Connection Rerouting Strategies for Mobile Networks Bruce A. Mah - PowerPoint PPT Presentation

Connection Rerouting Strategies for Mobile Networks Bruce A. Mah bmah@CS.Berkeley.EDU The Tenet Group University of California at Berkeley and International Computer Science Institute T Y • O I F S • R C E A V A L I I F N O U • R L L E E I G H T T N H T H I E E T R E B A • • • • 1 8 6 8 Hitachi-Tenet Meeting 6 July 1993 Connection Rerouting Strategies for Mobile Networks Page 1 of 22

Synopsis Motivation The Problem Connection Rerouting Strategies Conclusions Future Work The Infopad Connection Rerouting Strategies for Mobile Networks Page 2 of 22

Motivation Mobile Computing Devices ⇒ Mobile Networks Multimedia Applications ⇒ Real-Time Network Services Tenet Real-Time Scheme/Protocol Suite Connection Rerouting Strategies for Mobile Networks Page 3 of 22

Mobile Networks Server Switch Room-sized Microcell Base Station Mobile Host Mobile Hosts with wireless network interfaces Base Stations: Gateways between wireless and wired networks Backbone network: Conventional wired network or internetwork Connection Rerouting Strategies for Mobile Networks Page 4 of 22

The Tenet Real-Time Scheme Multimedia applications need hard real-time guarantees on network parameters, for example... Delay Delay jitter Bandwidth Buffer allocation Guarantee performance using... Admission control Network resource allocation Work on level of individual network conversations Requires a connection-oriented network layer Connection Rerouting Strategies for Mobile Networks Page 5 of 22

The Tenet Real-Time Protocol Suite Performance-Guaranteed Network Communication Application CMTP RMTP RCAP RTIP Device Drivers Continuous Media Transport Protocol (CMTP) Real-Time Message Transport Protocol (RMTP) Real-Time Internet Protocol (RTIP) Real-Time Channel Administration Protocol (RCAP) Connection Rerouting Strategies for Mobile Networks Page 6 of 22

The Tenet Real-Time Protocol Suite Tenet Suite I Performance-guaranteed, unreliable, connection-oriented, unicast real-time channels Tenet Suite II: The Sequel Performance-guaranteed, unreliable, connection-oriented, multicast real-time channels Connection Rerouting Strategies for Mobile Networks Page 7 of 22

The Problem How to re-route network connections when a host moves between cells? Connection Rerouting Strategies for Mobile Networks Page 8 of 22

More of the Problem What to do Determine crossover point Forward data (optionally) Reroute connection Information on impending handoffs Use as hints...don’t always have them Radio networks may have “dead spots” Infrared networks may have line-of-sight problems Connection Rerouting Strategies for Mobile Networks Page 9 of 22

Full Re-Establishment Establish new connection for every existing network connection. Problem: Long paths mean long handoff latencies. Connection Rerouting Strategies for Mobile Networks Page 10 of 22

Incremental Re-Establishment Only create the disjoint part of the connection to the new base station. Key: Find the crossover point! Connection Rerouting Strategies for Mobile Networks Page 11 of 22

Multicast-Based Re-Establishment Use multicast facilities of the network to support handoff Use lots of network bandwidth to reduce handoff latency Easy to build Connection Rerouting Strategies for Mobile Networks Page 12 of 22

Preliminary Analysis Compute values of metrics... Service disruption time (mobile host cannot receive downlink data) Buffer usage Excess bandwidth utilization in the network For different connection types... Distance to crossover point Distance between (physically) adjacent base stations For a given technology point... Latency, bandwidth of wireless and wired links Protocol processing time Control and data packet sizes Acquisition time during host migration Speed of cell transition Connection Rerouting Strategies for Mobile Networks Page 13 of 22

Results of Preliminary Analysis Service disruption time and downlink buffering in the base station vary linearly with forwarding path length (except for Multicast-Based re- establishment with hints). Uplink buffering on the mobile hosts is identical for all algorithms. Using hints trades excess allocation of resources in channels against needing to forward data. Multicast-Based re-establishment uses fewer network resources than Incremental Re-Establishment or Full Re-Establishment. For long base station-to-crossover point paths, all algorithms are about the same. Total path length only affects Full Re-Establishment. Connection Rerouting Strategies for Mobile Networks Page 14 of 22

Conclusions Hints are good We should investigate other multicast-based schemes, they look promising Considerations of network topology are important (want crossover point as close to the handoff site as possible) Connection Rerouting Strategies for Mobile Networks Page 15 of 22

Future Work Simulation using Ptolemy Capture dynamics of the network Attempt to measure network capacity Verification of handoff protocols Hint-based protocols Unreliable message delivery Implementation Infopad Implications of mobility on semantics of real-time guarantees? Connection Rerouting Strategies for Mobile Networks Page 16 of 22

The Infopad A Portable Multimedia Terminal University of California at Berkeley Faculty Bob Brodersen (electronics) Dave Messerschmitt (display server, video coding) Domenico Ferrari (backbone network and network protocols) Randy Katz (storage servers) Jean-Paul Linnartz (radio links) Connection Rerouting Strategies for Mobile Networks Page 17 of 22

Key Features of the Infopad Portable Terminals Lightweight: Size dictated by display Low power: battery operated Multimedia I/O Speech (input/output) Full Motion Video (output) Graphics/Text (output) Pen (input) Micro-Cellular Network 1-3 GHz band Cell size of ~30 feet in diameter Low power transmission(1-10 mW) “High” bit rate (1-2 MBps) Connection Rerouting Strategies for Mobile Networks Page 18 of 22

Applications Video on demand: Movies, news, programming Print media databases: Books, newspapers Supercomputer simulation and display Driver information and safety systems Videophone Home and office information services Remote sensing and actuation Emergency services Connection Rerouting Strategies for Mobile Networks Page 19 of 22

The Infopad Environment Fiber Optic Backbone 100 Mbps - 1 Gbps VIDEO DATABASE WIRELESS SPEECH COMPUTE BASE STATION RECOGNITION SERVERS Compressed Video LARGE COMMERCIAL DATABASE Airline schedule, Newspaper, ... PERSONAL COMMUNICATORS - Personal numbers - World wide coverage INFOPAD (A Portable Multimedia Terminal) - Video - Speech - X-terminal Connection Rerouting Strategies for Mobile Networks Page 20 of 22

What’s Special About Infopad? Power consumption is key No processor on Infopad: Too much power Connection endpoints may be on base stations Applications run on compute servers in the backbone network Process migration of display server during handoff?!? X as a display server Is this a Good Thing™? Asymmetric uplink/downlink channels Connection Rerouting Strategies for Mobile Networks Page 21 of 22

Plans for the Infopad Implement real-time protocols on Infopad backbone network Implement mobility on Infopad when prototype hardware is available Experiment on a virtual mobile network first? Connection Rerouting Strategies for Mobile Networks Page 22 of 22