Hi Ali,

Thanks a lot for your email.

Speaking as chair, could you please highlight to the working group the 
rationale of the change and associated use case ? Just to give the context…


To WG Folks,

Please review this change with care. There are two points that I would like to 
highlight:


-          We need to ensure that there is no current implementation using the 
value 255. Please raise your voice if you are aware of one.

-          The encoding of the mcast DF election algorithm could now be 
decorrelated from the base DF alg (applicable to Broadcast and Unknown 
traffic). The proposed encoding uses 3 bits for the mcast DF alg. We have to 
ensure that:

o   3 bits is enough

o   There will “never” (at least not mid term) be a requirement for variable 
parameters for mcast DF election (like in DF pref draft).

I will let some time to think about this change and raise your support or 
concerns.
The poll starts now and will end on Dec 5th.
This DF election framework will be an important component of EVPN and we need 
to ensure that we are providing the required level of flexibility to address 
the different use cases.

Thanks !


From: Ali Sajassi (sajassi) [mailto:[email protected]]
Sent: Wednesday, November 21, 2018 00:25
To: [email protected]
Cc: [email protected]
Subject: minor change to draft-ietf-bess-evpn-df-election-framework-05


Folks,

The authors of  the above draft are purposing a minor change to the draft and 
since the draft is currently under review by IESG, the chair has asked to send 
an email to the WG to solicit inputs and ensuring that there is no objection. 
The proposed change is as follow:

Currently, the above draft defines an eight-bit “DF Alg” field as shown in the 
following figure. The proposed change is to reduce the eight-bit field to a 
five-bit field.

*** OLD Text

              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
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             | Type=0x06     | Sub-Type(0x06)|   DF Alg      |    Bitmap     |
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             |     Bitmap    |            Reserved                           |
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   o DF Alg (1 octet) - Encodes the DF Election algorithm values
     (between 0 and 255) that the advertising PE desires to use for the
     ES. This document requests IANA to set up a registry called "DF Alg
     Registry" and solicits the following values:

     - Type 0: Default DF Election algorithm, or modulus-based algorithm
       as in [RFC7432<https://tools.ietf.org/html/rfc7432>].

     - Type 1: HRW algorithm (explained in this document).

     - Types 2-254: Unassigned.

     - Type 255: Reserved for Experimental Use.

***NEW Text

              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
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             | Type=0x06     | Sub-Type(0x06)| RSV |  DF Alg  |    Bitmap    |
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             |     Bitmap    |            Reserved                           |
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   o DF Alg (5 bits) - Encodes the DF Election algorithm values
     (between 0 and 31) that the advertising PE desires to use for the
     ES. This document requests IANA to set up a registry called "DF Alg
     Registry" and solicits the following values:

     - Type 0: Default DF Election algorithm, or modulus-based algorithm
       as in [RFC7432<https://tools.ietf.org/html/rfc7432>].

     - Type 1: HRW algorithm (explained in this document).

     - Types 2-30: Unassigned.

     - Type 31: Reserved for Experimental Use.


The remaining 3-bits of that octet (bits 16, 17, and 18 in the above figure) 
will be used by per-mcast-flow-df-election and will be expanded and described 
there and will be discussed in the next IETF as usual at the BESS WG session.

Regards,
Ali & other co-authors

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