23.5 Unordered Data
SCTP normally provides reliable ordered delivery
of data. SCTP also provides a reliable unordered service. A message
with the MSG_UNORDERED flag is sent with no order
constraints and is made deliverable as soon as it arrives.
Unordered data can be sent in any stream. No stream sequence number
is assigned. Figure 23.6
shows the changes needed to our client program to send the request
to the echo server with the unordered data service.
Figure 23.6 A
sctp_strcli that sends unordered data.
sctp/sctp_strcli_un.c
18 out_sz = strlen(sendline);
19 Sctp_sendmsg(sock_fd, sendline, out_sz,
20 to, tolen, 0, MSG_UNORDERED, sri.sinfo_stream, 0, 0);
Send data using unordered service
18鈥?0
This is nearly the same as the sctpstr_cli function
developed in Section 10.4. On
line 21, we see the single change made: The client explicitly
passes the MSG_UNORDERED flag to invoke the unordered
service. Normally, all data within a given stream is ordered with
sequence numbers. The MSG_UNORDERED flag causes the data
sent with this flag to be sent unordered, with no sequence number,
and can be delivered as soon as it arrives, even if other unordered
data that was sent earlier on the same stream has not yet
arrived.
|
