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时间:2010-07-20 23:38来源:蓝天飞行翻译 作者:admin
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4.7.3.8.3.4.1 When the SSNDPX receives a reset
SNPDU, it shall place the logical channel into the remote reset 4.7.3.9.6 ORIGINATING SSNDPX ERROR RECOVERY
state, execute the reset action and transmit a reset indication
packet to the IWF as required (see Table 4-24). 4.7.3.9.6.1 Transmission error resulting from the loss or
delay of SNPDUs shall be detected either by time-out when a
4.7.3.8.3.4.2 The SSNDPX shall transmit a reset confirm response is expected or by the fail LIDU reported by the link
SNPDU to its remote SSNDPX and shall return the logical layer.
Annex 10 - Aeronautical Telecommunications
4.7.3.9.6.2 The actions the SSNDPX follows upon timeout
shall be as summarized in Table 4-18.
4.7.3.9.6.3 The actions the SSNDPX shall follow when
it is informed by the link layer that the transmission of an
SNPDU has failed shall be as summarized in Table 4-19.
Receipt of a fail (dataiintempt) LIDU while the relevant LCN
is either in local/remote reset state or locauremote clear
request state, shall not cause the SSND sub-layer entity to
generate a (further) connection reset.
SNPDU. If no more storage is available, the SSNDPG shall
place the logical channel in the reset state and extend the reset
to the IWF.
...!
4.7.3.9.8.2.2 Stored data SNPDUs shall be processed to
create data packets whenever this can be done without creating
an out-of-sequence condition. Data packets shall be forwarded
to the IWF as soon as possible.
4.7.3.9.8.3 SSNDPA actions for
out-of-sequence SNPD Us
4.7.3.9.7 PROTOCOL ERROR
Note.- Two types of protocol error may occur at the
SSNDPX. These are:
If a data SNPDU is received which is not a duplicate but has
an SNPDU number not immediately following the SNPDU
number of the data SNPDU last received, the SSNDPA shall
initiate a reset of the connection.
a) a syntactical error which occurs when a received
SNPDU does not conform to the format speciJications
over the satellite subnetwork; and
b) a logicul error which occurs when the SSNDPX
receives from its peer entiiy an SNPDU that is not an
acceptable input to the current state of the logical
channel.
4.7.3.9.7.1 When the SSNDPX detects a protocol error,
it shall respond as indicated in Tables 4-21 to 4-24. These
tables are depicted for each logical channel state.
4.7.3.9.8 OUT-OF-SEQUENCE DATA
SNmU PROCEDURE
4.7.3.9.8.1 The SSNDPX shall process received data
SNPDUs in proper sequence, according to SNPDU number to
construct data packets to be forwarded to the IWF. The
SSNDPX shall discard duplicate SNPDUs.
Note.- The receiving link layer at the GES may deliver
SNPDUs to the SSNDPG in altered sequence. The SSNDPG
assembles data SNPDUs in proper sequence before forwarding
them to the 1WF
4.7.3.9.8.2 SSNDPG actions for
out-of-sequence data SNPDUs
A data SNPDU shall be defined as out of sequence if and only
if its SNPDU number does not immediately follow the
SNPDU number of the last received data SNPDU that has
been used in creating the last data packet.
Note.- SNPDU numbers are incremented modulo 256.
Thus, SNPDU number 0 follows SNPDU number 255.
4.7.3.9.8.2.1 If an out-of-sequence data SNPDU is not
a duplicate, the SSNDPG shall store the out-of-sequence data
4.7.3.10.1. GENERALS NPDU FORMAT
4.7.3.10.1.1 An SNPDU shall consist of at least two
octets. Octet 1 shall contain the D- and M-bits and the
SNPDU type identifier field. Octet 2 shall contain the logical
channel number field; depending on the particular SNPDU
type, additional octets may be required. The general SNPDU
format shall be as defined in Figure 4-13.
4.7.3.10.1.2 The D- and M-bits shall be bits 7 and 8,
respectively, in octet 1.
4.7.3.10.1.3 The M-bit shall be used in an M-bit
SNPDU sequence consisting of a sequence of data SNPDUs;
it shall be set to 0 in all other SNPDUs.
Note.- The D-bit may be used for end-to-end acknowledgement
(receipt confinnation).
4.7.3.10.1.4 The SNPDU type identifier field shall be
bits 1-6 in octet 1. The coding of the SNPDU type identifier
field shall be as defined in Table 4-15.
4.7.3.10.1.5 Octet 2 shall contain the logical channel
number field.
Note.- In the following sections, fields are defined in the
order they m y appear in the relevant SNPDU.
4.7.3.10.2 CONNECTIORNE QUEST SNPDO
4.7.3.10.2.1 The format of connection request SNPDU
shall be as defined in Figure 4-14.
Annex 10 - Aeronauiical Telecommunicatiuns Vulume lII
4.7.3.10.2.2 SNPDU type identifier field
4.7.3.10.2.2.1 Bits 1, 2, 3 and 6 shall be the following
indicator bits:
a) bit 1, facilities field present;
 
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