Re: [bess] Mail regarding draft-ietf-bess-rfc7432bis

["Matthew Bocci (Nokia)" <[e-mail]>]

Hi Authors

Resending this and including the WG. I believe this is a similar question to the one posted by Menachem on RFC8214.

Thanks in advance

Matthew

From: Matthew Bocci (Nokia) <[e-mail]>
Date: Monday, 15 January 2024 at 12:40
To: [e-mail] <[e-mail]>
Cc: [e-mail] <[e-mail]>
Subject: Mail regarding draft-ietf-bess-rfc7432bis
Hi Authors

There is there following restriction (highlighted in yellow) on the use of the control word in EVPN where the EL/ELI is used. I know this was inherited from RFC7432, but do you know why this is the case (in particular a SHOULD NOT)?

The head end PE has no idea what hashing mechanism is actually used downstream, regardless of whether the entropy label is inserted by it. The entropy label is just there to provide additional flow information if the downstream P router is load balancing based on the label stack, but it does not in itself prevent the P router from scanning below the bottom of stack and instead load balancing on the payload after checking the MPLS first nibble. This also seems to be superseded by RFC8469 and all the discussion over the years about making CW mandatory for MPLS-based services . It is also worth noting that CW is not just to prevent aliasing between IP and Ethernet traffic, but can be used to indicate OAM or other types of maintenance packets.

Can we just remove the text in yellow?

Thanks

Matthew


In order to avoid frame misordering described above, the following
   network-wide rules are applied:

   *  If a network uses deep packet inspection for its ECMP, then the
      the following rules for "Preferred PW MPLS Control Word" [RFC4385]
      apply:

      -  It MUST be used with the value 0 (e.g., a 4-octet field with a
         value of zero) when sending unicast EVPN-encapsulated packets
         over an MP2P LSP.

      -  It SHOULD NOT be used when sending EVPN-encapsulated packets
         over a P2MP or P2P RSVP-TE LSP.

      -  It SHOULD be used with the value 0 when sending EVPN-
         encapsulated packets over a mLDP P2MP LSP.  There can be
         scenarios where multiple links or tunnels can exist between two
         nodes and thus it is important to ensure that all packets for a
         given flows take the same link (or tunnel) between the two
         nodes.

   *  If a network uses entropy labels per [RFC6790], then the control
      word SHOULD NOT be used.