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concatenated to form an M-bit packet sequence. lowest acceptable value for data on a connection, need not be
supported.
4.7.3.16.10.2 If the user data field in the data SNPDUs of
an M-bit SNPDU sequence is greater than the default data
packet maximum user data field length, then these fields shall 4.7.4.2.3 RECOMMENDED FACILITIES
be segmented to form an M-bit packet sequence.
Recornmendation.- The following facilities should be
supported:
a) throughput class negotiation;
The SSNDPA shall support at least eight simultaneous, b) transit delay selection and indication;
independent logical channels.
c) fast select;
d) fast select acceptance.
4.7.4 IS0 8208 DCE
protocol operations
4.7.4.3 OPERATIONS
4.7.4.1 GENERALPR OVISIONS
4.7.4.3.1 EXTERNAL ~hTERACTIONS
4.7.4.1.1 The protocol between the IS0 8208 DCE and
the IS0 8208 DTE shall coniply with the IS0 8208 second Nore.-- The initiation of certain DCE procedures is
edition. directed by elements outside the IS0 8208 DCE. Likewise, the
2/lVOO
No. 75
Part I Annex 10 - Aeronautical Telecommunications
occurrence of certain IS0 8208 DCE events are to be reported Note I.- The IS0 8208 DCE is defined us a state machine.
appropriately. These external interactions include: An IS0 8208 packet receivedfrom the DTE can cause state
trunsitions, as can a packet receivedfim IWR The next state
a) mquesting of the l i d layel; transmission of outgoing trunsition ( i f any) that occurs when the I)CE receives a packet
packets; from the DTE is specified by Tables 4-29 to 4-34. These tables
are organized according to the hierarchy in Figure 4-31.
b) receiving, from the link layer; incoming packets;
Note 2.- Upon receiving a packet, the action is classified
c) accepting requests from the IWF to initiate certain as normal or erroneous under the ently "A = ". The resulting
IS0 8208 protocol procedures including: state is shown under the entry. "S = ".
I ) originate a virtual call,
2) accept a virtual call,
4.7.4.3.3.2 If a state transition is specified, the action
taken shall be as specified in Tables 4-29 to 4-34.
3) terminate a virtual cull,
4.7.4.3.4 DISPOSITION OF PACKETS
4) transfer data and interrupt information, and
When a packet is received from the Dm, the expressions in
5) re-initialize a logical channel. parentheses in Tables 4-29 to 4-34 specify whether the packet
shall be forwarded or not forwarded to the IWF. If no remark
in parentheses is listed or listed as not forwarded, then the
rl) reporting to the IWF the occurrence of certain IS0 8208 packet shall be discarded. The IS0 $208 DCE shall either
protocol events including: forward or not forward a packet from the lWF to the DTE in
a manner that is compatible with IS0 8208.
I ) receipt of an incoming request to set up a virtual cull,
2) receipt of the acceptance of u virtual call setup,
4.7.4.3.5 DIAGNOSTIC AND CAUSE CODES
3) termination of a virtual call,
For certain conditions, Tables 4-29 to 4-34 indicate a
4) receipt of data and interrupt inforination, and diagnostic code that shall be included in the packet generated
when entering the state indicated. The term, "D =", shill
5) re-initialization of u logical channel.
define the diagnostic code. When 'Y. = DIAG", the action
taken shall be to generate an IS0 8208 diagnostic packet and
transfer it to the-DTE; the diagnostic code indicated shall
4.7.4.3.1.1 The IS0 8208 DCE accept ISO 8208 define the entry in the diagnostic field of the packet. In the
packets from the IS0 8208 DTE without failure. cause field of any packet type, bit 8 of the cause field shall
always be set to 0, indicating that the condition was recognized
by the IS0 8208 interface.
4.7.4.3.2 LOGICALC HANNELS
Note.- Each virtual call and pemnent virtual circuit is Note.- The state Tables 4-29 to 4-34 are defined so that the
assigned a logical channel identifier which is a number in the SSNDPX and IS0 8208 DCE functions can operate
range firn I through 095. For each call, a simultaneously. While asynchronous operation is a suitable
channel ident@er is msigned during the call setup from im~lementatian it is a requirement for the
a range of previously agreed-upon logical channel identijiers. SSNDPX and ISO 8208 DCE operatiom.
For each permanent virtual circuit, a logical clrunnel identijier
is assigned in agreement with the DTE. A DCE's use oflogicul
channels is agreed upon for a period of time with the DTE.
4.7.4.3.6 DCETIMER
4.7.4.3.3 STATE TRANSITIONS Note.- Under certain circumstances, the DTE must
respond to a packet issuedfrom the DCE within a given time.
4.7.4.3.3.1 The specifications and definitions in IS0 8208
 
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