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Annotation of 43BSDReno/share/doc/smm/15.net/d.t, revision 1.1.1.1

1.1       root        1: .\" Copyright (c) 1983, 1986 The Regents of the University of California.
                      2: .\" All rights reserved.
                      3: .\"
                      4: .\" Redistribution and use in source and binary forms are permitted
                      5: .\" provided that the above copyright notice and this paragraph are
                      6: .\" duplicated in all such forms and that any documentation,
                      7: .\" advertising materials, and other materials related to such
                      8: .\" distribution and use acknowledge that the software was developed
                      9: .\" by the University of California, Berkeley.  The name of the
                     10: .\" University may not be used to endorse or promote products derived
                     11: .\" from this software without specific prior written permission.
                     12: .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
                     13: .\" IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
                     14: .\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
                     15: .\"
                     16: .\"    @(#)d.t 6.4 (Berkeley) 3/7/89
                     17: .\"
                     18: .nr H2 1
                     19: .\".ds RH "Out of band data
                     20: .br
                     21: .ne 2i
                     22: .NH
                     23: \s+2Out of band data\s0
                     24: .PP
                     25: Out of band data is a facility peculiar to the stream socket
                     26: abstraction defined.  Little agreement appears to exist as
                     27: to what its semantics should be.  TCP defines the notion of
                     28: ``urgent data'' as in-line, while the NBS protocols [Burruss81]
                     29: and numerous others provide a fully independent logical
                     30: transmission channel along which out of band data is to be
                     31: sent.
                     32: In addition, the amount of the data which may be sent as an out
                     33: of band message varies from protocol to protocol; everything
                     34: from 1 bit to 16 bytes or more.
                     35: .PP
                     36: A stream socket's notion of out of band data has been defined
                     37: as the lowest reasonable common denominator (at least reasonable
                     38: in our minds);
                     39: clearly this is subject to debate.  Out of band data is expected
                     40: to be transmitted out of the normal sequencing and flow control
                     41: constraints of the data stream.  A minimum of 1 byte of out of
                     42: band data and one outstanding out of band message are expected to
                     43: be supported by the protocol supporting a stream socket.
                     44: It is a protocol's prerogative to support larger-sized messages, or
                     45: more than one outstanding out of band message at a time.
                     46: .PP
                     47: Out of band data is maintained by the protocol and is usually not
                     48: stored in the socket's receive queue.
                     49: A socket-level option, SO_OOBINLINE,
                     50: is provided to force out-of-band data to be placed in the normal
                     51: receive queue when urgent data is received;
                     52: this sometimes amelioriates problems due to loss of data
                     53: when multiple out-of-band
                     54: segments are received before the first has been passed to the user.
                     55: The PRU_SENDOOB and PRU_RCVOOB
                     56: requests to the \fIpr_usrreq\fP routine are used in sending and
                     57: receiving data.

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