Bandwidth meter¶

This page is about a general overview of the Bandwith Meter tool in B.A.T.M.A.N.-Advanced.
This project was started by Edo Monticelli during the 2012 Google Summer Of Code and it is possible to read the final report here.
Since then, the project evolved a lot and the protocol used by it moved from a naïve Go-Back-N to the more sophisticated TCP NewReno.
More technical details are discussed on the technical page.

The main goal of the Bandwidth Meter is to measure the maximum reachable throughput in a TCP-like connection between two generic nodes in the network.

The bandwidth meter protocol¶

The goal of the protocol is to approximate the behavior of TCP in order to measure a bandwidth close to what a common TCP connection would achieve.
The bandwidth meter protocol is the implementation of TCP using NewReno as congestion handling mechanism.

Since the implementations of the bandwidth meter tries to reflect the TCP one, more details can directly be found in the following documents:

• RFC 5681 (TCP)
• RFC 6582 (NewReno extension)
• RFC 6298 (Retransmission Timeout computation)

During the test batman-adv sends ICMP packets only. For this purpose a new ICMP packet type has been created: the BW.
Received BW packets are directly passed to the bandwitdh meter submodule which is in charge of handling the test. It has two subtypes:

• MSG
• ACK

Since the test is performed unidirectionally, ACKs are not piggybacked on normal messages (like TCP does) and therefore two different packet types are used.
A node can participate in different tests at the same time, but with different end-points. This means that two or more tests cannot be performed at the same time between the same pair of nodes.

How to run a test¶

The bandwidth meter is controlled by using batctl. For this purpose a the new bw command has been added.
It is possible to start a test by issuing the following command:

# batctl bw -t 10000 <originator address>

where -t 10000 is an option telling batman-adv how much milliseconds the test should last.
While the test is running it is also possible to interrupt it by pressing CTRL+C: batctl will send a message to batman-adv and tell it to terminate the test. batctl will then print the throughput obtained so far.

Between two consecutive experiments at least two seconds must be waited, to ensure the connection on the receiver side has been properly closed.

Source code¶

batman-adv featuring the Bandwidth meter can be found at the main batman-adv git repository in the ordex/bw_meter branch