Seamless Mobility Management Using a Combination of MIP And

Seamless Mobility Management Using a Combination of MIP And

An architecture for seamless mobility management in various types of applications using a combination of MIP and SIP Karl Andersson1 and Christer Åhlund2 1Department of Computer Science and Electrical Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden 2Division of Mobile Networking and Computing, Luleå University of Technology, SE-931 87 Skellefteå, Sweden {karl.andersson, christer.ahlund}@ltu.se Abstract technologies at a certain moment and a certain place. The In the future, mobile users will have the possibility to use research question this paper tries to answer is targeted a variety of wireless access networks simultaneously towards finding an optimal mobility management making the vision “Always best connected” come true. solution for users of heterogeneous networks. The Internet Protocol (IP) will most likely be the least common divisor allowing service providers to deploy The rest of the paper is organized as follows: Chapter 2 services in a unified way regardless of access network describes briefly two of the most widespread mobility type (being wired or wireless). The 3GPP-led management solutions, MIP and SIP. Chapter 3 describes development of the IP Multimedia Subsystem (IMS) is a the suggested architecture. Chapter 4 presents our promising step towards the vision. However, there are a evaluation framework. Chapter 5 contains information number of obstacles along this way forward. Various about related work. Chapter 6 discusses the results and deployment difficulties related to already installed base outlines future work. of user and infrastructure equipment and service providers protecting their old investments are the most 2. Mobility management solutions common obstacles. In addition to those reasons, 2.1 Mobility management at the network layer somewhat conservative regulatory authorities, short- Handling mobility management at the network layer has comings in digital rights management, multiple several advantages since applications do not need to be standardization bodies proposing non-aligned solutions, aware of mobility. If the network layer handles all as well as non-uniformed and non-optimized use of radio mobility management, applications can, in theory, be spectrum do not improve the speed of change. used as if the user was running the application in a fixed environment since the user is reachable through a fixed Our research is performed within the area of seamless IP address. The network layer is extended with a suitable real-time multimedia distribution in heterogeneous mobility management module taking care of the delivery wireless access networks with a user-centric and end-to- of datagrams to the user’s current point of attachment to end system approach. Having proposed various the Internet. This mobility management solution works extensions to Mobile IP (MIP) including multihoming both for connection oriented flows (i.e. TCP connections) and port-based handling of flows, as well as solutions for and connection less flows (i.e. UDP traffic). global connectivity in ad hoc networks we now present a combined architecture using both MIP and Session The most well-known example of mobility management Initiation Protocol (SIP) for mobility management where at the network layer is Mobile IP (MIP) which is defined MIP is used for TCP connections and SIP is used for both for IPv4 [1] and IPv6 [2]. UDP traffic carrying real-time multimedia streams of data. MIP makes use of a mobility agent located in the home network, a home agent (HA), and, in MIP for IPv4, a 1. Introduction mobility agent in the visited network, a foreign agent The Internet Protocol (IP) has been extremely successful (FA). The HA is a specialised router responsible for in delivering a widespread protocol for host-to-host forwarding datagrams aimed for the end-user at the connectivity using the basic principle “keep the network mobile node (MN). The MN is assigned a home address simple”. However, merging the Internet with the (HoA) in the same subnet as the HA. The FA is ubiquitous cellular networks has proven to be a quite responsible for assigning a care of address (CoA) for the tough problem to solve. Mobility management is handled MN and forwarding datagrams for the MN. The MN can very well by the cellular networks at the layers below the also use a co-located address CoA. In that case, the MN network layer, but it has proven to be much harder to acquires an IP address using regular mechanisms like implement efficient mobility management solutions at the DHCP. The datagrams are transported from the network and higher layers. One of the basic challenges to originating host, correspondent node (CN), to the HA and deal with when introducing mobility management on then tunnelled through an IP tunnel using IP in IP higher layers is that network layer addresses not only are encapsulation to the MN. When the MN changes it used to identifying hosts but also to finding routes current point of attachment to the Internet it sends a between hosts on the Internet. binding update (BU) message to the HA indicating its new CoA. Datagrams in the direction from the MN to the Users of heterogeneous networks with multiple access CN are sent directly from the FA to the CN. Route networks included really need a mobility management optimization techniques exist