Internet DRAFT - draft-liu-idr-bgpls-extention-for-srv6-endxu
draft-liu-idr-bgpls-extention-for-srv6-endxu
SPRING Working Group G. Liu
Internet-Draft X. Fan
Intended status: Standards Track J. Dong
Expires: 10 September 2023 Huawei Technologies
9 March 2023
BGP Link State Extensions for SRv6 End.XU Function
draft-liu-idr-bgpls-extention-for-srv6-endxu-01
Abstract
The SRv6 END.XU function points to an underlying interface, which can
represent an underly link (or path) between two routers. This
document extends BGP-LS to advertise the link attributes of underlay
link and the END.XU SID information.
Status of This Memo
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This Internet-Draft will expire on 10 September 2023.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. The Link-State NLRI . . . . . . . . . . . . . . . . . . . . . 3
2.1. Node Descriptors . . . . . . . . . . . . . . . . . . . . 3
2.2. Link Descriptors . . . . . . . . . . . . . . . . . . . . 4
3. Advertising Underlay Link SRv6 SIDs . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 7
References . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Normative References . . . . . . . . . . . . . . . . . . . . . 7
Informative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
In [I-D.dong-spring-srv6-inter-layer-programming], a new SRv6
function called END.XU is defined to support SRv6 multi-layer network
programming. As a typical scenario, the END.XU function can be
applied to the optical network or MTN (Metro Transport Network), and
points to an underly interface, which can represent an underlying
link (or path) between two routers. This document extends the BGP-LS
protocol to advertise the link attributes of underlay link and the
END.XU SID information.
In [RFC7752], the Link-State NLRI includes the node/link/prefix
descriptors. In this document, only the node descriptors and link
descriptors are involved. This document uses the Link-State NLRI to
advertise the link attributes of underlay link. Moreover, this
document describes how to obtain local and peer information on the
underlay link carried by END.XU. For advertising the attributes of
nodes and links, this document inherits the node attribute TLV and
link attribute TLV from [RFC7752], which are not described in this
document.
Draft [I-D.ietf-idr-bgpls-srv6-ext] provides BGP-LS extensions
related to SRv6 SIDs. Link attributes involve the END.X/LAN END.X
SID TLV and link MSD types. This document focuses on advertising the
END.XU SID information.
1.1. Terminology
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1.2. 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.
2. The Link-State NLRI
This document inherits the Link-State NLRI [RFC7752] to advertise the
underlay link information. The Link-State NLRI includes the node
descriptors and the link descriptors.
2.1. Node Descriptors
The general format of node descriptors is shown in section 3.2 of
[RFC7752]. The field filling rules are described as follows:
Protocol-ID indicates the source protocol type of BGP-LS. If all
information derived from the IGP protocols, the corresponding
Protocol-ID MUST be used. If BGP-LS is sourcing local information
and some of the information of the underlay link (e.g., the Remote AS
Number and the Remote Router Identifier) is manually configured, this
field should be set to Static configuration (value 5).
Identifier indicates the routing universe. The identifier setting
varies depending on the scenario. If all information derived from
the IGP protocols, as described in section 3.2 of [RFC7752], the
NLRIs representing link-state objects (nodes, links, or prefixes)
from the same routing universe MUST have the same value of
Identifier. If BGP-LS is sourcing local information, the identifier
field is fixed to 0.
The sub-TLVs of node descriptor for underlay link are described as
follows:
+--------------------+-------------------+----------+
| Sub-TLV Code Point | Description | Length |
+--------------------+-------------------+----------+
| 512 | Autonomous System | 4 |
| 513 | BGP-LS Identifier | 4 |
| 514 | OSPF Area-ID | 4 |
| 515 | IGP Router-ID | Variable |
| TBD | Static Router-ID | Variable |
+--------------------+-------------------+----------+
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The value of TLV 512 or 513 is mandatory for underlay links. The
method of obtaining the value of TLV 512 is described in Section 3.2.
The setting of BGP-LS Identifier is the same as [RFC7752].
The values of TLV 514 and 515 are valid only when the BGP-LS source
is an IGP protocol.
For the underlay links, a new node descriptor sub-TLV needs to be
extended to cope with the scenario where there is no IGP protocol on
local router. For the new sub-TLV, the value of "Code Point" field
is TBD, the value of "Description" field is Static Router-ID, and the
"Length" field is variable. The value of Static Router-ID is the
global unique device identifier. It is flexible and can be an IPv6
address, a device identifier or a string name. The method of
obtaining the value of Static Router-ID is also described in
Section 3.2.
2.2. Link Descriptors
This document inherits all Sub-TLVs of the link descriptors in
[RFC7752], which is listed as follows:
+-----------+---------------------+--------------+------------------+
| TLV Code | Description | IS-IS TLV | Reference |
| Point | | /Sub-TLV | (RFC/Section) |
+-----------+---------------------+--------------+------------------+
| 258 | Link Local/Remote | 22/4 | [RFC5307]/1.1 |
| | Identifiers | | |
| 259 | IPv4 interface | 22/6 | [RFC5305]/3.2 |
| | address | | |
| 260 | IPv4 neighbor | 22/8 | [RFC5305]/3.3 |
| | address | | |
| 261 | IPv6 interface | 22/12 | [RFC6119]/4.2 |
| | address | | |
| 262 | IPv6 neighbor | 22/13 | [RFC6119]/4.3 |
| | address | | |
+-----------+---------------------+--------------+------------------+
For the static underlay link associated with END.XU, the IPv6
addresses of interfaces and neighbors, and the local and remote link
identifiers are the most basic TLV types. Whether the TLV is present
depends on the scenario. There are two typical application
scenarios:
1) Static underlay links are used as Layer 3 links. IPv6 addresses
are mandatory. The combination of interface and neighbor IPv6
addresses is used to uniquely identify a link. Whether the interface
and neighbor IPv6 addresses are reachable is optional. If IPv4/IPv6
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dual-stack coexists on the same static underlay link, the local and
remote link identifiers are mandatory to prevent the controller from
considering the underlay link as two different links.
