Browse Prior Art Database

Suppression of ACK/NACK Explosion for Reliable Multicast Protocol

IP.com Disclosure Number: IPCOM000123082D
Original Publication Date: 1998-May-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Related People

Takemura, T: AUTHOR [+2]

Abstract

Disclosed is a protocol to realize reliable transmission of data from one server to multiple clients using IP Multicast.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 74% of the total text.

Suppression of ACK/NACK Explosion for Reliable Multicast Protocol

   Disclosed is a protocol to realize reliable transmission
of data from one server to multiple clients using IP Multicast.

   Using IP Multicast, data packets sent from a server
reaches at a lot of clients almost at a time, and each client sends
an ACK or a NACK to the server.  As a result, a lot of ACKs and NACKs
are returned to the server at a time if a conventional multicast
protocol is used.  This situation is called "ACK/NACK explosion".  If
the "ACK/NACK explosion" occurred, the server can not correctly
receive ACK/NACK from clients.  This results in transmission failure.

   The protocol disclosed here suppresses "ACK/NACK explosion"
by multicasting a content of a NACK sent from one of clients to
other clients.  In this protocol, a NACK consists of a set of IDs
assigned to failed packets; i.e. a client informs the server of IDs
of packets it fails to receive.  On receiving NACKs, the server
re-transmits only the packets indicated in NACKs.

   This protocol consists from the following sequence:
  1.  A server transmits a series of packets for a data to
       clients using IP Multicast.
  2.  Each client receives the series of packets.
  3.  I) Only if a client fails to receive a series of packet,
          the client sends a NACK after a randomized waiting time
          elapsed.
     II) When the server receives NACKs from clients, it
          m...