Performance of DNS as Location Manager for Wireless Systems in IP Networks Abu Ahmed Sayeem Reaz, Mohammed Atiquzzaman, Shaojian Fu Telecommunications and Networks Research Lab School of Computer Science, University of Oklahoma, Norman, OK 73019-6151, USA. Email: {sayeem reaz, atiq, sfu}@ou.edu Keywords: Location Management, DNS, Mobility Manage- ment, IP Diversity Abstract— Domain Name System (DNS) can be deployed in the network as a Location Manager (LM) for mobility management. The suitability of Domain Name System (DNS) as an LM can be measured by how successfully it can serve to locate a mobile host. In this paper, we developed an analytical model to measure the performance of DNS as LM for mobility management techniques with IP Diversity support based on success rate which takes into account the radius of the subnet, the residence time of MH in that subnet, latency in the network and the overlapping distance of two neighboring subnets. Our analysis shows that for a reasonable overlapping distance, DNS can serve as an LM with very high success rate even under some high network latency. I. I NTRODUCTION Increasing demand for mobility in wireless data networks has given rise to various mobility management schemes. Mobility management consists of two fundamental operations: Handoff and Location Management. Handoff occurs when a mobile device changes its point of attachment while still continuing with the service that it has been providing. In a layered network architecture for data communications, handoff can be managed at different layers. For example, Mobile IP (MIP) [1] is a network layer based handoff management scheme from IETF, MSOCKS [2] is a transport layer solution, and IEEE 802.11b follows a Layer 2 solution for handoff. Location management refers to finding valid the IP address a Mobile Host (MH) by a Correspondent Node (CN) in order to initiate and establish a connection. There are two common choices for implementing a Location Manager (LM): Dedicated Location Manager, which is a separate network entity that serves as LM; and Domain Name System (DNS)[3], which provides name to IP mapping for locating a host in the Internet and supports dynamic secure updates [4]. DNS is a preferable option over dedicated LM because almost all connection establishments start with a name lookup from DNS [5] and it is already a part of the existing Internet infrastructure and unlike a dedicated LM, can be deployed without change in infrastructure. The research reported in this paper was funded by NASA Grant NAG3- 2922. We investigate the suitability and performance of using DNS as an LM for mobility management as illustrated in Fig. 1 for a transport layer based mobility management scheme based on IP diversity. Having more than one interface cards is becoming Subnet2 Subnet1 CN MH IP 1 DNS Overlapping Area Internet IP 2 Fig. 1. DNS as a Location Manager. common for mobile devices. During the handoff process, the MH has two IP addresses one for each of the neighboring subnets and communicates with both the APs at the same time with its multiple interface cards. This support for multiple IP address is called IP diversity, and our location management technique will be illustrated using a IP diversity enable mo- bility management scheme called Seamless IP diversity based Generalized Mobility Architecture (SIGMA) [6]. Each time a SIGMA enabled MH hands off to a new subnet, MH obtains a new IP address and it updates DNS with its new IP address (details in Sec. II-B). Role of DNS as LM is to serve the correct IP address for MH and failure to do so results in a query failure. This type of failure can occur when a CN obtains an address from the LM, but the MH hands off to a new point of attachment before the connection request from the CN arrives at the MH due to delay in the network. Thus, the success rate of an LM is determined by the fraction of queries that result in a successful connection to the MH. One of the earliest suggestions on using directory server for location management can be found in [7]. Two proposals ([8], [9]) discuss the use of DNS as location manager. However, the This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE GLOBECOM 2005 proceedings. 0-7803-9415-1/05/$20.00 (C) 2005 IEEE