Migrating operating system instances across distinct physical hosts is a useful tool for administrators of data centers and clusters: It allows a clean separation between hard-ware and software, and facilitates fault management, load balancing, and low-level system maintenance.By carrying out the majority of migration while OSes continue to run, we achieve impressive performance with minimal service downtimes; we demonstrate the migration of entire OS instances on a commodity cluster, recording service downtimes as low as 60ms. We show that that our performance is sufficient to make live migration a practical tool even for servers running interactive loads.In this paper we consider the design options for migrating OSes running services with liveness constraints, focusing on data center and cluster environments. We introduce and analyze the concept of writable working set, and present the design, implementation and evaluation of high-performance OS migration built on top of the Xen VMM.

/pdf/live-migration-of-virtual-machines-o3cs0reg9z.pdf

Live migration of virtual machines

This paper describes current and proposed protocols for mobility management for public land mobile network (PLMN)-based networks, mobile Internet protocol (IP) wireless asynchronous transfer mode (ATM) and satellite networks. The integration of these networks will be discussed in the context of the next evolutionary step of wireless communication networks. First, a review is provided of location management algorithms for personal communication systems (PCS) implemented over a PLMN network. The latest protocol changes for location registration and handoff are investigated for mobile IP followed by a discussion of proposed protocols for wireless ATM and satellite networks. Finally, an outline of open problems to be addressed by the next generation of wireless network service is discussed.

http://www.cs.tcd.ie/~htewari/papers/ieee99.pdf

Mobility management in next-generation wireless systems

An overview of vertical handover decision strategies in heterogeneous wireless networks

Today, many people carry numerous portable devices, such as laptops,mobile phones, PDAs and mp3 players, for use in their professional andprivate lives. For the most part, these devices are used separatelyNthatis, their applications do not interact. Imagine, however, if they could inter-act directly: participants at a meeting could share documents or presenta-tions; business cards would automatically find their way into the addressregister on a laptop and the number register on a mobile phone; as com-muters exit a train, their laptops could remain online; likewise, incoming e-mail could now be diverted to their PDAs; finally, as they enter the office,all communication could automatically be routed through the wirelesscorporate campus network.These examples of spontaneous, ad hoc wireless communicationbetween devices might be loosely defined as a scheme, often referred toas ad hoc networking, which allows devices to establish communication,anytime and anywhere without the aid of a central infrastructure. Actually,ad hoc networking as such is not new, but the setting, usage and playersare. In the past, the notion of ad hoc networks was often associated withcommunication on combat fields and at the site of a disaster area; now,as novel technologies such as Bluetooth materialize, the scenario of adhoc networking is likely to change, as is its importance.In this article, the authors describe the concept of ad hoc networkingby giving its background and presenting some of the technical challengesit poses. The authors also point out some of the applications that can beenvisioned for ad hoc networking

/pdf/wireless-ad-hoc-networking-the-art-of-networking-without-a-5ca07b2y2r.pdf

Wireless ad hoc networking—The art of networking without a network

So far virtual machine (VM) migration has focused on transferring the run-time memory state of the VMs in local area networks (LAN). However, for wide-area network (WAN) migration it is crucial to not just transfer the VMs image but also transfer its local persistent state (its file system) and its on-going network connections. In this paper we address both: by combining a block-level solution with pre-copying and write throttling we show that we can transfer an entire running web server, including its local persistent state, with minimal disruption --- three seconds in the LAN and 68 seconds in the WAN); by combining dynDNS with tunneling, existing connections can continue transparently while new ones are redirected to the new network location. Thus we show experimentally that by combining well-known techniques in a novel manner we can provide system support for migrating virtual execution environments in the wide area.

Live wide-area migration of virtual machines including local persistent state

Mobile IP has been designed within the Internet Engineering Task Force (IETF) to serve the needs of the burgeoning population of mobile computer users who wish to connect to the Internet and maintain communications as they move from place to place. The basic protocol is described, with details given on the three major component protocols: agent advertisement, registration, and tunneling. Then route optimization procedures are outlined, and further topics of current interest are described. The available tunneling mechanisms are shown, which the home agent uses to forward datagrams from the home network to the mobile computer. Having covered the details of the base mobile IP specification, we then describe further protocol messages which help to decrease the inefficiency associated with inserting the home agent in the routing path of data destined for mobile computers. Finally, we summarize and discuss the current problems facing mobile IP, as well as a few areas of active protocol development.

C.E. Perkins

Papers

Mobile IP