Today, the average computer or smartphone has several wired and wireless interfaces and most networks can provide multiple paths between any source/destination pair. However, when Vint Cerf and Bob Kahn conceived the Internet Protocol TCP (Transmission Control Protocol) back in 1974, it was logical to only consider a protocol for a single network path – it was all that existed at this time.
Over the years, this had become a major limitation for the many new bandwidth-hungry applications running on interface-rich devices. For example, when a mobile host moves, it needs to restart all its established TCP connections – leading to slower connections in the best-case scenario and connection errors in the worst case.
Fortunately, three exciting FP7 projects – TRILOGY, TRILOGY 2 and CHANGE – have addressed this problem (among others) by inventing and applying Multipath TCP (MPTCP). This novel take on TCP was originally conceived and devised by the FP7 project TRILOGY. TRILOGY 2 and CHANGE then took the Multipath TCP protocol work forward to produce incredible throughput records for multipath communications.
Essentially, MPTCP allows data to be sent over several paths simultaneously. The sending device can adapt rapidly to network conditions by sending more of the traffic over the emptier paths and avoiding paths that are congested. This improves network resilience and efficiency over standard TCP. Even if one path fails, network efficiency is improved through the pooling of resources.
An important application area for Multipath TCP is in mobile devices, where it can enable access and use of WiFi and 3G/4G interfaces in parallel. In addition, Multipath TCP-equipped smartphones can move from one WiFi network to another without losing connectivity or having to restart their data-stream. In servers, Multipath TCP facilitates the combination of several high-speed links to increase performance and delivery to individual users.
Partners in the CHANGE and TRILOGY 2 projects have demonstrated throughput rates of 52 gigabits per second (Gbps) across a single TCP connection using six parallel 10 Gbps links – a new record for data transfer over a TCP connection. This is the equivalent of sending more than an entire DVD’s worth of data every second.
This impressive demonstration of just what the protocol is capable of was carried out in Belgium using the Université Catholique de Louvain’s implementation of Multipath TCP.
Meanwhile, Apple has included Multipath TCP, as designed by TRILOGY, TRILOGY 2, and CHANGE, in the IOS 7 operating system. It is currently only implemented for SIRI connections with Apple servers, but this is probably the first consumer product to be shipped to end-users with the technology built in.
As we evolve towards the era of cloud services and users seek more guarantees for reliable access and efficient throughput we can expect more and more implementation of the technology. As Multipath TCP is fully backwards compatible with existing TCP implementations and network equipment, this will be straightforward.
TRILOGY, TRILOGY 2, and CHANGE have addressed a clear need in the evolution of the internet. By getting their solution ratified by the Internet Engineering Task Force, the projects have ensured that their innovative solutions for greater throughput and efficiency will improve the quality of experience for users of internet services for many years to come. Another success story for FP7!