN-HA distance is low and the MN-CN distance is high. s HD increases as either the MN-HA or the MN-CN distance increases. performs worse than H.323 at high MN-CN distances and low MN-HA distances. SIP s HD is similar to that of. Figure 4 shows a 3-D graph of the signaling overhead cost (SOC) for different values of the MN-CN and MN-HA distances. MIPv4-CoA s SOC increases as either the MN-CN or the MN-HA distance increases. The performance is better than most schemes as the MN-CN distance increases, but IEEE Communications Society / WCNC /05/$ IEEE

6 Fig. 3. Handover Delay for different MN-CN and MN-HA distances Fig. 4. SOC for different MN-CN and MN-HA distances worse than most schemes as the MN-HA distance increases. MIPv4-FA s SOC is slightly worse than that of MIPv4-CoA, and the SOC increases as either the MN-HA or the MN-CN distance increases. MIP-RO s SOC is fixed as the MN-HA distance increases. The SOC increases as the MN-CN distance increases, and the performance heavily degrades. MIP-RR s SOC increases as either the MN-CN or the MN-HA distance increases. The SOC is amongst the worse as the MN-HA and MN-CN are small, but the performance compared to the other schemes improves as either distance increases. MIP-RT s SOC increases as either the MN-CN or the MN-HA distance increases. This performance is the worst of all schemes for small MN-CN distances regardless of the MN-HA distance. As the MN-CN distance increases, MIP-RT s performance becomes better than that of several schemes. s SOC increases with both MN-CN and MN-HA distances. However, is much more affected by the MN- CN distance increase. MIP-LR s SOC is fixed as the MN- HA distance increases, and increases as the MN-CN distance increases. MIP-LR s performance degrades and becomes the worst of all schemes as the MN-CN distance increases. s SOC increases as either the MN-CN or the MN-HA distance increases, and performs worse than several schemes. H.323 s SOC increases as either the MN-CN or the MN-HA distance increases. H.323 s SOC is the worst at high MN-CN and MN-CA distances, but is slightly better for either small MN-CN or MN-HA distance, regardless of the other distance. s SOC increases as either the MN-HA or the MN- CN distance increases. performs better than several schemes as the MN-HA distance increases while the MN-CN distance is small. However, as the MN-CN distance increases, s SOC increases for small MN-HA distances, and performs the worst of all schemes. SIP s SOC is always slightly better than that of. Handover delay in unit time H323 SIPMS MIPLR MIPv4RT MIPv4RR MIPvRO MIPv4 CoA MIPV4 FA Handover Delay for different MN speeds Speed per unit time (in cells) Fig. 5. Handover Delay for different MN speeds Figure 5 shows the effect of the MN s speed on the handover delay. We vary X, the number of cells the MN traverses in a unit of time measure, for fixed MN-CN and MN- HA distances such that the HA is located between the MN and the CN. We notice from the results that, as the speed increases, the handover delay increases. However, this increase is not pronounced as X varies from 5 to 40 cells per unit of time measure. Hence, the increase in MN s speed leads to an increase in the handover delay for all mobility schemes at fixed MN-CN and MN-HA distances. On the other hand, Figure 6 shows the effect of the MN s speed on the signaling overhead cost for the same scenario. We notice from the results that, as the speed increases, the signaling overhead cost increases. However, this increase is more pronounced than the HD s increase as X varies from IEEE Communications Society / WCNC /05/$ IEEE

