Internet DRAFT - draft-decraene-mpls-slid-encoded-entropy-label-id
draft-decraene-mpls-slid-encoded-entropy-label-id
MPLS B. Decraene, Ed.
Internet-Draft Orange
Updates: 6790 (if approved) C. Filsfils
Intended status: Standards Track Cisco Systems, Inc.
Expires: 15 June 2023 W. Henderickx
Nokia
T. Saad
V. Beeram
Juniper Networks
L. Jalil
Verizon
12 December 2022
Using Entropy Label for Network Slice Identification in MPLS networks.
draft-decraene-mpls-slid-encoded-entropy-label-id-05
Abstract
This document updates [RFC6790] to extend the use of the TTL field of
the Entropy Label in order to provide a flexible set of flags called
the Entropy Label Control field.
This document also defines a solution to encode a slice identifier in
MPLS in order to distinguish packets that belong to different slices,
to allow enforcing per network slice policies (.e.g, Qos).
The slice identification is independent of the topology. It allows
for QoS/DiffServ policy on a per slice basis in addition to the per
packet QoS/DiffServ policy provided by the MPLS Traffic Class field.
In order to minimize the size of the MPLS stack and to ease
incremental deployment the slice identifier is encoded as part of the
Entropy Label.
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/.
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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This Internet-Draft will expire on 15 June 2023.
Copyright Notice
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document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Entropy Label Control field . . . . . . . . . . . . . . . . . 3
4. Slice Identifier . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Ingress LSR . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Transit LSR . . . . . . . . . . . . . . . . . . . . . . . 5
4.3. Bandwidth-Allocation Slice . . . . . . . . . . . . . . . 5
4.4. Backward Compatibility . . . . . . . . . . . . . . . . . 5
4.5. Benefits . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Examples of more ELC usages . . . . . . . . . . . . . . . . . 6
5.1. End to end absolute loss measurements . . . . . . . . . . 6
5.2. Programmed sampling of packets . . . . . . . . . . . . . 6
6. Deployment Considerations . . . . . . . . . . . . . . . . . . 7
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
10. Changes / Authors Notes . . . . . . . . . . . . . . . . . . . 7
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
12.1. Normative References . . . . . . . . . . . . . . . . . . 8
12.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
This document defines a solution to encode a slice identifier in MPLS
in order to provide QoS on a per slice basis. It allows for QoS/
DiffServ policy on a per slice basis in addition to the per packet
QoS/DiffServ policy provided by the MPLS Traffic Class field. The
slice identification is independent of the topology and the QoS of
the network, thus enabling scalable network slicing.
This document encodes the slice identifier in a portion of the MPLS
Entropy Label (EL) defined in [RFC6790] . This has advantages as it
avoids the use of additional label which would increase the size of
the label stack. This also reuses the data plane processing of the
Entropy Label on the egress LSR, the signaling of the Entropy Label
capability from the egress to the ingress [RFC9088] [RFC9089] , and
the signaling capability of transit routers to read this label
[RFC8491] which allows for an easier and faster incremental
deployment.
2. Requirements Language
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.
3. Entropy Label Control field
[RFC6790] defines the MPLS Entropy Label. [RFC6790] section 4.2
defines the use of the Entropy Label Indicator (ELI) followed by the
Entropy Label (EL) and the MPLS header fields (Label, TC, S, TTL) in
each. [RFC6790] also specifies that the TTL field of the EL must be
set to zero by the ingress LSR.
Following the procedures of [RFC6790] EL is never used for forwarding
and its TTL is never looked at nor decremented:
* An EL capable Egress LSR performs a lookup on the ELI and as a
result pop two labels: ELI and EL.
* An EL non-capable Egress LSR performs a lookup on the ELI and as a
result must drop the packet as specified in [RFC3031] for the
handling of an invalid incoming label.
Hence essentially the TTL field of the EL behaves as a reserved field
which must be set to zero when sent and ignored when received.
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This documents extends the TTL field of the EL and calls it the
Entropy Label Control (ELC) field. The ELC is a set of eight flags:
ELC0 for bit 0, ELC1 for bit 1,..., ELC7 for bit 7.
Given that the MPLS header is very compact (32 bits) with no reserved
bits and that MPLS is used within a trusted administrative domain,
the semantic of these bits is not standardized but defined on a per
administrative domain basis. This allows for increased re-use and
flexibility of this scarce resource. As a consequence, an
application using one of those buts MUST allow the choice of the bit
by configuration by the network operator.
