Portus

Portus is an implementation of a congestion control plane (CCP). It is a library that can be used to write new congestion control algorithms in user-space.

Congestion control algorithm implementations live in independent crates which use this library for common functionality. Each algorithm crate provides a binary which runs a CCP with that algorithm activated.

Setup

1. Install rust, and use the nightly toolchain. See http://rust-lang.org/ for details.
2. make. This will build and lint the portus library and bundled algorithm libraries and binaries, and run unit tests.

Notes

• The ipc::netlink and ipc::kp modules will only compile on Linux. If the CCP kernel module (github.mit.edu/nebula/ccp-kernel) is loaded, the test will refuse to run.

Run

Once you've built portus, algorithms can be run as follows:

sudo ./ccp_generic_cong_avoid/target/debug/reno

All algorithms support the --ipc flag, allowing you to specify the method of inter-process communication between the CCP and your datapath of choice. For example, our current implementation of the linux kernel datapath uses netlink sockets, while our implementation of the mtcp/dpdk datapath uses unix sockets.

Individual algorithms may also allow you to set algorithm-specific parameters from the command line. Run with --help to view them.

Writing a new congestion control algorithm

Congestion control algorithms should implement the CongAlg trait, specifying:

Config

Algorithms specify Config, a configuration struct, to define parameters to pass to new instantiations. This allows algorithms to customize their parameters.

create(Datapath, Config, DatapathInfo)

create() is called to initialize state for a new flow. portus will pass in Datapath, a handle to send messages to the datapath (i.e., to set the congestion window via a send pattern), Config, an instance of the custom configuration struct created by the CCP binary and passed into portus::start(), and DatapathInfo, which contains the flow's 5-tuple and the MSS the datapath will use.

Note that almost all algorithm implementations will install a fold function in the create() handler; otherwise, no further measurements will be reported.

measure(Measurement)

measure() is called when the CCP gets a message as specified by the installed send pattern and/or fold function. The Measurement contains fields specified in the fold function; these can be accessed with .get_field(field_name, scope). An example follows.

let scope = Datapath.install_measurement("(def (Report.foo 0))");
...
let zero = Measurement.get_field("Report.foo", scope);

close()

Algorithms may optionally specify a handler when about to be deallocated.