Generalized MPLS (GMPLS) Protocol Extensions for Multi-Layer and Multi-Region Networks (MLN/MRN)
updates
- rfc-4202 — Routing Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)
- rfc-4203 — OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)
- rfc-4206 — Label Switched Paths (LSP) Hierarchy with Generalized Multi-Protocol Label Switching (GMPLS) Traffic Engineering (TE)
- rfc-4874 — Exclude Routes - Extension to Resource ReserVation Protocol-Traffic Engineering (RSVP-TE)
- rfc-4974 — Generalized MPLS (GMPLS) RSVP-TE Signaling Extensions in Support of Calls
- rfc-5307 — IS-IS Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)
Extracted elements (25)
Hybrid nodes in MRN environments have internal links between switching elements (e.g., PSC and TDM) with finite capacities that cannot be inferred from interface switching capabilities alone. A separate Interface Adjustment Capability Descriptor (IACD) is introduced to advertise these internal adjustment capacities so path computation can account for them when computing multi-region TE-LSPs.
In MRN signaling, when a TE link advertises multiple Switching Capabilities via multiple ISCD sub-TLVs, an ERO alone cannot select a particular SC. Rather than extending ERO inclusion semantics, this document extends the XRO to carry a Switching Capability subobject for exclusion, since concentrating exclusions in XRO avoids complex consistency checks and transpositions at FA-LSP head-ends.
For backward compatibility, edge LSRs MUST be able to process Call Attributes (Section 5.1) if edge-to-edge association is selected, and both edge and intermediate LSRs MUST support processing of the LSP ATTRIBUTE object (Section 5.2) if the Soft FA method is used.
For path-provisioned PSC LSPs, the Peak Data Rate in SENDER_TSPEC/FLOWSPEC MUST be set to 0. For L2SC LSPs, CIR, EIR, CBS, and EBS MUST be set to 0 in the Ethernet Bandwidth Profile TLV. For TDM and LSC LSPs, a NULL Label value is used to prevent data-plane resource allocation since labels are tightly coupled with resource allocation in those technologies.
The Call Inheritance Flag (bit 0 of Call Attributes Flags TLV) MUST be set to 1 to indicate that the established call association should be translated into a TE link advertisement. Its default value SHALL be 1. Setting it to 0 results in a hidden TE link or, if previously advertised, triggers deletion of the corresponding Opaque LSA (set to MaxAge) and the corresponding FA-LSP SHOULD be torn down.
The Lower Switching Capability field in the IACD sub-TLV MUST be set to the value of the Switching Capability of the ISCD sub-TLV advertised for the same TE link. If multiple ISCD sub-TLVs are advertised, the Lower SC value MUST be set to the SC to which the adjustment capacity is associated.
The Notify message establishing the edge-to-edge association MUST carry an LSP_TUNNEL_INTERFACE_ID Object to identify unnumbered and numbered FA-LSPs per RFC 3477 and RFC 4206.
The Upper Switching Capability field in the IACD sub-TLV MUST be set to one of the values defined in RFC 4202. Max LSP Bandwidth processing MUST follow the rules specified in RFC 4202.
The XRO SC subobject MUST follow the set of one or more numbered or unnumbered interface subobjects to which it refers. In the case of a loose-hop ERO subobject, the XRO SC subobject MUST precede the loose-hop subobject identifying the tail-end node/interface of the traversed region(s).
XRO Label subobjects MUST follow the numbered or unnumbered interface subobjects to which they refer and, when present, MUST also follow the Switching Capability subobject. The corresponding label values MUST be compatible with the SC capability to be explicitly excluded.
The Call Attributes Flags TLV (Type 1 within CALL_ATTRIBUTES) carries a 32-bit-aligned bit array. Unassigned bits MUST be set to zero on transmission. Absent bits (due to foreshortening or absent TLV) MUST be treated as present and zero.
The CALL_ATTRIBUTES object (class 202, C-Num form 11bbbbbb, C-Type 1) signals attributes for or reports operational state of a call, modeled on the LSP_ATTRIBUTES object from RFC 5420. LSRs that do not recognize it pass it transparently. It carries Call Attributes TLVs in its value field.
