Update to Include Route Object
(IRO) specification in Path Computation Element communication
Protocol (PCEP)Huawei TechnologiesDivyashree Techno Park, WhitefieldBangaloreKarnataka560066Indiadhruv.ietf@gmail.com
Routing
PCE Working Group
The Path Computation Element Communication Protocol (PCEP) provides
for communications between a Path Computation Client (PCC) and a
PCE, or between two PCEs. RFC 5440 defines the Include Route Object
(IRO) to specify network elements to be traversed in the computed
path. The specification did not specify if the IRO contains an
ordered or un-ordered list of sub-objects. During recent discussions,
it was determined that there was a need to define a standard
representation to ensure interoperability. It was also noted
that there is a benefit in handling of an attribute of the IRO's
sub-object, the Loose hop bit (L bit).This document updates RFC 5440 regarding the IRO specification.The Path Computation Element Communication Protocol (PCEP) provides
for communications between a Path Computation Client (PCC) and a PCE,
or between two PCEs. defines the Include
Route Object (IRO) to specify network
elements to be traversed in the computed path. The specification did
not define if the IRO is an ordered or un-ordered list of sub-objects.
In addition, it defined the Loose hop bit (L bit) to have no meaning
within an IRO. describes the use of an IRO to indicate the sequence of
domains to be traversed during inter-domain path computation.During recent discussions, it was determined that there was a need
to define a standard representation to ensure interoperability.This document updates the IRO specifications in section 7.12 of
.Section 7.12 of describes the IRO as an optional object used to specify
a set of network elements to be traversed in the computed path.
It stated that the Loose hop bit (L bit) in the sub-object has
no meaning within an IRO. It did not mention if the IRO contains an ordered or
un-ordered list of sub-objects. Section 7.12 of regarding the IRO
specification is updated to remove the last line in the section 7.12
of , that states : Further, the Section 7.12 of is updated
to add the following two statements at the end of the first paragraph. - The content of an IRO is an ordered list of sub-objects
representing a series of abstract nodes (refer to section 4.3.2
of ). - The L Bit of an IRO sub-object is set based on the loose or strict
hop property of the sub-object; it is set
if the sub-object represents a loose hop. If the bit is not set, the
sub-object represents a strict hop. The
interpretation of the Loose bit (L bit) is as per section 4.3.3.1 of .Because of the lack of clarity in , it is possible
to encounter implementations that always interpret the IRO sub-objects as loose.
When these implementations interwork with an implementation conforming to
this document, the following impact might be seen:
If a non-conforming (to this document) PCC sends an IRO to a
conforming (to this document) PCE, then the PCE may unexpectedly
fail to find a path (since the PCC may think of the IRO sub-objects
as loose hops, but the PCE interprets them as strict hops).If a conforming PCC sends an IRO containing strict hops to a
non-conforming PCE, then the PCE may erroneously return a path
that does not comply with the requested strict hops (since the PCE
interprets them all as loose hops). The PCC may check the
returned path and find the issue or it may end up using an incorrect
path.This update in the IRO specification does not introduce any
new security considerations, apart from those mentioned in
. Clarification in the
supported IRO ordering or Loose hop bit handling will not have any negative security impact.
It is worth noting that PCEP operates over TCP. An analysis of the
security issues for routing protocols that use TCP (including PCEP)
is provided in .This document makes no requests to IANA for action.A special thanks to PCE chairs for guidance regarding this work.Thanks to Francesco Fondelli for his suggestions in clarifying the L bit usage.Thanks to Adrian Farrel for his review and comments.Thanks to Jonathan Hardwick for document shepherding and providing text in .Thanks to Deborah Brungard for her comments and being the responsible AD.Thanks to Peter Yee for Gen-ART review.Thanks to Alvaro Retana for comments during the IESG review.