Internet DRAFT - draft-richardson-anima-l2-friendly-acp
draft-richardson-anima-l2-friendly-acp
anima Working Group M. Richardson
Internet-Draft Sandelman Software Works
Intended status: Standards Track W. Pan
Expires: 12 January 2023 Huawei Technologies
11 July 2022
Autonomic Control Plane design for Layer-Two Switched Networks
draft-richardson-anima-l2-friendly-acp-03
Abstract
This document proposes a design for an L2 aware Autonomic Control
Plane that can be deployed easily to layer-two (Ethernet) switched
technologies that are common on Campus/Enterprise network
architectures.
This document leverages the hop-by-hop announcement used in LLDP, but
runs bulk data over normal IPv6 Link-Local unicast ethernet frames.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 12 January 2023.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
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 . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Other constraints . . . . . . . . . . . . . . . . . . . . . . 4
4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
The creation and maintenance of the Autonomic Control Plane described
in [RFC8994] requires creation of hop-by-hop discovery of adjacent
systems. There are Campus L2 systems that are not broadcast safe
until they have been connected to their Software Defined Networking
(SDN) controller. The use of the stable connectivity provided by
[RFC8368] can provide the SDN connectivity required.
There is a bootstrap interlocking problem: the network may be unsafe
for ACP discovery broadcasts without the support of Spanning Tree
Protocol (STP) or similar mechanisms until configured, yet it can not
be automatically configured until the ACP discovery (and onboarding
process) is done. Meantime, because of STP complicated topological
calculations, the convergence can be very slow for larger networks.
This can delay on-boarding.
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In addition, forming a campus-wide network by default and using
enabling STP does not work. STP is not secure and could be easily
spoofed by malicious or untrusted devices. On manually configured
networks today, STP is turned off on "access" ports, and enabled only
for trunk ports. But in an autonomic network, it is not possible to
know a-priori which ports will be trunk ports, so STP would have to
be on by default if it is was to be used.
What is needed is a way to send IPv6 traffic between these L2
switching devices in a way that is never forwarded, regardless of how
the network is eventually configured. This is not just an inital
configuration problem: devices may be added and removed at any time,
due to needed expansion of capacity, planned upgrades, or devices
failures.
This document proposes using LLDP for what it is good at: announcing
capabilities, while using normal EtherType 0x86DD IPv6 frames for the
normal ACP transport.
1.1. 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.
2. Protocol
A new TLV for LLDP is allocated and called the GRASP-DULL. The
contents of the new TLV are the payload of the normal [RFC8994] GRASP
DULL M_FLOOD, AN_ACP message.
The LLDP subsystem in the control plane CPU needs to forward these
messages along to the ACP GRASP daemon, and it needs to also include
the source MAC address (and port number) from which the LLDP message
was received.
The ACP GRASP daemon can see the origin IPv6 Link-Local address from
the GRASP DULL packet, and can now create an IPv6 neighbour cache
entry (NCE) for that combination. By forcing this NCE entry, the
node avoids the need to do an unsafe multicast IPv6 Neighbor
Discovery.
The node SHOULD unicast a Neighbor Advertisement to the corresponding
node to establish that node's NCE.
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At this point it is possible to initiate the right key management
daemon (IKEv2, etc.) using unicast IPv6 datagrams that only need
unicast Ethernet packets.
It is likely that many L2 switching fabrics may not support IPsec
ESP, or L3 routing. It was always the case that the ACP might have
to be implemented as a software fabric in a control plane CPU. This
is not a significant hurdle, as the ACP is not intended to be used
for customer data, only control plane communication, and often only
as a last resort.
In addition to normal operation, devices may need to be onboarded.
[RFC8995] section 4.1.1 defines the AN_PROXY message to be used for a
new pledge to discover which neighbors are willing to act as
onboarding proxies.
This M_FLOOD message will fit into the same GRASP DULL M_FLOOD
message that contains the AN_ACP message.
After discover of an eligible neighbour, onboarding proceeds with a
TCP connection over IPv6 link-local addresses, using unicast Ethernet
frames.
LLDP traffic also uses a destination multicast address:
01:80:c2:00:00:0e, 01:80:c2:00:00:03, or 01:80:c2:00:00:00. The use
of this destination address facilitiates transmission of the traffic
through unmanaged switches ("dumb ethernet switches"), as well as
allowing for seperation of provider and customer traffic in provider
bridged (IEEE 802.1ad) situations.
3. Other constraints
On broadcast unsafe L2 networks, IPv6 Duplicate Address Detection
(DAD) MUST be turned off. Only auto-configured IPv6 link-local
addresses using SLAAC or stable-IID [RFC7217] may be used.
A pledge that is in an L2 network that is broadcast unsafe MUST NOT
do mDNS queries as described in [RFC8995] appendix B.
4. Privacy Considerations
The LLDP messages commonly contain information that uniquely
identifies a specific piece of switching equipment. The addition of
the GRASP DULL message will also now reveal the link-local IPv6
addresses of the device. This additional information is either
derived from ethernet addresses (so no new information), or will be
derived using [RFC7217].
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5. Security Considerations
Unclear as yet.
6. IANA Considerations
IANA is asked to allocate a TLV from the "IANA Link Layer Discovery
Protocol (LLDP) TLV Subtypes" https://www.iana.org/assignments/ieee-
802-numbers/ieee-802-numbers.xhtml#iana-lldp-tlv-subtypes
for the GRASP DULL L2 announcement.
7. Acknowledgements
Paul Congdon was very helpful in understanding how LLDP was actually
processed in production equipment.
8. Changelog
1. A specific LLDP method for announcement using normal IPv6
datagrams described.
2. Document renamed, focus changed.
9. References
9.1. 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>.
[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>.
[RFC8994] Eckert, T., Ed., Behringer, M., Ed., and S. Bjarnason, "An
Autonomic Control Plane (ACP)", RFC 8994,
DOI 10.17487/RFC8994, May 2021,
<https://www.rfc-editor.org/info/rfc8994>.
[RFC8995] Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructure (BRSKI)", RFC 8995, DOI 10.17487/RFC8995,
May 2021, <https://www.rfc-editor.org/info/rfc8995>.
9.2. Informative References
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[RFC7217] Gont, F., "A Method for Generating Semantically Opaque
Interface Identifiers with IPv6 Stateless Address
Autoconfiguration (SLAAC)", RFC 7217,
DOI 10.17487/RFC7217, April 2014,
<https://www.rfc-editor.org/info/rfc7217>.
[RFC8368] Eckert, T., Ed. and M. Behringer, "Using an Autonomic
Control Plane for Stable Connectivity of Network
Operations, Administration, and Maintenance (OAM)",
RFC 8368, DOI 10.17487/RFC8368, May 2018,
<https://www.rfc-editor.org/info/rfc8368>.
Authors' Addresses
Michael Richardson
Sandelman Software Works
Email: mcr+ietf@sandelman.ca
Wei Pan
Huawei Technologies
Email: william.panwei@huawei.com
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