Internet DRAFT - draft-wang-lsr-flex-algo-link-loss
draft-wang-lsr-flex-algo-link-loss
Network Working Group Y. Wang
Internet-Draft G. Xu
Intended status: Standards Track X. Geng
Expires: 23 August 2024 J. Dong
Huawei
20 February 2024
IGP Flexible Algorithm with Link Loss
draft-wang-lsr-flex-algo-link-loss-01
Abstract
IGP Flexible Algorithms allow IGPs to compute constraint-based paths.
Since link packet loss rate plays an important role in network
evaluation, links with high packet loss rate should be bypassed
during forwarding. This draft proposes a path computation method
based on a maximum link loss constraint to prune unsatisfied links in
Flexible Algorithms.
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 BCP 14 [RFC2119]
[RFC8174] when, and only when, they appear in all capitals, as shown
here.
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
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Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 23 August 2024.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Exclude Maximum Link Loss Sub-TLV . . . . . . . . . . . . . . 4
2.1. IS-IS Exclude Maximum Link Loss Sub-TLV . . . . . . . . . 4
2.2. OSPF Exclude Maximum Link Loss Sub-TLV . . . . . . . . . 5
3. Calculation of Flexible Algorithm Paths . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
4.1. IS-IS Sub-Sub-TLVs for Flexible Algorithm Definition
Sub-TLV . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. OSPF Sub-Sub-TLVs for Flexible Algorithm Definition
Sub-TLV . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Normative References . . . . . . . . . . . . . . . . . . 6
5.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Link packet loss rate (link loss) is a measure of the percentage of
data packets that are lost during transmission over a network. It is
an important performance metric that directly impacts the quality of
service, network congestion, security, and overall network
efficiency. Ensuring a low packet loss rate is essential for
maintaining efficient and secure network operations. Consequently,
It is necessary to avoid passing through links with a high packet
loss rate during forwarding.
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The link loss is advertised by the Unidirectional Link Loss Sub-TLV
defined in [RFC8570] by IS-IS and [RFC7471] by OSPF, which describes
the loss (as a packet percentage) between two directly connected IS-
IS neighbors. This Sub-TLV is carried in the Application-Specific
Link Attributes Sub-TLV advertised by IS-IS [RFC9479] or OSPF
[RFC9492]. The link packet loss rate can be measured by methods such
as TWAMP [RFC5357] and STAMP [RFC8762], which is beyond the scope of
this draft.
IGP Flexible Algorithms allow IGPs to compute constraint-based paths
[RFC9350]. Current path computation methods are based on calculating
the minimum cost of the path from the source to the destination.
Flex-Algorithm has already supported path computation with the IGP
cost, the minimum link delay and the traffic-engineering metric.
[I-D.ietf-lsr-flex-algo-bw-con] defines a family of generic metrics
(e.g. bandwidth based metric type) and bandwidth related constraints
to support path computation based on bandwidth. However, current
calculation types and metric types cannot support path computation
based on link loss, since the cost of the path should be defined as
the maximum/minimum value among all passing links.
To overcome the above issue, there are two solutions. First, new
operators like maximum value operator can be defined, which works as
a step function. When the link loss exceeds a threshold, the cost of
the link is set to the maximum. Second, new Flexible Algorithm
Definition (FAD) constraints can be defined to exclude links that do
not meet the link loss requirements during path calculation. The
second method is specifically demonstrated in this draft. The
general ideas are as below.
1. The link loss is used as a link constraint for path
computation. That is, the link whose loss rate is greater than
the specified value is excluded.
2. Metric-type remains unchanged: igp, te, and delay.
With a new FAD constraint Sub-TLV advertised by IGP, links with low
packet loss rate will be selected for path computation. The new
Exclude Maximum Link Loss Sub-TLVs are defined in Section 2. The
Flex-Algorithm calculation method based on link loss is presented in
Section 3.
