Disruption-tolerant sessions: a socket layer for mobility-aware applications on the internet

Author(s)

Bruno Yuji Lino Kimura

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Ciências Matemáticas e de Computação (ICMC/SB)
• Defense date: 2012-10-16

Examining board members

Edson dos Santos Moreira; Daniel Macedo Batista; Nelson Luis Saldanha da Fonseca; Hélio Crestana Guardia; Jo Ueyama

• Advisor: Edson dos Santos Moreira

Abstract

Nowadays services available on the Internet can be accessed from mobile devices while they roam across heterogeneous wireless networks. Due to the inherent reasons of device mobility, however, the access to such services is frequently involved with delay and disruptions. The most common reasons are: i) losing radio signal at places where mobile access coverage area is not available; ii) frame error, losses, and fading on the radio signal when the mobile device moves away from the Base Station; iii) changes on the devices IP address over ongoing transmission, while the mobile node migrates among different wireless networks. As result, networked application fails with disruptions on TCP connections established in the mobile users path. Handling seamlessly mobility on the Internet is a technical challenge of the Mobile Computing Paradigm. It has been widely researched over the last decade. Several solutions have been proposed to work from the Link Layer to the Application Layer. Most of them, however, work intrusively and require modifications in the classical TCP/IP protocol stack, as well as rely on additional network infrastructure to support mobile end-to-end communication. Besides increasing the cost of deployment and maintenance, intrusive and infrastructure dependent strategies may not present suitable performance. In this sense, we devised an architecture to handle mobility at the Application level by means of communication sessions that do not fail with delay, disruption or disconnection. Such sessions work only at the end-systems in a such way that: are fully transparent to the adjacent layers of Transport and Application; do not require additional network infrastructure to forward and manage the communication between two mobile peers; and do not impose any modification on the legacy protocols from the TCP/IP stack. The concept of Disruption-Tolerant Sessions is implemented in Linux by means of a general purpose API extended from the Socket interface. Such API is a transparent layer placed on top of the Socket to provide mobility awareness to the Application Layer. To do so, session services are provided for: tracking mobile peers along the session duration; detecting disruptions over TCP connection caused by mobility of the local or remote peer; suspending and resuming sessions with efficiency, security and reliability. Experiments conducted in emulated and real systems (off-the-shelf hardware and open source software) showed the desired efficiency. Besides introducing little overhead on the goodput, disruptions are detected in a range of microseconds and suspended sessions are resumed in milliseconds. With performance greater than the general IP layer mobility solution, the proposed sessions do not require software adaptation in the core of the network infrastructure (AU)

• FAPESP's process: 08/06777-9 - A Proposal of a User-Space Architecture for Full Mobility Management in Next Generation Networks (NGN).
• Grantee: Bruno Yuji Lino Kimura
• Support Opportunities: Scholarships in Brazil - Doctorate