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RE: LMP Question: TE link FSM
Hello Jonathan,
The new Init state seems useful and I have no difficulties with it.
However, I still have a couple of problems with the TE FSM:
1) It appears that the DOWN state has a functioning CC but no links.
Transition #9 moves from DEGRADED, where there are links but no CC, to
DOWN, where there is a CC but no links. This looks like 2 transitions to
me, because 2 independent things happened. At least it's different from
transition #9 from UP, which has CC and links, to DOWN, which has CC and
no links.
2) It seems to me that if there is an INIT state, the CC could go down
there too.
My goal here is to have a state machine which is useful (i.e.
explanatory and representative) and has feasible transitions between
states. I don't care about the labels of the states.
So here's another proposal which I believe keeps everything in your Oct
15th version and addresses the two points above:
--------------------
Off: No control channel, no 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.
Up: This is the normal operational state of the TE link. At
least
one primary CC is required to be operational between the
nodes
sharing the TE link.
Degraded: In this state, all primary CCs are down, but the TE link still
includes some allocated data links.
Inactive: No control channel, some data links locally allocated to TE.
1 : evDCUp: One or more data channels have been added 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.
+--------+
| |
+------------>| Off |
| | |
| +--------+
| | ^
| 7| |8
| v |
| +--------+
| | |
| | Down |<---------+
9| | | |
| +--------+ |
| | ^ |
| 1| |9 |
| v | |
+--------+ 7 +--------+ |
| |------>| |<-+ |
| Inact | | Init | |3,5,6 |9
| |<------| |--+ |
+--------+ 8 +--------+ |
| |
2,4| |
v |
+--------+ 7 +--------+ |
| |------>| |----------+
| Deg | | Up |
| |<------| |
+--------+ 8 +--------+
| ^
| |
+--+
2,3,4,5,6
Regards,
George R. Young
edgeflow Inc.
329 March Rd., Kanata, ON, Canada, K2K 2E1
phone: +1 613-270-9279 Ext 287
fax: +1 613-270-9268
>-----Original Message-----
>From: Jonathan Lang [mailto:jplang@calient.net]
>Sent: Monday, October 15, 2001 2:17 PM
>To: George Young
>Cc: Jonathan Lang
>Subject: RE: LMP Question: TE link FSM
>
>
>George,
> I agree that we need an intermediate state, but I don't
>think it should be
>the Empty state. We have modified the document as follows:
>
>Updated description
>--------------------
>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.
>Up: This is the normal operational state of the TE link. At least one
>primary
> CC is required to be operational between the nodes sharing
>the TE link.
>Degraded: In this state, all primary CCs are down, but the TE
>link still
>includes
> some allocated data links.
>
>1 : evDCUp: One or more data channels have been added 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.
>
> +--------+
> | |
> +------------>| Down |<---------+
> | | | |
> | +--------+ |
> | | ^ |
> | 1| |9 |
> | v | |
> | +--------+ |
> | | |<-+ |
> | | Init | |3,5,6 |9
> | | |--+ |
> 9| +--------+ |
> | | |
> | 2,4| |
> | v |
> +--------+ 7 +--------+ |
> | |------>| |----------+
> | Deg | | Up |
> | |<------| |
> +--------+ 8 +--------+
> | ^
> | |
> +--+
> 2,3,4,5,6
>
>
>> -----Original Message-----
>> From: George Young [mailto:george.young@edgeflow.com]
>> Sent: Tuesday, October 09, 2001 12:24 PM
>> To: ccamp@ops.ietf.org
>> Subject: LMP Question: TE link FSM
>>
>>
>> I have some problems with the TE FSM in draft-ietf-ccamp-lmp-01.txt.
>>
>> There are 4 combinations of CC UP/Down and None/Some Data Channels
>> Allocated, but only 3 states in the FSM. Also, the TE Link
>> Events should
>> be related to whether the links are allocated to the TE, not whether
>> they are currently carrying data. Transition 4 is shown but the note
>> indicates it should not happen.
>>
>> Here is a proposal for a modified TE Link FSM.
>>
>> 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 control channels available and no data
>> links are allocated to the TE link.
>>
>> Empty: At least one control channel is available and no data
>> links are allocated to the TE link.
>>
>> Up: This is the normal operational state of the TE
>> link. At
>> least one primary CC and one or more data-bearing links
>> is
>> required to be operational between the nodes sharing
>> the TE
>> link.
>>
>> Degraded: In this state, all primary CCs are down, but
>> the TE link
>> still includes some allocated data links.
>>
>> 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 primary control
>> channel(s) and the data links. Every event has its number and a
>> symbolic name. Description of possible control channel events is
>> given below.
>>
>> 1 : evCCUp: First active CC goes Up.
>> 2 : evDCUp: One or more data channels are UP and
>> LinkSummaryAck message has been received
>> acknowledging the TE link configuration.
>> 3 : evDCDown: Last data channel of TE link has been
>> removed.
>> 4 : evCCDown: Last active CC goes Down.
>> 5 : evReconfig: Successful TE reconfiguration, LinkSummaryAck
>> message
>> 6 : evReconfigFail: Unsuccessful TE reconfiguration attempt,
>> LinkSummaryNack
>> message
>>
>> 11.2.3. TE Link FSM Description
>>
>> Figure 4 illustrates operation of the LMP TE Link FSM in
>a form of
>> a state transition diagram.
>>
>>
>> +--------+
>> | |
>> | Down |
>> | |
>> +--------+
>> | ^
>> 1| 4|
>> | |
>> v |
>> +--------+
>> | |<---+
>> | Empty | | 6
>> | |----+
>> +--------+
>> | ^
>> 2| 3|
>> | |
>> v |
>> +--------+ 1 +--------+
>> | |------>| |<---+
>> | Deg | | Up | | 6
>> | |<------| |----+
>> +--------+ 4 +--------+
>> | ^
>> | |
>> +---+
>> 5
>>
>> 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.
>>
>> Regards,
>> George R. Young
>> edgeflow Inc.
>> 329 March Rd., Kanata, ON, Canada, K2K 2E1
>> phone: +1 613-270-9279 Ext 287
>> fax: +1 613-270-9268
>>
>