in Mobile IP enabling the solution at higher layers in order to leverage all available CN to send datagrams directly to the FA and CN without One important cornerstone in the architecture is to travelling through the HA. perform measurements continuously on all available network interfaces at each time using MIP in a Unfortunately, MIP has some serious drawbacks delaying multihomed version [6] and a policy model [7]. The global-wide deployment, indeed some of which will be decision of what interfaces to monitor is based on user solved when IPv6 is introduced, but nevertheless making preferences. Figure 1 shows the used policy-based MIP not being optimal for roll-out on today’s Internet. decision model including a policy decision point (PDP) Drawbacks include the introduction of encapsulation and a policy enforcement point (PEP), extended with a overhead when tunnelling datagrams, the necessity of policy repository (PR). deploying mobility agents, and problems with sending datagrams directly from the visited network to the CN with source addresses not being topological correct. 2.2 Mobility management at the application layer The above mentioned problems when introducing mobility management at the network layer has led researchers to seek solutions for mobility management at Figure 1. Policy-based decision model higher layers. Descriptions of mobility management implemented at the transport layer and the introduction of The PR is responsible for delivery of requested policy a separate mobility layer above the transport layer exist in parameters to the PDP. The PR contains information such the literature[3]. However, the idea of handling mobility as user preferences, access network performance and cost management at the application layer using the session of available access networks. The PR can obtain initiation protocol[4] (SIP) as mobility management information through measurements of the environment. protocol seems to be the most popular idea in current The PDP is the control entity that evaluates access research. networks through policy decisions. The policy decisions are based on the parameters received from the PR. If the SIP is an end-to-end signalling protocol designed for PDP decides that a handover is motivated, the PDP initiating, maintaining, and terminating sessions on the informs the PEP to perform a handover. The PEP Internet, mainly targeted for multimedia applications, but receives policy decisions from the PDP and performs the suitable for any type of session-oriented application. In actual handover. The PEP is said to enforce the policy addition to the client side, SIP user agent (UA), it makes decision[8]. use of three types of servers: SIP proxy servers, SIP redirect servers, and SIP registrars. SIP messages are The access network performance of what interface to use carried both on top of TCP and UDP and are routed from is based on the policy value expressed in formulas (1-4) endpoint to endpoint through available servers. SIP has shown below. A detailed explanation of the formulas can inherited structures from both SMTP and HTTP making be found in [9]. To estimate a network’s capacity, the it easier to develop and deploy light-weight relative network load (RNL) is calculated in the MN. implementations when combined with email and web RNL represents a quality value for each network based client software. SIP has become the state-of-the-art protocol for signalling in both IP telephony and other on delay (or round trip time, RTT) and jitter values. zn is types of multimedia applications. SIP is also the core protocol of 3GPP IP Multimedia Subsystem (IMS)[5], the mean value of the RTT value ( rttn ) for MIP BU making its deployment to real applications even faster. It messages between the MN and its HA. x is the mean should also be mentioned that SIP is designed for n handling both pre-session mobility and mid-session value of times between arrivals of MIP BU messages at mobility. the MN, and Vn is the variance between these messages. h determines the size of the history window for the SIP has, however, some drawbacks due to its placement weighted average calculations. For example, when h = 5 in the layered protocol hierarchy. SIP can not, for the most recent value will contribute 20 per cent to the example, do anything to broken TCP connections due to calculated xn , zn and Vn values. changes of network layer addresses at handovers. Additionally, if SIP is to be used as a general mobility 1 h − 1 (1) management solution, already existing applications need zn rtt n += zn −1 h h to be rewritten completely in order to be mobility-aware.

View Full Text

Details

  • File Type
    pdf
  • Upload Time
    -
  • Content Languages
    English
  • Upload User
    Anonymous/Not logged-in
  • File Pages
    4 Page
  • File Size
    -

Download

Channel Download Status
Express Download Enable

Copyright

We respect the copyrights and intellectual property rights of all users. All uploaded documents are either original works of the uploader or authorized works of the rightful owners.

  • Not to be reproduced or distributed without explicit permission.
  • Not used for commercial purposes outside of approved use cases.
  • Not used to infringe on the rights of the original creators.
  • If you believe any content infringes your copyright, please contact us immediately.

Support

For help with questions, suggestions, or problems, please contact us