PCEP Extension for Fine Grain Optical Transport Network (fgOTN)

Introduction As SDH phases out in operators’ networks, Fine Grain Optical Transport Network (fgOTN) technology complementing the existing OTN with an additional fgOTN path layer network is used as an alternative to carry private line services. A new fine grain ODU layer network has been defined in ITU-T to carry these signals across the OTN networks, to provide flexible N*10Mbps bandwidth TDM-based transport capabilities. ITU-T has a series of recommendations for fgOTN (fine grain OTN ). The fgOTN overview is defined in , fgOTN layer architecture is defined in , fgOTN Interface and server adaptation is defined in , fgOTN equipment is defined in, fgOTN synchronization is defined in , fgOTN management requirements is defined in and protocol-neutral information model is defined in . provides the PCEP extensions required for GMPLS applications, for example, for Optical Transport Networks (OTNs) and Wavelength Switched Optical Networks (WSONs). Due to the new features of fgOTN technology, PCEP needs to be extended. The requirements were analyzed in .

Requirements on the PCEP computed path information For each computed fgOTN path, the information carried by the PCEP should at least include: 1) fgOTN path information 2) fgOTN path protection type 3) Path role (working path/backup path) 4) fgOTN path bandwidth 5) fgOTN path list: a) node identifier b) Path identifier

PCEP Extention for fgOTN path set-up The centralized computation model of PCE architecture seems to be suitable for the fine-granularity transport network, while the PCEP (PCE communication protocol) needs to be extended to meet the fine-granularity transport requirements. The protocol and signaling should support the application of fine-granularity path set-up/update/removal and resource management. The extention for fgOTN path set-up is suggested as follows: Attribute Length (bits) Value Connection Identifier (LSP Object) 96 Composed of three tuples (Source Node Identifier, Destination Node Identifier, Service Index, each 32 bits) Protection Type (LSPA Object's Protection Attributes) 8 Includes 1+1 Protection, 1+1, Path Protection, No Protection, etc. Primary/Backup Flag (LSPA Object, Protection Attributes) 8 Set to 1 to indicate working path, set to 0 to indicate protection path Small timeslot granularity (Generalized Bandwidth Object) 8 Timeslot granularity, requires fgOTN's timeslot granularity. Timeslot granularity is defined by YD/T 4856-2024 and ITU-T G.709.20 standards; 0 – 10Mbps (fgOTN) fgOTN Bandwidth (Generalized Bandwidth Object) 16 Integer, expressed in terms of the number of time slots Routing Information (LIST) See Table2 Destination node identifier, fgOTN's ingress/egress fgOTN channel number length is 10 bits Refer to RFC5440 for RP object's B Flag bit to determine simplex or duplex. For simplex connections, routing information (LIST) will generate unidirectional exchanges. For duplex connections, routing information for both ingress and egress will generate bidirectional exchanges. Attribute Length (bits) Network Element Identifier 32 Ingress 32 Ingress ODU Service Layer Channel Number 16 Ingress fgOTN Channel Number 16 Egress 32 Egress ODU Service Layer Channel Number 16 Egress fgOTN Channel Number 16

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