DeNet WG Quan Xiong
Internet-Draft Jinghai Yu
Intended status: Standards Track ZTE Corporation
Expires: September 12, 2019 March 11, 2019
DetNet QoS Policy
draft-xiong-detnet-qos-policy-01
Abstract
This document proposes a Quality of Service (QoS) policy to apply
Differentiated Services (DiffServ) model for Deterministic Networking
(DetNet) and defines a DetNet DiffServ mechanism including DetNet IP
and MPLS encapsulation.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. DetNet DiffServ Overview . . . . . . . . . . . . . . . . . . 3
2.1. DetNet Classifiers . . . . . . . . . . . . . . . . . . . 4
2.2. DetNet Traffic Conditioners . . . . . . . . . . . . . . . 4
2.2.1. Scheduler . . . . . . . . . . . . . . . . . . . . . . 5
2.2.2. Order . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. DetNet DSCP . . . . . . . . . . . . . . . . . . . . . . . 5
2.4. DetNet PHB . . . . . . . . . . . . . . . . . . . . . . . 5
2.5. DetNet Queuing . . . . . . . . . . . . . . . . . . . . . 6
3. DetNet IP DiffServ Consideration . . . . . . . . . . . . . . 6
4. DetNet MPLS DiffServ Consideration . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Informative References . . . . . . . . . . . . . . . . . 7
8.2. Normative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
As defined in [I-D.ietf-detnet-architecture], Deterministic
Networking (DetNet) provides a capability to carry specified unicast
or multicast data flows for real-time applications with extremely low
data loss rates and bounded latency. DetNet and non-DetNet packets
may be allowed to transmitted in the same network and more than one
DetNet flows which has different priorities may be forwarded through
the DetNet domain. The DetNet Class of Service (CoS) should be taken
into consideration to provide Quality of Service (QoS) for DetNet
services.
As discussed in [I-D.ietf-detnet-dp-sol-ip], Differentiated Services
(DiffServ) can be used to provide traffic forwarding treatment for
DetNet network. The DiffServ architecture as specified in [RFC2475]
defined a model that traffic entering a DiffServ domain is classified
and conditioned at the boundaries and marked with a DiffServ Code
Point (DSCP) defined in [RFC2474]. The DSCP is used at transit nodes
to select the Per Hop Behavior (PHB) that determines the scheduling
treatment. And [RFC3270] provide a solution to support DiffServ for
traffic marked with Traffic Class (TC) [RFC5462] transported over an
MPLS network.
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This document proposes a QoS policy to apply DiffServ model for
DetNet network and defines a DetNet DiffServ mechanism including
DetNet IP and MPLS encapsulation.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
1.2. Terminology
The terminology is defined as [I-D.ietf-detnet-architecture],
[RFC3270], [RFC2475] and [RFC2474].
2. DetNet DiffServ Overview
The DetNet network needs to be capable of supporting differentiated
services dividing to one or more contiguous DiffServ domains. The
key components within a DiffServ domain including traffic
classification and conditioning functions, and PHB-based forwarding.
The customers may specify packet classification policy, traffic
profiles and actions to DetNet flows which are in-profile or out-of-
profile at the boundary. The DiffServ domains may support different
PHB groups internally and different codepoint->PHB mappings at the
transit nodes. The DetNet DiffServ process for packets is as
Figure 1 shown.
+---------+
| Meter |-----------------------------------+
+----->| (DetNet |------------------+ |
| | Profile)|--+ | |
| +---------+ | | |
| V V V
DetNet+------------+ +----------+ +------------+ +---------+
Flow | Classifier | | Marker | |Shaper/Order| | Queuing |
=====>| (DetNet |====>| (DetNet |====>| Dropper/ |====>| (DetNet |
| BA/MF) | | DSCP) | | Scheduler/ | | PHB) |
+------------+ +----------+ +------------+ +---------+
Figure 1: Overview of a DetNet DiffServ mechanism
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2.1. DetNet Classifiers
As defined in [RFC2475], packet classifiers select packets in a
traffic stream based on the information of packet header including
two types of classifiers, the BA (Behavior Aggregate) and MF (Multi-
Field) Classifier. The difference is that the BA classifies packets
based on the CoS field and the latter one based on more other header
fields.
