teas

Summary

The TEAS working group convened for IETF 113, discussing the status of several working group documents, a liaison from ETSI, and detailed presentations on the ACTN Applicability to R-POI, Network Slicing Framework, and YANG Model for IETF Network Slice Services. Key decisions included moving several mature drafts towards Working Group Last Call and addressing specific technical feedback for documents still in progress, particularly around scope, terminology, and the inclusion of examples.

Key Discussion Points

Working Group Document Status (Co-Chairs)

General Status: 22 WG documents, 3 on the agenda. draft-ietf-teas-signaling-extension-jar-for-smp is currently with the AD. One recent adoption poll is moving towards publication after issues are addressed.
Enhanced VPN Framework (draft-ietf-teas-enhanced-vpn-framework): A new revision was published with more details on service data model applicability and VTN/NRP relationship. Authors believe it is almost ready for Last Call and requested further WG review.
PCC Use Cases (draft-ietf-teas-pcc-use-cases): Authors have completed pending items. Chairs intend to take this document to Last Call, requesting WG review.
3272 Best Document (draft-ietf-teas-3272bis): Several revisions published, with one more (covering AQM) pending. The editor states no further changes are planned. Recommended for Last Call, requiring thorough WG review due to its size.
YANG Path Computation Model (draft-ietf-teas-yang-path-computation): Revisions 17 and 18 published. Authors believe it's ready for Last Call and requested WG review.

Liaison Communication

A liaison from the ETSI NFV group was received via email, outlining perceived gaps in TEAS's work and indicating that ETSI members plan to participate and contribute to TEAS.
The AD was asked to follow up on the formal liaison process for ETSI, as the communication was received outside of typical channels.

ACTN Applicability to R-POI (draft-ietf-teas-actn-poi-applicability)

Document Updates: Recent revisions included reordering sections, aligning content to Segment Routing Traffic Engineering (SR-TE) end-to-end scope, adding inter-link discovery details, and expanding the conclusion section to cover identified gaps and new spun-out work (e.g., inventory model, path computation, discovery capabilities).
SR-TE Discussion: Ongoing discussions on binding L3VPN and SR-TE paths, with multiple options under consideration. These discussions will continue on R-POI calls after IETF 113, with engagement from the Spring WG.
Inter-domain Link Setups: The document details a process for the MDSC to fulfill L2/L3 VPN service requests by setting up optical tunnels via optical PNCs and subsequent IP links via packet PNCs, including dynamic discovery mechanisms like LLDP.
Gaps and Work in Progress: Further documentation is needed on setting up SR-TE paths after IP link establishment and rerouting existing SR-TE paths for optimization or failure recovery.
WG Feedback: A concern was raised that the document, initially technology-agnostic (mentioning both SR-TE and RSVP-TE), has become heavily focused on SR-TE (94 mentions vs. 1 for RSVP-TE). Authors were encouraged to clarify that SR-TE is used as a detailed example, not the exclusive technology, and to maintain a technology-agnostic approach where possible before specific examples.

Network Slicing Framework (draft-ietf-teas-network-slice-framework)

Recent Revisions: Draft 08 incorporated feedback from the October interim, with significant editorial review. Draft 09 (pending submission) will include a section on Service Function Chaining (SFC) realization and a clarification in 4.1.2 about operator-realized slices potentially being an SLA. Section 5.4, deemed redundant, will be removed.
Resolved Discussions:
- Hub and Spoke: Text detailing how hub-and-spoke is reflected in service and realization will be re-added.
- Scope (5G, IP/MPLS): Consensus emerged that the framework should not be limited to 5G requirements or IP/MPLS networks, but rather be generic and technology-agnostic, taking advice from 5G use cases. Realization details for sub-IP networks belong in other documents.
Worked Examples: A discussion was held on the necessity of including worked examples. While other documents are exploring specific mapping examples (e.g., 5G slices to IETF slices), volunteers (Reza, Kirti, Luis) offered to contribute text for examples if deemed necessary.
Ongoing Mailing List Discussions:
- Service vs. Realization: Suggestion to include text clarifying the distinction.
- SDP vs. SAP: No change deemed necessary for the draft, but awareness of generic SAP concepts.
- Receiver SLOs: An active thread without a definitive conclusion, potentially leading to a "group SLO" concept.
- Multiplexing: A new discussion thread initiated by Wim Henderickx to clarify the scope of multiplexing and mapping aspects in an abstract realization layer.

