SCTP Administrator's Guide

Glossary
Association A protocol relationship between two SCTP endpoints. The association also contains the protocol
state information that includes verification tags and the currently active set of Transmission
Sequence Numbers (TSNs). An association can be uniquely identified by the transport addresses
used by the endpoints in the association.
Bundling An optional multiplexing operation, where more than one user message can be carried in the
same SCTP packet. Each user message occupies its own DATA chunk.
Chunks A unit of information within an SCTP packet, consisting of a chunk header and chunk-specific
content.
Cookie
Preservative
parameter
The sender of the INIT uses this parameter to suggest to the receiver of the INIT for a longer
life-span of the State Cookie.
Endpoints The logical sender or receiver of SCTP packets. On a multi-homed host, an SCTP endpoint is
represented to its peers as a combination of a set of eligible destination transport addresses to
which SCTP packets can be sent and a set of eligible source transport addresses from which SCTP
packets can be received. All transport addresses used by an SCTP endpoint must use the same
port number but the endpoint can use multiple IP addresses. A transport address is unique to an
SCTP endpoint. Therefore, a transport address used by an SCTP endpoint must not be used by
another SCTP endpoint.
HEARTBEAT An endpoint should send this chunk to its peer endpoint to probe the reachability of a particular
destination transport address defined in the present association.
Hostname
parameter
The sender of INIT uses this parameter to pass its Host Name (in place of its IP addresses) to its
peer. The peer is responsible for resolving the name.
INIT ACK
The INIT ACK chunk is used to acknowledge the initiation of an SCTP association.
Maximum
Transmission
Unit
The Maximum Transmission Unit (MTU) determines the maximum size of the packet that is
supported by a communications protocol.
Message Data submitted to SCTP by the Upper Layer Protocol (ULP).
Partial
Delivery
Partial Delivery is invoked when a message is large in size and the SCTP stack needs to begin
delivery of the message to help free some of the resources held by it during re-assembly of the
data.
Partial
Reliability
(PR)_SCTP
Partial Reliability (PR)_SCTP allows the sender to choose the retransmission behavior on a per
message basis. Timed reliability service is one of the partial reliability services provided. Timed
reliability means that the user can specify the lifetime of a message: when the lifetime expires and
the message is not acknowledged, the sender stops the retransmission and drops the packet.
Path The route taken by the SCTP packets sent by one SCTP endpoint to a specific destination transport
address of its peer SCTP endpoint. Sending to different destination transport addresses does not
necessarily guarantee getting separate paths.
RAW IP RAW IP is a non-formatted protocol, unlike TCP and UDP. It works at network and transport
layers. A socket associated with RAW IP is known as a raw socket. UDP and TCP sockets just
receive the payload or the data, whereas RAW Sockets receive the header info of the packet along
with the data.
Receive
Window
An SCTP variable that a sender uses to store the most recently calculated receiver window (in
bytes) of its peer. The value of rwnd indicates the space available in the receiver's inbound buffer.
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