In DetNet DiffServ model, BA and MF can be applied for packets
classification. After classification, the flows can be seperated
from DetNet and non-DetNet. As specified in
[I-D.ietf-detnet-dp-sol-ip], no DetNet specific encapsulation is
defined to support DetNet IP flow identification and DetNet service
delivery. So the DetNet IP classifiers is the same as defined in
[RFC2474] and [RFC2475]. As defined in
[I-D.ietf-detnet-dp-sol-mpls], DetNet service Label (S-Label) is used
to identify a DetNet flow and forwarding labels (F-Labels) are used
to provide LSP-based connectivity in DetNet MPLS header. The S-Label
and F-Labels can be used in combination with MPLS TC filed in MF
classifier. And DetNet MPLS BA classifier select packets based on
the MPLS TC field only as defined in [RFC5462].
2.2. DetNet Traffic Conditioners
As mentioned in [I-D.ietf-detnet-architecture], DetNet flows can be
shaped or scheduled. The rate limiting of DetNet traffic and the
starvation avoiding of non-DetNet traffic, e.g., at the ingress of
the DetNet domain must be applied by traffic policing and shaping
functions. As [RFC2475] defined, the traffic conditioner may contain
four elements: meter, marker, shaper and dropper. Traffic
conditioning performs metering, shaping, policing and/or re-marking
to ensure the traffic which entering the DiffServ domain conforms to
the service provisioning policy.
In DetNet, the traffic policing and conditioning SHOULD include
meter, marker, shaper, dropper, scheduler and order. A meter with a
DetNet Profile is used to measure the DetNet flows selected by a
DetNet classifier and the result of the meter with respect to a
packet may be used to trigger a DetNet action including a marking,
shaping, dropping, scheduling or ordering. A marker is used to set
the Cos field of a DetNet packet to a DetNet DSCP (section 2.3),
mapping the marked packet to a DetNet PHB. A Shaper may apply
specific shaping algorithms implemented by DetNet network, e.g.,
credit-based shaper [IEEE802.1Qav]. A dropper is used to discard
some of the non-DetNet packets to provide the QoS of the DetNet flows
when congestion occurs.
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2.2.1. Scheduler
As decribed in [I-D.ietf-detnet-architecture], the DetNet flows can
be scheduled to achieve time-based synchronization for scheduled
traffic. This document proposes a new type of action for DetNet
traffic conditioning named Scheduler action. A scheduler may apply
specific scheduling and related Queuing algorithms implemented by
DetNet network, e.g., Time-gated queues [IEEE802.1Qbv] and Cyclic
Queuing and Forwarding [IEEE802.1Qch].
2.2.2. Order
As defined in [I-D.ietf-detnet-dp-sol-mpls], DetNet control word
(d-CW) containing sequencing information for packet replication and
duplicate elimination purposes. Sequence Number is different packet-
by-packet. Based on Detnet MPLS date plane encapsulation, this
document proposes a new type of action for DetNet traffic
conditioning named order action which used to reorder the packets
within a DetNet flow that are received out of order.
2.3. DetNet DSCP
The DetNet DSCP carried in CoS field in IP header and TC field in
MPLS header may be uesd to mark packets at ingress nodes and select a
DetNet PHB (section 2.4) at transit nodes. DetNet DSCP MUST be
defined to one or more particular values, which MUST be unique for
codepoints in the standard space.
[Ed.note: We need to define one or more DetNet DSCP values and
related DetNet PHB for DetNet-specific treatment.]
2.4. DetNet PHB
As specified in [RFC2475], per-hop behaviors are defined to permit a
reasonably granular means of allocating buffer and bandwidth
resources at each node among competing traffic streams. PHB groups
will usually share a common constraint such as a packet scheduling or
buffer management policy. According to [RFC4594], Default Forwarding
(DF) PHB, Assured Forwarding (AF) PHBs, Expedited Forwarding (EF) PHB
and Class Selector (CS) PHBs have been defined to provide forwarding
treatment. These PHBs can be used to forward DetNet flows based on
the requirement.
This document defines a new type of Deterministic Networking (DN) PHB
which is intended for traffic requiring extremely low data loss rates
and bounded latency for DetNet. The DN PHB may include a set of PHB
classes, e.g., DN1,DN2,etc. And the number of the class is the same
with the DetNet DSCP values. The DSCP in IP header and TC in MPLS
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header should be mapped to DN PHB with the relevant PHB specification
which may be completed in future discussion.
