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RE: LMP Question: TE link FSM
George,
Please see inline.
Thanks,
Jonathan
> -----Original Message-----
> From: George Young [mailto:george.young@edgeflow.com]
> Sent: Tuesday, October 16, 2001 6:45 AM
> To: Jonathan Lang
> Cc: ccamp@ops.ietf.org
> Subject: 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.
The DOWN state does not assume there is/isn't a functioning CC. Transition
#9 moves from a state where there are links (but no CC) to DOWN where there
are no links (and in this case no CC).
>
> 2) It seems to me that if there is an INIT state, the CC could go down
> there too.
I'm not sure I understand this comment. The CC has its own FSM that it goes
through to come back up.
>
> 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
> >>
> >
>