Internet DRAFT - draft-cbs-teas-5qi-to-dscp-mapping
draft-cbs-teas-5qi-to-dscp-mapping
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
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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.
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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
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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.
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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.
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[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}.
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[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 │
│ │ │ │ │ │ │
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├────┼────┼───────────┼─────────────┼────────┼───────────────────┤
│ 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 │
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├────┼────┼───────────┼─────────────┼────────┼───────────────────┤
│ 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.
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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.
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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
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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:
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* 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.
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┌────────────────────────────────────────────────────┐
│ │ 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
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
7.2. Informative References
[draft-henry-tsvwg-diffserv-to-qci]
"Diffserv to QCI Mapping", 19 April 2023,
<https://datatracker.ietf.org/doc/html/draft-henry-tsvwg-
diffserv-to-qci-04>.
[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,
<https://datatracker.ietf.org/doc/html/draft-henry-tsvwg-
diffserv-to-qci-04>.
[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,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-5g-
ns-ip-mpls-03>.
[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,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
ietf-network-slices-25>.
[ORAN-WG9] "O-RAN Xhaul Packet Switched Architectures and Solutions",
February 2024,
<https://orandownloadsweb.azurewebsites.net/
specifications>.
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[RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration
Guidelines for DiffServ Service Classes", RFC 4594,
DOI 10.17487/RFC4594, August 2006,
<https://www.rfc-editor.org/rfc/rfc4594>.
[RFC7806] Baker, F. and R. Pan, "On Queuing, Marking, and Dropping",
RFC 7806, DOI 10.17487/RFC7806, April 2016,
<https://www.rfc-editor.org/rfc/rfc7806>.
[TS-23.203]
"3GPP TS 23.203: Policy and charging control
architecture", 23 December 2021,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3145>.
[TS-23.207]
"3GPP TS 23.207 End-to-end Quality of Service (QoS)
concept and architecture", 25 March 2022,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=814>.
[TS-23.501]
"3GPP TS 23.501: System architecture for the 5G System
(5GS)", 25 March 2022,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3144>.
[TS-23.502]
"3GPP TS 23.502: Procedures for the 5G System (5GS)", 19
December 2023,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3145>.
[TS-29.213]
"3GPP TS 29.213 Policy and Charging Control signalling
flows and Quality of Service (QoS) parameter mapping", 21
March 2022,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=1673>.
[TS-29.513]
"3GPP TS-29.513 5G System; Policy and Charging Control
signalling flows and QoS parameter mapping; Stage 3", 7
June 2023,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=810>.
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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
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