Suppression of ACK/NACK Explosion for Reliable Multicast Protocol
Original Publication Date: 1998-May-01
Included in the Prior Art Database: 2005-Apr-04
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.
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...