2) Static underlay links are used as point-to-point links instead of
Layer 3 links. A point-to-point link does not require additional IP
addresses. Therefore, the local and remote link identifiers are
unique link identifiers, and must be used as mandatory.
Sections 3.1 and 3.2 describe three key parameters of the underlay
link, including AS number, static router ID, and link identifier.
The following describes how to obtain the three parameters.
The value of the local parameters can be obtained from the control
management module of the local device.
The remote parameter value can be controlled in either of the
following two ways:
If the controller is used, the controller obtains the AS number, IPv6
address, and link identifier of remote device. Then, the controller
delivers them to the local device through the northbound interface.
Finally, local device advertises the underlay link state information
and the END.XU SID information to the controller.
If there is no controller, only the link-layer protocol on the static
underlay link can be used to obtain the peer AS, IPv6 address, and
link identifier (such as LLDP). The link-layer protocol-based
parameter obtaining requires the extension of the link-layer protocol
and is not described in this document.
3. Advertising Underlay Link SRv6 SIDs
Based on [I-D.ietf-idr-bgpls-srv6-ext], the BGP-LS attributes related
to the static underlay link carried by END.XU include the node
attributes via the BGP-LS Node NLRI and the link attributes via the
BGP-LS Link NLRI. The node attributes inherit the content in section
3 of [I-D.ietf-idr-bgpls-srv6-ext]. For the link attributes, this
document inherits the SRv6 END.X SID Sub-TLV [RFC9352] to advertise
the SRv6 END.XU SID information.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Endpoint Behavior | Flags | Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Weight | Reserved | SID (16 octets) ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont ...) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont ...) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont ...) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont ...) | Sub-TLVs (variable) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Endpoint Behavior: 2 octet field. The Endpoint Behavior code point
for this SRv6 END.XU SID as defined in section 6 of
[I-D.dong-spring-srv6-inter-layer-programming].
Flags: 1 octet of flags. B-Flag is fixed to 0. S-Flag is fixed to
0. P-Flag is fixed to 1 for static configuration and 0 for dynamic
allocation.
Algorithm: 1 octet field. END.XU function carries a pure static
underlay link. No algorithm is used. Therefore, the value is fixed
to 0.
Weight: 1 octet field. The value represents the weight of the SID
for load balancing. The use of the weight is defined in [RFC8402].
Reserved: 1 octet field that MUST be set to 0 and ignored on receipt.
SID: 16 octet field. This field encodes the advertised SRv6 SID as
128-bit value.
4. Security Considerations
TBD
5. IANA Considerations
IANA is requested to allocate one Sub-TLV Code Point for node
descriptor：
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+--------------------+-------------------+----------+
| Sub-TLV Code Point | Description | Length |
+--------------------+-------------------+----------+
| TBD | Static Router-ID | Variable |
+--------------------+-------------------+----------+
Acknowledgements
The authors would like to thank Jie Dong and Yongjian Hu for their
review and comments.
References
Normative References
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>.
[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>.
[RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic
Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119,
February 2011, <https://www.rfc-editor.org/info/rfc6119>.
[RFC9352] Psenak, P., Ed., Filsfils, C., Bashandy, A., Decraene, B.,
and Z. Hu, "IS-IS Extensions to Support Segment Routing
over the IPv6 Data Plane", RFC 9352, DOI 10.17487/RFC9352,
February 2023, <https://www.rfc-editor.org/info/rfc9352>.
[RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008,
<https://www.rfc-editor.org/info/rfc5307>.
[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>.
[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>.
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[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>.
Informative References
[I-D.ietf-idr-bgpls-srv6-ext]
Dawra, G., Filsfils, C., Talaulikar, K., Chen, M.,
Bernier, D., and B. Decraene, "BGP Link State Extensions
for SRv6", Work in Progress, Internet-Draft, draft-ietf-
idr-bgpls-srv6-ext-14, 17 February 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
bgpls-srv6-ext-14>.
[I-D.dong-spring-srv6-inter-layer-programming]
Dong, J., Han, L., Du, Z., and M. Wang, "SRv6 for Inter-
Layer Network Programming", Work in Progress, Internet-
Draft, draft-dong-spring-srv6-inter-layer-programming-04,
23 October 2022, <https://datatracker.ietf.org/doc/html/
draft-dong-spring-srv6-inter-layer-programming-04>.
Authors' Addresses
GuoLiang Liu
Huawei Technologies
101 software Avenue, Yuhua District
Nanjing
210012
China
Email: liuguoliang@huawei.com
Xingpeng Fan
Huawei Technologies
No.9 Huanhu Road, Songshan Lake High-tech Industrial Development Zone
Dongguan
523808
China
Email: fanxingpeng1@huawei.com
Jie Dong
Huawei Technologies
Huawei Campus, No.156 Beiqing Road
Beijing
100095
China
Email: jie.dong@huawei.com
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