Glossary

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.

A unit of information within an SCTP packet, consisting of a chunk header and chunk-specific content.

An SCTP variable that limits the data (in bytes) that a sender can send to a particular destination transport address before receiving an acknowledgement.

The Maximum Transmission Unit (MTU) determines the maximum size of the packet that is supported by a communications protocol.

Data submitted to SCTP by the Upper Layer Protocol (ULP).

The route taken by the SCTP packets sent by one SCTP endpoint to a specific destination transport address of its peer SCTP endpoint

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.

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 TSNs. An association can be uniquely identified by the transport addresses used by the endpoints in the association.

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.

The unit of data delivery across the interface between SCTP and the connectionless packet network (for example, IP). An SCTP packet contains the common SCTP header, possible SCTP control chunks, and user data encapsulated within SCTP DATA chunks.

An SCTP variable. This is the threshold (in bytes) that the endpoint uses to determine whether to perform slow start or congestion avoidance on a particular destination transport address.

A uni-directional logical channel established from one to another associated SCTP endpoint, within which all user messages are delivered in sequence except for those submitted to the unordered delivery service.

A 16-bit sequence number used by SCTP to assure sequenced delivery of the user messages within a given stream. One stream sequence number is attached to each user message.

The transmission control block (TCB) is an internal data structure created by an SCTP endpoint for each SCTP association. TCB contains the status and operational information for the endpoint to maintain and manage the association.

The transmission sequence number (TSN) is a 32-bit sequence number used by SCTP. One TSN is attached to each chunk containing user data to permit the receiving SCTP endpoint to acknowledge its receipt and detect duplicate deliveries.

A transport address is defined by the network layer address, the transport layer protocol, and the transport layer port number. In the case of SCTP running over IP, a transport address is defined by the combination of an IP address and an SCTP port number (where SCTP is the transport protocol).

Unordered messages are "unordered" with respect to any other message, this includes both other unordered and ordered messages. Unordered message can be delivered before or later than ordered messages sent on the same stream.

A 32-bit unsigned integer that is randomly generated. The verification tag provides a key that allows a receiver to verify that the SCTP packet belongs to the current association and is not an old or stale packet from a previous association.