TEAS Working Group L. M. Contreras, Ed. Internet-Draft Telefonica Intended status: Informational I. Bykov, Ed. Expires: 5 September 2024 Ribbon Communications K. G. Szarkowicz, Ed. Juniper Networks 4 March 2024 5QI to DiffServ DSCP Mapping Example for Enforcement of 5G End-to-End Network Slice QoS draft-cbs-teas-5qi-to-dscp-mapping-00 Abstract 5G End-to-End Network Slice QoS is an essential aspect of network slicing, as described in both IETF drafts and the 3GPP specifications. Network slicing allows for the creation of multiple logical networks on top of a shared physical infrastructure, tailored to support specific use cases or services. The primary goal of QoS in network slicing is to ensure that the specific performance requirements of each slice are met, including latency, reliability, and throughput. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 5 September 2024. Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. Contreras, et al. Expires 5 September 2024 [Page 1] Internet-Draft Slice QoS Mapping March 2024 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. 5G QoS . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. 5G user traffic classes types . . . . . . . . . . . . . . . . 4 4.1. Scope of the Transport Network . . . . . . . . . . . . . 4 4.2. Example of the mapping . . . . . . . . . . . . . . . . . 4 4.3. Example of the grouping . . . . . . . . . . . . . . . . . 7 5. 5G user, service traffic classes co-existence in Multi-service network . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.1. QoS model with single priority queue . . . . . . . . . . 9 5.2. QoS model with multiple priority queues . . . . . . . . . 11 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 7.1. Normative References . . . . . . . . . . . . . . . . . . 12 7.2. Informative References . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 1. Introduction 5G End-to-End Network Slice QoS is an essential aspect of network slicing, as described in both IETF drafts and the 3GPP specifications. Network slicing allows for the creation of multiple logical networks on top of a shared physical infrastructure, tailored to support specific use cases or services. The primary goal of QoS in network slicing is to ensure that the specific performance requirements of each slice are met, including latency, reliability, and throughput. This document provides an example of possible mapping of 5QI values to DSCP marking, as well as some groupings that can facilitate the enforcement of the 5G Network Slice end-to-end. The mapping and grouping described are provided for illustration purposes only, and should not be considered as deployment guidance. Contreras, et al. Expires 5 September 2024 [Page 2] Internet-Draft Slice QoS Mapping March 2024 2. Terminology 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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. The following abbreviations are used in this document: 5GC: 5G Core Network 5QI: 5G QoS Identifier QFI: QoS Flow Identifier ARP: Allocation and Retention Priority S-NSSAI: Single Network Slice Selection Assistance Information RAN: Radio Access Network TN: Transport Network CN: Mobile Core Network DSCP: Differentiated Services Code Point 3. 5G QoS In the context of 5G, the 5QI is a scalar value used to differentiate QoS characteristics in the 5G System (5GS). It indicates the QoS that a specific data flow must receive. As mentioned in [TS-23.501], the 5QI to QoS mapping is provided by the 5G QoS profile, which includes parameters such as priority level, packet delay budget, packet error rate, etc. [I-D.ietf-teas-ietf-network-slices] focuses on how network slices can be instantiated, managed, and monitored by utilizing existing IETF protocols and models. It introduces the concept of the IETF Network Slice Controller (NSC), which interacts with higher-level Network Management Systems (NMSs) and orchestrates network resources to create network slices. The NSC may interact with other network controllers (including Path Computation Element (PCE)), to manage and optimize the underlying network. Contreras, et al. Expires 5 September 2024 [Page 3] Internet-Draft Slice QoS Mapping March 2024 [I-D.ietf-teas-5g-ns-ip-mpls] discusses the mapping between the 5G QoS framework and the Differentiated Services (DiffServ) model. The DiffServ model uses the DSCP, a 6-bit field in the IPv4 or IPv6 packet header, to classify and prioritize traffic. The mapping between 5QI and DSCP enables the proper handling and forwarding of packets based on their corresponding QoS