acknowledged.
9 : evAdminDown: The administrator has requested that the control
channel is brought down administratively.
10: evNbrGoesDn: A packet with ControlChannelDown flag is received
from the neighbor.
11: evHelloRcvd: A Hello packet with expected SeqNum has been
received.
12: evHoldTimer: The HelloDeadInterval timer has expired indicating
that no Hello packet has been received. This moves
the control channel back into the Negotiation
state, and depending on the local configuration,
this will trigger either
12a) the sending of periodic Config messages,
12b) a period of waiting to receive Config
messages from the remote node.
13: evSeqNumErr: A Hello with unexpected SeqNum received and
discarded.
14: evReconfig: Control channel parameters have been reconfigured
and require renegotiation.
15: evConfRet: A retransmission timer has expired and a Config
message is resent.
16: evHelloRet: The HelloInterval timer has expired and a Hello
packet is sent.
17: evDownTimer: A timer has expired and no messages have been
received with the ControlChannelDown flag set.
11.1.3. Control Channel FSM Description
Figure 3 illustrates operation of the control channel FSM in a form
of FSM state transition diagram.
+--------+
+----------------->| |<--------------+
| +--------->| Down |<----------+ |
| |+---------| |<-------+ | |
| || +--------+ | | |
| || | ^ 2,9| 2| 2|
| ||1b 1a| | | | |
| || v |2,9 | | |
| || +--------+ | | |
| || +->| |<------+| | |
| || 4,7,| |ConfSnd | || | |
| || 14,15+--| |<----+ || | |
| || +--------+ | || | |
| || 3,8a| | | || | |
| || +---------+ |8b 14,12a| || | |
| || | v | || | |
| |+-|------>+--------+ | || | |
| | | +->| |-----|-|+ | |
| | |6,14| |ConfRcv | | | | |
| | | +--| |<--+ | | | |
| | | +--------+ | | | | |
| | | 5| ^ | | | | |
| | +---------+ | | | | | | |
| | | | | | | | | |
| | v v |6,12b | | | | |
| |10 +--------+ | | | | |
| +----------| | | | | | |
| | +--| Active |---|-+ | | |
10,17| | 5,16| | |-------|---+ |
+-------+ 9 | 13 +->| | | | |
| Going |<--|----------+--------+ | | |
| Down | | 11| ^ | | |
+-------+ | | |5 | | |
^ | v | 6,12b| | |
|9 |10 +--------+ | |12a,14 |
| +----------| |---+ | |
| | Up |-------+ |
+------------------| |---------------+
+--------+
| ^
| |
+---+
11,13,16
Figure 3: Control Channel FSM
Event evCCDn always forces the FSM to the down state. Events
evHoldTimer and evReconfig always force the FSM to the Negotiation
state (either ConfSnd or ConfRcv).
11.2. TE Link FSM
The TE Link FSM defines the states and logics of operation of the LMP
TE Link.
11.2.1. TE Link States
An LMP TE link can be in one of the states described below. Every
state corresponds to a certain condition of the TE link and is
usually associated with a specific type of LMP message that is
periodically transmitted to the far end via the associated control
channel or in-band via the data links.
Down: There are no data links allocated to the TE link.
Init: Data links have been allocated to the TE link, but the
configuration has not yet been synchronized with the LMP
neighbor. The LinkSummary message is periodically
transmitted to the LMP neighbor.
Up: This is the normal operational state of the TE link. At
least one LMP control channel is required to be
operational between the nodes sharing the TE link. As
part of normal operation, the LinkSummary message may be
periodically transmitted to the LMP neighbor or generated
by an external request.
Degraded: In this state, all LMP control channels are down, but the
TE link still includes some data links that are allocated
to user traffic.
11.2.2. TE Link Events
Operation of the LMP TE link is described in terms of FSM states and
events. TE Link events are generated by the packet processing
routines and by the FSMs of the associated control channel(s) and the
data links. Every event has its number and a symbolic name.
Descriptions of possible events are given below.
1 : evDCUp: One or more data channels have been enabled and
assigned to the TE Link.
2 : evSumAck: LinkSummary message received and positively
acknowledged.
3 : evSumNack: LinkSummary message received and negatively
acknowledged.
4 : evRcvAck: LinkSummaryAck message received acknowledging the
TE Link Configuration.
5 : evRcvNack: LinkSummaryNack message received.
6 : evSumRet: Retransmission timer has expired and LinkSummary
message is resent.
7 : evCCUp: First active control channel goes up.
8 : evCCDown: Last active control channel goes down.
9 : evDCDown: Last data channel of TE Link has been removed.
11.2.3. TE Link FSM Description
Figure 4 illustrates operation of the LMP TE Link FSM in a form of
FSM state transition diagram.