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2. Exclude Maximum Link Loss Sub-TLV
A new Exclude Maximum Link Loss Sub-TLV is defined as a sub-TLV of
the FAD TLV. To guarantee loop free forwarding, all routers that
participate in a Flex-Algorithm MUST agree on the FAD. Selected
nodes within the IGP domain MUST advertise FADs as described in
Sections 5, 6, and 7 of [RFC9350].
The Exclude Maximum Link Loss Sub-TLV is proposed to specify the
upper limit of the link loss. When this Sub-TLV is carried in a FAD
TLV, all links with packet loss rate larger than the defined maximum
link loss value will be excluded from the Flex-Algorithm topology.
2.1. IS-IS Exclude Maximum Link Loss Sub-TLV
IS-IS Flex-Algorithm Exclude Maximum Link Loss Sub-TLV (FAEML) is a
sub-TLV of the IS-IS FAD sub-TLV. It has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max Link Loss |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 252(TBA)
Length: 3 octets
Max Link Loss: This 24-bit field carries link packet loss as a
percentage of the total traffic sent over a configurable interval.
The basic unit is 0.000003%, where (2^24 - 2) is 50.331642%. This
value is the highest packet-loss percentage that can be expressed.
Therefore, measured values that are larger than the field maximum
SHOULD be encoded as the maximum value.
Figure 1: IS-IS FAEML Sub-TLV
The FAEML sub-TLV MUST appear at most once in the FAD Sub-TLV. If it
appears more than once, the IS-IS FAD Sub-TLV MUST be ignored by the
receiver.
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The maximum link loss advertised in FAEML Sub-TLV MUST be compared
with the link loss advertised in Sub-Sub-TLV 36 [RFC8570] of ASLA
Sub- TLV [RFC9479]. If L-Flag is set in the ASLA sub-TLV, the
maximum link loss advertised in FAEML sub-TLV MUST be compared with
the link loss advertised by the sub-TLV 36 of the TLV
22/222/23/223/141 [RFC5305] as defined in [RFC9479] Section 4.2.
If the link loss is larger than the maximum link loss advertised in
FAEML sub-TLV, the link MUST be excluded from the Flex-Algorithm
topology. If a link does not have the link loss advertised but the
FAD contains the FAEML sub-TLV, then it MUST NOT be excluded from the
Flex-Algorithm topology.
2.2. OSPF Exclude Maximum Link Loss Sub-TLV
OSPF Flex-Algorithm Exclude Maximum Link Loss Sub-TLV (FAEML) is a
sub-TLV of the OSPF FAD sub-TLV. It has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max Link Loss |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 252(TBA)
Length: 3 octets
Max Link Loss: This 24-bit field carries link packet loss as a
percentage of the total traffic sent over a configurable interval.
The basic unit is 0.000003%, where (2^24 - 2) is 50.331642%. This
value is the highest packet-loss percentage that can be expressed.
Therefore, measured values that are larger than the field maximum
SHOULD be encoded as the maximum value.
Figure 2: OSPF FAEML Sub-TLV
The FAEML sub-TLV MUST appear at most once in the FAD Sub-TLV. If it
appears more than once, the IS-IS FAD Sub-TLV MUST be ignored by the
receiver.
The maximum link loss advertised in FAEML Sub-TLV MUST be compared
with the link loss advertised in Sub-Sub-TLV 30 [RFC7471] of ASLA
Sub- TLV [RFC9492]. The ASLA Sub-TLV is advertised in Extended Link
Opaque LSAs [RFC7684] for OSPFv2 and E-Router-LSAs [RFC8362] for
OSPFv3.
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If the link loss is larger than the maximum link loss advertised in
FAEML sub-TLV, the link MUST be excluded from the Flex-Algorithm
topology. If a link does not have the link loss advertised but the
FAD contains the FAEML sub-TLV, then it MUST NOT be excluded from the
Flex-Algorithm topology.
