Details
Minor Description
It should be possible to specify the desired Differentiated Services class, as outlined in RFC 2475 (http://tools.ietf.org/html/rfc2475), or Type of Service value, on outgoing TCP/IP packets by specifying a diffServ or typeOfService Tcp Transport Option (http://activemq.apache.org/tcp-transport-reference.html).
e.g. tcp://somehost:61616?trace=false&soTimeout=60000&diffServ=AF21
e.g. tcp://somehost:61616?trace=false&soTimeout=60000&typeOfService=3
I am part of a student group (http://maljub01.svnrepository.com/comp190/trac.cgi/wiki) at Tufts University that is implementing this functionality in ActiveMQ for potential use by MIT Lincoln Labs as part of the NextGen Network Enabled Weather Program (https://wiki.ucar.edu/display/NNEWD/The+NNEW+Wiki)..
We would like to contribute our changes back to the ActiveMQ trunk, if possible. Attached is a initial patch against the 5.3.0 release version, which implements setting the Differentiated Services class via a Tcp Transport Option on the connection URI.
Some notes about this approach:
The basic underlying mechanism for actually setting the bits in the packet headers is the java.net.Socket.setTrafficClass method. This was
the most elegant implementation out of all the possible implementations that we came up with.
In order for setTrafficClass to work in JDK 6, it is necessary to set the System property java.net.preferIPv4Stack to be true. We found that this has precedent in ActiveMQ (http://activemq.apache.org/multicast-watch-out-for-ipv6-vs-ipv4-support-on-your-operating-system-or-distribution-or-network.html), but we are hoping that this issue will be resolved in JDK 7, so that we can use the IPv6 stack when possible.
In addition, the current implementation only sets the specified Differentiated Services bits on the outgoing packets, and has no control over the Acknowledgments sent back for those packets. We have yet to find an elegant and cross-platform way to have the ActiveMQ Broker find out what the Differentiated Services bits on the incoming packets are directly in Java, although we are considering approaches that would involve calling a shell script from TcpTransportServer that would utilize IPtables.
We would like to know if might be interested in accepting this work into the ActiveMQ trunk. The sooner you let us know one way or another, the better, as this is a single-semester project.