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station ca~i,norte ceive the transmission.
6.5.3.1 1.2 SREI frame. The multi-selective reject option
in IS0 4335 shall be used LO request the retransmission of
more than one INFO frame. The SREJ (F=O) frame shall be
generated only after receipt of an out-of-order INFO (P=O).
The SKEJ (F=l) shall be generated only after receipt of an
INFO (P=l), RR (P=l) or SREJ (P=l). The SRH (P=l) frame
shall be generated only in accordancc with the procedures of
6.5.3.4.4- A DLE shall acknowledge those frames which were
received correctly but out of order by including in the SREJ
information field an octet with bits 6-8 set to the INFO
frame's sequence number and bit 1 set to 1. Although the F bit
may be set to 0, the SREJ frame shall always acknowledge
INFO frames up to N(r)-1 (where N(r) is the value in the
control field).
Note.- AVLC has extended the standard IS0 4335 SRE.1
functionality to selectively acknowledge frames. In IS0 4335,
the octets in the information field which were requesting
retransmission of frames had bit position I set by default to 0.
6.5.3.11.3 FRMR frame. If a DLE receives an illegal
frame (as defined by IS0 4333, it shall transmit a FRMR
(P=l) to reset the link (c.g. state variables, timers and queues).
A DLE, on receiving or transmitting a UA (F=l), shall reset
the link (no XID exchange required). A DLE shall use the
normal T1 and N2 procedures during the FRMR/UA
exchange. A DLE transmitting the FlWR shall also retransmit
the F M K either upon expiration of Timer T4 or upon receipt
of any frame other than a UA (F=l). A DLE receiving an
illegal FRMR shall either discard the frame or treat it as a
valid FRMR.
6.5.3.1 1.4 UA frame. The UA frame shall be used only
to acknowledge a FRMR.
6.5.3.11.5 UIframe. UI frames shall be used solely to
support connectionless data transfer required to provide
broadcast services.
Note.- The TEST commancL/response exchange has been
included in AVLC to allow a station to perform a Zoopback
test using logic that is isolated from the normal frame
processing.
6.5.4 VDL management entity
6.5.4.1 Services, The services of the VME shall be as
follows:
a) link provision; and
b) link change notifications.
6.5.4.1.1 Linkprovisio~i,A. VME shall have an LME for
each peer LME. Hence, a ground VME shall have an LME per
aircraft and an aircraft VME shall have an LME per ground
system. An LME shall establish a link between a local DLE
and a remote DLE associated with jts peer LME. A ground
LME shall determine if an aircraft station is associated with its
peer aircraft LME by comparing the aircraft address; two
aircraft stations with identical aircraft addresses are associated
with the same LME. An aircraft LME shall determine if a
ground station is associated with its peer ground LME by
Part I Annex 10 - Aeronautical Telecommunications
bit-wise logical ANDing the DLS address with the station
ground system mask provided by the peer ground LME; two
ground stations with identical masked DLS addresses are
associated with the same LME. Each aircraft and ground LME
shall monitor all transmissions from its peer's stations to
maintain a reliable link between some ground station and the
aircraft while the aircraft is in coverage of an acceptable
ground station in the ground system.
Note.- I f an aircraft receives a frame from a ground
station, only one LME will process and react to that frame.
Thus the qualifiing phrase 'yrom a ground station associated
with its peer ME" will not be included and should be
understood to be implied.
6.5.4.1.2 Link change notificutiorts. The VME shall
notify the intermedialc-system system management entity (ISSME)
of changes in link connectivity supplying information
contained in the XTD frames received.
6.5.4.2 EXCHANGIDEE NTITY (XD)
PARAMETER FORMATS
Note.- IS0 8885 defines certuin public parameters as
receive and transmit which ure referred to herein as uplink
and downli~zk respectively.
6.5.4.2.2.1 HDLC public parameter set identijier: The
HDLC parameter setshall be identified by the IS0 IA5
character string "8885: 1993" encoded as per Table 6-1 1. This
parameter shall be included whenever any of the public
parameters are sent. It shall be the first public parameter sent
as per IS0 8885.
6.5.4.2.2.2 Timer Tl parameter. This parameter defines
the value of the downlink Timer T1 that an aircraft DLE shall
use. The values shall be defined in units of milliseconds for
Tlmin and Tlmax and in hundredths for Tlmult and Tlexp.
The timer values shall be encod~d as 4 unsigned 16-bit
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附件10--航空电信an10_v3_1ed_amend_72(18)
