anima Working Group M. Richardson Internet-Draft Sandelman Software Works Intended status: Standards Track L. Xia Expires: 10 September 2020 Huawei 9 March 2020 IPv6 over Link-Local Discovery Protocol draft-richardson-anima-ipv6-lldp-03 Abstract This document describes a mechanism to encapsulate IPv6 packets over the Link Layer Discovery Protocol (LLDP). The LLDP is a single layer-two protocol with its own ethertype. It is never forwarded, which is a desireable property when building the IPv6-over-IPsec- over-IPv6-Link-Local tunnels that make up the ANIMA Autonomic Control Plane (ACP). This unorthodox encapsulation avoids unwanted interactions between the ACP packets and native packet forwarding engines, as well as being safe for layer-2 switches which might otherwise have no IPv6 capabilities. 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/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 10 September 2020. Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ Richardson & Xia Expires 10 September 2020 [Page 1] Internet-Draft v6-LLDP March 2020 license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. LLDP Encapsulation . . . . . . . . . . . . . . . . . . . 3 2.2. Content of Payload - option 1 - entire IPv6 packet . . . 4 2.3. Content of Payload - option 2 - elided IPv6 packet . . . 5 2.4. Content of Payload - option 3 - RFC8138 compressed packet . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Privacy Considerations . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 7. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction The IEEE802.1AB Link Layer Discovery Protocol (LLDP) is a one-hop, vendor-neutral link-layer protocol used by network devices or Things for advertising their identity, capabilities, and neighbors on an IEEE 802 local area network. The LLDP uses its own ethertype (0x88cc), and so is distinct from production IPv4 or IPv6 traffic that might appear on a network. Switching equipment is usually configured such that it does not forward LLDP packets. Its Type-Length-Value (TLV) design allows for "vendor-specific" extensions to be defined. IANA has a registered IEEE 802 organizationally unique identifier (OUI) defined as documented in [RFC7042]. The creation and maintenance of the Autonomic Control Plane described in [I-D.ietf-anima-autonomic-control-plane] 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 Richardson & Xia Expires 10 September 2020 [Page 2] Internet-Draft v6-LLDP March 2020 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. LLDP provides a way for the above problem, as it is never forwarded to other ports, and it discovers all compliant layer-2 devices in a network, even if they do not normally do layer-3 forwarding. Additionally, LLDP has the advantage that received LLDP frames are already configured in routing fabrics to be send up to the control plane processor, with information identifying which physical port they were received on. This is exactly the desired data flow for the [I-D.ietf-anima-autonomic-control-plane]: all traffic goes to the control plane processor. This document provides a way to transmit the IPv6 Link-Layer packets that are needed for formation of the [I-D.ietf-anima-autonomic-control-plane] over the LLDP. Those packets types include: IPv6 Neighbor Discovery, GRASP DULL over IPv6 Link-Local, IPsec ESP and IKEv2 packets. 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 2.1. LLDP Encapsulation The LLDP vendor-specific frame has the following format: +--------+--------+----------+---------+-------------- |TLV Type| len | OUI |subtype | IPv6 fragment | =127 | |= 00 00 5E| = TBD | |(7 bits)|(9 bits)|(3 octets)|(1 octet)|(0-507 octets) +--------+--------+----------+---------+-------------- where: Richardson & Xia Expires 10 September 2020 [Page 3] Internet-Draft v6-LLDP March 2020 * TLV Type = 127 indicates a vendor-specific TLV * len = indicates the TLV string length * OUI = 00 00 5E is the organizationally unique identifier of IANA * subtype = TBD (as assigned by IANA for this document) * IPv6 fragment, up to 507 octets of packet. The vendor-specific frame has a limit of 507 octets, while IPv6 has a minimum MTU of 1280 bytes. An LLDP frame can contain more than one TLV, and ethernet accomodates up to 1500 bytes (often larger), so it should all fit. Two possible solutions are discussed here: 1. use three subtype TLV values. The first 507 octets go into the first TLV, the second 507 octets go into the second TLV, etc. three TLVs of 507 octets payload each results in a maximum payload size of 1521, which exceeds the ethernet payload size of 1500 bytes. Given the overhead of 6 bytes per TLV, this results in an MTU of 1464 bytes within the 1500 byte ethernet payload space. 