3,7,8
+--+
| |
| v
+--------+
| |
+------------>| Down |<---------+
| | | |
| +--------+ |
| | ^ |
| 1| |9 |
| v | |
| +--------+ |
| | |<-+ |
| | Init | |3,5,6 |9
| | |--+ 7,8 |
9| +--------+ |
| | |
| 2,4| |
| v |
+--------+ 7 +--------+ |
| |------>| |----------+
| Deg | | Up |
| |<------| |
+--------+ 8 +--------+
| ^
| |
+--+
2,3,4,5,6
Figure 4: LMP TE Link FSM
In the above FSM, the sub-states that may be implemented when the
link verification procedure is used have been omitted.
11.3. Data Link FSM
The data link FSM defines the states and logics of operation of a
data link within an LMP TE link. Operation of a data link is
described in terms of FSM states and events. Data links can either
be in the active (transmitting) mode, where Test messages are
transmitted from them, or the passive (receiving) mode, where Test
messages are received through them. For clarity, separate FSMs are
defined for the active/passive data links; however, a single set of
data link states and events are defined.
11.3.1. Data Link States
Any data link can be in one of the states described below. Every
state corresponds to a certain condition of the data link.
Down: The data link has not been put in the resource pool
(i.e., the link is not ’in service’)
Test: The data link is being tested. An LMP Test message is
periodically sent through the link.
PasvTest: The data link is being checked for incoming test
messages.
Up/Free: The link has been successfully tested and is now put
in the pool of resources (in-service). The link has
not yet been allocated to data traffic.
Up/Alloc: The link is up and has been allocated for data
traffic.
11.3.2. Data Link Events
Data link events are generated by the packet processing routines and
by the FSMs of the associated control channel and the TE link.
Every event has its number and a symbolic name. Description of
possible data link events is given below:
1 :evCCUp: First active control channel goes up.
2 :evCCDown: LMP neighbor connectivity is lost. This indicates
the last LMP control channel has failed between
neighboring nodes.
3 :evStartTst: This is an external event that triggers the
sending of Test messages over the data link.
4 :evStartPsv: This is an external event that triggers the
listening for Test messages over the data link.
5 :evTestOK: Link verification was successful and the link can
be used for path establishment.
(a) This event indicates the Link Verification
procedure (see Section 5) was successful
for this data link and a TestStatusSuccess
message was received over the control
channel.
(b) This event indicates the link is ready for
path establishment, but the Link
Verification procedure was not used. For
in-band signaling of the control channel,
the control channel establishment may be
sufficient to verify the link.
6 :evTestRcv: Test message was received over the data port and a
TestStatusSuccess message is transmitted over the
control channel.
7 :evTestFail: Link verification returned negative results. This
could be because (a) a TestStatusFailure message
was received, or (b) the Verification procedure
has ended without receiving a TestStatusSuccess or
TestStatusFailure message for the data link.
8 :evPsvTestFail: Link verification returned negative results. This
indicates that a Test message was not detected and
either (a) the VerifyDeadInterval has expired or
(b) the Verification procedure has ended and the
VerifyDeadInterval has not yet expired.
9 :evLnkAlloc: The data link has been allocated.
10:evLnkDealloc: The data link has been de-allocated.
11:evTestRet: A retransmission timer has expired and the Test
message is resent.
12:evSummaryFail: The LinkSummary did not match for this data port.
13:evLocalizeFail: A Failure has been localized to this data link.
14:evdcDown: The data channel is no longer available.
11.3.3. Active Data Link FSM Description
Figure 5 illustrates operation of the LMP active data link FSM in a
form of FSM state transition diagram.
+------+
| |<-------+
+--------->| Down | |
| +----| |<-----+ |
| | +------+ | |
| |5b 3| ^ | |
| | | |7 | |
| | v | | |
| | +------+ | |
| | | |<-+ | |
| | | Test | |11 | |
| | | |--+ | |
| | +------+ | |
| | 5a| 3^ | |
| | | | | |
| | v | | |
|12 | +---------+ | |
| +-->| |14 | |
| | Up/Free |----+ |
+---------| | |
+---------+ |
9| ^ |
| | |
v |10 |
+---------+ |
| |13 |
|Up/Alloc |------+
| |
+---------+
Figure 5: Active LMP Data Link FSM
11.3.4. Passive Data Link FSM Description
Figure 6 illustrates operation of the LMP passive data link FSM in a
form of FSM state transition diagram.
+------+
| |<------+
+---------->| Down | |
| +-----| |<----+ |
| | +------+ | |
| |5b 4| ^ | |
| | | |8 | |
| | v | | |
| | +----------+ | |
| | | PasvTest | | |