RSVP-TE Signaling Extensions in Support of Flexi-Grid Dense Wavelength Division Multiplexing (DWDM) Networks
Extracted elements (15)
Implementations may support only a subset of possible slot widths and central frequencies; for example, limiting central frequency granularity to 12.5 GHz (only even n values) or slot widths to 25 GHz (only even m values), without violating the protocol.
In centralized Spectrum Assignment (SA), the assigned frequency slot is fully specified in the RSVP-TE Path message. In distributed SA, only the slot width is specified in the Path message, allowing network elements to select the actual frequency slot when processing RSVP-TE messages.
The SSON traffic parameters (using m * 12.5 GHz slot width encoding) are also applicable to fixed-grid networks, because fixed-grid channel spacings (12.5, 25, 50, 100 GHz and multiples of 100 GHz) are all multiples of 12.5 GHz. This enables common signaling for both flexi-grid and legacy DWDM networks.
There are no differences between the signaling procedures for LSP control in flexi-grid networks (RFC 7698) and those for fixed-grid networks (RFC 7689); only the TSpec, FlowSpec, and label formats differ. Both distributed SA and centralized SA procedures can be applied.
For bidirectional LSPs, the Path message MUST be able to specify the central frequency to be used for reverse-direction traffic.
Frequency slot information MUST be present in a Resv message to indicate, hop by hop, the central frequency of the allocated resource. Combined with the slot width, the central frequency identifies the resources reserved for the LSP.
The slot width MUST be carried in the signaling message during LSP establishment, enabling nodes along the LSP to know how much frequency resource has been requested in a Path message and how much has been allocated by a Resv message.
The SSON traffic parameters carried in both SENDER_TSPEC and FLOWSPEC objects MUST have the format defined in Figure 1, with the m field (16 bits) specifying slot width as m * 12.5 GHz, and Reserved bits MUST be set to zero and ignored upon receipt.
A 'compound label', constructed from a concatenation of flexi-grid labels as described in RFC 7699 Section 4.3, is used when signaling an LSP that uses multiple flexi-grid slots.
Flexible-grid labels are encoded as described in RFC 7699 and can appear in any RSVP-TE object or sub-object that can carry a label. The m parameter forms part of both the label and the traffic parameters.
The frequency slot for a flexi-grid LSP is defined as [(central frequency) - (slot width)/2] to [(central frequency) + (slot width)/2], where central frequency in THz is 193.1 + n * 0.00625 (n is any integer) and slot width in GHz is 12.5 * m (m is a positive integer).
Two new RSVP-TE Class Types are defined: SSON SENDER_TSPEC (Class 12, C-Type 8) carried in Path messages to indicate requested frequency resource, and SSON FLOWSPEC (Class 9, C-Type 8) carried in Resv messages to indicate actual resource reservation.
IANA allocated two new Class Types in the 'Resource Reservation Protocol (RSVP) Parameters' registry: C-Type 8 for FLOWSPEC (Class 9) named 'SSON FLOWSPEC', and C-Type 8 for SENDER_TSPEC (Class 12) named 'SSON SENDER_TSPEC'.
This document introduces no new security considerations beyond those of RFC 3473 (GMPLS RSVP-TE). Implementers are referred to RFC 5920 for a discussion of security considerations for MPLS and GMPLS networks.
The SSON traffic parameters object is a 32-bit structure: m (16 bits, positive integer encoding slot width as m * 12.5 GHz) followed by Reserved (16 bits, set to zero). Used in both SENDER_TSPEC (Class 12, C-Type 8) and FLOWSPEC (Class 9, C-Type 8).