requirements. To achieve this mapping, the 5G system should have a pre-configured mapping table that associates each 5QI value with a specific DSCP value. When a User Plane Function (UPF) in the 5G system receives packets from a data flow with a specific 5QI, it will consult the mapping table and mark the packets with the appropriate DSCP value before delivering the flow to the network. This marking allows the network to treat and forward the packets according to their QoS requirements based on the DiffServ model. In summary, QoS in the context of network slicing ensures that each slice meets its specific performance requirements. The 5QI is used to differentiate QoS characteristics in 5G systems, and its mapping to DSCP enables the network to classify and prioritize traffic according to their QoS requirements based on the DiffServ model. 4. 5G user traffic classes types 4.1. Scope of the Transport Network The 5G System leverages on the transport network to deliver the traffic flows and interconnect its components. The connectivity between the radio base station (i.e., gNB) and the UPF is tunneled using GTP. It is at the UPF where the GTP tunnel is terminated and where the different 5G flows can be handled according to its corresponding 5QI. Thus, traffic to and from other UPF or an external Data Network (DN) can be marked accordingly by means of corresponding DSCP values. Assuming that both segments, i.e. gNB to UPF, and UPF to DN, can be implemented by means of an IETF Network Slice Service, this implies that forwarding of the 5G flows can be aware or not of the expected service QoS. [I-D.ietf-teas-5g-ns-ip-mpls] provides more details about 5QI-aware and -unaware connectivity models. 4.2. Example of the mapping The following summary of recommendations for 5QI to DSCP mapping is captured on the table {#qos-table}. Contreras, et al. Expires 5 September 2024 [Page 4] Internet-Draft Slice QoS Mapping March 2024 [RFC4594] recommendations provide a framework for how to mark packets with DSCP values to ensure they receive the appropriate level of service for the network, transporting multiple services and service classes within the same infrastructure, representing common or "default" slice. The mapping exercise in [I-D.henry-tsvwg-diffserv-to-qci] expands this framework to 3GPP services and introduces translation of these recommendations into the transport context. The table below is resulting the mapping example of 3GPP services transport resources for a "flat" network slicing scenario as per [TS-23.501] Table 5.7.4-1: Standardized 5QI to QoS characteristics mapping, [TS-23.203] Table 6.1.7-A: Standardized QCI characteristics and [TS-23.502] 1:1 mapping between 5QI and QCI, Procedures for the 5G System (5GS), Annex C. ┏━━━━┳━━━━┳━━━━━━━━━━━┳━━━━━━━━━━━━━┳━━━━━━━━┳━━━━━━━━━━━━━━━━━━━┓ ┃5QI ┃QCI ┃ Resource ┃ Recommended ┃Priority┃ Service ┃ ┃ ┃ ┃ type ┃ DSCP value ┃ level ┃ example ┃ ┣━━━━╋━━━━╋━━━━━━━━━━━╋━━━━━━━━━━━━━╋━━━━━━━━╋━━━━━━━━━━━━━━━━━━━┫ │ 1 │ 1 │ GBR │ EF (DSCP46) │ 20 │ Conversational │ │ │ │ │ │ │ Voice │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 2 │ 2 │ GBR │AF42 (DSCP36)│ 20 │ Conversational │ │ │ │ │ │ │ Video │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 3 │ 3 │ GBR │AF41 (DSCP34)│ 30 │ Real Time │ │ │ │ │ │ │ Gaming, V2X │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 4 │ 4 │ GBR │AF43 (DSCP38)│ 50 │Non-Conversational │ │ │ │ │ │ │ Video │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 65 │ 65 │ GBR │ EF (DSCP46) │ 7 │ Mission Critical │ │ │ │ │ │ │ PTT (MCPTT) │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 66 │ 66 │ GBR │ EF (DSCP46) │ 20 │ Mission Critical │ │ │ │ │ │ │ PTT Voice │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 67 │ 67 │ GBR │ EF (DSCP46) │ 15 │ Mission Critical │ │ │ │ │ │ │ Video UP │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 75 │N/A │ GBR │ EF (DSCP46) │ 2.5 │ V2X messages over │ │ │ │ │ │ │ MBMS bearer │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 5 │ 5 │ Non-GBR │CS5 (DSCP40) │ 10 │ IMS Signalling │ │ │ │ │ │ │ │ Contreras, et al. Expires 5 September 2024 [Page 5] Internet-Draft Slice QoS Mapping March 2024 ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 6 │ 6 │ Non-GBR │AF31 (DSCP26)│ 60 │ TCP-Based │ │ │ │ │ │ │signalling,buffered│ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 7 │ 7 │ Non-GBR │AF11 (DSCP10)│ 70 │Voice, 100ms Video │ │ │ │ │ │ │ streaming, Gaming │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 8 │ 8 │ Non-GBR │AF12 (DSCP12)│ 80 │ 300ms Video │ │ │ │ │ │ │ streaming, Gaming │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 9 │ 9 │ Non-GBR │AF13 (DSCP14)│ 90 │ 300ms Video │ │ │ │ │ │ │ streaming, Gaming │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 10 │ 10 │ Non-GBR │ 0? │ 90 │ 1100ms Video │ │ │ │ │ │ │ streaming, Gaming │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 69 │ 69 │ Non-GBR │CS5 (DSCP 40)│ 5 │ Mission critical │ │ │ │ │ │ │ delay sensitive │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 70 │ 70 │ Non-GBR │AF31 (DSCP26)│ 55 │ Mission critical │ │ │ │ │ │ │ Data │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 79 │ 79 │ Non-GBR │AF41 (DSCP34)│ 65 │ V2x Messages │ │ │ │ │ │ │ │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 80 │ 80 │ Non-GBR │AF21 (DSCP18)│ 68 │ Low Latency eMBB, │ │ │ │ │ │ │ AR/VR │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 82 │ 82 │GBR, Delay │ EF (DSCP46) │ 19 │Discrete Automation│ │ │ │ critical │ │ │ small packets │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 83 │ 83 │GBR, Delay │ EF (DSCP46) │ 22 │Discrete Automation│ │ │ │ critical │ │ │ big packets │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 84 │ 84 │GBR, Delay │ EF (DSCP46) │ 24 │ Intelligent │ │ │ │ critical │ │ │ Transport Systems │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 85 │ 85 │GBR, Delay │ EF (DSCP46) │ 21 │ Electricity │ │ │ │ critical │ │ │ Distribution │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 86 │N/A │GBR, Delay │ EF?(DSCP46) │ 18 │ V2x Collision │ │ │ │ critical │ │ │ Avoidance │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 87 │N/A │GBR, Delay │ EF?(DSCP46) │ 25 │Interactive Service│ │ │ │ critical │ │ │ Motion Track Data │ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 88 │N/A │GBR, Delay │ EF?(DSCP46) │ 25 │ Int. Ser. AI/ML │ │ │ │ critical │ │ │ image recognition │ Contreras, et al. Expires 5 September 2024 [Page 6] Internet-Draft Slice QoS Mapping March 2024 ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 89 │N/A │GBR, Delay │ EF?(DSCP46) │ 25 │ Visual content │ │ │ │ critical │ │ │rendering small pck│ ├────┼────┼───────────┼─────────────┼────────┼───────────────────┤ │ 90 │N/A │GBR, Delay │ EF?(DSCP46) │ 25 │ Visual content │ │ │ │ critical │ │ │ rendering big pck │ └────┴────┴───────────┴─────────────┴────────┴───────────────────┘ 4.3. Example of the grouping The mapping in [I-D.henry-tsvwg-diffserv-to-qci] attemps to make an individual association of 5QI to DSCP values that sometimes cannot result straightforward. A different strategy has been performed in [ORAN-WG9] where the different 5QI types are grouped in classes based on their main Service Level Objectives, nominally the corresponding expected latency, packet loss requirement and traffic type (i.e., guaranteed or non-guaranteed bit rate). For example, the following grouping could be considered: * 5QI/QCI Group 1: flows with 5QIs showing low latency (< 20 ms) and packet loss in the range 10^-4 to 10^-6, corresponding to 5QIs 80, 82, 83, 84, 85, 86. * 5QI/QCI Group 2: flows with 5QIs showing moderate latency values (< 100 ms) with diverse packet loss levels, corresponding to 5QIs 3, 65, 69, 75, 79. * 5QI/QCI Group 3: rest of 5QI of GBR type. * 5QI/QCI Group 4: rest of 5QIs of non-GBR type. 5. 5G user, service traffic classes co-existence in Multi-service network Service provider networks are nowadays typically multiservice. It means, they carry different categories of traffic, like, for example, business traffic, residential traffic, mobile traffic, and so on. Moreover, each category of the traffic might further have different flow types. Again, examples are residential voice (residential phone service implemented via VoIP - voice over IP), IPTV, best effort Internet, etc. Contreras, et al. Expires 5 September 2024 [Page 7] Internet-Draft Slice QoS Mapping March 2024 Therefore, it is expected that 5G mobile traffic, and other traffic might be mixed over the same transport infrastructure. Appropriate resource allocation and QoS strategy is required to ensure that SLOs for traffic with more demanding requirements are met. This is especially important during network failures and traffic rerouting. Such events should not negatively impact priority traffic (e.g. voice or mobile signaling), but may impact less important traffic (e.g. best effort Internet) Typical router hardware has 8 queues. Thus, the large number of flows, with various SLO requirements must be squeezed into maximum 8 queues. In addition to 5G user plane 5QI grouping discussed in Section 4.3, other