Mobility Management

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3rd International Conference: Sciences of Electronic, Technologies of Information and Telecommunications March 27-31, 2005 – TUNISIA

SETIT 2005

Mobility Issues in Hierarchical Mobile IP
Aisha H. A. Hashim, Farhat Anwar, Shaffiah Mohd and Hatina Liyakthalikh Department of Electrical and Computer Engineering Faculty of Engineering International Islamic University Malaysia aisha@iiu.edu.my farhat@iiu.edu.my shaffiah@yahoo.com hatina_banun@yahoo.com Abstract: Mobile IP is a powerful protocol that supports Internet mobility. Micro-mobility approach was introduced because Mobile IP suffers in case of frequent movement, i.e. intra-domain mobility. Micro-mobility protocols aim to handle local movement of Mobile Nodes (MNs) without interaction with the Home Agent (HA) through the Internet. This has the benefit of reducing delay and packet loss during handoff and eliminating registration between MN and possibly distant Home Agents (HA) when MN remain inside their local coverage areas. The Hierarchical Mobile IP (HMIP) protocol handles Mobile IP registration locally using a hierarchy of foreign agents. In HMIP, registration messages are sent by the MNs to update their respective location information. This registration messages will establish tunnels between neighboring foreign agents along the path from the mobile node to a gateway foreign agent (GFA). This will form a network of tunnels where packets addressed to the MN will travel. The aim of this research is to study and evaluate HMIP protocol. The paper presents mobility issues in HMIP. The performance analysis of the protocol is carried out using NS-2 simulator. Some recommendation was suggested to improve mobile communication in HMIP. Key words: Hierarchical, Mobile IP, Micro-mobility, Performance Analysis.

1 Introduction
Mobile IP is an Internet standards protocol, which enhances the existing Internet Protocol (IP) to accommodate mobility. Over the Internet, when a Mobile Node (MN) moves and attaches itself to another domain, it needs a new IP address. With this all the existing connections with the home network will be terminated. Mobile IP was introduced to overcome this problem. But later on, Mobile IP itself experiences its own other discrepancies. This is when micro-mobility protocols were proposed and implemented. One of the protocols is HMIP. For HMIP protocol a hierarchy of foreign agent is employed to locally manage registration. Hierarchical schemes reduce handoff latency by employing a hierarchical network structure in minimizing the location update signalling with external network. The hierarchical structure separates mobility into micromobility (within one domain) and macro-mobility (between domains).

1.1 Mobile IP When a MN that is not in its home network received packets, the packets will be routed through its Home Agent (HA). Conversely, the packets from the MN to the Correspondent Nodes (CN) will be routed directly without the need of the its HA. This process is called triangle routing. Figure 1 illustrates triangular routing. Nonetheless, Mobile IP encounters some problems. For instance, in triangular routing, if the CN and the MN are in the same domain but not in the home network of the MN, they will experience unnecessary delay as they have to be first routed to the HA that resides in the home network. One way to improve this is Route Optimization. Route Optimization (Debalina 2002) is an extension proposed to the basic Mobile IP protocol. In this case, packets from the CN are routed directly to the MN's CoA without having to go through the HA.

SETIT2005 network sitting on top of IP. Tunnels connect the gateway foreign agent to other foreign agents at the network access points (Chew 2002).

Figure 1. Triangular Routing Due to frequent change of MN’s point-ofattachment, a few disadvantages occurred. The disadvantages are delay in handoff, packet loss and signaling load. Therefore HMIP protocol is proposed. 1.2 Hierarchical Mobile IP A...
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