4. Slice Identifier
Each network slice in an MPLS domain is uniquely identified by a
Slice Identifier (SLID) [I-D.bestbar-teas-ns-packet] . This section
encodes the SLID in a portion of the MPLS Entropy Label defined in
[RFC6790] .
The number of bits to be used for encoding the SLID in the EL is
governed by a local policy and uniform within a network slice policy
domain.
4.1. Ingress LSR
When an ingress LSR classifies that a packet belongs to the slice and
that the egress has indicated via signaling that it can process EL
for the tunnel, the ingress LSR pushes an Entropy Label with the:
* SLID encoded in the most significant bits of the Entropy Label.
* the entropy information encoded in the remaining lower bits of the
Entropy Label as described in section 4.2 of [RFC6790] .
* SPI bit (SLID Presence Indicator) set in one bit of the ELC field.
The choice of the ELC field used for SPI, and the number of bits to
be used for encoding the SLID MUST be configurable by the network
operator.
The slice classification method is outside the scope of this
document.
The encoding of the Slide ID in the Entropy Label is in line with the
specification of the Flow Label as the slide identification _is_ a
property of the flow:
* For a given flow it is constant in all packets.
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* It's a property specific to the flow so would typically be used to
determine the Entropy Label.
4.2. Transit LSR
Any LSR that forwards a packet with the SPI bit set MUST use the SLID
to select a slice and apply per-slice policies.
There are many different policies that could define a slice for a
particular application or service. The most basic of these is
bandwidth-allocation, an implementation complying with this
specification SHOULD support the bandwidth-allocation slice as
defined in the next section.
4.3. Bandwidth-Allocation Slice
A per-slice policy is configured at each interface of each router in
the domain, with one traffic shaper per SLID. The bit rate of each
shaper is configured to reflect the bandwidth allocation of the per-
slice policy.
If shapers are not available, or desirable, an implementation MAY
configure one scheduling queue per SLID with a guaranteed bandwidth
equal to the bandwidth-allocation for the slice. This option allows
a slice to consume more bandwidth than its allocation when available.
Per-slice shapers or queues effectively provides a virtual port per
slice. This solution MAY be complemented with a per-virtual-port
hierarchical DiffServ policy. Within the context of one specific
slice, packets are further classified into children DiffServ queues
which hang from the virtual port. The Traffic Class value in the
MPLS header SHOULD be used for queue selection.
4.4. Backward Compatibility
The Entropy Label usage described in this document is consistent with
[RFC6790] as ingress LSRs freely chooses the EL of a given flow, and
transit LSRs treat the EL as an opaque set of bits.
As per [RFC6790] an ingress LSR that does not support this extension
has the SPI bit cleared, and thus does not enable the SLID semantic
of the Entropy bits. Hence, SLID-aware transit LSRs will not
classify these packets into a slice.
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4.5. Benefits
From a Segment Routing architecture perspective, this network slice
identifier for SR-MPLS is inline with the network slice identifier
for SRv6 proposed in [I-D.filsfils-spring-srv6-stateless-slice-id] .
From an SR-MPLS perspective, using the EL to carry the network slice
identifier has multiple benefits:
* This limits the number of labels pushed on the MPLS stack compared
to using a pair of labels (ELI+EL) for flow entropy plus two or
three labels for the slice indicator and the slice identifier.
This is beneficial for the ingress LSR which may have limitations
with regards to the number of labels pushed, for the transit LSR
which may have limitations with regards to the label stack depth
to be examined during transit in order to read both the entropy
and the SLID. This presents additional benefit to network
operators by reducing the packet overhead for traffic carried
through the network;
* This avoids defining new extensions for the signaling of the
egress capability to support the slice indicator and the slice
identifier;
* This improves incremental deployment as all egress LSRs supporting
EL can be sent the slice identifier from day one, allowing slice
classification on transit LSRs.
5. Examples of more ELC usages
5.1. End to end absolute loss measurements
This section describes the usage of a ELC flag to enable packet loss
measurements, as described in section 3.1 of [RFC8321] .
TBD
5.2. Programmed sampling of packets
This section describes the usage of a ELC flag to detect end to end
packet loss.
