Link Discovery Protocol (LLDP) Extensions for Segment Routing over IPv6 (SRv6)
draft-gong-spring-lldp-srv6-extensions-00
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| Document | Type | Active Internet-Draft (individual) | |
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| Authors | Liyan Gong , Changwang Lin | ||
| Last updated | 2024-09-30 | ||
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draft-gong-spring-lldp-srv6-extensions-00
Network Working Group L. Gong
Internet Draft China Mobile
Intended status: Standards Track C. Lin
Expires: March 29, 2025 New H3C Technologies
September 29, 2024
Link Discovery Protocol (LLDP) Extensions for Segment Routing over
IPv6 (SRv6)
draft-gong-spring-lldp-srv6-extensions-00
Abstract
This document describes the method of carrying SRv6 Locator
information through the LLDP protocol to simplify SRv6 deployment.
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This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction...................................................3
1.1. Requirements Language.....................................3
2. Use Cases......................................................4
2.1. Problem...................................................4
2.2. Solution..................................................4
3. LLDP Extension.................................................6
3.1. SRv6 Locator TLV..........................................6
3.2. SRv6 Capabilities TLV.....................................8
4. Security Considerations........................................9
5. IANA Considerations............................................9
6. References.....................................................9
6.1. Normative References......................................9
Authors' Addresses...............................................10
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1. Introduction
The Link Layer Discovery Protocol (LLDP) [802.1AB] is a standard
link layer protocol that allows network devices to discover
neighbors and exchange information.
With Segment Routing (SR) [RFC8402], a node steers a packet through
an ordered list of instructions, which are called segments.Segments
are identified through Segment Identifiers (SIDs). SR can be
directly instantiated on the IPv6 data plane through the use of the
Segment Routing Header (SRH) defined in [RFC8754].
SRv6 refers to this SR instantiation on the IPv6 data plane. The
network programming paradigm [RFC8986] is central to SRv6. It
describes how any behavior can be bound to a SID and how any network
program can be expressed as a combination of SIDs.
For SRv6 networking, the SRv6 Locator information of each device
within an autonomous system is usually carried by IGP protocols,
while BGP is used for inter-domain advertising. Hosts typically do
not support complex routing protocols, and thus cannot dynamically
advertise their own Locator information. This presents challenges
for deploying SRv6 networks. Therefore, a simplified SRv6 deployment
method is needed to enable SRv6 Locator routing between access
devices and hosts. This document describes a method for carrying
SRv6 Locator information via the LLDP protocol to simplify SRv6
deployment.
The SRv6 Locator sub-TLV announces SRv6 Locators -- a form of
summary address for the set of topology-/algorithm-specific SIDs
instantiated at the node. The SRv6 Capabilities sub-TLV announces
the ability to support SRv6.
This document specifies the IETF Organizationally Specific TLV for
LLDP, which includes the SRv6 Locator sub-TLV and the SRv6
Capabilities sub-TLV.
1.1. 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.
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2. Use Cases
2.1. Problem
As shown in Figure 1, the SRv6 network comprises Host, Access, Spin,
and Core segments. Information is exchanged between the Host and
Access via LLDP, between Access and Spin through IGP, and between
Spin and Core using BGP.
The SRv6 Locator information is transmitted between Access and Spin
using the IGP protocol, and between Spin and Core using the BGP
protocol. However, since Hosts generally do not support complex
routing protocols, they cannot automatically transmit their SRv6
Locator information to the devices. This limitation complicates the
deployment of SRv6 networks.
+----+ LLDP+------+ IGP +------+BGP +------+
|Host+-----+Access+-----+ Spin +----+ Core +
+----+ +------+ +------+ +------+
Figure 1
2.2. Solution
By extending the LLDP protocol to carry SRv6 Locator information,
Hosts and Access devices can exchange all SRv6 Locator information
within an SRv6 network via LLDP, facilitating the deployment of
SRv6.
The SRv6 Locator are advertised in IGP, and collected by the
controller using NETCONF or BGP-LS.
The srv6 locator are advertised in LLDP between the host and access
through LLDP, and are advertised via IGP within the domain. This
information is collected by the controller using NETCONF or BGP-LS.
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+----------+ BGP-LS
|Controller|<-----------------+
+----------+ |
^ ^ |
NETCONF | | NETCONF |
| +----------+ |
| | |
| | |
+----+ LLDP+------+ IGP +------+BGP +------+
|Host+-----+Access+-----+ Spin +----+ Core +
+----+ +------+ +------+ +------+
^ ^
| |
+--- LLDP --+
SRv6 Locator
Figure 2
The specific process is as follows:
1) Enable LLDP on both Host and Access.
2) The Host advertises the SRv6 locator FC00:0:11::/48 and its SRv6
capability through LLDP.