7 Signaling Overhead Cost in unit time Signaling Overhead Cost in unit cost H323 SIPMS MIPLR MIPv4RT MIPv4RR MIPvRO MIPv4 CoA MIPV4 FA Signaling Overhead Cost for different MN speeds Speed per unit time (in cells) Fig. 7. Fig. 6. SOC for different MN speeds Signaling Overhead Cost for different MN active sessions and mobility rate H323 SIPMS MIPLR MIPv4RT MIPv4RR MIPvRO MIPv4 CoA MIPV4 FA Normalization Rate N SOC for different number of MN active sessions and mobility rate 5 to 40 cells per unit of time measure. Hence, the increase in MN s speed mainly leads to an increase in the signaling overhead cost for all mobility schemes at a fixed MN-CN and MN-HA distance. Finally, Figure 7 shows the effect of the number of MN s active sessions and mobility rate on the signaling overhead cost. We vary the normalization rate N from 1 to 100, i.e. the number of data packets sent by the MN before a registration is needed. We notice a steep increase in the signaling overhead cost as the rate increases, which is expected given additional data packets sent. Notice that the rate of SOC increase for MIP-RT is the highest. This is due to the fact that the packet delivery cost for MIP-RT is high due to the triangular routing in both MN-CN and CN-MN transmissions. TABLE IV SUMMARY OF BEST APPROACHES Distances HD Best SOC Best Small MN-CN, MN-HA, MIP-RR, SIP-MS Small MN-CN, High MN-HA MIP-LR, MIP-RO MIP-RO, MIP-LR High MN-CN, Small MN-HA, MIP-RR MIP-RT, High MN-CN, MN-HA, MIP-RR MIP-LR, MIP-RO VI. CONCLUSIONS In this paper, we analyzed and compared different approaches to achieve seamless mobility in all-ip networks. Three parameters are computed for the different approaches: handoff delay, registration/binding update cost, and packet delivery cost. The various schemes are compared based on several criteria of interest for efficient mobility performance. Using a mobility model, we ran simulations where the different approaches have been compared for different MN-CN and MN-HA distances, different MN speeds, and different MN active sessions and frequency of registration/binding updates. The main contribution of this paper is that it provides a detailed analysis of all these schemes, and Table IV can be used as a quick reference to identify situations in which an all-ip mobility solution performs best according to our study. Future work will involve a more detailed analysis of the variables used, and a study of other mobility models. REFERENCES [1] P. Reinbold and O. Bonaventure, IP Micro-Mobility Protocols, IEEE Communications Surveys, vol. 5, pp , Oct [2] R. Farha and A. Leon-Garcia, Comparison of approaches for mobility in all-ip networks. Manuscript under preparation. [3] C. Perkins, IP Mobility Support for IPv4. RFC 3344, Aug [4] R. Droms, Dynamic Host Configuration Protocol. RFC 2131, Mar [5] C. Perkins and D. Johnson, Route Optimization in Mobile IP. Internet Draft, Feb [6] E. Gustafsson, A. Jonsson, and C. Perkins, Mobile IPv4 Regional Registration. draft-ietf-mobileip-reg-tunnel-07.txt, Nov [7] G. Montenegro, Reverse Tunneling for Mobile IP. RFC 3024, Jan [8] C. Castellucia and L. Bellier, Hierarchical Mobile IPv6. draftcastellucia-mobileip-hmipv6-00.txt, July [9] R. Jain, T. Raleigh, M. Bereschinsky, and C. Graff, Mobile IP with Location Registers (MIP-LR). draft-jain-miplr-00.txt, Feb [10] R. Singh et. al., : a quick (and dirty?) push for mobility support, in Proceedings of the 2nd IEEE Workshop on Mobile Computing Systems and Applications (WMCSA), pp , Feb [11] H. Schulzrinne and E. Widlund, Application-Layer Mobility Using SIP, ACM SIGMOBILE Mobile Computing and Communications Review, vol. 4, pp , July [12] A. Dutta et. al., Application Layer Mobility Management Scheme for Wireless Internet. IEEE 3GWireless, May [13] F. Vakil et. al., Supporting Mobility for TCP with SIP. draft-itsumosipping-mobility-tcp-00.txt, June [14] G. T.-G. M. 23, Reply LS on Technical Report on Mobility between H.323 Mutlimedia Systems and GPRS/IMT2000 Networks. ITU-T COM 16 - LS 15 - E (S ), Feb [15] Y. Wand et. al., Performance Analysis of Mobile IP Extended with Routing Agents, in Proceedings of the 2nd European IASTED International Conference on Parallel and Distributed Systems, July [16] S. Galli et. al., An Analytical Approach to the Performance Evaluation of Mobility Protocols: The Handoff Delay Case, in Proceedings of the IEEE Vehicular Technology Conference (VTC), IEEE Communications Society / WCNC /05/$ IEEE