Haggle - A European Union funded project in Situated and Autonomic Communications

Publication List | SLEF | Network Coding | Partners | People

Haggle leverages human communities for forwarding data
Haggle is a new autonomic networking architecture designed to enable communication when network connectivity is intermittent. In particular, Haggle exploits opportunistic contacts between mobile users to deliver data to the destination.

We depart from the existing TCP/IP protocol suite, completely eliminating layering above the data-link. Instead, we only use functions that are absolutely necessary, but also sufficient to support a large range of current and future applications. The focus is on applications that are more oriented to the human way of communicating (and, more generally, the way communities of any type of entities communicate).

Self-Limiting Epidemic Forwarding (SLEF)

SLEF adjusts the spread and the rate to the network conditions
We define the self-limiting epidemic service as a broadcast dissemination service for short messages in ad-hoc environments, that is limited to a local scope around each source. A typical application is chatting or a bulletin board among users in a traffic jam, in a railway hall, on a campus, or, in contrast, along a desert highway. In all these cases, broadcast functionality is needed; if there were no limits in network bandwidth, node storage capacity, or node processing power, then a flooding mechanism would be sufficient. However, it may not be desirable, neither from the user's nor from the network's viewpoint, to reach all users that can be reached by epidemic forwarding (in rush hour this may be users spanning hundreds of kilometers along highways).

We design and evaluate a self-limiting service that adapts to a wide range of conditions (mobility, traffic, dense or sparse user population). The scope limit should adapt to node density and number of active users. In a dense environment with 100% active users (users chatting in traffic jam, crowd on campus), the information generated by one user should remain in close vicinity, reaching approximately 100 nodes for instance. In a similar environment but with only a small fraction of active users (i.e. few users generating fresh information, but many relaying), the spread could be much larger in kilometers. Note that, in these dense cases, the problem is congestion and information overflow rather than lack of connectivity. On the other hand, in a sparse environment (desert highway, or area with very small penetration of the system) the service should have a much wider spread. Last, transitions from a dense to a sparse environment may occur without user control, so we want the service to smoothly adapt to such changes.

Our system design introduces the following main novel characteristics:
  1. manipulation of TTL by aging mechanisms,
  2. control of forwarding factor by self-inhibition and inter-inhibition, and
  3. control of rate of injection by sources.
All these mechanisms adapt to network conditions as discussed above.

SLEF publications

Back to top

Network Coding for Opportunistic Networks

Network Coding for Opportunistic Networks
Network Coding is a new approach to forwarding: a node does not simply forward received packets following routing paths, but combines received packets from different nodes into a linear combination with random coefficients and broadcasts it to its neighbors. When a node receives these different linear combinations, it solves the corresponding system of linear equations to find the packets that have been mixed. This approach is known to have better resilience to changes due to intermittent connectivity and node mobility, and to achieve higher throughput than classical approaches. We exploit it here in the context of opportunistic networks.

Network Coding publications


Back to top


Back to top




Back to top