Inter-domain Network Slicing via BGP-LU
draft-zhou-idr-inter-domain-lcu-00
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Jin Zhou , Chunning Dai , Shaofu Peng | ||
| Last updated | 2020-01-03 | ||
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| Formats | plain text htmlized pdfized bibtex | ||
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| Consensus boilerplate | Unknown | ||
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| IESG | IESG state | I-D Exists | |
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draft-zhou-idr-inter-domain-lcu-00
IDR Working Group J. Zhou
Internet-Draft Chunning. Dai
Intended status: Standards Track Shaofu. Peng
Expires: July 3, 2020 ZTE Corp.
Dec 31, 2019
Inter-domain Network Slicing via BGP-LU
draft-zhou-idr-inter-domain-lcu-00
Abstract
This document aims to solve inter-domain network slicing problems
using existing technologies. It attempts to establish multiple BGP-
LU LSPs of different colors for a prefix to stitch multiple network
segments.
Status of This Memo
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This Internet-Draft will expire on July 3, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements notation . . . . . . . . . . . . . . . . . . . . 2
3. Color . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
4. Advertising multiple paths . . . . . . . . . . . . . . . . . 3
5. Generating Labels by Path . . . . . . . . . . . . . . . . . . 4
6. Deploy Considerations . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
As described in [I-D.peng-teas-network-slicing], in the traditional
end to end inter-domain network slicing, BGP-LU is used as a
distributed slicing scheme. [RFC8277] specifies a set of procedures
for using BGP to advertise that a specified router has bound a
specified MPLS label to a specified address prefix. It's an
effective way for inter-domain labels, but it does not have the
ability to select the underlying network resources.
This document describes the colored BGP-LU LSP, in which the routing
prefix not only carries a label(or a sequence of labels), but also
carries an unique color attribute which helps to select the
underlying logic slice.
[RFC7911] defines a BGP extension that allows the advertisement of
multiple paths of the same address prefix. It can help with optimal
routing and in a network by providing potential alternate or backup
paths. In this document, it is not used for the link backup. It is
only used to advertise multiple paths, whether intra-domain or inter-
domain.
2. Requirements notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Color
[I-D.ietf-idr-tunnel-encaps] introduces the concept of color, which
is used as one of the KEY of SR policy
[I-D.ietf-spring-segment-routing-policy]. The color of SR policy
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defines a TE purpose, which includes a set of constraints such as
bandwidth, delay, TE metric, etc.
Color is used a policy keyword to help routing decisions and can be
carried through Community attribute [I-D.ietf-idr-tunnel-encaps] in
BGP. Each UPDATE SHOULD contain a Color Extended Community with a
specific color value, the Color Sub-TLV is only an opaque extended
community.
4. Advertising multiple paths
Consider the following LSR topology in Figure 1: PE1---ASBR1---ASBR2
---PE2. Packet transfers from PE2 to PE1. The overlay service of
PE1 to PE2 has two colors, color1 and color2.
.----. .------.
( ) ( )
.-( )-. .-( )-.
+---+---color1----+----+ +---+----color1----+---+
|PE1|\---SR-TE1---/|AS |-sub-if1 with slice1-|AS |\---SR-TE1---/|PE2|
| |/---SR-TE2---\|BR1|-sub-if2 with slice2-|BR2|/---SR-TE2---\| |
+---+---color2---- +---+ +---+--color2------+---+
( ) ( )
'--( AS1 )--' '--( AS2 )--'
( ) ( )
'-' '-'
Figure 1: Network Slicing Example
According to the extended NLRI Encodings in [RFC7911], in order to
advertise multiple paths for the same address prefix, PE1 MUST encode
two different NLRIs to advertise the two paths. Every NLRI has a
unique Path Identifier.
+--------------------------------+
| Path Identifier (4 octets) |
+--------------------------------+
| Length (1 octet) |
+--------------------------------+
| Prefix (variable) |
+--------------------------------+
The Path Identifier only identifies a path, not carrying any
particular semantics. It MAY be generated from the two-tuple
<Prefix,Color>. Also, it MAY be generated from the information
containing Prefix and Color.
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Finally, There are two BGP UPDATE NLRIs from PE1 to ASBR1, <prefix,
pathid1> with color1 extended community and <prefix, pathid2> with
color2 extended community. Pathid1 and pathid2 in two UPDATE NLRI
MUST be different. As described in [RFC8277], they have the same
label value, however, different label value is also possible.