TBD
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6. Deployment Considerations
The number of bits to be used for encoding the SLID in the EL affects
the number of effective entropy bits. The total number of raw bits
available for encoding entropy is not changed as the slice ID is part
of the flow identification and contains some entropy. However this
is expected to reduce the effective number of entropy bit as the
slice ID is likely to less effectively encode entropy information
compared to the use of a good hash function. The effective reduction
of entropy depends on how good the [RFC6790] entropy value is
computed (which is implementation dependent) and the statistical
distribution of the usage of slice identifier. In order to minimize
this reduction, network operators should set the size of the field
encoding the slice identifier to the minimum size required for the
number of slides used in deployment.
7. Implementation Status
The following hardware platforms support "end-to-end" network
slicing/ partitioning as described in Section 4 :
* Cisco NCS platforms based on Broadcom Jericho2 family of ASIC.
The support includes the ingress as well as the transit LSRs
roles.
8. Security Considerations
The MPLS forwarding plane is insecure. If an adversary can affect
the forwarding plane, then they can inject data, remove data, corrupt
data, or modify data.
This documents additionnally allows an adversary to change the slice
of a packet, and to add or remove indicators/flags.
Link-level security mechanisms can help mitigate some on-link
attacks, but does nothing to preclude hostile nodes.
9. IANA Considerations
This document has no IANA actions.
10. Changes / Authors Notes
[RFC Editor: Please remove this section before publication]
00: Initial version.
01: New co-author
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02: Editorial precision that the slice ID is a component of flow
entropy hence inline with the use of entropy label.
03: Refresh.
04: New sections: Implementation Status, Security Considerations,
Deployment Considerations, Requirements Language, IANA
Considerations. Editorial: replace "SR-MPLS" by "MPLS".
05: Refresh.
11. Acknowledgements
Authors would like to thanks Zafar Ali for his contributions.
12. References
12.1. Normative References
[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>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, DOI 10.17487/RFC6790, November 2012,
<https://www.rfc-editor.org/info/rfc6790>.
[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/info/rfc8174>.
[RFC9088] Xu, X., Kini, S., Psenak, P., Filsfils, C., Litkowski, S.,
and M. Bocci, "Signaling Entropy Label Capability and
Entropy Readable Label Depth Using IS-IS", RFC 9088,
DOI 10.17487/RFC9088, August 2021,
<https://www.rfc-editor.org/info/rfc9088>.
[RFC9089] Xu, X., Kini, S., Psenak, P., Filsfils, C., Litkowski, S.,
and M. Bocci, "Signaling Entropy Label Capability and
Entropy Readable Label Depth Using OSPF", RFC 9089,
DOI 10.17487/RFC9089, August 2021,
<https://www.rfc-editor.org/info/rfc9089>.
12.2. Informative References
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[I-D.bestbar-teas-ns-packet]
Saad, T., Beeram, V. P., Dong, J., Wen, B., Ceccarelli,
D., Halpern, J. M., Peng, S., Chen, R., Liu, X.,
Contreras, L. M., Rokui, R., and L. Jalil, "Realizing
Network Slices in IP/MPLS Networks", Work in Progress,
Internet-Draft, draft-bestbar-teas-ns-packet-10, 5 May
2022, <https://www.ietf.org/archive/id/draft-bestbar-teas-
ns-packet-10.txt>.
[I-D.filsfils-spring-srv6-stateless-slice-id]
Filsfils, C., Clad, F., Camarillo, P., Raza, S., Voyer,
D., and R. Rokui, "Stateless and Scalable Network Slice
Identification for SRv6", Work in Progress, Internet-
Draft, draft-filsfils-spring-srv6-stateless-slice-id-06,
29 July 2022, <https://www.ietf.org/archive/id/draft-
filsfils-spring-srv6-stateless-slice-id-06.txt>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>.
[RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli,
L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi,
"Alternate-Marking Method for Passive and Hybrid
Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321,
January 2018, <https://www.rfc-editor.org/info/rfc8321>.
[RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
"Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491,
DOI 10.17487/RFC8491, November 2018,
<https://www.rfc-editor.org/info/rfc8491>.
Authors' Addresses
Bruno Decraene (editor)
Orange
Email: bruno.decraene@orange.com
Clarence Filsfils
Cisco Systems, Inc.
Belgium
Email: cf@cisco.com
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Wim Henderickx
Nokia
Copernicuslaan 50
95134 Antwerp 2018
Belgium
Email: wim.henderickx@nokia.com
Tarek Saad
Juniper Networks
Email: tsaad@juniper.net
Vishnu Pavan Beeram
Juniper Networks
Email: vbeeram@juniper.net
Luay Jalil
Verizon
Email: luay.jalil@verizon.com
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