Re: Moving right along ... generalized-signaling-06

[Stephen Trowbridge <sjtrowbridge@lucent.com>]

John,
The problem here is that this is not compatible with transport plane protection.
Assume you do 1:n MSP protection according to ITU Rec. G.841. The operation of
the protection group is controlled by exchange of the K1, K2 bytes in the
MSOH of the PROTECTION MS. If the control plane reuses the protection MS at
for a different LSP at a time when the state of the protection group is
"No Request" (assuming no extra traffic carried on the protection section in the
transport plane), this disables the protection since the endpoints of the
protection group are no longer able to exchange K1, K2 over the protection
channel. Even though the payload is unused and irrelevant to the transport
plane at this point, the exchange of overhead is essential to proper operation
of the protection group.
Regards,
Steve

John Drake wrote:
> 
> Steven,
> 
> The basic idea is that if a connection is of type 'secondary', then other
> LSPs of type 'primary' between the same or different source/destination
> pairs MAY use its resources in intermediate nodes, until that LSP is
> converted into a 'primary' with a subsequent Path/Resv flow.  At this point,
> other LSPs that were using its resources may get pre-empted.  Think of the
> primary/secondary mechanism as a way to ensure temporal priority while
> allowing network resources to be re-used; i.e., an LSP of type 'secondary'
> is carrying no data.
> 
> So in the 1:1 case the protect LSP could be established either as a primary
> or secondary LSP, while in the 1:N case the protect LSP would be established
> as a secondary.
> 
> Thanks,
> 
> John
> 
> -----Original Message-----
> From: Stephen Trowbridge [mailto:sjtrowbridge@lucent.com]
> Sent: Thursday, December 13, 2001 12:15 PM
> To: John Drake
> Cc: Maarten Vissers; ccamp@ops.ietf.org
> Subject: Re: Moving right along ... generalized-signaling-06
> 
> John,
> It would seem from this standpoint, ANY transport plane protection
> must use "primary" for all trails. You have already made this argument
> for the 1+1 case to carry the permanently bridged copy of the payload.
> 
> In 1:1 or 1:n, when protection is not being used to carry one/any of
> the normal traffic signals, it may either carry a null signal (no bridge)
> or transport plane extra traffic. Even if the transport plane has only
> a null signal on protection, the control plane cannot itself place extra
> traffic on any portion of the end-to-end protection channel as this is
> where the APS protocol is carried to coordinate the 1:1 or 1:n protection.
> The protection channel overhead is chosen to carry the APS since it is
> necessary to exchange APS bytes to complete a switch when working channels
> are failed. If the protection channel has failed and APS cannot be
> exchanged,
> normal traffic signals will not be selected from protection.
> Regards,
> Steve
> 
> John Drake wrote:
> >
> > Maarten,
> >
> > That's fine, however it's beside the point.  The semantics of
> > Primary/Secondary refer to the control plane and whether the node
> > establishing a given LSP is planning to use it at the time it's
> established
> > or at a later time.  As I indicated in an earlier note, 1+1 transport
> plane
> > protection would be accomplished in the control plane by establishing two
> > LSPs of type Primary.  The control plane really doesn't care which LSP the
> > transport plane is using as Working and which as Protect, although that
> > information is available to the control plane at the LSP endpoints.
> >
> > Thanks,
> >
> > John
> >
> > -----Original Message-----
> > From: Maarten Vissers [mailto:mvissers@lucent.com]
> > Sent: Thursday, December 13, 2001 12:15 AM
> > To: ccamp@ops.ietf.org
> > Subject: Re: Moving right along ... generalized-signaling-06
> >
> > There exist well defined protection terminology in ITU-T for the transport
> > plane. "Working" and "Protection" are being used and not
> primary/secondary.
> > E.g.
