GMPLS Signaling Extensions for Control of Evolving G.709 Optical Transport Networks
updated by
- rfc-7892 — IANA Allocation Procedures for the GMPLS OTN Signal Type Registry
updates
- rfc-4328 — Generalized Multi-Protocol Label Switching (GMPLS) Signaling Extensions for G.709 Optical Transport Networks Control
Extracted elements (27)
A new OTN-TDM Switching Type is introduced (defined in RFC 7138) rather than reusing the existing G.709 switching type from RFC 4328, specifically to support backward compatibility with RFC 4328 while enabling control of new G.709-2012 ODU containers.
The G-PID value 47 was renamed from 'G.709 ODUj' to 'ODU-2.5G' to clarify it applies specifically to 2.5 Gbps TS granularity, since the new ODU-1.25G (value 66) and ODU-any (value 67) G-PIDs are needed to distinguish 1.25 Gbps granularity interfaces introduced by G.709-2012.
The ODUflex(CBR) bit rate tolerance (100 ppm) is implicit in the Signal Type and not explicitly signaled, while the nominal bit rate is signaled as an IEEE 754 single-precision float. This allows nodes to compute the exact number of tributary slots for each HO ODUk link independently, since TS bit rates differ between ODU2, ODU3, and ODU4.
Nodes supporting this document SHOULD support RFC 7138 for backward compatibility with deployed RFC 4328 implementations. A node supporting both sets of procedures is not required to act as a signaling version translator. Nodes that do not support this document will generate a PathErr with 'Routing problem/Switching Type' per RFC 3473.
VCAT (Virtual Concatenation) is supported only for ODU1, ODU2, and ODU3 Signal Types per G.709-2012; VCAT of OPU0, OPU2e, OPU4, and OPUflex is not supported. The One LSP approach for VCGs requires the explicit ordered list of labels to reflect the order of VCG members.
For hitless ODUflex(GFP) bandwidth adjustment, the Shared Explicit (SE) style MUST be used when creating a resizable ODUflex connection (Signal Type = 21). If SE style is not used when performing bandwidth adjustment, an error with 'Conflicting reservation style' MUST be generated.
For non-ODUflex Signal Types, the Bit_Rate field MUST be set to zero on transmission and MUST be ignored on receipt; transit nodes SHOULD pass it unmodified.
For ODUflex Signal Types, the NVC field MUST be set to 0 and the Multiplier (MT) field MUST be set to 1.
For ODUk-to-OTUk mapping, the Length field MUST be set to 0 and the Bit Map MUST NOT be included. The TPN field MUST be set to 0.
If the MT field is received with a zero value, the node MUST generate a PathErr with 'Traffic Control Error/Bad Tspec value'. If Signal Type is not ODU1/ODU2/ODU3 and NVC is not 0, the node MUST similarly generate a PathErr.
Intermediate and egress nodes MUST verify that they and their interfaces can support the requested Signal Type, NVC, and Bit_Rate values; if not, the node MUST generate a PathErr with 'Traffic Control Error/Service unsupported'.
The Bit_Rate field for ODUflex(CBR) MUST be used to determine the actual bandwidth to correctly compute the number of tributary slots N to reserve, using a ceiling formula that accounts for bit rate tolerances.
The Bit_Rate field for ODUflex(GFP) MUST be equal to one of the 80 values derived from n*ODU2.ts (n=1..8), n*ODU3.ts (n=9..32), or n*ODU4.ts (n=33..80), as recommended by G.709-2012.
The OTN-TDM FLOWSPEC object received in a Resv message SHOULD be identical to the OTN-TDM SENDER_TSPEC in the corresponding Path message. If they do not match, a ResvErr with 'Traffic Control Error/Bad Flowspec value' MUST be generated.
The TPN field MUST be set to 0 when an LO ODUj maps into OTUk (j=k). For multiplexing into HO ODU1/ODU2/ODU3, only the lower 6 bits are significant; for HO ODU4, only the lower 7 bits are significant; other bits MUST be set to 0.
When a downstream node assigns a TPN for ODUj-to-ODUk multiplexing, the TPN MUST NOT collide with TPN values used by existing LO ODU connections in the selected HO ODU link, and the Expected MSI (ExMSI) MUST be configured using this TPN.
When an upstream node receives a Resv with an unacceptable OTN-TDM label, it MUST generate a ResvErr with 'Routing problem/Unacceptable label value'. When a downstream node receives a Path with an unacceptable UPSTREAM_LABEL, it MUST generate a PathErr with the same indication.
Signal Type field (8 bits) in OTN-TDM Traffic Parameters identifies the ODU container type. New values defined include: 4 (ODU4), 9 (OCh at 100 Gbps), 10 (ODU0), 11 (ODU2e), 20 (ODUflex(CBR)), 21 (ODUflex(GFP-F) resizable), and 22 (ODUflex(GFP-F) non-resizable).
The Length field (12 bits) in the OTN-TDM Generalized Label indicates the total number of TSs in the HO ODUk link. Values of 4 and 16 indicate 2.5 Gbps TS granularity; values 2, 8, 32, and 80 indicate 1.25 Gbps TS granularity.
The OTN-TDM SENDER_TSPEC object (Class 12, C-Type 7) and OTN-TDM FLOWSPEC object (Class 9, C-Type 7) carry Traffic Parameters for OTN-TDM switching. The format includes an 8-bit Signal Type, 16-bit NVC (Number of Virtual Components), 16-bit Multiplier (MT), and a 32-bit Bit_Rate field encoded as IEEE single-precision floating-point.
Two new G-PID types are defined: ODU-1.25G (value 66) for transport of digital paths at 1.25–100 Gbps via 1.25 Gbps TS granularity, and ODU-any (value 67) for transport via either 1.25 Gbps or 2.5 Gbps TS granularity using a fallback procedure.
IANA assigned C-Type value 7 (OTN-TDM) in both the 'Class Types or C-Types - 9 FLOWSPEC' and 'Class Types or C-Types - 12 SENDER_TSPEC' subregistries of the RSVP Parameters registry.
IANA created a new 'OTN Signal Type' subregistry under GMPLS Signaling Parameters, defining values 0–22 (with 12–19 and 23–255 unassigned). New values added by this document: 4 (ODU4), 9 (OCh at 100 Gbps), 10 (ODU0), 11 (ODU2e), 20 (ODUflex(CBR)), 21 (ODUflex(GFP-F) resizable), 22 (ODUflex(GFP-F) non-resizable). New assignments require Standards Action.
IANA extended the 'Generalized PIDs (G-PID)' subregistry of GMPLS Signaling Parameters with new values 59–70 (including Framed GFP, STM-1, STM-4, InfiniBand, SDI, SDI/1.001, DVB_ASI, ODU-1.25G, ODU-any, Null Test, Random Test, 64B/66B GFP-F Ethernet) and updated values 47 and 56.
This document introduces no new security considerations beyond those in RFC 3473 and RFC 4328, as it only differs in specific signaling information communicated. RFC 5920 provides an overview of security vulnerabilities and protection mechanisms for the GMPLS control plane.
ODUflex(GFP) hitless bandwidth resizing involves two states: increasing (ingress sends Path with SE style, triggers BWR after LCR on every hop, then PathTear to remove old state) and decreasing (ingress sends Path with SE style, triggers BWR after LCR handshake, then ResvErr to tear down old state).
The OTN-TDM GENERALIZED_LABEL object contains a 12-bit TPN (Tributary Port Number), 8-bit Reserved, 12-bit Length (number of bits in Bit Map), a variable-length Bit Map indicating tributary slots assigned to the LO ODUj, and padding bits to align to a 4-byte boundary.