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RE: [PWE3] status signalling of MPLS PW state
Luca,
The problem with setting the CE facing administrative status to down as a
way to tear down the PW is that in case of logical attachments circuits
(like VLAN as example) you may do not have one. Another reason as I stated
earlier is that the physical interface administrative status may be used
separately from the PW administrative status.
An EMS application has a separate admin can be used for tearing the PW. If
an implementation want to tie it together to the physical port admin it is
OK, but should be left for the implementer decision.
If there is an agreement on that, than there is a need in the status to
inform about the physical port administrative status.
David
> -----Original Message-----
> From: Luca Martini [mailto:luca@level3.net]
> Sent: Friday, June 13, 2003 8:18 PM
> To: David Allan
> Cc: 'Andrew G. Malis'; Himanshu Shah; Hamid Ould-Brahim; pwe3@ietf.org
> Subject: Re: [PWE3] status signalling of MPLS PW state
>
>
> Andy helped me get to the version below.
>
> I changed to a PW status TLV , that is used in the LDP
> notification message.
> ( it makes coding a little harder , but it's difficult to
> justify another
> message type. )
> Also changed the definitions of the PW faults.
> Now there are 32 bits of PW status.
> I still need to finish a iana section to allocate more bits.
>
> any more comments ?
>
> Luca
> .Pb "Signaling of Pseudo Wire Status"
>
> .Pc "Use of Label Mappings."
> The PEs MUST send PW label mapping messages to their peers as
> soon as the PW
> is configured and administratively enabled, regardless of the
> CE-facing
> interface state. The PW label should not be withdrawn unless the user
> administratively configures the CE-facing interface down (or the PW
> configuration is deleted entirely). A simple label withdraw
> method SHOULD
> also be supported as an alternative.
>
> .Pc "Signaling PW status."
> The PE devices use an LDP TLV to indicate status to their
> remote peers. This
> PW Status TLV contains more information than the alternative
> simple Label
> Withdraw message.
>
> The format of the PW Status TLV is:
> .DS 0 0
> 0 1 2 3
> 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |1|0| PW Status (0x0???) | Length |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | Status Code |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> .DE
>
> Where status is a 4 octet bit field:
>
> .nf
> 0x00000000 - Pseudo Wire forwarding ( clear all failures )
> 0x00000001 - Pseudo Wire Not Forwarding
> 0x00000002 - Local Customer-facing PW ( ingress ) Receive Fault
> 0x00000004 - Local Customer-facing PW ( egress ) Transmit Fault
> 0x00000008 - Local PSN-facing PW ( ingress ) Receive Fault
> 0x00000010 - Local PSN-facing PW ( egress ) Transmit Fault
> .En
>
> The above status codes can be logically combined to indicate
> more then a
> single failure at once. Each fault can be cleared by sending
> an appropriate
> status message with the respective bit cleared. The presence
> of the lowest
> bit (PW Not Forwarding) acts only as a generic failure
> indication when there
> is a link-down event for which none of the other bits apply.
>
> The Status TLV is transported to the remote PW peer via the
> LDP notification
> message. The format of the Notification Message is:
>
> .DS 0 0
> 0 1 2 3
> 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |1| Notification (0x0001) | Message Length |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | Message ID |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | PW FEC TLV |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | PW Status TLV |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> .DE
>
> The PW FEC TLV SHOULD not include the interface parameters as they are
> ignored in the context of this message. When a PE's CE-facing
> interface
> encounters an error, use of the new message allows the PE to
> send a single
> Status message, using a PW FEC TLV with only the group ID
> set, to denote
> this change in status for all affected PW connections.
>
>
>
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