QoS-oriented MPTCP Extensions for Multimedia Multi-homed Systems

The increasing number of interfaces using different access technologies in modern devices gives opportunities for enhancing the Quality of Service (QoS) delivered to multimedia and interactive data transfers involved in distributed applications. In the current Internet, the presence of "middleboxes" such as Network Address Translators (NAT) or firewalls hardly lets applications use any Transport protocol but the well-known Transmission Control Protocol (TCP). Currently under standardization at the IETF, the new Multipath-TCP (MPTCP) protocol uses several TCP flows to make use of the multiple interfaces available on the end terminals, thus improving both network availability and QoS, still being capable to cross over middle boxes. Although originally being fully reliable and fully ordered, its two sub-layers architecture gives opportunity to use QoS techniques over fully reliable paths. This paper studies the QoS benefits induced by the implementation of the "partial reliability" concept in MPTCP for interactive video applications. Two different mechanisms are experimented with the aim to enhance global quality of video transmission over paths close to 3G networks characteristics. The Internet Engineering Task Force (IETF) MPTCP working group\´s ns-2 implementation is used for the experimentations. The Evalvid toolkit over ns-2 is used to measure the QoS benefits expressed in terms of Peak Signal to Noise Ratio (PSNR).