< draft-cc-lsr-flooding-reduction-02.txt   draft-cc-lsr-flooding-reduction-03.txt >
Network Working Group H. Chen Network Working Group H. Chen
Internet-Draft D. Cheng Internet-Draft D. Cheng
Intended status: Standards Track Huawei Technologies Intended status: Standards Track Huawei Technologies
Expires: September 11, 2019 M. Toy Expires: September 12, 2019 M. Toy
Verizon Verizon
Y. Yang Y. Yang
IBM IBM
A. Wang A. Wang
China Telecom China Telecom
X. Liu X. Liu
Volta Networks Volta Networks
Y. Fan Y. Fan
Casa Systems Casa Systems
L. Liu L. Liu
March 10, 2019 March 11, 2019
LS Distributed Flooding Reduction LS Distributed Flooding Reduction
draft-cc-lsr-flooding-reduction-02 draft-cc-lsr-flooding-reduction-03
Abstract Abstract
This document proposes an approach to flood link states on a topology This document proposes an approach to flood link states on a topology
that is a subgraph of the complete topology per underline physical that is a subgraph of the complete topology per underline physical
network, so that the amount of flooding traffic in the network is network, so that the amount of flooding traffic in the network is
greatly reduced, and it would reduce convergence time with a more greatly reduced, and it would reduce convergence time with a more
stable and optimized routing environment. The approach can be stable and optimized routing environment. The approach can be
applied to any network topology in a single area. In this approach, applied to any network topology in a single area. In this approach,
every node in the area automatically calculates a flooding topology every node in the area automatically calculates a flooding topology
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Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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3.3. Flooding Topology Consistency . . . . . . . . . . . . . . 7 3.3. Flooding Topology Consistency . . . . . . . . . . . . . . 7
3.4. Flooding Topology Protection . . . . . . . . . . . . . . 7 3.4. Flooding Topology Protection . . . . . . . . . . . . . . 7
4. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 8 4. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 8
4.1. Extensions for Operations . . . . . . . . . . . . . . . . 8 4.1. Extensions for Operations . . . . . . . . . . . . . . . . 8
4.1.1. Extensions to OSPF . . . . . . . . . . . . . . . . . 8 4.1.1. Extensions to OSPF . . . . . . . . . . . . . . . . . 8
4.1.2. Extensions to IS-IS . . . . . . . . . . . . . . . . . 10 4.1.2. Extensions to IS-IS . . . . . . . . . . . . . . . . . 10
4.2. Extensions for Consistency . . . . . . . . . . . . . . . 11 4.2. Extensions for Consistency . . . . . . . . . . . . . . . 11
4.2.1. Extensions to OSPF . . . . . . . . . . . . . . . . . 11 4.2.1. Extensions to OSPF . . . . . . . . . . . . . . . . . 11
4.2.2. Extensions to IS-IS . . . . . . . . . . . . . . . . . 12 4.2.2. Extensions to IS-IS . . . . . . . . . . . . . . . . . 12
5. Flooding Behavior . . . . . . . . . . . . . . . . . . . . . . 12 5. Flooding Behavior . . . . . . . . . . . . . . . . . . . . . . 12
5.1. Nodes Perform Flooding Reduction without Failure . . . . 12 5.1. Nodes Perform Flooding Reduction without Failure . . . . 13
5.1.1. Receiving an LS . . . . . . . . . . . . . . . . . . . 12 5.1.1. Receiving an LS . . . . . . . . . . . . . . . . . . . 13
5.1.2. Originating an LS . . . . . . . . . . . . . . . . . . 13 5.1.2. Originating an LS . . . . . . . . . . . . . . . . . . 13
5.1.3. Establishing Adjacencies . . . . . . . . . . . . . . 13 5.1.3. Establishing Adjacencies . . . . . . . . . . . . . . 13
5.2. An Exception Case . . . . . . . . . . . . . . . . . . . . 14 5.2. An Exception Case . . . . . . . . . . . . . . . . . . . . 14
5.2.1. Multiple Failures . . . . . . . . . . . . . . . . . . 14 5.2.1. Multiple Failures . . . . . . . . . . . . . . . . . . 14
5.2.2. Changes on Flooding Topology . . . . . . . . . . . . 14 5.2.2. Changes on Flooding Topology . . . . . . . . . . . . 14
6. Operations on Flooding Reduction . . . . . . . . . . . . . . 14 6. Operations on Flooding Reduction . . . . . . . . . . . . . . 15
6.1. Configuring Flooding Reduction . . . . . . . . . . . . . 14 6.1. Configuring Flooding Reduction . . . . . . . . . . . . . 15
6.1.1. Configurations for Distributed Flooding Reduction . . 14 6.1.1. Configurations for Distributed Flooding Reduction . . 15
6.2. Migration to Flooding Reduction . . . . . . . . . . . . . 15 6.2. Migration to Flooding Reduction . . . . . . . . . . . . . 15
6.2.1. Migration to Distributed Flooding Reduction . . . . . 15 6.2.1. Migration to Distributed Flooding Reduction . . . . . 15
6.3. Roll Back to Normal Flooding . . . . . . . . . . . . . . 15 6.3. Roll Back to Normal Flooding . . . . . . . . . . . . . . 15
7. Manageability Considerations . . . . . . . . . . . . . . . . 16 7. Manageability Considerations . . . . . . . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16 8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
9.1. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . 16 9.1. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . 16
9.2. IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . 16 9.2. IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . 17
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
11.1. Normative References . . . . . . . . . . . . . . . . . . 17 11.1. Normative References . . . . . . . . . . . . . . . . . . 17
11.2. Informative References . . . . . . . . . . . . . . . . . 18 11.2. Informative References . . . . . . . . . . . . . . . . . 18
Appendix A. Algorithms to Build Flooding Topology . . . . . . . 18 Appendix A. Algorithms to Build Flooding Topology . . . . . . . 19
A.1. Algorithms to Build Tree without Considering Others . . . 19 A.1. Algorithms to Build Tree without Considering Others . . . 19
A.2. Algorithms to Build Tree Considering Others . . . . . . . 20 A.2. Algorithms to Build Tree Considering Others . . . . . . . 20
A.3. Connecting Leaves . . . . . . . . . . . . . . . . . . . . 22 A.3. Connecting Leaves . . . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23
1. Introduction 1. Introduction
For some networks such as dense Data Center (DC) networks, the For some networks such as dense Data Center (DC) networks, the
existing Link State (LS) flooding mechanism is not efficient and may existing Link State (LS) flooding mechanism is not efficient and may
have some issues. The extra LS flooding consumes network bandwidth. have some issues. The extra LS flooding consumes network bandwidth.
