Wave and Equation Based Rate Control (WEBRC) Building Block
RFC 3738

Network Working Group                                            M. Luby
Request for Comments: 3738                              Digital Fountain
Category: Experimental                                          V. Goyal
                                                                  M.I.T.
                                                              April 2004

      Wave and Equation Based Rate Control (WEBRC) Building Block

Status of this Memo

   This memo defines an Experimental Protocol for the Internet
   community.  It does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2004).  All Rights Reserved.

Abstract

   This document specifies Wave and Equation Based Rate Control (WEBRC),
   which provides rate and congestion control for data delivery.  WEBRC
   is specifically designed to support protocols using IP multicast.  It
   provides multiple-rate, congestion-controlled delivery to receivers,
   i.e., different receivers joined to the same session may be receiving
   packets at different rates depending on the bandwidths of their
   individual connections to the sender and on competing traffic along
   these connections.  WEBRC requires no feedback from receivers to the
   sender, i.e., it is a completely receiver-driven congestion control
   protocol.  Thus, it is designed to scale to potentially massive
   numbers of receivers attached to a session from a single sender.
   Furthermore, because each individual receiver adjusts to the
   available bandwidth between the sender and that receiver, there is
   the potential to deliver data to each individual receiver at the
   fastest possible rate for that receiver, even in a highly
   heterogeneous network architecture, using a single sender.

Luby & Goyal                 Experimental                       [Page 1]
RFC 3738                  WEBRC Building Block                April 2004

Table of Contents

   1.  Introduction. . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Rationale . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Functionality . . . . . . . . . . . . . . . . . . . . . . . .   6
       3.1. Sender Operation . . . . . . . . . . . . . . . . . . . .   9
            3.1.1. Sender inputs and initialization. . . . . . . . .   9
            3.1.2. Sending packets to the session. . . . . . . . . .  10
       3.2. Receiver Operation . . . . . . . . . . . . . . . . . . .  12
            3.2.1. Receiver inputs and initialization. . . . . . . .  12
            3.2.2. Receiver measurements and calculations. . . . . .  13
                   3.2.2.1. Average loss probability . . . . . . . .  13
                   3.2.2.2. Average round-trip time. . . . . . . . .  16
                   3.2.2.3. Rate Equation. . . . . . . . . . . . . .  16
                   3.2.2.4. Epochs . . . . . . . . . . . . . . . . .  17
                   3.2.2.5. Average reception rate . . . . . . . . .  17
                   3.2.2.6. Slow start . . . . . . . . . . . . . . .  19
                   3.2.2.7. Target rate. . . . . . . . . . . . . . .  20
            3.2.3. Receiver events . . . . . . . . . . . . . . . . .  20
                   3.2.3.1. Packet reception . . . . . . . . . . . .  20
                   3.2.3.2. First packet after join. . . . . . . . .  20
                   3.2.3.3. Time slot change . . . . . . . . . . . .  20
                   3.2.3.4. Loss event . . . . . . . . . . . . . . .  21
                   3.2.3.5. Epoch change . . . . . . . . . . . . . .  21
                   3.2.3.6. Join the next higher layer . . . . . . .  21
                   3.2.3.7. Join timeout . . . . . . . . . . . . . .  23
                   3.2.3.8. Exceptional timeouts . . . . . . . . . .  23
   4.  Applicability Statement . . . . . . . . . . . . . . . . . . .  23
       4.1. Environmental Requirements and Considerations. . . . . .  23
   5.  Packet Header Fields. . . . . . . . . . . . . . . . . . . . .  25
       5.1. Short Format Congestion Control Information. . . . . . .  26
       5.2. Long Format Congestion Control Information . . . . . . .  27
   6.  Requirements From Other Building Blocks . . . . . . . . . . .  28
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  28
   8.  References. . . . . . . . . . . . . . . . . . . . . . . . . .  29
       8.1. Normative References . . . . . . . . . . . . . . . . . .  29
       8.2. Informative References . . . . . . . . . . . . . . . . .  30
   9.  Authors' Addresses. . . . . . . . . . . . . . . . . . . . . .  31
   10. Full Copyright Statement. . . . . . . . . . . . . . . . . . .  32

Luby & Goyal                 Experimental                       [Page 2]