flows occurring in the network must be taken into account. Table 1 provides an example of typical flows - together with their very high level latency/jitter requirements - that can be observed in the multiservice transport network used to transport 4G/5G flows, and residential/bussines services. Flow type Per-hop latency Per-hop jitter CIPRI (RoE) ~1-20 μs ~1-20 μs eCPRI CU-plane ~1-20 μs ~1-20 μs OAM with aggressive timers ~1 ms ~1 ms 5QI/QCI Group 1 ~1 ms ~1 ms Low latency traffic ~1 ms ~1 ms Network Control ~5 ms ~1-3 ms 4G/5G C-plane and M-plane ~5 ms ~1-3 ms 5QI/QCI Group 2 ~5 ms ~1-3 ms 5QI/QCI Group 3 ~10 ms ~5 ms Guaranteed business traffic ~10 ms ~5 ms 5QI/QCI Group 4 ~10-50 ms ~5-25 ms Best effort none none Figure 1: High-level latency estimations Note: Per-hop latency includes all latency contributors of the transport node, which includes frame transmission delay, self- queueing delay, queuing delay, store-and-forward delay, etc. Values specified in the table are very raw, high-level sample estimations. Exact per-hop requirements depend on the overall network budget, number of hops, budget allocated to fibers, etc. The table intends to emphasize only relative order of magnitude for per-hop latency/ jitter to illustrate the process of assigning traffic to QoS queues. Both Common Public Radio Interface (CPRI), transmitted in Ethernet frames using Radio over Ethernet (RoE) encapsulation, as well as eCPRI Control and User plane (CU-plane), which uses Ethernet frames or IP packets, have very strict latency/jitter requirements, expressed in microseconds. Contreras, et al. Expires 5 September 2024 [Page 8] Internet-Draft Slice QoS Mapping March 2024 Next are low latency (lower miliseconds) flows, like Operations, Administration and Maintenance (OAM) with aggressive timers. Typical examples here are Bidirectional Forwardig Detection (BFD) packets with, e.g., 3x10 miliseconds end-to-end timers, or, CFM (Connectivity Fault Management) frames, again with few miliseconds timers. 5QI/QCI Group 1, as well as residential/business low latency traffic has similar latency requirements. Traffic with medium latency requirements is network control (OSPF, IS-IS, BGP, LDP, PTP aware-mode, ...), mobile control and management plane (C-plane, M-plane), and 5QI/QCI Group 2 traffic. Worth to note is, that only PTP with physical layer time stamping is recommended for 5G applications, as PTP without physical layer time stamping accommodates to much jitter on the end-to-end path between grand master and the client. Jitter of PTP packets with physical layer time stamping is properly accounted based on time stamps, without the need to treat PTP as strict priority traffic. However, QoS features should ensure that PTP packets are not dropped during congestion. Traffic sustaining higher latency is guaranteed business traffic, as well 5QI/QCI Group 3 traffic. And, finally, 5QI/QCI Group 4 and other best effort traffic does not have any specific latency requirements - it is simply served as best effort, if the resources are still available after serving higher priority traffic flows discussed earlier. Depending on the hardware support, there are many QoS models available in the transport nodes. It is out-of-scope for this document to discuss traffic flow mappings to QoS queues in all possible QoS models. However, examples of two most common models are reviewed for reference. 5.1. QoS model with single priority queue In this model, one of the queues is a priority queue, and remaining queues are non-priority queues. Non-priority queues are served only, if the priority queue is empty, which gives strict precedence to priority queue. Non-priority queues are served in a round robin (RR) fashion. Depending on the queueing implementation this can be plain round robin, or weighted round robing (WRR), where non-priority queue with higher weight is served more frequently than non-priority queue with lower weight. This results in lower congestion probability for the queue with higher weight. More advanced scheduling schemes for non-priority queues include weighted deficit round robin (WDRR), or weighted modified deficit round robin (WMDRR). It is out of scope for this document to discuss all possible queue scheduling algoritms. However, the reader is encouraged to read [RFC7806] for more Contreras, et al. Expires 5 September 2024 [Page 9] Internet-Draft Slice QoS Mapping March 2024 information. In single priority queue model, example flow to queue mapping is outlined in Figure 2. ┌────────────────────────────────────────────────────┐ │ PQ | CPRI (RoE), eCPRI CU-P │ Max BW └────────────────────────────────────────────────────┘ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ▲ ┌────────────────────────────────────────────────────┐│ │ │ 100│NPQ-6 | aggressive OAM, 5QI Group 1, low latency │ Max BW │ ├────────────────────────────────────────────────────┤│ │ │ W5│NPQ-5 | relaxed OAM, network control (IGP, PTP, ...)