> > a 1+1 architecture has one working connection, one protection connection
> and
> > a
> > permanent bridge.
> >
> > Besides working/protection indication for the transport entity, there is
> > - "active" and "standby" to indicate if the signal is selected from the
> > working
> > or protection transport entity; i.e. if selector selects from working, the
> > working is active and protection is standby, if the selector selects from
> > protection the working is standby and the protection is active.
> > - "normal" and "extra traffic" signal. The normal signal is protected.
> >
> > Regards,
> >
> > Maarten
> >
> > neil.2.harrison@bt.com wrote:
> > >
> > > Jonathan....review the text below....I think the problem is 1:1.
> > >
> > > neil
> > >
> > > > -----Original Message-----
> > > > From: Jonathan Lang [mailto:jplang@calient.net]
> > > > Sent: 12 December 2001 17:46
> > > > To: 'Ben Mack-Crane'; John Drake
> > > > Cc: Lou Berger; Kireeti Kompella; ccamp@ops.ietf.org
> > > > Subject: RE: Moving right along ... generalized-signaling-06
> > > >
> > > >
> > > > Ben,
> > > >   Please see inline.
> > > >
> > > > Thanks,
> > > > Jonathan
> > > >
> > > > > -----Original Message-----
> > > > > From: Ben Mack-Crane [mailto:Ben.Mack-Crane@tellabs.com]
> > > > > Sent: Wednesday, December 12, 2001 8:56 AM
> > > > > To: John Drake
> > > > > Cc: Lou Berger; Kireeti Kompella; ccamp@ops.ietf.org
> > > > > Subject: Re: Moving right along ... generalized-signaling-06
> > > > >
> > > > >
> > > > > See comment below.
> > > > >
> > > > > Regards,
> > > > > Ben
> > > > >
> > > > > John Drake wrote:
> > > > > >
> > > > > > Snipped
> > > > > >
> > > > > > -----Original Message-----
> > > > > > From: Ben Mack-Crane [mailto:Ben.Mack-Crane@tellabs.com]
> > > > > > Sent: Tuesday, December 11, 2001 6:38 AM
> > > > > > To: Lou Berger
> > > > > > Cc: Kireeti Kompella; ccamp@ops.ietf.org
> > > > > > Subject: Re: Moving right along ... generalized-signaling-06
> > > > > >
> > > > > > >
> > > > > > > >
> > > > > > > >7) In Protection Information it states "The resources
> > > > > allocated for a
> > > > > > > >    secondary LSP MAY be used by other LSPs until the
> > > > > primary LSP fails
> > > > > > > >    over to the secondary LSP."  This may not always be
> > > > > the case.  An
> > > > > > > >    explicit flag indicating whether or not extra
> > > > > traffic may use the
> > > > > > > >    secondary path resources is needed.
> > > > > > >
> > > > > > > ??? This is the purpose of this bit.
> > > > > >
> > > > > > This is not clear from the definition.  The bit is defined
> > > > > as indicating
> > > > > > the LSP is a secondary (or protecting) LSP and in 1+1
> > > > protection the
> > > > > > secondary LSP may not be used for extra traffic.
> > > > > >
> > > > > > Perhaps the problem here is that protection features are
> > > > > being defined
> > > > > > before the protection framework and requirements are
> > > > done.  Is this
> > > > > > presupposing some particular outcome of the recovery work in CAMP?
> > > > > >
> > > > > > JD:  I think the definition of the bit is fine.  For both
> > > > > 1+1 and 1:1
> > > > > > protection, there would be a pair of Primary LSPs between
> > > > the source
> > > > > > and destination, rather than a Primary and a Secondary.
> > > > >
> > > > > This is an unusual use of terms.  I have never encountered a case
> > > > > where both the working and recovery paths are call "primary."
> > > > >
> > > > > This is not consistent with either draft-mpls-recovery-framework
> > > > > or with draft-lang-ccamp-recovery.  I think this is a sign that the
> > > > > protection work is immature and not ready for progressing to RFC.
> > > > >
> > > > For 1+1 path protection, both working/recovery paths are
> > > > carrying user data
> > > > traffic and it is an endpoint decision as to which path is
> > > > actually the
> > > > working/recovery path.  At a transit node, both paths need to
> > > > be treated as
> > > > primary, as the resources are currently being used and
> > > > obviously can't be
> > > > used for Extra Traffic.
> > > >