2. use the same subtype TLV value, repeated three times. The second method seems more obvious but it is unclear if all LLDP subsystems would permit TLVs to be repeated, or if they would keep the TLVs in the correct order. While the IANA has only 253 available TLVs, and perhaps a request for three values might seem excessive, if this resource was depleted, a new OUI could be used. An OUI specific to this effort could be allocated, or a vendor OUI could be used during prototyping. 2.2. Content of Payload - option 1 - entire IPv6 packet The simplest encapsulation would put the entire IPv6 packet, including the IPv6 header in. This takes a bit more space, but provides the maximum flexibility. This flexibility may come at a cost of creating a new attack surface for devices. Any L2 connected device may not inject IPv6 frames into the control plane of the adjacent devices. Richardson & Xia Expires 10 September 2020 [Page 4] Internet-Draft v6-LLDP March 2020 2.3. Content of Payload - option 2 - elided IPv6 packet The [I-D.ietf-anima-autonomic-control-plane] use case only sends IPv6 Link-Local packets. The IPv6 source and destination address are always directly related to the L2 Ethernet headers, with the use of SLAAC derived IIDs, and the prefix "fe80". This proposal is to include only the fields: 1. Payload Length 2. Next Header The Hop Limit is always 1 for Link-Local packets. The Flow Label is always 0. Note that in the [I-D.ietf-anima-autonomic-control-plane] a mesh of IPsec tunnels is created on top of ESP packets over IPv6 Link-Local, and within that tunnel all of IPv6 packets can be sent. The use of hard coding of so many values significantly limits the attack surface possible. 2.4. Content of Payload - option 3 - RFC8138 compressed packet An option similar to above, yet providing a bit more flexibility is to use [RFC8138] compression of packets as it done on low powered 802.15.4 networks. This results in compression that is close to what option 2 provides, yet providing a lot of flexibility. This option requires more code, may be subject to new attacks on the decompression code, and expands the attack surface to all of IPv6, as well as the [RFC8138] compression code. 3. Privacy Considerations YYY 4. Security Considerations LLDP is relatively simple and does not provide any protections to the traffic over it. The IPv6 packets over the LLDP SHOULD be protected by all the existing best current practices. The device control plane processor will be subject to the Deny of Service (DoS) attack if excessive IPv6 packets over LLDP frames are Richardson & Xia Expires 10 September 2020 [Page 5] Internet-Draft v6-LLDP March 2020 send up. Certain protecting mechanisms like rate limit and filtering can be considered. 5. IANA Considerations 6. Acknowledgements Hello. 7. Changelog 8. References 8.1. Normative References [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC7042] Eastlake 3rd, D. and J. Abley, "IANA Considerations and IETF Protocol and Documentation Usage for IEEE 802 Parameters", BCP 141, RFC 7042, DOI 10.17487/RFC7042, October 2013, . [I-D.ietf-anima-autonomic-control-plane] Eckert, T., Behringer, M., and S. Bjarnason, "An Autonomic Control Plane (ACP)", Work in Progress, Internet-Draft, draft-ietf-anima-autonomic-control-plane-22, 3 February 2020, . [RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie, "IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138, April 2017, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . 8.2. Informative References [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, . Richardson & Xia Expires 10 September 2020 [Page 6] Internet-Draft v6-LLDP March 2020 Authors' Addresses Michael Richardson Sandelman Software Works Email: mcr+ietf@sandelman.ca Liang Xia (Frank) Huawei Email: frank.xialiang@huawei.com Richardson & Xia Expires 10 September 2020 [Page 7]