│ │ ├────────────────────────────────────────────────────┤│ │ │ W4│NPQ-4 | 5G CM-P, other management │ W ├────────────────────────────────────────────────────┤│ │ R W3│NPQ-3 | 5QI Group 2, medium latency │ R ├────────────────────────────────────────────────────┤│ │ │ W2│NPQ-2 | 5QI Group 3, guaranteed business traffic │ │ ├────────────────────────────────────────────────────┤│ │ │ 0│NPQ-1 | unused │ │ ├────────────────────────────────────────────────────┤│ │ │ 0│NPQ-0 | 5QI Group 4, best effort │ ▼ └────────────────────────────────────────────────────┘│ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ Figure 2: Flow mapping with single priority queue Note: : The numbers and flow grouping are provided for illustration purposes only and should not be considered as deployment guidance. Priority queue is used to serve strict priority traffic, with microseconds latency requirements. Therefore, CPRI/RoE and eCPRI control and user plane is mapped to priority queue. This queue is always served before non-priority queues, and only when this queue is empty, non-priority queues are served. This has two implications: * the latency of packets served via priority queue is lower (lowest possible in given hardware platform), compared to latency of the packets served by non-priority queue * priority queue can starve non-priority queues, if the traffic volume served by priority queue reaches link capacity. The first characteristic of priority scheduling is anticipated. However, the second characteristics might cause full drops in non- priority queues. Therefore, when priority queue is used, following two measures must be considered: Contreras, et al. Expires 5 September 2024 [Page 10] Internet-Draft Slice QoS Mapping March 2024 * network capacity must be dimensioned in such a way, so that expected maximum CPRI/eCPRI traffic volume does not take entire link capacity. For example, good practice is to dimension the network so that expected maximum CPRI/eCPRI traffic volume do not exceed certain percentage of link capacity, and perform network upgrade, if the limit is crossed. * priority queue is policed/rate-limited to the expected maximum CPRI/eCPRI traffic volume plus some small (10-20%) additional threshold (Max BW in Figure 2) With these measures CPRI/eCPRI traffic can be served without drops and extra latency, while some capacity resources on the link are guaranteed for non-priority traffic. Non-priority queues are served in WRR (or some sort of more advanced weighted scheduling) manner. Traffic with low latency (miliseconds) range should be served via non-priority queue with considerably (order of magnitude) higher weight comparing to other non-priority queues. This causes very frequent queue servicing, which minimizes the delay of the packets served via this queue, as packets do not need to stay to long in the queue. This is the scheduling behavior similar to priority scheduling, therefore policing/rate-limiting of this queue is strongly recommended to avoid nearly starvation of other non-priority queues. Remaining traffic flows might be distributed across remaining non- priority queues, grouping the flows with similar characteristics in the same queue, and providing weights based on network dimensioning, taking into account expected traffic volumes. Queue buffer sizes in all cases must be aligned to maximum latency requirements of the traffic flows assigned to the queue. Non-priority queue for the best effort traffic should have lowest possible weight, so that it is served only in the case there is no packet waiting in any other queue. 5.2. QoS model with multiple priority queues In this model, there are multiple priority queues, serviced strictly in priority order. Remaining, non-priority queues, are serviced in WRR (or some enhanced version of WRR) manner. Example flow to queue mapping using multiple priority QoS model is outlined in Figure 3. Contreras, et al. Expires 5 September 2024 [Page 11] Internet-Draft Slice QoS Mapping March 2024 ┌────────────────────────────────────────────────────┐ │ │ PQ-1 | CPRI (RoE), eCPRI CU-P │ Max BW │ └────────────────────────────────────────────────────┘ │ ┌────────────────────────────────────────────────────┐ │ │ PQ-0 | aggressive OAM, 5QI Group 1, low latency │ Max BW ▼ └────────────────────────────────────────────────────┘ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ▲ ┌────────────────────────────────────────────────────┐│ │ │ W5│NPQ-5 | relaxed OAM, network control (IGP, PTP, ...)