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

messages and the detection of message loss, and the Stream ID/Stream Sequence Number
(SID/SSN) pair that determines the sequence of delivery of the received data.
Conservation of Data Boundaries
In SCTP, a sending application can construct a message out of a block of data bytes
and instruct SCTP to transport the message to a receiving application. SCTP guarantees
the delivery of this message (data block) in its entirety. It also indicates to the receiver
about both the beginning and end of the data block. This is called conservation of
message boundaries.
SCTP Graceful Shutdown Feature
SCTP does not support a "half-open" connection, which can occur in TCP. In a half-open
connection, even though an endpoint indicates that it has no more data to send, the
other endpoint continues to send data indefinitely. SCTP, on the other hand, assumes
that when the shutdown procedure begins, both the endpoints will stop sending new
data across the association. It also assumes that it needs only to clear up
acknowledgements of the previously sent data.
The SCTP shutdown feature uses a three-message procedure to gracefully shutdown
the association, in which each endpoint has confirmed the receipt of the DATA chunks
before completing the shutdown process. When an immediate shutdown is required,
SCTP sends anABORT message to an endpoint.
SCTP Support for IPv4 and IPv6 Addresses
SCTP supports both IPv4 and IPv6 address parameters in an SCTP packet, as defined
in RFC 2960 (Stream Control Transmission Protocol). When an association is set up, the
SCTP endpoints exchange the list of addresses of the endpoints in the INIT and
INIT-ACK chunks. The address of the endpoint is represented by the following
parameters: an IPv4 address parameter with value 5 and an IPv6 address parameter
with value 6. The INIT chunks can contain multiple addresses, which can be an IPv4
or IPv6 addresses.
SCTP Data Exchange Features
SCTP provides the following features to ensure reliable exchange of data between
endpoints:
• In SCTP, data is transmitted in the form of packets. Each packet contains a DATA
chunk and a control chunk. An SCTP endpoint acknowledges the receipt of a
DATA chunk by sending a SACK chunk to the other endpoint. The SACK chunk
indicates the range of cumulative TSNs and non-cumulative TSNs, if any. The
non-cumulative TSNs indicate gaps in the received TSN sequence. When SCTP
SCTP Features 7