Traffic Engineering Extensions to OSPF for GMPLS Control of Evolving G.709 Optical Transport Networks
Extracted elements (27)
A single new Switching Capability value (OTN-TDM = 110) is used for both fixed and flexible ODUs to avoid proliferating switching type values. The distinction between fixed and variable containers is made inside the SCSI via sub-TLV types (Type 1 vs Type 2), not via separate switching capabilities.
For fixed containers, the encoding advertises only the count of available ODU containers (16 bits) rather than available bandwidth (32 bits as in prior GMPLS encoding). This halves the per-container advertisement size while preserving path computation accuracy for fixed-size ODUs.
For ODUflex, Unreserved Bandwidth is included even though it does not precisely indicate how many LSPs can be set up (since spatial TS allocation is unknown). It is included as a heuristic aid during path computation to differentiate links with the same MAX LSP Bandwidth but different amounts of total free capacity.
All implementations MAY also support advertisement as defined in RFC 4203. When nodes support both methods, implementations MUST support configuration of which advertisement method is followed, enabling nodes following each method to identify compatible peers for path computation.
A different ISCD MUST be used for each different muxing hierarchy (muxing tree) and different TS granularity supported within the TE-Link. A single ISCD MAY be used for unbundled or bundled links supporting homogeneous multiplexing hierarchies and the same TS granularity.
Hierarchies with the same muxing tree but different exported TS granularity MUST be considered as non-homogeneous hierarchies and require separate ISCDs.
MAX LSP Bandwidth values MUST be encoded in IEEE floating point format (bytes/second). The document provides a table of floating point hex values for ODU0 through ODU4 and ODU2e.
The Switching Capability Specific Information (SCSI) MUST include one Type 1 sub-TLV for each fixed container and one Type 2 sub-TLV for each variable container. The muxing hierarchy tree MUST be encoded as an order-independent list.
To reduce advertised data, it is RECOMMENDED to bundle component links with homogeneous hierarchies as described in RFC 4201.
When a received LSA includes a sub-TLV not formatted according to the precise specifications, the problem SHOULD be logged and the wrongly formatted sub-TLV MUST NOT be used for path computation.
When both ODUflex(GFP-F) resizable (Signal Type 21) and non-resizable (Signal Type 22) are supported, only Signal Type 21 SHALL be advertised, as it implies support for Type 22 adaptation.
When supporting these extensions, both fixed and flexible ODUs MUST use Switching Capability = OTN-TDM and Encoding Type = G.709 ODUk (Digital Path) as defined in RFC 4328. The ISCD MUST then be interpreted as defined in RFC 4203.
A new Switching Capability value OTN-TDM (110) is defined for interfaces supporting G.709 OTN switching. This value is registered in the GMPLS Signaling Parameters 'Switching Types' registry.
G.709 OTUk physical links are represented as TE-Links in GMPLS TE topology. TE-Links may be single-hop (one OTUk link) or multi-hop (spanning multiple OTUk links via forwarding adjacencies). Both types advertise ODU Switching Capability.
Maximum LSP Bandwidth (32 bits, Type 2 sub-TLV): Maximum bandwidth allocatable to a single LSP at a given priority, in bytes/second in IEEE floating point. MUST be calculated as: (# available TSs) × (ODTUk.ts nominal bit rate) × (1 - HO OPUk bit rate tolerance).
Padding field: Ensures 32-bit alignment of Stage fields. Length in bytes = 4 - (Num_of_stages % 4). MUST be set to zero on transmission and MUST be ignored on receipt. Unreserved Padding (16 bits) similarly aligns Unreserved ODUj fields when the number of priorities is odd.
Priority (8 bits): Bitmap indicating which of the 8 priority levels (0 = highest, 7 = lowest) are advertised in the sub-TLV. A bit MUST be set for each represented priority, and at least one priority MUST be advertised which SHALL be priority 0 unless overridden by local policy.
Signal Type (8 bits): Indicates the ODU type being advertised in a Bandwidth sub-TLV. Values are defined in RFC 7139. For ODUflex, three distinct signal types are defined: 20 = ODUflex(CBR), 21 = ODUflex(GFP-F) resizable, 22 = ODUflex(GFP-F) non-resizable.
Stage fields (8 bits each): Each Stage field identifies a Signal Type in the multiplexing hierarchy used to transport the signal. Stage fields MUST be ordered from the lowest-order ODU to the highest-order ODU (ascending toward server layer). The number of Stage fields MUST equal Num of stages.
T flag (bit 17) indicates whether the advertised Signal Type can be terminated; S flag (bit 18) indicates whether it can be switched. Both MUST be set or cleared appropriately; a value of 0 in both T and S MUST NOT be used.
TSG (3 bits): Tributary Slot Granularity field indicates the supported tributary slot type. Values: 0 = ignored (non-multiplexed), 1 = 1.25/2.5 Gbps with fallback, 2 = 2.5 Gbps only (RFC 4328 interfaces), 3 = 1.25 Gbps only; values 4-7 are reserved.
Unreserved ODUj (16 bits, Type 1 sub-TLV): Indicates the count of unreserved ODUs of the advertised Signal Type at a particular priority level. One field MUST be present per bit set in the Priority field; fields MUST NOT be present for unadvertised priorities.
IANA assigned Switching Type value 110 (OTN-TDM capable) in the 'Switching Types' section of the 'Generalized Multi-Protocol Label Switching (GMPLS) Signaling Parameters' registry and in the IANA-GMPLS-TC-MIB.
IANA created a new sub-registry 'Types for sub-TLVs of OTN-TDM SCSI' under the 'OSPF Traffic Engineering TLVs' registry. Values: 0 = Reserved, 1 = Unreserved Bandwidth for fixed containers, 2 = Unreserved/MAX Bandwidth for flexible containers, 3-65535 = Unassigned. New assignments require Standards Action.
This document extends RFC 4203 and specifies contents of Opaque LSAs in OSPFv2. Opaque LSAs are not used for SPF computation, so extensions have no direct effect on IP routing. Tampering with GMPLS TE LSAs may affect the underlying optical/SONET-SDH transport. Security mechanisms from RFC 2328 and analysis from RFC 6863 apply. RFC 5920 should be consulted for detailed MPLS/GMPLS security threats and defensive techniques.
Bandwidth sub-TLV Type 1 (Unreserved Bandwidth for fixed containers) encodes: Type (16 bits) = 1, Length (16 bits), Signal Type (8 bits), Num of stages (8 bits), flags T|S|TSG|Res (8 bits), Priority bitmap (8 bits), Stage fields (8 bits each), Padding to 32-bit align, and Unreserved ODUj fields (16 bits each per advertised priority).
Bandwidth sub-TLV Type 2 (Unreserved/MAX LSP Bandwidth for flexible/variable containers) encodes the same header fields as Type 1, followed by Unreserved Bandwidth (32 bits IEEE float per priority) and MAX LSP Bandwidth (32 bits IEEE float per priority).