z/OS® V2R1 Communications
Server provides the following TCP support for selective acknowledgments:
- Generation of TCP selective acknowledgments as defined in RFC
2018
- Exploitation of incoming TCP selective acknowledgments to improve
TCP retransmission processing as defined in RFC 3517
A TCP connection might experience poor performance when multiple
packets are lost from one window of data. With the limited information
available from cumulative acknowledgments, a TCP sender can learn
about only a single lost packet per round-trip time. A Selective Acknowledgment
(SACK) mechanism, combined with a selective repeat retransmission
policy, can help to overcome these limitations. The receiving TCP
sends back SACK packets to the sender informing the sender of data
that has been received. The sending TCP can then retransmit only the
missing data segments.
Using the TCP support for selective acknowledgments
To
use the TCP support for selective acknowledgments, perform the appropriate
tasks in
Table 1.