IDR Working Group Louis Chan
INTERNET-DRAFT
Intended status: Experimental Juniper Networks
Expires: Oct 15, 2020 Apr 16, 2020
Color Operation with BGP Label Unicast
draft-chan-idr-bgp-lu2-01.txt
Abstract
This document specifies how to carry colored path advertisement via an enhancement
to the existing protocol BGP Label Unicast. It would allow backward compatibility
with RFC8277.
The targeted solution is to use stack of labels advertised via BGP Label Unicast
2.0 for end to end traffic steering across multiple IGP domains. The operation is
similar to Segment Routing.
This proposed protocol will convey the necessary reachability information to the
ingress PE node to construct an end to end path
Status of this Memo
This Internet-Draft is submitted in full conformance with the provisions of BCP 78
and BCP 79.
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than as "work in progress."
This Internet-Draft will expire on Oct 15, 2020.
Copyright Notice
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Table of Contents
1. Introduction...................................................2
2. Conventions used in this document..............................3
3. Carrying Label Mapping Information with Color and Label Stack..4
3.1. Color extended community for BGP Labeled Unicast..........4
3.2. Color extended community for service prefixes.............5
4. Uniqueness of path entries.....................................5
5. AIGP consideration.............................................5
6. Explicit Withdraw of a <color, prefix>.........................6
7. Error Handling Procedure.......................................6
8. Controller Compatibility.......................................6
9. Security Considerations........................................6
10. IANA Considerations...........................................6
11. References....................................................7
11.1. Normative References.....................................7
11.2. Informative References...................................7
12. Acknowledgments...............................................8
1. Introduction
The proposed protocol is aimed to solve interdomain traffic steering, with
different transport services in mind. One application is low latency service across
multiple IGP domains, which could scale up to 100k routers network.
BGP is a flexible protocol. With additional of color attribute to BGP Label
Unicast, a path with specific color would be given a meaning in application - a low
latency path, a fully protected path, or a path for diversity.
The stack of labels would mean an end to end path across domains through each ABR
or ASBR. Each ABR or ASBR will take one label from the stack, and hence pick the
forwarding path to next ABR, ASBR, or the final destination.
And the label in the stack may be derived from any of the below
- Prefix SID
- Binding SID for RSVP LSP
- Binding SID for SR-TE LSP
- Local assigned label
The enhancement to the original RFC8277 is to add color extended community, with
multiple advertisement allowed. The result is similar to multi-topology BGP-LU with
different colors.
A new [BGP-CAP] should be required to enable such slicing.
On the other hand, to enable the service prefixes to be mapped accordingly, the
L3VPN, L2VPN, EVPN and prefix with BGP signaling, the color extended community is
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also added there. In the PE node, the service prefixes with color will be matched
to a transport tunnel with the same color.
The following is an example. Between PE1 and PE2, there is a VPN service running
with label 16, which is associated with color 100.
PE1----ABR1-----ABR2-----PE2
PE1 will send the following labels with a color 100 path plus VPN label
[2001 13001 801 16], where
2001 - SR label to reach ABR1
13001 - a Binding-SID label for ABR1-ABR2 tunnel. Underlying tunnel type is RSVP-TE
801 - a Binding-SID label for ABR2-PE2 tunnel. Underlying tunnel type is SR-TE
16 - a VPN label, which is signaled via other means
[2001 13001 801] denotes the label stack for this color 100 path to reach PE2
The document here is going to describe how PE1 gains enough information to build
this label stack across routing domains.
If PE1 wants to reach PE2 with another colored path, say color 200, the label stack
could be different.
At the same time, this architecture is also controller friendly, since all the
notation is Segment Routing compatible, like use of Binding-SID.
2. Conventions used in this document
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 RFC 2119 [RFC2119].
In this document, these words will appear with that interpretation only when in
ALL CAPS. Lower case uses of these words are not to be interpreted as carrying
significance described in RFC 2119.
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3. Carrying Label Mapping Information with Color and Label Stack
3.1. Color extended community for BGP Labeled Unicast
The addition of Color Extended Community is an opaque extended community from
RFC4360 and RFC5512. The draft allows multiple color values advertisement.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x03 | 0x0b |C|O| Reserved |X|X|X|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Color Value ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ 0x03 | 0x0b |C|O| Reserved |X|X|X|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Color Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Color value advertisement format
Both in BGP update and MP_UNREACH_NLRI message, multiple color extended communities
could be included. It means that multiple colors, indicating different kind of
services, could share the same label stack.
If only one color extended community is specified, only prefix with that color
value is updated or withdrawn.
If a MP_UNREACH_NLRI message without any color specified is received for a given
prefix, that prefix with color(s) should not be affected.