2.5. DetNet Queuing
As discussed in [I-D.ietf-detnet-architecture],the nodes in DetNet
network shall queue each received packets to one of the potential
transmission ports and provide storage for queued packets, awaiting
to submit these for transmission. A port provides one or more queues
corresponding to the number of traffic classes. The queuing
mechanism should be configured and implemented to DetNet nodes.
As defined in [RFC4594], Priority Queuing (PQ) was defined to queue
the packets in priority sequence and Rate Queuing (RQ)selects packets
according to the specified rate including Weighted Fair Queuing (WFQ)
and Weighted Round Robin (WRR). Active Queue Management (AQM) also
be defined to use packet dropping or marking to manage the depth of a
queue.
As per IEEE 802.1 WG, queuing and transmission selection algorithms
also can be used for queue scheduling in DetNet network.
3. DetNet IP DiffServ Consideration
As specified in [I-D.ietf-detnet-dp-sol-ip], no DetNet specific
encapsulation is defined to support DetNet IP flow identification and
DetNet service delivery. So the DetNet IP classification is the same
as defined in [RFC2474] and [RFC2475]. But the recommended DetNet
DSCP may be uesd to mark packets to select a DetNet PHB and the
transit nodes should implement mechanisms performing the PHB. The
mapping of DSCP to PHBs MUST be configurable. Implementations should
support the recommended codepoint-to-PHB mappings in their default
configuration.
4. DetNet MPLS DiffServ Consideration
As defined in [I-D.ietf-detnet-dp-sol-mpls], DetNet S-Label and
F-Labels can be used in combination with MPLS TC filed in MF
classifier. The BA classifier is the same with the [RFC3270].
Two types of LSPs including Explicitly TC-encoded-PSC LSP (E-LSP) and
Label-Only-Inferred-PSC LSP (L-LSP) follows the definition of
[RFC3270] and can be used to support DetNet explicit routes in MPLS-
TE LSP. A E-LSP can be used to support one or more DetNet flows and
a L-LSP can be established for one flow. E-LSP and L-LSP can use a
signaled TC->PHB mapping to forward packets whose corresponding PHBs
are defined in this document.
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In DetNet MPLS network, DetNet Layer Two Service is supported in TSN
over MPLS. The LSP egressing over egde nodes can use the
preconfigured PHB->802.1 mapping as defined in [RFC3270].
As specified in [RFC3270], there may be more than one LSP carrying
the same flow. Two or more LSPs can be merged into one LSP at one
egressing LSR. It can be used to perform the packet replication
(PRF) at ingress nodes and the packet elimination (PEF) at the egress
nodes in DetNet DiffServ model. The order action which defined in
this document can be used for packet ordering functionality (POF).
5. Security Considerations
TBD.
6. IANA Considerations
TBD.
7. Acknowledgements
TBD.
8. References
8.1. Informative References
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<https://www.rfc-editor.org/info/rfc2475>.
8.2. Normative References
[I-D.ietf-detnet-architecture]
Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", draft-ietf-
detnet-architecture-11 (work in progress), February 2019.
[I-D.ietf-detnet-dp-sol-ip]
Korhonen, J. and B. Varga, "DetNet IP Data Plane
Encapsulation", draft-ietf-detnet-dp-sol-ip-01 (work in
progress), October 2018.
[I-D.ietf-detnet-dp-sol-mpls]
Korhonen, J. and B. Varga, "DetNet MPLS Data Plane
Encapsulation", draft-ietf-detnet-dp-sol-mpls-01 (work in
progress), October 2018.
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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/info/rfc2119>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>.
[RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
Protocol Label Switching (MPLS) Support of Differentiated
Services", RFC 3270, DOI 10.17487/RFC3270, May 2002,
<https://www.rfc-editor.org/info/rfc3270>.
[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/info/rfc4594>.
[RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching
(MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
Class" Field", RFC 5462, DOI 10.17487/RFC5462, February
2009, <https://www.rfc-editor.org/info/rfc5462>.
Authors' Addresses
Quan Xiong
ZTE Corporation
No.6 Huashi Park Rd
Wuhan, Hubei 430223
China
Phone: +86 27 83531060
Email: xiong.quan@zte.com.cn
Jinghai Yu
ZTE Corporation
50 Software Avenue, YuHuaTai District
Nanjing, Jiangsu 210012
China
Phone: +86 025 26774049
Email: yu.jinghai@zte.com.cn
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