[mpls] ELI as a reserved label

[Curtis Villamizar <[e-mail]>]

The Entropy Label Indicator (ELI) is called for in
draft-kompella-mpls-entropy-label-01.txt

After brief discussion with Stewart and with Kireeti and Lucy Yong,
there were three uses of ELI that would benefit from making the ELI a
reserved label.  It may be premature to make any such request and the
remaining reserved label number space is sparse, so this will be
floated as a separate draft, and put on hold awaiting advancement of
the drafts that depend on it.

The three benefits of making ELI a reserved label are in:

  1.  Extending any use of entropy-label to P2MP (where there are
      multiple egress and the possibility of each egress requiring a
      separate entropy label value is problematic for the ingress).

  2.  Extending any use of entropy-label to any arbitrary position in
      the label stack such that in an aggregation LSP with aggregates
      both MPLS-TP and MPLS LSP, load split on the MPLS LSPs is
      simplified and not impacted by limiting label stack depth for
      the MPLS-TP LSPs.  This is when label stack hash is limited to
      support MPLS-TP as proposed in
      draft-villamizar-mpls-tp-multipath-00.txt .

  3.  Providing a means to carry indication of large flow as described
      in draft-yong-pwe3-enhance-ecmp-lfat-01.txt and
      draft-yong-pwe3-lfc-fat-pw-01.txt without changing the use of TC
      in a forwarding LSP label.

This would reuse one reserved label for three purposes.

This email is to gauge the reaction to this proposal (preferably among
those familiar with these drafts) before taking the time to write a
new draft proposing that a reserved label be allocated.

Curtis