SCTP Release Notes HP-UX 11i v2, HP-UX 11i v3 (5900-1238, October 2010)

misinterpretation can cause an SCTP sender to stop sending packets. This results in
under-utilization of the network link. Depending on the severity of the error, the sender
can remain in a state of congestion, which affects the performance of the association.
SCTP contains the PKTDROP chunk that discovers packets that are dropped because of
errors other than congestion. After receiving the PKTDROP chunk, an SCTP endpoint
can inform its peer that it has received an SCTP packet with an incorrect CRC32C or
Adler-32 checksum. The peer can then retransmit the SCTP packet without modifying
the congestion window.
For information on packet drop scenarios, see draft-stewart-sctp-pktdrprep-02.txt
(Stream Control Transmission Protocol (SCTP) Packet Drop Reporting) at:
http://tools.ietf.org/html/draft-stewart-sctp-pktdrprep-02
SCTP Support for Partially Reliable Data Transmission
SCTP supports partially reliable data transmission service (PR-SCTP) that enables an
SCTP sender to signal the receiver that it must not expect data from the SCTP sender.
PR-SCTP enables ordered and unreliable data transfer service between endpoints, in
addition to unordered and unreliable data transfer (similar to UDP). PR-SCTP employs
similar congestion control and congestion avoidance algorithms as SCTP, for both
reliable or partially reliable data traffic.
The communication failure detection and protection capabilities of reliable SCTP data
traffic are also applicable to partially reliable data traffic. PR-SCTP enables an endpoint
to detect a failure destination address quickly and to failover to an alternate destination
address. It also notifies when the destination address becomes unreachable.
The chunk bundling capability in SCTP enables reliable and unreliable messages to be
multiplexed over a single PR-SCTP association. Multiplexing enables a single protocol
(that is SCTP) to be used to transmit different types of messages, instead of using
separate protocols.
SCTP includes the following parameter and chunk to support the partially reliable data
transmission service:
The Forward-TSN-Supported
parameter
This is an optional parameter in the INIT and
INIT ACK chunks. When an association is
initialized, the SCTP sender must include this
parameter in the INIT or INIT ACK chunk to
inform its peer that it supports partially reliable
data service.
The Forward Cumulative TSN
(FORWARD TSN) chunk
The receiver sends this chunk to a sender to
inform its support for PR-SCTP. An SCTP sender
uses this chunk to inform the receiver to move
its cumulative received TSN forward, because
the missing TSNs are associated with data chunks
SCTP Features 9