Diameter transport over SCTP.

This module implements diameter transport over SCTP using gen_sctp(3). It can be specified as the value of a transport_module option to diameter:add_transport/2 and implements the behaviour documented in diameter_transport(3).


start({Type, Ref}, Svc, [Opt]) -> {ok, Pid, [LAddr]} | {error, Reason}

The start function required by diameter_transport(3).

Options raddr and rport specify the remote address and port for a connecting transport and not valid for a listening transport: the former is required while latter defaults to 3868 if unspecified. Multiple raddr options can be specified, in which case the connecting transport in question attempts each in sequence until an association is established.

Option accept specifies remote addresses for a listening transport and is not valid for a connecting transport. If specified, a remote address that does not match one of the specified addresses causes the association to be aborted. Multiple accept options can be specified. A string-valued Match that does not parse as an address is interpreted as a regular expression.

Remaining options are any accepted by gen_sctp:open/1, with the exception of options mode, binary, list, active and sctp_events. Note that options ip and port specify the local address and port respectively.

Multiple ip options can be specified for a multihomed peer. If none are specified then the values of Host-IP-Address in the diameter_service record are used. (In particular, one of these must be specified.) Option port defaults to 3868 for a listening transport and 0 for a connecting transport.


An insufficiently large receive buffer may result in a peer having to resend incoming messages: set the inet(3) option recbuf to increase the buffer size.

An insufficiently large send buffer may result in outgoing messages being discarded: set the inet(3) option sndbuf to increase the buffer size.

The transport_data field of record diameter_packet is used to communicate the stream on which an inbound message has been received, or on which an outbound message should be sent. The value will be of the form {stream, Id} for an inbound message passed to a handle_request/3 or handle_answer/4 callback. For an outbound message, {outstream, Id} in the return value of handle_request/3 or prepare_retransmit/3 sets the outbound stream, the stream id being interpreted modulo the number of outbound streams. Any other value, or not setting a value, causes successive such sends to cycle though all outbound streams.