Flow Control

Description

This piece of software is intended to allow profile scheduling of network flows. With this approach of bandwidth sharing, flows' rate are limited in a time-dependant manner according to a profile generated by a scheduler. Scheduler and FLOC are jointly able to provide flow and performance isolation.
To achieve this goal, FLOC allows specification of rate limitation that can vary with time. They can be applied on a per-token basis, UID based, PID based. When a new application is launched, it gets registred to FLOC daemon and registers every new sockets. This can be done either by explicit call to FLOC functions or by using LD_PRELOAD to hijack connect() function.
When a socket matches criteria of one limitation, socket gets tagged and the limitation's filter (tc filter ...) will queue packets in the proper rate limited queue.
Next section describes the three interfaces of FLOC: Control, Application and Kernel.

Example of flow schedule

Example of flow profile

Interfaces

Control: This interface provides control over reservations. It permits creation of new reservations with associated time-dependant rate profile. Reservations are identified by a tokens.

C1 := connect localhost
[1204108510] L0 := {C1} limit 197.84401 token 0x000001185A7504AC
[1204108514] modify limit L0 197.84401
[1204108528] modify limit L0 50.317043
[1204108572] modify limit L0 164.279423
[1204108578] modify limit L0 0
[1204108601] modify limit L0 197.84401
[1204108610] del limit L0

Application: Applications have to register their sockets in order to benefit of FLOC rate control. They associate a token to one or several sockets that will share the rate profile of it. This can be achieved by hijacking libc's connect() function or by calling FLOC functions directly from C code as shown in the code snippet below.

int main()
{
  /* Usual connect() stuff */
  int sockfd = socket(...);
  connect(sockfd, ...);

  /* FLOC code */
  id_t proc;
  id_t flow;

  /* Create connection to FLOC daemon */
  sfc_connect(); 
  /* Register token "ABCDEFABCDEF" */
  proc = sfc_proc_new("ABCDEFABCDEF");

  /* Add flow */
  flow = sfc_flow_add(proc, sockfd, NULL, NULL);

  /* Wait for mark/classid */
  sfc_wait(proc, flow);
  fprintf(stderr, "[FLOC] go\n");

  write(sockfd, "Hello", 5);

  /* Flow unregistration */
  sfc_flow_del(proc, flow);

  close(sockfd);
}

Kernel: FLOC (through tc) makes Linux kernel to modify rate control rules (qdisc, filters, packet marks).

Download

Version 0.12 Wed Jun 3 16:14:38 CEST 2009 (MD5 88676104bc614df55cc18549a88735a5)

Links

The FLOC software has been transfered to the INRIA spinoff LYaTiss. For any information please contact:contact@lyatiss.com