The MPLS WG Archive

[sven.van_den_bosch@alcatel.be]

Hi,

During the MPLS meeting there was some discussion on our proposal (see
draft-vandenbosch-mpls-fa-considerations-01.txt) to add an additional
sub-TLV (subTLV 10) to the resource class specification in
draft-katz-yeung-ospf-traffic-06.txt. This subTLV could exist only in
combination with subTLV9 in which case subTLV9 would denote resource
classes to be used in an INCLUDE statement and subTLV10 in an EXCLUDE
statement (example given in the draft).
During the discussion it was made clear that the solution would cover most,
but not all cases. Some analysis is provided below:
- Elementary resource class specifications:
  . INCLUDE ANY: can be converted to OR-list of INCLUDEs
  . INCLUDE ALL: addressed for FA by sub-TLV 9
  . EXCLUDE ANY: seems pointless, OR-list of EXCLUDEs
  . EXCLUDE ALL: addressed for FA by new sub-TLV 10
- How to handle combinations: any AND/OR list of the previous
  . INCLUDE(X) AND INCLUDE(Y) == INCLUDE(X,Y)
  . INCLUDE(X) OR INCLUDE(Y) == ?
  . EXCLUDE(X) AND EXCLUDE(Y) == EXCLUDE(X,Y)
  . EXCLUDE(X) OR EXCLUDE(Y) == EXCLUDE(X,Y)
  . INCLUDE(X) AND EXCLUDE(Y) == INCLUDE(X) if X,Y non-overlapping
  . INCLUDE(X) OR EXCLUDE(Y) == EXCLUDE(Y), If X,Y non-overlapping

Note that a provider will be able to know whether or not it is safe to use
this (by not specifying INC OR INC) and that the solution has mnore general
applicability (e.g. for bundled links). There was some support for this
during the meeting. If this is felt to be useful, we would like to request
this modification in the appropriate WGs (OSPF,ISIS) with support from the
MPLS community.

Best regards,
Sven.