OSPF-TE Extensions for General Network Element Constraints
Extracted elements (15)
If no Connectivity Matrix sub-TLV is included in an advertisement, it is assumed that the switches support symmetric switching. This default avoids the overhead of advertising connectivity matrices for the common symmetric case.
Static information sub-TLVs (e.g., Connectivity Matrix, Port Label Restrictions) should be separated from dynamic information sub-TLVs and advertised in separate OSPF-TE LSAs. This avoids unnecessary updates of static information when only dynamic information changes, improving routing scalability.
The Connectivity Matrix sub-TLV and Port Label Restrictions sub-TLV can be placed in separate LSAs to allow MTU-safe distribution. The Port Label Restrictions sub-TLV is carried in a Link TLV, of which there can be at most one per LSA per RFC 3630.
To handle LSAs that might exceed the IP MTU, large connectivity matrices can be decomposed into sub-matrices, each with a unique matrix identifier per RFC 7579. This decomposition is straightforward because a connectivity matrix consists only of pairs of input and output ports.
Existing management tools and MIB modules (RFC 6825) do not yet handle the additional TE parameters defined in this document. Augmentation of the MIB or development of a YANG module in TEAS would be needed to read or exchange the new connectivity matrix and port label restriction information.
Prior to receiving any Connectivity Matrix sub-TLV, path computation assumes any-port-to-any-port reachability (standard GMPLS assumption). Once a sub-TLV is received, connectivity is known to be restricted. Intermediate states (partial receipt of decomposed matrices) may cause transient path computation errors, which are handled by existing GMPLS mechanisms.
The Connectivity Matrix sub-TLV may be optional in some specific technologies such as WSON networks depending on the control-plane implementation. Its absence signals symmetric switching capability.
A mechanism MAY be applied such that static information and dynamic information of one TE link are contained in separate Opaque LSAs, e.g., the Port Label Restrictions sub-TLV could be nested in separate top-level Link TLVs and advertised in separate LSAs.
When new sub-TLVs or their encodings are malformed, the proper action is to log the problem and ignore just the malformed sub-TLVs in GMPLS path computations, rather than ignoring the entire LSA.
All sub-TLVs defined in this document are nested in top-level TLVs (Node Attribute TLV or Link TLV) and contained in Opaque LSAs. Flooding rules for Opaque LSAs follow RFC 2328, RFC 5250, RFC 3630, and RFC 4203.
The Connectivity Matrix sub-TLV (Type 14) is a sub-TLV of the Node Attribute TLV defined in RFC 5786. It represents either potential connectivity for asymmetric switches (e.g., ROADMs) or fixed connectivity for asymmetric devices such as multiplexers. One sub-TLV contains one matrix; multiple occurrences are permitted within the Node Attribute TLV.
The Port Label Restrictions sub-TLV (Type 34) is a sub-TLV of the Link TLV defined in RFC 3630. It describes label restrictions that a network element and link may impose on a port, indicating which labels may or may not be used. The sub-TLV may occur more than once to specify complex port constraints within the Link TLV.
IANA assigned Type 14 (Connectivity Matrix) in the 'Types for sub-TLVs of TE Node Attribute TLV (Value 5)' sub-registry of the 'Open Shortest Path First (OSPF) Traffic Engineering TLVs' registry.
IANA assigned Type 34 (Port Label Restrictions) in the 'Types for sub-TLVs of TE Link TLV (Value 2)' sub-registry of the 'Open Shortest Path First (OSPF) Traffic Engineering TLVs' registry.
This document does not introduce any further security issues beyond those already discussed in RFC 3630, RFC 4203, and RFC 5250. For general security aspects relevant to GMPLS-controlled networks, RFC 5920 applies.