What are the benefits and drawbacks of using BABEL in a hybrid wireless network?

1 What is BABEL?

BABEL is a loop-avoiding distance-vector routing protocol, developed to be robust, efficient, and adaptable to changing network conditions. To achieve these goals, it employs incremental updates, which only sends routing information when there is a change in the network topology or the link quality, instead of periodically flooding the network with full routing tables. This reduces bandwidth consumption and convergence time. Hysteresis is also applied to avoid flapping routes by preventing a node from switching to a slightly better route unless it is significantly better than the current one. Additionally, BABEL supports multiple routes to the same destination and can use different metrics to select the best route depending on the link type, such as hop count for wired links, ETX for wireless links, or latency for satellite links. This allows BABEL to exploit the diversity of the network and improve its performance and resilience.

2 How does BABEL work?

BABEL operates in two phases: route discovery and route maintenance. In the route discovery phase, BABEL nodes exchange hello messages with their neighbors to establish bidirectional links and measure their quality. Then, they send update messages to advertise their routes to other nodes. An update message contains a sequence number, a metric, and a prefix that identifies the destination network. The sequence number is used to detect and avoid routing loops, while the metric is used to compare the quality of different routes. The prefix can be either a host address or a network address, depending on the level of aggregation that BABEL supports.

In the route maintenance phase, BABEL nodes keep sending hello messages to monitor their links and update messages to refresh their routes. If a link fails or a route becomes invalid, BABEL nodes send a request message to ask for a new route to the destination. If a node receives a request message, it either replies with an update message containing a valid route, or forwards the request message to other nodes. BABEL also uses a mechanism called feasibility condition to prevent nodes from accepting worse routes than their current ones, which helps to avoid routing loops and suboptimal paths.

3 What are the benefits of using BABEL?

BABEL is an advantageous routing protocol for hybrid wireless networks, as it can handle heterogeneous link types and metrics, provide multiple routes to the same destination, reduce the routing overhead and convergence time, avoid routing loops and suboptimal paths, and support network aggregation. It does this by adapting to different network scenarios and requirements, switching between routes dynamically according to the link quality and traffic load, sending incremental updates and applying hysteresis, using sequence numbers and feasibility condition, and using prefixes instead of host addresses.

4 What are the drawbacks of using BABEL?

BABEL has some limitations and challenges that need to be taken into account when used in hybrid wireless networks. Instability and oscillations can occur in networks with high mobility or frequent link failures, as the hysteresis mechanism and the delay of update messages can be a factor. Additionally, BABEL may consume more energy and memory than other routing protocols, particularly in large and dense networks. Moreover, it may find it difficult to find optimal routes in networks with asymmetric links or interference due to the use of bidirectional links and ETX metric. Lastly, there may be compatibility issues with other routing protocols or network architectures due to the lack of standardization and interoperability of BABEL.