Re: [PWE3] status signalling of MPLS PW state

[Luca Martini <luca@level3.net>]

Does anybody else agree with this different way of writing this ?
I think that pretty much either way works.

Luca


Hamid Ould-Brahim wrote:
> Luca,   > yes , i did that , look in the iana draft, it's in there. I
>  > left it in this
>  > thread for discussion only.
> Okay. I looked at the PW-IANA draft. I think that part needs to be 
> reworked in order to reflect exactly the usage of the status field.   In 
> pw-iana draft:   "   As specified in [1], a new PW status TLV contains a 
> 32 bit field, PW
>    status value 0 is reserved to clear all failures. PW Status Bits 0
>    through 4 are defined in this document. PW Status Bits 6 through 15
>    are to be assigned by IANA using the "IETF Consensus" policy defined
>    in RFC2434. PW Status Bits 16 through 23 are to be assigned by IANA,
>    using the "First Come First Served" policy defined in RFC2434. PW
>    Status Bits 24 through 31 are vendor-specific, and values in this
>    range are not to be assigned by IANA.
>
>    PW status is a 4 octet bit field as follows:
>
>            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"   
> Since the structure is a bit field and since in that structure some 
> bits/set of bits are reserved. The above codepoints do not exactly 
> reflect the intent. For example, it is not that 0x00000002 that makes 
> the local customer-facing PW receive fault but it is the setting of bit 
> number 1 that indicates this problem is happening.   I suggest to layout 
> the bit structure with each bit having its own description. Using the 
> pw-IANA description above (btw I think there is a typo with respect to 
> bit number 5 which appears as 6 in the iana draft), my suggestion is to 
> rewrite the above to:       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
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>    |N|I|E|R|T|  IANA ASSIGNED      |   IANA FCFS   |     VENDOR    |
>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>    N: The "not forwarding bit". When this bit is set, it indicates the
>       PE sending the status is in "not forwarding" state.
>    I: Local Customer-facing PW ( ingress ) Receive Fault
>    E: Local Customer-facing PW ( egress ) Transmit Fault
>    R: Local PSN-facing PW ( ingress ) Receive Fault
>    T: Local PSN-facing PW ( egress ) Transmit Fault
>
>    A value of 0x00000000 is reserved and indicates that the status
>    of the Pseudo-wire is forwarding.      Obviously the NIERT bits can 
> be set independently (and that    makes status combination).
> Hamid.
>  


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