3. Calculation of Flexible Algorithm Paths
A new rule is added to the rules used to prune links from the
topology during the Flex-Algorithm computation in Section 13 of
[RFC9350].
1. Check if any exclude FAEML rule is part of the Flex-Algorithm
definition. If such exclude rule exists and the link has link
loss advertised, check if the link satisfies the FAEML rule. If
not, the link MUST be pruned from the computation.
4. IANA Considerations
4.1. IS-IS Sub-Sub-TLVs for Flexible Algorithm Definition Sub-TLV
Type: 252(TBA)
Description: IS-IS Exclude Maximum Link Loss Sub-TLV
Reference: This document Section 2.1
4.2. OSPF Sub-Sub-TLVs for Flexible Algorithm Definition Sub-TLV
Type: 252(TBA)
Description: OSPF Exclude Maximum Link Loss Sub-TLV
Reference: This document Section 2.2
5. References
5.1. 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>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <https://www.rfc-editor.org/info/rfc5305>.
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[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <https://www.rfc-editor.org/info/rfc7684>.
[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>.
[RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and
F. Baker, "OSPFv3 Link State Advertisement (LSA)
Extensibility", RFC 8362, DOI 10.17487/RFC8362, April
2018, <https://www.rfc-editor.org/info/rfc8362>.
[RFC9350] Psenak, P., Ed., Hegde, S., Filsfils, C., Talaulikar, K.,
and A. Gulko, "IGP Flexible Algorithm", RFC 9350,
DOI 10.17487/RFC9350, February 2023,
<https://www.rfc-editor.org/info/rfc9350>.
[RFC9479] Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and
J. Drake, "IS-IS Application-Specific Link Attributes",
RFC 9479, DOI 10.17487/RFC9479, October 2023,
<https://www.rfc-editor.org/info/rfc9479>.
[RFC9492] Psenak, P., Ed., Ginsberg, L., Henderickx, W., Tantsura,
J., and J. Drake, "OSPF Application-Specific Link
Attributes", RFC 9492, DOI 10.17487/RFC9492, October 2023,
<https://www.rfc-editor.org/info/rfc9492>.
5.2. Informative References
[I-D.ietf-lsr-flex-algo-bw-con]
Hegde, S., Britto, W., Shetty, R., Decraene, B., Psenak,
P., and T. Li, "Flexible Algorithms: Bandwidth, Delay,
Metrics and Constraints", Work in Progress, Internet-
Draft, draft-ietf-lsr-flex-algo-bw-con-07, 26 September
2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
lsr-flex-algo-bw-con-07>.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, DOI 10.17487/RFC5357, October 2008,
<https://www.rfc-editor.org/info/rfc5357>.
[RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S.
Previdi, "OSPF Traffic Engineering (TE) Metric
Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015,
<https://www.rfc-editor.org/info/rfc7471>.
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[RFC8570] Ginsberg, L., Ed., Previdi, S., Ed., Giacalone, S., Ward,
D., Drake, J., and Q. Wu, "IS-IS Traffic Engineering (TE)
Metric Extensions", RFC 8570, DOI 10.17487/RFC8570, March
2019, <https://www.rfc-editor.org/info/rfc8570>.
[RFC8762] Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple
Two-Way Active Measurement Protocol", RFC 8762,
DOI 10.17487/RFC8762, March 2020,
<https://www.rfc-editor.org/info/rfc8762>.
Authors' Addresses
Yifan Wang
Huawei
Huawei Bld., No. 156 Beiqing Rd.
Beijing
100095
China
Email: wangyifan82@huawei.com
Guoqi Xu
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing
100095
China
Email: xuguoqi@huawei.com
Xuesong Geng
Huawei
Huawei Bld., No. 156 Beiqing Rd.
Beijing
100095
China
Email: gengxuesong@huawei.com
Jie Dong
Huawei
Huawei Bld., No. 156 Beiqing Rd.
Beijing
100095
China
Email: jie.dong@huawei.com
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