3) The Access device learns the SRv6 locator FC00:0:11::/48 via LLDP.
4) Using IGP, the Access device re-advertises the SRv6 locator
FC00:0:11::/48 obtained from LLDP to the Spine device.
5) The Spine device learns the SRv6 locator FC00:0:11::/48 route
through IGP.
6) A BGP neighbor relationship is established between the Spine and
Core devices, and the learned SRv6 locator FC00:0:11::/48 is sent
to the Core using BGP-LS routes.
7) The Core device learns the SRv6 locator FC00:0:11::/48 via BGP-LS.
8) A BGP neighbor relationship is established between the Core device
and the controller, and the SRv6 locator FC00:0:11::/48 is sent to
the controller via BGP-LS routes.
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3. LLDP Extension
3.1. SRv6 Locator TLV
LLDP TLVs that belong to an organization are identified by the
inclusion of the organization's OUI (Organizationally Unique
Identifier) and an organizationally defined subtype in the initial
octets of the information field.
This document defines a new IETF specific subtype, SRv6 Locator,
under the IANA OUI. The LLDP IETF Organizationally Specific TLV of
the new-defined subtype carries the local SRv6 Locator, which 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 (127) |Length (variable)| OUI (3 Octets) 00-00-5E |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OUI Continued | Subtype (TBD) | SRv6 Locator TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRv6 Locator TLV Continued |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Type: IETF Organizationally Specific TLV type value, 127.
o Length: Length of the remainder of the TLV, variable.
o OUI: Organizationally Unique Identifier. For IETF use, this field
is the IANA OUI (00-00-5E) as specified in RFC 7042.
o Subtype: Subtype for SRv6 locator, TBD.
o SRv6 Locator: SRv6 locator.
The format of each SRv6 Locator TLV is as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type | Length |R|R|R|R| MTID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LocSize | Locator (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|sub-tlv-len | Sub-Tlvs (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Sub-Type: 8 bits, The Sub-TLV Type value for locator shall be 1.
o Length: 8 bits, variable.
o MTID: 12 bits, Multi-Topology Identifier.
o Metric: 32 bits, Cost.
o Flags: 8 bits, Reserved.
o Algorithm: 8 bits Algorithm:
- 0: Shortest Path First (SPF).
- 1: Strict Shortest Path First (Strict SPF).
o Loc Size: 8 bits, Locator Length.
o Locator (variable): Variable length, indicates the advertised
SRv6 Locator.
o sub-tlv-len: 8 bits, Sub-TLV Length.
o Sub-TLVs (variable): Variable length, contains Sub-TLVs such as
SRv6 End SID Sub-TLV.
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3.2. SRv6 Capabilities TLV
To support the SRv6 functionality, the Host also needs to advertise
SRv6-related capabilities through LLDP. The LLDP extension format
for SRv6 capabilities is as follows:
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 (127) |Length (variable)| OUI (3 Octets) 00-00-5E |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OUI Continued | Subtype (TBD2)| SRv6 Capbility TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRv6 Capbility TLV Continued |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Type: IETF Organizationally Specific TLV type value, 127.
o Length: Length of the remainder of the TLV, variable.
o OUI: Organizationally Unique Identifier. For IETF use, this field
is the IANA OUI (00-00-5E) as specified in RFC 7042.
o Subtype: Subtype for SRv6 Capabilities, TBD2.
o SRv6 Capbility TLV: SRv6 Capbility sub-TLV, format as follow:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type | Length | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| optional sub-sub-TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Sub-Type: 8 bits, The Sub-TLV Type value for SRv6 capability
shall be 1.
o Length: 8 bits, variable.
o Flags: 8 bits, Reserved.
o optional sub-sub-TLVs, such as Node MSD sub-TLV.
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For optional MSD sub-sub-TLVs, the format is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-sub-Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSD-Type | MSD-Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSD-Type | MSD-Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o sub-sub-Type: 8 bits, The sub-sub-TLV Type value for MSD shall be
1.
o Length: 8 bits, variable.
o MSD-Type: 8 bits.
o MSD-Value: 8 bits.
4. Security Considerations
TBD.
5. IANA Considerations
TBD.
6. References
6.1. Normative References
[802.1AB] "IEEE Standard for Local and metropolitan area networks-
Station and Media Access Control Connectivity Discovery",
IEEE Std 802.1AB-2016, 29 January 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, May 2017.
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[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986, DOI
10.17487/RFC8986, February 2021, <https://www.rfc-
editor.org/info/rfc8986>.
Authors' Addresses
Liyan Gong
China Mobile
China
Email: gongliyan@chinamobile.com
Changwang Lin
New H3C Technologies
China
Email: linchangwang.04414@h3c.com
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