YANG Model for IETF Network Slice Services (draft-ietf-teas-yang-teas-slice)

Objective: To define a northbound, technology-agnostic YANG interface for an IETF Network Slice Service Controller, translating requests into technology-specific southbound implementations.
Key Changes:
- Aligned network slice connection with the framework's "connectivity construct" definition.
- Introduced "network connection groups" to group connections with similar SLO/SLE characteristics.
- Removed network slice type and EP roll fields.
- Introduced network slice tag (NStack) for extensibility (e.g., customer name, 5G app details, higher-layer realization awareness), designed as optional and extensible without augmentation.
- Added details on access port/connection actions between Customer Edge (CE) and Provider Edge (PE).
Modeling: Supports point-to-point, point-to-multipoint, and any-to-any connection types, allowing for unidirectional connections to support different upstream/downstream SLOs.
Issues in Progress:
- Further refinement of network slice groups (e.g., adding hub-and-spoke, defining connectivity type at the network layer for inheritance).
- Discussion on formal import of RFC 9181 (common YANG model) structure, considering its applicability beyond L2/L3 VPNs.
- Incorporating statistical parameters for SLOs as the framework evolves, leveraging the model's extensibility.
- Aligning terminology for "access port" and clarifying "access point node ID."
- Addressing multi-homing.
WG Feedback:
- Suggestion to change "VPN type for access" to a more technology-agnostic "layer of access (L1/L2/L3)" in the northbound model. Authors agreed.
- Concerns about the scope of RFC 9181 for a common YANG model, with suggestions for extension or separating common/specific parts in the model.
- Clarification on connection groups: Authors preferred maintaining independent connection groups for design simplicity over complex logic for abstracting shared SLOs.
- Discussion on "protection" as an SLO: Authors clarified this is a framework-level question; if defined in the framework, the YANG model would import it. Greg H. suggested protection is an operator realization choice not necessarily exposed to clients, recommending mailing list discussion.

Decisions and Action Items

WG Document Last Call Preparation: Authors of draft-ietf-teas-enhanced-vpn-framework, draft-ietf-teas-pcc-use-cases, draft-ietf-teas-3272bis, and draft-ietf-teas-yang-path-computation are encouraged to prepare for Working Group Last Call, pending final reviews.
ETSI Liaison Follow-up: The AD will investigate the formal liaison process for ETSI and identify the appropriate liaison manager.
ACTN R-POI Scope Clarification: Authors of draft-ietf-teas-actn-poi-applicability will update the document to clarify that SR-TE is an example rather than the sole or exclusive technology for applicability, ensuring a technology-agnostic approach where possible.
Network Slicing Framework Examples: Reza Rokui, Kirti K. K. K., and Luis M. Contreras will coordinate with Adrian Farrel to determine the need for and contribute text for worked examples in draft-ietf-teas-network-slice-framework.
YANG Slice Services Terminology: The authors of draft-ietf-teas-yang-teas-slice will update the document to change "network slice endpoint" (NSE) to "SDP" and clarify "VPN type for access" to "layer of access (L1/L2/L3)" in the next revision.

Next Steps

Working Group Review: All working group members are encouraged to thoroughly review the drafts highlighted for Last Call preparation (enhanced-vpn-framework, pcc-use-cases, 3272bis, yang-path-computation).
ACTN R-POI Calls: The R-POI authors will resume their calls from March 29th to continue discussions on SR-TE integration and multi-layer IP link setups.
Network Slicing Framework: Adrian Farrel will post draft 09 and continue addressing the five active mailing list issues (service vs. realization, SDP/SAP, receiver SLOs, multiplexing) in anticipation of Last Call.
YANG Model for IETF Network Slice Services: Authors will proceed with addressing the 4-5 identified issues, including the terminology alignment and further discussion on RFC 9181 reuse and multi-homing.
Mailing List Discussions: Participants are encouraged to contribute to the ongoing mailing list discussions, particularly on receiver SLOs and multiplexing.
Virtual Interims: If any participants wish to schedule virtual interims, they should contact the chairs.

Session Date/Time: 23 Mar 2022 13:30

TEAS Session Minutes - IETF 113 Vienna

Summary

The TEAS working group discussed various drafts related to IETF Network Slices, including updates to common TE types, solutions for realizing network slices, service delivery models, use cases, scalability considerations, and YANG models for Network Resource Partitions (NRPs). Key discussions revolved around the adoption of several drafts, the alignment of terminology (NRP vs. VTN), the relationship between different YANG models for NRPs, and the practical deployment experiences of operators. A central theme was ensuring consistency and identifying gaps in existing IETF tools for network slicing.

