Branches Explained¶
The batman project that started with a basic protocol and a single userspace routing daemon, attracted quite some attention over the years which led to many new ideas and concepts meant to improve the project. These ideas often resulted in proof-of-concept "branches" of which some turned out to be impractical and disappeared but others came to stay. As a consequence different names were created to distinguish these concepts as the name "batman" became a broader term for everything around the project. This page aims to shed some light on all these different names to make it easier to understand the differences.
numbers, numbers¶
Whenever Roman numerals (as III or IV) are mentioned they refer to the version of B.A.T.M.A.N.'s routing algorithm and thus describe how the routing information are flooded and how they are handled to make the best routing decision possible.
Arabic numerals are used to distinguish the implementation's version. Next to the routing algorithm many features and goodies are added to simplify the users life.
Example: batmand 0.2 uses the B.A.T.M.A.N. III routing algorithm.
batmand¶
Historically, the first implementation of the B.A.T.M.A.N. routing protocol was a user space daemon named batmand. Batmand operates on layer 3 (IP layer) of the OSI model by altering the routing table and offers everything you would expect from a standard routing daemon. Almost all real-world implementations of mesh routing algorithms have started on layer 3 - and most of them still work exclusively on layer 3 today. Check our batmand doc section if you want to learn more about is capabilities.
Note: batmand has not been developed further for a couple of years, but is still actively used by a few projects. Therefore, sources and documentation are still available. Most of the active development today is performed on batman-adv.
BMX¶
Initially, the BMX branch was used to implement and test new features and concepts to overcome certain limitations of the routing algorithm. It started on the code base of batmand 0.3 but, over time, developed into a completely different direction, so that a re-integration became impossible.
Today, it is an independent project hosted at http://www.bmx6.net.
batman-adv¶
Early 2007 some developers started experimenting with the idea of routing on layer 2 (Ethernet layer) instead of layer 3. As only little knowledge about routing on this low level was available at that time, a first prototype was developed, operating in userspace in form of a daemon but already using layer 2. To differentiate from the layer 3 routing daemon the suffix "adv" (spoken: advanced) was chosen - the batman-adv userspace daemon was born. It uses the routing algorithm of batman 0.3, but instead of sending UDP packets and manipulating routing tables, it provides a virtual network interface and transparently transports packets on its own.
However, the virtual interface in userspace imposed a significant overhead for low-end wireless access points which led to a re-implementation as a kernel module. The batman-adv userspace daemon has been removed, so today "batman-adv" refers to the kernel module only. Currently, most of the development happens around batman-adv which is part of the official Linux kernel since 2.6.38.
To understand the implications of routing on layer 2, the batman-adv page should be a good starting point Further documentation is available in our batman-adv doc section.
batctl¶
As batman-adv operates in kernelland a handy tool to manage the module and debug the network became necessary. The batctl tool was created to fill that gap and, since then, has become a valuable companion of batman-adv.
alfred¶
alfred is a user space daemon for distributing arbitrary local information over the mesh/network in a decentralized fashion. This data can be anything which appears to be useful - originally designed to replace the batman-adv visualization (vis), you may distribute hostnames, phone books, administration information, DNS information, the local weather forecast ...
Alfred does not strictly require batman-adv to operate, but can use neighborhood information from batman-adv when available. It is a nice additional service if there are additional information to be distributed over a mesh, but alfred is not required to run a batman-adv mesh network.