A General Flow ID for MPLS Network Action

Many MNAs affiliate to specific flows or exhibit different behavior to different flows. For example, the network operator may apply certain OAM on a number of selected flows and collect per flow data. However, in MPLS networks, the labels are used to identify paths but not flows. If multiple flows sharing the same path require the same MNA, the LSR may need to differentiate the flows and execute the action on a per-flow basis. The flow information can be extracted from the L3/L4 header in the MPLS payload by deep packet inspection, which incurs significant processing overhead. Alternatively, each flow-based MNA may carry its own unique identifier to differentiate the flows. However, this approach has several issues. First, one packet may have multiple MNAs that require a flow identification. There will be obvious data redundancy if each MNA carries its own flow identifier. Second, limited by the MNA ISD encoding and size, the flow identifier may have to be tailored to a sub-optimal size, resulting in poor scalability. Third, A customized flow identifier per MNA may cause network management difficulties and waste network resources. Therefore, it is desired to have a General Flow Identifier (GFI) which can be shared by all the MNAs relying on it. In this draft, we propose a new ISD item for GFI using the encoding format described in . We also list the possible use cases which can use the GFI.

The following terminology and acronyms are used in this document. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here. General Flow Identifier MPLS Network Action In Stack Data

As shown in , an Opcode is assigned for GFI and the encoding of GFI takes the LSE Format C as specified in , in which the GFI uses the 20-bit data field.

The GFI can have multiple possible use cases: IOAM-DEX is used as a trigger for collecting IOAM data locally or exporting it to a receiving entity (or entities). The Flow ID in the IOAM-DEX Option-Type is an optional field representing the flow identifier. The Flow ID can be used to correlate the exported data of the same flow from multiple nodes and from multiple packets. An on-path telemetry method using packet-marking, referred to as PBT-M, does not carry the telemetry data in user packets but sends the telemetry data through a dedicated packet. The MPLS encoding of PBT-M described in can take advantage of the GFI to help correlate the postcards and identify the flow under test. The Alternate Markingtechnique described in can use GFI to identify the flow under test. The GFI can be used as an entropy label for load balancing on multiple paths. RFC8964 defines the MPLS dataplane for Deterministic Networking. A DetNet "service" label is used between DetNet nodes that implement the DetNet service sub-layer functions. An S-Label is used to identify a DetNet flow at the DetNet service sub-layer at a receiving DetNet node. Within MNA architecture, the GFI can be used as the S-Lable.

TBD

This document requires a new option code assigned to indicate GFI.

The comments and suggestions of the following are gratefully acknowledged: TBD