Cabletron Systems Netlink FRX8000, User Manual

Page: 171 / 468

Configuring SNA 11-23
The link station will reset
T1
when it receives one of these:
●
A REJ (Reject) LPDU, provided a Command LPDU with P bit set to
B‘1’
is not
outstanding.
●
A Response LPDU with the
F
bit set to
B ‘1’
.
●
An Information or Supervisory LPDU with an N
(R)
greater than the last N
(R)
received and less than or equal to the line station’s V
(S)
, provided a Command
LPDU with
P
bit set to
B‘1’
is not outstanding.
If additional LPDUs are set from the remote link station after the local station has reset
T1
, the timer will be restarted if acknowledgments of or responses to those LPDUs are
outstanding. If no acknowledgments/responses are outstanding, the link station will
start the inactivity timer. (See “Reply Timer - T1” later.)
If
T1
expires and acknowledgments/responses are still outstanding, the link station
will send one of the following, then restart T1:
●
A Supervisory LPDU with the
P
bit set to
B‘1’
to solicit remote link station
status.
●
Any Unnumbered LPDUs that were not responded to the first time they were
sent.
If acknowledgments/responses are still outstanding after N2 tries (see that entry
on page 11-18), the link station will declare the link inoperative.
The value specified for
T1
should allow for any delays introduced by the MAC sub-
layer (e.g., queuing).
Rcv Ack Timer - T2
is used by the link station to delay sending an acknowledgment of a received Infor-
mation LPDU. The timer is started when the LPDU is received and reset when the
acknowledgment is sent. If the timer expires before the acknowledgment is sent, it
must be sent as soon as possible.
Inactivity Timer - Ti
is used by the link station to detect an inoperative condition in either the remote link
station or the transmission medium. The timer will be started if
T1
has been reset (for
one of the reasons listed under “
Reply Timer - T1
” earlier), and additional LPDUs have
been sent by the remote link station, and there are no outstanding acknowledgments
or responses from the local link station.
If the local station does not receive an LPDU before
Ti
expires, the station must send
an LPDU with the
P
bit set to
B‘1’
to solicit the remote station’s status. Recovery then
proceeds as described under “
Reply Timer - T1
” earlier.
LPDUs before Ack - N3
is the number of Information LPDUs that will be received before sending an acknowl-
edgment. This parameter is used in conjunction with
T2
to allow stations to reduce
traffic. A counter is initialized to
N3
, and will be decremented by one each time a valid
sequential Information LPDU is received. When the counter reaches
0
an acknowl-
edgment is sent.