The IACD sub-TLV in IS-IS is an optional sub-TLV of the Extended IS Reachability TLV (TLV 22) with Type 27. Its format is identical to the OSPF variant. Multiple IACD sub-TLVs MAY be present and do not affect processing of the ISCD sub-TLV defined in RFC 5307.
The IACD sub-TLV is defined as an optional sub-TLV of the OSPF TE Link TLV (Type 2) with Type 25. Multiple IACD sub-TLVs MAY be present within a given TE Link TLV. Its presence does not modify the format or processing of the existing ISCD sub-TLV.
The Interface Adjustment Capability Descriptor (IACD) is a TE link sub-TLV that describes the adjustment capability between two switching layers at a hybrid node, including Lower SC, Lower Encoding, Upper SC, Upper Encoding, Max LSP Bandwidth at eight priority levels (IEEE 754 float, bytes/second), and variable Adjustment Capability-specific information.
The Pre-Planned LSP flag (bit 6 of the Attributes Flags TLV in LSP_ATTRIBUTES/LSP_REQUIRED_ATTRIBUTES per RFC 5420) controls whether an LSP is fully data-plane provisioned (value 0) or established only in the control plane without committing data-plane resources (value 1). Transitioning from 1 to 0 via re-signaling commits data-plane resources.
The XRO Label subobject (Type 3) complements RFC 4874 with label-based exclusion. Its encoding mirrors the Label ERO subobject from RFC 3473, substituting an L bit (0=MUST exclude, 1=SHOULD avoid) for the direction bit.
The XRO Switching Capability (SC) subobject (Type 35) enables explicit identification of switching capabilities to be excluded during multi-region resource selection. It carries an L bit (0=MUST exclude, 1=SHOULD avoid), Attribute field (1=applies to preceding interface subobject), and the Switching Cap value to exclude, with a fixed length of 4 bytes.
IANA created the CALL_ATTRIBUTES RSVP object class (class number 202, C-Type 1) and established a 'Call Attributes TLV' registry (types 0=Reserved, 1=Call Attributes Flags TLV; range 0–32767 RFC Required, 32768–65535 Private Use) and a 'Call Attributes Flags' registry (bit 0 = Call Inheritance Flag; RFC Required policy).
IANA registered the Interface Adjustment Capability Descriptor (IACD) as sub-TLV Type 25 of the OSPF TE Link TLV (Value 2) in the OSPF Traffic Engineering TLVs registry, and as sub-TLV Type 27 of IS-IS TLV 22 (and TLVs 141 and 222) in the IS-IS sub-TLV registry.
IANA registered two new XRO subobject types for RFC 4874 C-Type 1: Type 3 (Label) and Type 35 (Switching Capability). IANA also registered Pre-Planned LSP flag as bit 6 in the Attributes Flags TLV of RFC 5420.
Call initiation MUST remain strictly under control of the TE domain administrator. Edge nodes MUST ensure isolation of their call controller so it is not reachable via external TE domains. Security associations MUST be established between edge nodes initiating and terminating calls, and IKEv2 (RFC 5996) MUST be used for mutual authentication and maintaining these security associations to prevent man-in-the-middle attacks.
Each Call Attributes TLV is encoded as: Type (16 bits), Length (16 bits, total including T+L+V), Value (variable). The TLV MUST be padded to 4-octet alignment with zero to three trailing zeros; the Length field does not count padding.
The IACD sub-TLV (OSPF Type 25, IS-IS Type 27) encodes: Lower SC (8 bits), Lower Encoding (8 bits), Upper SC (8 bits), Upper Encoding (8 bits), followed by eight 4-octet IEEE floating-point Max LSP Bandwidth fields (priority 0–7), and variable Adjustment Capability-specific information.
XRO SC subobject (Type 35): L bit (1 bit), Type=35 (7 bits), Length (8 bits, value=4), Attribute (8 bits, 0=reserved, 1=applies to preceding interface subobject), Switching Cap (8 bits).