5. Generating Labels by Path
To realize the inter-domain multiple paths, the border routers of per
domain SHOULD consider the diversity of paths when generating the
labels.
<1.1.1.1, path-id1> <1.1.1.1, path-id1> <1.1.1.1, path-id1>
<color1, label200> <color1, label201> <color1, label201>
------------------------------------------------------------------>
.----. .------.
( ) ( )
.-( )-. .-( )-.
+---+---color1----+----+ +---+----color1----+---+
|PE1|\---SR-TE1---/|AS |-sub-if1 with slice1-|AS |\---SR-TE1---/|PE2|
| |/---SR-TE2---\|BR1|-sub-if2 with slice2-|BR2|/---SR-TE2---\| |
+---+---color2---- +---+ +---+--color2------+---+
( ) ( )
'--( AS1 )--' '--( AS2 )--'
( ) ( )
'-' '-'
------------------------------------------------------------------->
<1.1.1.1, path-id2> <1.1.1.1, path-id2> <1.1.1.1, path-id2>
<color2, label200> <color2, label202> <color2, label202>
Label Exchange Tables:
ASBR1: ASBR2:
inLabel outLabel nextHop inLabel outLabel nextHop
201 200 SR-TE1 201 201 sub-if1
202 200 SR-TE2 202 202 sub-if2
PE2:
prefix color outLabel nextHop
1.1.1.1 1 201 SR-TE1
1.1.1.1 2 202 SR-TE2
Figure 2: Details of Network Slicing Example
Suppose ASBR1 receives two paths from PE1, with next hop 1.1.1.1,
path identifier 1 and 2, ASBR1 MUST modify the next hop to itself,
and generate two new labels based on two paths. As depicted in
Figure 2, <1.1.1.1, color1> generates label 201, <1.1.1.1, color2>
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generates label 202. Both of them are the local label exchange table
items. Similarly, ASBR2 also generates two different labels based on
the two paths. As shown in Figure 2, multiple end to end BGP-LU LSP
are established.
So, at the entry node of per domain, BGP-LU LSP generated for
specific color is over intra-domain SR-TE or SR Best-effort path
generated for the color again. At exit node of per domain, BGP-LU
LSP generated for specific color selects inter-domain forwarding
resource per color.
6. Deploy Considerations
o The premise of this document is that all border routers SHOULD
have the same understanding of a color value. For example, PE1
understands color1 representing a low packet loss rate, and ASBR1
must think so and apply it to the local forwarding policy.
o All BGP routers(PE1--ASBR1, ASBR1---ASBR2, ASBR2---PE2) SHOULD be
BGP-LU neighbors in advance.
o All routers require the ADD-PATH Capability which is described in
chapter 4 of [RFC7911].
o If any Router Reflector existed in the network, it SHOULD support
this function. Later will discuss Confederation.
7. Security Considerations
TBD
8. References
8.1. Normative References
[I-D.ietf-idr-tunnel-encaps]
Patel, K., Velde, G., and S. Ramachandra, "The BGP Tunnel
Encapsulation Attribute", draft-ietf-idr-tunnel-encaps-15
(work in progress), December 2019.
[I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture", draft-
ietf-spring-segment-routing-policy-06 (work in progress),
December 2019.
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[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>.
[RFC7911] Walton, D., Retana, A., Chen, E., and J. Scudder,
"Advertisement of Multiple Paths in BGP", RFC 7911,
DOI 10.17487/RFC7911, July 2016,
<https://www.rfc-editor.org/info/rfc7911>.
[RFC8277] Rosen, E., "Using BGP to Bind MPLS Labels to Address
Prefixes", RFC 8277, DOI 10.17487/RFC8277, October 2017,
<https://www.rfc-editor.org/info/rfc8277>.
8.2. Informative References
[I-D.peng-teas-network-slicing]
Peng, S., Chen, R., Mirsky, G., and F. Qin, "Packet
Network Slicing using Segment Routing", draft-peng-teas-
network-slicing-02 (work in progress), December 2019.
Authors' Addresses
Jin Zhou
ZTE Corp.
Email: zhou.jin6@zte.com.cn
Chunning Dai
ZTE Corp.
Email: dai.chunning@zte.com.cn
Shaofu Peng
ZTE Corp.
Email: peng.shaofu@zte.com.cn
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