GMPLS OSPF-TE Extensions in Support of Flexi-Grid Dense Wavelength Division Multiplexing (DWDM) Networks
Extracted elements (21)
A non-overlapping set of available frequency ranges is disseminated (rather than individual slot assignments) to allow efficient resource management and RSA (Routing and Spectrum Assignment) procedures, as described in RFC 7698 Section 4.8.
Available frequency ranges (rather than specific wavelength points) are advertised for flexi-grid DWDM links because the slot width m is unknown before allocation, unlike fixed-grid where wavelengths map to predefined central frequencies with implicit bandwidth.
The Frequency Availability Bitmap uses m=1 as a basic unit for each bitmap bit, and a centralized Spectrum Assignment process must check consecutive available basic slots to determine feasibility for larger slot widths (higher m values).
Devices or applications using flexi-grid may only support a subset of possible slot widths and central frequencies; the Port Label Restrictions field with RstType=5 conveys these per-port constraints to enable correct path computation.
This document extends RFC 4203 (OSPF-TE ISCD) and RFC 7580 (Port Label Restrictions) to carry flexi-grid-specific information; implementations must use Opaque LSAs as defined in RFC 3630 and the GMPLS TE extensions in RFC 4203.
At least one priority level MUST be advertised in the Frequency Availability Bitmap sub-TLV. If only one priority level is advertised, it MUST be at priority level 0 (the highest priority).
For flexi-grid DWDM links, channel spacing (C.S.) MUST be set to 5 to denote 6.25 GHz granularity, as defined in RFC 7699.
In order to support all possible applications and implementations, central frequency granularity, slot width granularity, and slot width range (min and max) SHOULD be advertised for a flexi-grid DWDM link.
In the Port Label Restrictions field for flexi-grid, the Switching Capability and Encoding fields MUST be consistent with those specified in the ISCD as described in Section 4.1.
One Max Slot Width field MUST be present for each bit set in the Priority field of the Frequency Availability Bitmap sub-TLV, and each present field MUST be ordered to match the Priority field.
The 'Max LSP Bandwidth at priority x' fields (x from 0 to 7) in the generic ISCD MUST be set to zero and MUST be ignored for flexi-grid DWDM links, as they are not meaningful in this context.
The Unreserved Padding field (16 bits) MUST be included when k (number of priority levels) is odd, and MUST be omitted when k is even, to ensure 32-bit alignment of the Max Slot Width fields.
When the Switching Capability is set to Flexi-Grid-LSC (152), the Encoding Type MUST be set to lambda as defined in RFC 3471.
A new Switching Capability value of 152, named Flexi-Grid-LSC, is defined for the Interface Switching Capability Descriptor (ISCD) to identify flexi-grid capable interfaces in OSPF-TE.
The Bitmap field in the Frequency Availability Bitmap sub-TLV represents basic frequency slot availability: a bit set to 1 means the corresponding nominal central frequency is available for a flexi-grid LSP with m=1; a bit set to 0 means it is unavailable.
The flexi-grid Port Label Restrictions field defines Central Frequency Granularity (C.F.G) as a positive integer multiple of C.S., and Slot Width Granularity (S.W.G) as a positive integer multiple of 2*C.S., enabling expression of a port's supported slot width subset.
IANA assigned value 11 with name 'Frequency Availability Bitmap' for Switching Type 152 (Flexi-Grid-LSC) in the 'Generalized SCSI TLV Types' sub-registry of the GMPLS Signaling Parameters registry.
IANA assigned value 152 with name 'Flexi-Grid-LSC' in the 'Switching Types' sub-registry of the GMPLS Signaling Parameters registry to identify the new flexi-grid switching capability.
This document introduces no new security issues beyond those in RFC 3630 and RFC 4203. The OSPF security mechanisms from RFC 2328 apply to the Opaque LSAs carrying flexi-grid information, and the OSPF security analysis in RFC 6863 applies to these extensions.
The flexi-grid Port Label Restrictions field (RstType=5) encodes: MatrixID (8 bits), RstType=5 (8 bits), Switching Cap (8 bits), Encoding (8 bits), C.S. (4 bits), Central Frequency Granularity C.F.G (8 bits), Slot Width Granularity S.W.G (8 bits), and Min Slot Width (16 bits).
The Frequency Availability Bitmap sub-TLV (Type=11) is a new Generalized SCSI TLV encoding available frequency spectrum for flexi-grid links. It contains: Type (16 bits), Length (16 bits), Priority bitmap (8 bits), Max Slot Width per priority (16 bits each), C.S. (4 bits), Starting n (16 bits), No. of Effective Bits (12 bits), and a variable-length Bitmap field.