GMPLS OSPF Enhancement for Signal and Network Element Compatibility for Wavelength Switched Optical Networks
Extracted elements (21)
Path computation synchronization is simple: until a Resource Block Information sub-TLV is received for a system, path computation cannot use the other four sub-TLVs because the nature of the resources (wavelength converters, regenerators, etc.) is unknown. Once received, computation proceeds with whatever sub-TLVs are available.
Resource Block Pool State and Resource Block Shared Access Wavelength Availability sub-TLVs are dynamic in nature (changing when connections are established or torn down), while the remaining sub-TLVs are static. This distinction allows dynamic sub-TLVs to be separated and advertised with multiple TE LSAs per OSPF router.
Typical WSON node configurations (several hundreds of channels with an OEO element) produce Optical Node Property TLVs of less than 350 bytes, well within IP MTU. For rare cases exceeding the MTU, IP fragmentation/reassembly or packing sub-TLVs into separate LSAs are acceptable methods.
If path computation proceeds with out-of-date or missing WSON sub-TLV information, it may either yield a path that does not exist in the network or fail to find a path that actually exists. Both situations are already encountered with GMPLS out-of-date constraint information.
If more than one copy of a sub-TLV is received in the same LSA, the redundant sub-TLV SHOULD be ignored. If the same sub-TLV is advertised in a different TE LSA (packaging error), the sub-TLV with the largest LSA ID SHOULD be picked.
If new sub-TLVs or their encodings are malformed, a proper implementation SHOULD log the problem and MUST stop sending the LSA containing malformed TLVs or sub-TLVs. Errors SHOULD be logged for the local operator, and implementations MUST provide a configurable rate limit on such logs.
The label format defined in RFC 6205 MUST be used when advertising interfaces with a WSON-LSC type Switching Capability. Duplicated sub-TLVs identified by this label format are to be ignored.
When Switching Capability is set to WSON-LSC and Encoding Type to Lambda, the ISCD MUST be interpreted as in RFC 4203 with the optional inclusion of one or more Switching Capability Specific Information (SCSI) sub-TLVs.
When using the extensions defined in this document, at least one Optical Node Property TLV MUST be advertised in each LSA. More than one MAY be advertised in a single LSA for fine-grained topology changes, and implementations MUST support receiving multiple Optical Node Property TLVs in an LSA.
A new Switching Capability value WSON-LSC (value 151) is defined for the Interface Switching Capability Descriptor (ISCD). It must be used with Encoding Type = Lambda (as defined in RFC 3471).
Five sub-TLVs are defined for the Optical Node Property TLV: Resource Block Information (value 1), Resource Accessibility (value 2), Resource Wavelength Constraints (value 3), Resource Block Pool State (value 4), and Resource Block Shared Access Wavelength Availability (value 5), all with variable length. Encodings are defined in RFC 7581.
Resource Accessibility sub-TLV describes the structure of the resource pool in relation to the switching device, indicating the ability of an ingress port to reach a resource block and of a resource block to reach a particular egress port.
Resource Block Information sub-TLV represents resource signal constraints and processing capabilities of a node, as defined in RFC 7446.
Resource Block Pool State sub-TLV describes the usage state of a resource encoded as either a list of integer values or a bitmap indicating whether a single resource is available or in use. This information is dynamic and changes with connection establishment or teardown.
Resource Wavelength Constraints sub-TLV describes limited input or output wavelength ranges of resources such as wavelength converters, and structural constraints on which wavelengths can reach or leave resources.
The Optical Node Property TLV is a new top-level TLV for use in the OSPF TE LSA (defined in RFC 3630). It describes a single WSON node's signal compatibility constraints and node properties, and is comprised of a set of optional sub-TLVs with no ordering requirements.
IANA created a new registry 'Types for sub-TLVs of WSON-LSC SCSI' with values 0 (Reserved), 1 (Available Labels), 2 (Shared Backup Labels), and 3-65535 (Unassigned). Registration procedure is Standards Action.
IANA registered a new top-level TLV value 6 ('Optical Node Property') in the 'Top Level Types in TE LSAs' registry under 'Open Shortest Path First (OSPF) Traffic Engineering TLVs'.
IANA registered switching type value 151 ('WSON-LSC') in the 'Switching Types' registry under 'GMPLS Signaling Parameters', and added the corresponding entry wsonlsc(151) to the IANAGmplsSwitchingTypeTC MIB.
This document does not introduce security issues beyond those in RFC 3630 and RFC 4203. Opaque LSAs are not used for SPF computation or normal routing, so the extensions have no direct effect on IP routing. However, tampering with GMPLS TE LSAs may affect the underlying transport, and the security mechanisms of RFC 2328 apply to Opaque LSAs in OSPFv2.
The WSON ISCD Switching Capability Specific Information (SCSI) contains a variable number of Bandwidth sub-TLVs: Type 1 (Available Labels) and Type 2 (Shared Backup Labels), as defined in RFC 7579. Multiple sub-TLVs of each type are permitted and their order is arbitrary.