164 lines
5.7 KiB
Plaintext
164 lines
5.7 KiB
Plaintext
.NC "Network Service Interface"
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.sh 1 "Connectionless Network Service"
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.pp
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This section describes the interface to the ISO connectionless network service.
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There are really two interfaces to the CLNS: the internal interface
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and the IPC interface.
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The internal interface is based on
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procedure calls. It is used only within the kernel. The IPC interface
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allows a user process to access the CLNS directly. This is used only
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for testing and debugging purposes.
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.sh 2 "Primitives"
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.pp
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The CLNS is, by definition, connectionless. Therefore, there are no
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primitives associated with connection establishment or connection release.
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There is one primitive associated with data transfer: N-UNITDATA.
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The parameters to a N-UNITDATA request are: source NSAP address,
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destination NSAP address, quality of service, and user data.
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The parameters of a N-UNITDATA indication are identical to those of the
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request.
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In this implementation, the quality of service parameter is not supported.
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.sh 2 "Internal Interface"
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.pp
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Within the kernel, an N-UNITDATA request is effected by the procedure
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\fIclnp_output()\fR:
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.(b
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\fC
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.TS
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tab(+);
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l s s.
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clnp_output(m0, isop, datalen, flags)
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.T&
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l l l.
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+struct mbuf+*m0;+/* data */
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+struct isopcb+*isop;+/* ISO protocol control block */
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+int+datalen;+
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+int+flags;+/* flags */
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.TE
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\fR
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.)b
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This procedure will construct a DT NPDU, route it, and transmit it on
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the appropriate subnetwork. \fIM0\fR is an mbuf chain containing the
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user data portion of the N-UNITDATA request. \fIIsopcb\fR is the iso protocol
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control block previously allocated. \fIClnp_output\fR will use the following
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fields: \fIisop_laddr\fR, isop_faddr, isop_route, isop_options,
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isop_optindex, \fI and \fRisop_clnpcache\fR.
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\fIDatalen\fR specifies the number of bytes of user data.
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The \fIflags\fR parameter will be discussed in a subsequent chapter.
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.pp
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A N-UNITDATA indication occurs when a DT NPDU arrives. The indication is
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generated by calling the appropriate upper layer protocol input routine.
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In the case of TP, the procedure \fItpclnp_input()\fR is called:
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.(b
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\fC
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.TS
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tab(+);
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l s s.
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tpclnp_input(m, src, dst, len)
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.T&
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l l l.
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+struct mbuf+*m;+/* DT NPDU */
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+struct iso_addr+*src;+/* source of packet */
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+struct iso_addr+*dst;+/* destination of packet */
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+int+len;+/* length of clnp header */
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.TE
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\fR
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.)b
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\fIM\fR contains the entire DT NPDU packet. \fILen\fR indicates the size
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of the CLNP header. In other words, the user data of the DT NPDU begins
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\fIlen\fR bytes into \fIm\fR. \fISrc\fR and \fIdst\fR indicate the
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source and destination NSAP addresses of the packet.
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.sh 3 "CLNP/Subnetwork Interface"
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.pp
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The design of the interface between the subnetwork and the CLNP is
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determined by the design of the Unix network interface drivers. CLNP
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follows the conventional mechanisms for exchanging packets with a network
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interface. See the section on Network Interface Drivers in Chapter Five
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for more information on these conventions.
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.sh 2 "IPC (\*(lqRaw\*(rq) Interface"
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.pp
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The IPC interface to the CLNS allows direct (called \*(lqraw\*(rq)
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access to CLNP.
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This interface is intended for testing and debugging only.
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Its use results in the
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transmission of CLNP datagrams with nonstandard identification fields.
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These raw packets may be rejected by a system not employing the same
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convention. See the section on network implementation for more information
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about the conventions.
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.pp
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In order to gain access to the raw interface
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a \fIsocket\fR, with address family AF_ISO and type SOCK_RAW must be created.
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With this socket in hand,
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the system calls \fIsendto()\fR and \fIrecvfrom()\fR can be used to
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transmit and receive raw CLNP datagrams.
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.sh 3 "Sending raw datagrams"
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.pp
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The format of the \fIsendto()\fR system call is:
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.(b
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\fC
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.TS
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tab(+);
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l s s.
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cc = sendto(s, msg, len, flags, to, tolen)
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.T&
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l l l.
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int+cc,s;
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char+*msg;
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int+len,flags;
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struct sockaddr+*to;
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int+to;
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.TE
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\fR
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.)b
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\f\fIS\fR is the socket previously created. \fIMsg\fR is a pointer to
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the data for the NPDU. CLNP will prepend a header to this data before
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transmission. \fILen\fR specifies the number of bytes of data. The
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\fIflags\fR parameter is unused and should be zero. \fITo\fR specifies the
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NSAP address to be used as the destination address. The size (in bytes)
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of \fIto\fR is given in \fItolen\fR. CLNP will automatically insert
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the source address based upon the route taken by the packet. The number of
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user data bytes transmitted is returned as \fIcc\fR. See \fIsendto(2)\fR
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for more information on this system call.
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.sh 3 "Receiving raw datagrams"
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.pp
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The format of the \fIrecvfrom()\fR system call is:
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.(b
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\fC
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.TS
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tab(+);
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l s s.
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cc = recvfrom(s, buf, len, flags, from, fromlen)
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.T&
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l l l.
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int+cc,s;
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char+*buf;
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int+len,flags;
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struct sockaddr+*from;
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int+*fromlen;
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.TE
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\fR
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.)b
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When used with a CLNP raw socket \fIs\fR, \fIrecvfrom()\fR will read a
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NPDU from the CLNS. If no packet is available, the call will block.
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\fIBuf\fR specifies a buffer of \fIlen\fR bytes into which the NPDU will
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be read. The entire packet, including the header, will be read into the
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buffer. The \fIflags\fR parameter is unused, and should be zero. If
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\fIfrom\fR is non-zero, the source address of the NPDU is filled in.
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\fIFromlen\fR is a value-result parameter, initialized to the size of
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the buffer associated with \fIfrom\fR, and modified on return to
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indicate the actual size of the address stored there. The total number
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of bytes received (header and data) is returned as \fIcc\fR.
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See \fIrecvfrom(2)\fR for more information about this system call.
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.sh 1 "Connection Oriented Network Service"
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.pp
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The ARGO Connection Oriented Network Service (CONS) is not a complete
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implementation of the
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OSI network service.
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It is that subset of the OSI network service that is used
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by ARGO Transport and by ARGO CLNP.
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.\" FIGURE
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.so figs/NS_primitives.nr
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.pp
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.CF
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shows which CONS service elements are provided.
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