│ │ ├────────────────────────────────────────────────────┤│ │ │ W4│NPQ-4 | 5G CM-P, other management │ │ ├────────────────────────────────────────────────────┤│ │ W W3│NPQ-3 | 5QI Group 2, medium latency │ R ├────────────────────────────────────────────────────┤│ │ R W2│NPQ-2 | 5QI Group 3, guaranteed business traffic │ │ ├────────────────────────────────────────────────────┤│ │ │ 0│NPQ-1 | unused │ │ ├────────────────────────────────────────────────────┤│ │ │ 0│NPQ-0 | 5QI Group 4, best effort │ ▼ └────────────────────────────────────────────────────┘│ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ Figure 3: Flow mapping with multiple priority queues Note: : The numbers and flow grouping are provided for illustration purposes only and should not be considered as deployment guidance. The main difference comparing to the previous example is the 2nd priority queue (PQ-0), dedicated to low latency flows, like OAM with aggressive timers, or 5GI Group 1 flows. PQ-0 queue is only served, when the PQ-1 queue is empty. Thus, while both PQ-1 and PQ-0 queues are used to serve traffic with low latency requirements, traffic served via PQ-1 will observe smaller latency compared to traffic served via PQ-0. As already discussed previously, rate-limiter/ policer should be used on both priority queues to avoid complete starvation of non-priority queues. 6. Acknowledgments The contribution of L.M. Contreras has been partially funded by the Spanish Ministry of Economic Affairs and Digital Transformation and the European Union - NextGenerationEU under projects 6GBLUR-smart (Ref. TSI-063000-2021-56) and 6GBLUR-joint (Ref. TSI- 063000-2021-57). 7. References 7.1. Normative References Contreras, et al. Expires 5 September 2024 [Page 12] Internet-Draft Slice QoS Mapping March 2024 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 7.2. Informative References [draft-henry-tsvwg-diffserv-to-qci] "Diffserv to QCI Mapping", 19 April 2023, . [I-D.henry-tsvwg-diffserv-to-qci] Henry, J., Szigeti, T., and L. M. Contreras, "Diffserv to QCI Mapping", Work in Progress, Internet-Draft, draft- henry-tsvwg-diffserv-to-qci-04, 13 April 2020, . [I-D.ietf-teas-5g-ns-ip-mpls] Szarkowicz, K. G., Roberts, R., Lucek, J., Boucadair, M., and L. M. Contreras, "A Realization of Network Slices for 5G Networks Using Current IP/MPLS Technologies", Work in Progress, Internet-Draft, draft-ietf-teas-5g-ns-ip-mpls- 03, 28 February 2024, . [I-D.ietf-teas-ietf-network-slices] Farrel, A., Drake, J., Rokui, R., Homma, S., Makhijani, K., Contreras, L. M., and J. Tantsura, "A Framework for Network Slices in Networks Built from IETF Technologies", Work in Progress, Internet-Draft, draft-ietf-teas-ietf- network-slices-25, 14 September 2023, . [ORAN-WG9] "O-RAN Xhaul Packet Switched Architectures and Solutions", February 2024, . Contreras, et al. Expires 5 September 2024 [Page 13] Internet-Draft Slice QoS Mapping March 2024 [RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration Guidelines for DiffServ Service Classes", RFC 4594, DOI 10.17487/RFC4594, August 2006, . [RFC7806] Baker, F. and R. Pan, "On Queuing, Marking, and Dropping", RFC 7806, DOI 10.17487/RFC7806, April 2016, . [TS-23.203] "3GPP TS 23.203: Policy and charging control architecture", 23 December 2021, . [TS-23.207] "3GPP TS 23.207 End-to-end Quality of Service (QoS) concept and architecture", 25 March 2022, . [TS-23.501] "3GPP TS 23.501: System architecture for the 5G System (5GS)", 25 March 2022, . [TS-23.502] "3GPP TS 23.502: Procedures for the 5G System (5GS)", 19 December 2023, . [TS-29.213] "3GPP TS 29.213 Policy and Charging Control signalling flows and Quality of Service (QoS) parameter mapping", 21 March 2022, . [TS-29.513] "3GPP TS-29.513 5G System; Policy and Charging Control signalling flows and QoS parameter mapping; Stage 3", 7 June 2023, . Contreras, et al. Expires 5 September 2024 [Page 14] Internet-Draft Slice QoS Mapping March 2024 Authors' Addresses Luis M. Contreras (editor) Telefonica Email: luismiguel.contrerasmurillo@telefonica.com Ivan Bykov (editor) Ribbon Communications Email: Ivan.Bykov@rbbn.com Krzysztof G. Szarkowicz (editor) Juniper Networks Email: kszarkowicz@juniper.net Contreras, et al. Expires 5 September 2024 [Page 15]