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In other words, when the failures happen, each of the nodes within a In other words, when the failures happen, each of the nodes within a
given distance to a failure point, adds all its local links to the given distance to a failure point, adds all its local links to the
flooding topology temporarily until a new flooding topology is built. flooding topology temporarily until a new flooding topology is built.
In another way, each node computes and maintains a small number of In another way, each node computes and maintains a small number of
backup paths. For a backup path for a link L on the flooding backup paths. For a backup path for a link L on the flooding
topology, a node N computes and maintains it only if the backup path topology, a node N computes and maintains it only if the backup path
goes through node N. Node N stores the links (e.g., local link L1 goes through node N. Node N stores the links (e.g., local link L1
and L2) attached to it and on the backup path. When link L fails and and L2) attached to it and on the backup path. When link L fails and
there are one or more failures on the flooding topology, node N adds there are one or more failures on the flooding topology (and
the links (e.g., L1 and L2) to the flooding topology temporarily additionally the number of nodes collected through traversing the
until a new flooding topology is built. flooding topology is less than the number of live nodes in the area),
node N adds the links (e.g., L1 and L2) to the flooding topology
temporarily until a new flooding topology is built. Note that
checking the additional condition will slow down the convergence when
the flooding topology is split. It is optional.
Suppose that the two end nodes of link L is A and B, and A's ID is Suppose that the two end nodes of link L is A and B, and A's ID is
smaller than B's. Node N computes a path from A to B with minimum smaller than B's. Node N computes a path from A to B with minimum
hops and whose links are not on the flooding topology. This path is hops and whose links are not on the flooding topology. This path is
a backup path for link L. a backup path for link L. A backup path can be computed before link
L fails or computed after link L fails and there is a need for it.
Using the former will make the convergence time shorter. For the
former, when the pre-computed backup path is broken because of
failures, a new backup path needs to be computed.
Similarly, for a backup path for a connection crossing a node M on Similarly, for a backup path for a connection crossing a node M on
the flooding topology, a node N computes and maintains it only if the the flooding topology, a node N computes and maintains it only if the
backup path goes through node N. Node N stores the links (e.g., backup path goes through node N. Node N stores the links (e.g.,
local link La and Lb) attached to it and on the backup path for node local link La and Lb) attached to it and on the backup path for node
M. M.
4. Protocol Extensions 4. Protocol Extensions
The extensions comprises two parts: one part is for operations on The extensions comprises two parts: one part is for operations on
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sub-TLV in a RI LSA from the leader, which indicates the current sub-TLV in a RI LSA from the leader, which indicates the current
flooding reduction is to be rolled back to normal flooding. After flooding reduction is to be rolled back to normal flooding. After
receiving the sub-TLV, it stops computing flooding topology and receiving the sub-TLV, it stops computing flooding topology and
flooding link states over a flooding topology. It floods link states flooding link states over a flooding topology. It floods link states
using all its local links instead of the local links on the flooding using all its local links instead of the local links on the flooding
topology. topology.
Note that the OSPF area leader sub-TLV defined in Note that the OSPF area leader sub-TLV defined in
[I-D.ietf-lsr-dynamic-flooding] needs to be extended to allow users [I-D.ietf-lsr-dynamic-flooding] needs to be extended to allow users
to roll back to normal flooding. The Flooding Reduction Instruction to roll back to normal flooding. The Flooding Reduction Instruction
sub-TLV defined in the previous version of this draft supports this. sub-TLV defined in version 01 of this draft supports this.
4.1.2. Extensions to IS-IS 4.1.2. Extensions to IS-IS
Similar to OSPF, the IS-IS Dynamic Flooding sub-TLV and area leader Similar to OSPF, the IS-IS Dynamic Flooding sub-TLV and area leader
sub-TLV are also defined in [I-D.ietf-lsr-dynamic-flooding]. sub-TLV are also defined in [I-D.ietf-lsr-dynamic-flooding].
Every node supporting the distributed flooding reduction MUST Every node supporting the distributed flooding reduction MUST
indicate its algorithms for flooding topology computation in an IS-IS indicate its algorithms for flooding topology computation in an IS-IS
Dynamic Flooding sub-TLV in an LSP to be advertised to the leader. Dynamic Flooding sub-TLV in an LSP to be advertised to the leader.
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