rfc-7896

Update to the Include Route Object (IRO) Specification in the Path Computation Element Communication Protocol (PCEP)

D. Dhody

date2016-06 streamIETF areartg wgpce statusPROPOSED STANDARD pages5 canonicalhttps://www.rfc-editor.org/rfc/rfc7896 doi10.17487/RFC7896

The Path Computation Element Communication Protocol (PCEP) enables 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 does not specify if the IRO contains an ordered or unordered list of subobjects. 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 the handling of an attribute of the IRO's subobject, the L bit. This document updates RFC 5440 regarding the IRO specification.

updates

rfc-5440 — Path Computation Element (PCE) Communication Protocol (PCEP)

Extracted elements (7)

design-rationale §1

RFC 5440's original IRO specification was ambiguous about ordering and declared the L bit meaningless, leading to divergent implementations. This document was created to establish a standard representation and L bit semantics to ensure interoperability among PCEP implementations.

routing

interoperability-note §3

A conforming PCC that sends an IRO with strict hops (L bit unset) to a non-conforming PCE may receive an incorrect path, because the non-conforming PCE interprets all subobjects as loose hops regardless of the L bit.

routing

interoperability-note §3

A non-conforming PCC (pre-RFC 7896) that treats all IRO subobjects as loose hops and sends an IRO to a conforming PCE may unexpectedly cause the PCE to fail path computation, because the PCE now interprets unset L bits as strict hops.

routing

normative-requirement §2.1 MUST

The content of an IRO is an ordered list of subobjects representing a series of abstract nodes, as defined in Section 4.3.2 of RFC 3209. This updates RFC 5440 Section 7.12, which previously left ordering unspecified.

routing

normative-requirement §2.1 MUST

The L bit of an IRO subobject is set based on the loose or strict hop property: it is set if the subobject represents a loose hop, and not set if it represents a strict hop. Interpretation follows Section 4.3.3.1 of RFC 3209. This removes the prior RFC 5440 statement that 'the L bit of such sub-object has no meaning within an IRO.'

routing

protocol-element §2

The Include Route Object (IRO) is an optional PCEP object used to specify a set of network elements to be traversed in a computed path. This document clarifies that the IRO's subobject list is ordered and that the L bit encodes loose/strict hop semantics.

routing

security-consideration §4

The IRO specification update introduces no new security considerations beyond those in RFC 5440. Clarification of IRO ordering and L bit handling does not have a negative security impact. PCEP operates over TCP and security analysis for TCP-based routing protocols is covered in RFC 6952.

security, routing