Key Discussion Points

Updates to Common TE Types (RFC 8776):
- Proposed minor, backward-compatible updates to ietf-te-types module in RFC 8776.
- Addition of bandwidth-scientific-notation typedef (from draft-ietf-yang-lpt-topp) for broader applicability (e.g., LSPs, tunnels, non-packet technology).
- Addition of encoding-and-switching-type grouping (from packet-computation draft) for broader applicability and model alignment.
- The proposed process is an update document containing only the changed te-types module, not a full bis document, with comments for the RFC editor on changes.
Solution for Network Slices in Packet Networks:
- Draft revision 08 received detailed review comments during the working group adoption poll.
- Some comments related to individual solutions driven in other WGs will be removed to keep this document generic.
- The document status will be changed to Informational based on poll feedback.
Service Delivery Model for Network Slicing:
- Proposed augmentation to support Point-to-Multipoint (P2MP), Multipoint-to-Point (MP2P), and Multipoint-to-Multipoint (MP2MP) communication types using replication-groups and receiver-constraint-group YANG constructs.
- Discussion on the model's relationship to existing service models and the approach of augmentation versus referencing topology models. Concerns raised about potential naming confusion with existing NVI models.
Use Cases and Attributes for NSI:
- Documenting use cases for the Northbound Slice Interface (NSI), including 5G (public/private), NFV-based services, network sharing, SD-WAN, and O-RAN splits.
- Added content on private 5G networks and a summary of attributes and procedures (work in progress).
- Discussion on providing concrete feedback to the framework and YANG model documents based on the use case analysis.
Scalability Considerations for NRP:
- Draft renamed from "VTN scalability" to "NRP scalability" to align with IETF Network Slicing terminology.
- Provides scalability analysis and optimization suggestions for NRPs in both control and data planes.
YANG Data Model for NRP Policies:
- Defines a data model for provisioning and managing NRP policies, supporting three modes: control plane only partitioning, data plane partitioning, and both.
- Key elements include resource reservation, flow aggregate selectors (for data plane identification), per-hop behaviors (QoS policies), and topology filters.
- Clarification that the model covers bandwidth reservation, data plane selector, and control plane/topology.
NRP YANG Module:
- Presents an NRP model covering instantiation, monitoring, and modification.
- Distinguishes itself from the NRP Policy model by focusing on customized NRP topologies (derived from physical/filtered L3, TE, SR topologies) and monitoring capabilities.
- Discussion on whether "link-specific resources" are a property of slice realization or NRP resources.
Instantiating IETF Network Slices in SP Networks:
- Explores reusing existing IETF machinery (YANG models, architectures) to operate network slices and identifies potential gaps.
- Discussed architectural options and a preliminary mapping between the NSC NBI YANG model and the L3 Service Model, highlighting potential mismatches (e.g., packet error rate).
Mapping 3GPP Network Slices to IETF Network Slices:
- Investigates how 3GPP network slicing concepts, particularly Endpoint Transport (EP Transport) parameters, can be mapped to IETF network slices.
- A preliminary mapping exercise was presented, focusing on parameters like IP address, logical interface info, and QoS profile.
Framework for End-to-End IETF Network Slicing:
- Framework covers 5G end-to-end network slicing and inter-domain IETF network slicing.
- Aligned terminology to use NRP and discussed mapping 5G S-NSSAI to Global and Domain NRP IDs.
Deployment Status and Considerations for IETF Network Slices:
- Presented two real-world operator deployment cases using Network Slicing based on VPN+ technologies:
  1. Multi-Industrial Networks (China Telecom): SRv6-based network using virtual sub-interfaces and SRv6 SIDs, IS-IS policies with link affinity. Observations: Any-to-Any connections require large policy provisioning, considering optimized SRv6 best-effort slicing, data plane VTN/resource ID for scalability, and hierarchical slicing for future per-customer needs.
  2. Fixed Mobile Convergence (FMC) Network: SR-MPLS (SR-ISIS) based for mobile, enterprise, and broadband services, using Flexible Ethernet and virtual sub-interfaces. Observations: Automation is crucial, considering high-scalability slicing solutions and slice ID mechanisms.

Decisions and Action Items

Updates to Common TE Types: The proposed process of an update document containing only the changed te-types module of RFC 8776 was generally accepted, with the full model to be included and changes noted for the RFC editor.
Solution for Network Slices in Packet Networks:
- Decision: Change document status to Informational (based on adoption poll feedback).
- Action Item: Authors to issue revision 09 addressing immediate concerns and adding a new section for open issues.
- Action Item: If no further concerns, republish as a 00-wg-document.
Use Cases and Attributes for NSI:
- Action Item: More discussion on the mailing list is needed regarding WG adoption, particularly any objections.
Scalability Considerations for NRP:
- Action Item: More discussion on the mailing list is needed before polling for WG adoption.
Deployment Status and Considerations for IETF Network Slices:
- Decision: The presented cases are real deployments.

Next Steps

Updates to Common TE Types: WG review of technical content and proposed process. If accepted, ready for WG adoption soon. Update draft based on comments.
Solution for Network Slices in Packet Networks: Authors to issue revision 09 by end of week/early next week. Notify WG and solicit further feedback.
Service Delivery Model for Network Slicing: Continue discussion on mailing list.
Use Cases and Attributes for NSI: Complete work in progress, add data center interconnection use case, elaborate summary section, scan for additional use cases. Prepare new version for the next meeting.
NRP YANG Models (Policy and Module): Continue discussion on the mailing list, particularly on the relationship and differences between the two NRP YANG models.
Instantiating IETF Network Slices in SP Networks: Work on version 04 (editorial fixes, new architectural options). Detail implementation options and collect operational requirements.
Mapping 3GPP Network Slices to IETF Network Slices: Prepare a more detailed document for the next IETF and collect feedback. Influence 3GPP parameters through liaison.
Framework for End-to-End IETF Network Slicing: Solicit comments and refine the draft. Chairs suggested considering combining this short document with an existing working group document.
Considerations for Hierarchical IETF Network Slices: Solicit feedback on use cases, requirements, and realization considerations.
Deployment Status and Considerations for IETF Network Slices: Collect comments/feedback and add more network slice deployment cases and information to the draft in the future.