If color extended community is not present in a BGP update message, it would be
treated as normal BGP-LU without any color.
3 bits of XXX is reserved here for the draft.
The meaning for XXX is interpreted as sub-slice of color, with 0 to 7 in decimal,
or 000b and 111b in binary. These sub-slice could be used in either of the
following case.
a) Primary path and fallback paths in order of preference
0 primary path
1 first and most preferred backup path
7 least preferred backup path
b) ECMP paths up to 8, since all paths should be active in forwarding plane.
Color value 0 is reserved for future interoperability purpose.
Color value 1 - 31 are not recommended to use, and this range is reserved for
future use.
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3.2. Color extended community for service prefixes
The same format of color extended community is advertised with service prefixes.
The order of the color extended community could be interpreted as
- Order of primary and fallback colors
- Or, ECMP of equal split between color paths
The above would be interpreted by the receiving PE upon its local configuration.
It is optional to enable sub-slice notation.
But if sub-slice bits are used, it will be used to map directly to each of the sub-
slice path. If sub-slice path is not available for mapping, it should just fallback
to resolving by color.
4. Uniqueness of path entries
a) Use of color can be considered to slice into multiple BGP Label Unicast RIB.
Therefore, it should be treated as unique entries for the <color, prefix>.
e.g. <color, prefix>, [labels]
<1, 10.1.1.1/32>, [100 200]
<2, 10.1.1.1/32>, [100 200]
<null, 10.1.1.1/32>, [100 200]
All these 3 NLRI are considered different but valid entries for different color
instances.
b) With sub-slice notation
<color-sub, prefix>, [labels]
<1-0, 10.1.1.1/32>, [100 200]
<1-1, 10.1.1.1/32>, [101 300]
<1-7, 10.1.1.1/32>, [102 400]
These 3 NLRI are distinct, and the second and third NLRI could be used for
backup or ECMP purpose.
5. AIGP consideration
AIGP (RFC7311) would be also used in here to embed certain metric across.
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6. Explicit Withdraw of a <color, prefix>
According to RFC8277, MP_UNREACH_NLRI can be used to remove binding of a <color,
prefix>.
Compatibility is set to 0xC00000 to specify the use of color. Multiple color
extended communities could be applied here.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Compatibility |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix ~
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: NLRI for Withdrawal
7. Error Handling Procedure
If BGP receiver could not handle the NLRI, it should silently discard with error
logging.
8. Controller Compatibility
The proposed architecture is compatible with controller for end to end
provisioning. Persistent label, like Binding-SIS is recommended to be used. Hence,
controller could learn these labels from the network, and program specific end to
end path.
Controller could also be deployed based on domain by domain perspective. e.g.
Optimizing latency of a RSVP LSP, or maintain the bandwidth and loading between SR-
TE LSPs.
9. Security Considerations
10. IANA Considerations
TBD. It will require a new BGP capability code to enable such color operation.
New SAFI might be required as well.
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11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels",
BCP 14, RFC 2119, March 1997.
11.2. Informative References
[RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in BGP-4", RFC
3107, DOI 10.17487/RFC3107, May 2001,
<https://www.rfc-editor.org/info/rfc3107>.
[RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
Communities Attribute", RFC 4360, February 2006
<https://www.rfc-editor.org/info/rfc4360>.
[RFC5512] Mohapatra, P. and E. Rosen, "The BGP Encapsulation Subsequent Address
Family Identifier (SAFI) and the BGP Tunnel Encapsulation Attribute", RFC
5512, April 2009.
<https://www.rfc-editor.org/info/rfc5512>.
[RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J., and D.
McPherson, "Dissemination of Flow Specification Rules", RFC 5575, DOI
10.17487/RFC5575, August 2009,
<http://www.rfc-editor.org/info/rfc5575>.
[RFC7311] Mohapatra, P., Fernando, R., Rosen, E., and J. Uttaro,
"The Accumulated IGP Metric Attribute for BGP", RFC 7311,
DOI 10.17487/RFC7311, August 2014,
<https://www.rfc-editor.org/info/rfc7311>.
[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>.
[BGP-CAP] Chandra, R. and J. Scudder, "Capabilities Advertisement
with BGP-4", RFC 2842, May 2000.
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12. Acknowledgments
The following people have contributed to this document:
Jeff Haas, Juniper Networks
Shraddha Hedge, Juniper Networks
Santosh Kolenchery, Juniper Networks
Shihari Sangli, Juniper Networks
Krzysztof Szarkowicz, Juniper Networks
Yimin Shen, Juniper Networks
Authors Addresses
Louis Chan (editor)
Juniper Networks
2604, Cityplaza One, 1111 King's Road
Taikoo Shing
Hong Kong
Phone: +85225876659
Email: louisc@juniper.net
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