Inter-Domain Routing P. Lapukhov
Internet-Draft Facebook
Intended status: Standards Track E. Aries, Ed.
Expires: May 3, 2018 P. Marques
Juniper Networks
E. Nkposong
Salesforce.com Inc
October 30, 2017
Use of BGP for Opaque Signaling
draft-lapukhov-bgp-opaque-signaling-04
Abstract
Border Gateway Protocol with multi-protocol extensions (MP-BGP)
enables the use of the protocol for dissemination of virtually any
information. This document proposes a new Address Family/Subsequent
Address Family to be used for distribution of opaque data. This
functionality is intended to be used by applications other than BGP
for exchange of their own data on top of BGP mesh. The structure of
such data SHOULD NOT be interpreted by the regular BGP speakers,
rather the goal is to use BGP purely as a convenient and scalable
communication system.
Requirements Language
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].
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 May 3, 2018.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. BGP Opaque Data AFI . . . . . . . . . . . . . . . . . . . . . 3
3. BGP Key-Value SAFI . . . . . . . . . . . . . . . . . . . . . 3
4. BGP VPN Key-Value SAFI . . . . . . . . . . . . . . . . . . . 3
5. Capability Advertisement . . . . . . . . . . . . . . . . . . 3
6. Disseminating Key-Value associations . . . . . . . . . . . . 3
6.1. Publishing a Key-Value binding . . . . . . . . . . . . . 4
6.2. Removing a Key-Value binding . . . . . . . . . . . . . . 5
7. Manageability Considerations . . . . . . . . . . . . . . . . 6
7.1. Propagating multiple values for the same key . . . . . . 6
7.2. Automatic filtering . . . . . . . . . . . . . . . . . . . 6
7.3. Filtering via policy . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. Security Considerations . . . . . . . . . . . . . . . . . . . 7
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
11.1. Normative References . . . . . . . . . . . . . . . . . . 7
11.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Implementation of Multiprotocol Extensions for BGP-4 [RFC4760] gives
the ability to pass arbitrary data in BGP protocol messages. This
capability has been leveraged by many for dissemination of non-
routing related information over BGP (e.g. "Dissemination of Flow
Specification Rules" [RFC5575] as well as "North-Bound Distribution
of Link-State and TE Information using BGP" [RFC7752]). However,
there has been no channel defined explicitly to disseminate data with
arbitrary payload. The intended use case is for applications other
than BGP to leverage the protocol machinery for distribution
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(broadcasting) of their own state in the network domain. Publishers
and consumers will use BGP UPDATE messages over TCP transport to
submit and receive opaque data. It is up to the BGP implementation
to provide a custom API for message producers or consumers, if
needed.
2. BGP Opaque Data AFI
This document introduces a new AFI known as a "BGP Opaque Data AFI",
with the actual code-point value to be assigned by IANA. The purpose
of this AFI is to exchange opaque information within a BGP network.
The propagation scope of the opaque data is to be controlled by the
usual means of BGP policy, except that the policy SHOULD not match on
NLRI information in any form other than an opaque string.
3. BGP Key-Value SAFI
This document introduces a new SAFI known as "BGP Key-Value SAFI"
with the actual code-point value to be assigned by IANA. The purpose
of this SAFI is exchange of opaque information structured as Key-
Value associations.
4. BGP VPN Key-Value SAFI
This document introduces a new SAFI known as a "BGP VPN Key-Value
SAFI" with the actual code-point value to be assigned by IANA. The
purpose of this SAFI is exchange of opaque information structured as
a Key-Value association within a Virtual Private Network provided as
a service. The [RFC4364] defines a method and procedures for
implementing VPNs using BGP as a control plane. All the procedures
of [RFC4364] apply to the BGP VPN Key-Value SAFI. Under this SAFI,
the NLRI for the opaque information has the mandatory 8 bytes of
Route Distinguisher at the beginning of the NLRI field.
5. Capability Advertisement
A BGP speaker that wishes to exchange Opaque Data MUST use the
Multiprotocol Extensions Capability Code, as defined in [RFC4760], to
advertise the corresponding AFI/SAFI pair.
6. Disseminating Key-Value associations
This document proposes a distributed, eventually consistent Key-Value
store on top of existing BGP protocol transport mechanism. The "Key"
and "Value" portions are to be encoded within the NLRI part of
MP_REACH_NLRI attribute.
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o Publishers advertise keys along with associated values into the
routing domain. The BGP network disseminates that state by
propagating the encoded data following the usual BGP protocol
operations.
o Consumers receive the information via BGP protocol UPDATE
messages, active as passively listening BGP speakers. Only
publishers and consumers of the opaque data are supposed to
interpret its contents. The rest of the BGP network acts merely
as a dissemination system.
Multiple publishers can advertise the same key bound to different
values. Only the "Key" part of MP_REACH_NLRI filed MUST be used to
differentiate unique advertisements in such case. It is also
possible for the advertised associations to have the same Key-Value
pairs, but differ in some other BGP attributes. In that case, the
BGP implementation MUST follow the regular best-path selection logic
to prevent duplicate information in the network. A consumer will
receive the value created by the publisher "closest" in terms of BGP
best-path selection logic, based on the policies that exist in the
routing domain.
6.1. Publishing a Key-Value binding
The encoding scheme proposed below follows the semantics of a Key-
Value association. The "Key" and "Value" are stored in the NLRI
section of the MP_REACH_NLRI attribute, as illustrated on Figure 1.
+---------------------------------------------------------+
| Address Family Identifier (2 octets) |
+---------------------------------------------------------+
| Subsequent Address Family Identifier (1 octet) |
+---------------------------------------------------------+
| Length of Next Hop Address (1 octet), must be zero |
+---------------------------------------------------------+
| Reserved (1 octet), must be zero |
+---------------------------------------------------------+
| Opaque Key Length (2 octets) |
+---------------------------------------------------------+
| Opaque Key Data (variable) |
+---------------------------------------------------------+
| Opaque Value Data (variable) |
+---------------------------------------------------------+
Figure 1: MP_REACH_NLRI Layout
o The AFI/SAFI values are to be allocated by IANA.
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o Length of Next Hop Address: must be zero, indicating empty next-
hop.
o Opaque Key Length: identifies the size of the Key field in octets,
an unsigned integer value. The field MUST have a value of at
least one octet under the Key-Value SAFI and at least 9 octets
under the VPN Key-Value SAFI. Violating this requirement MUST
cause the receiver to ignore the advertised Key-Value association.
o Opaque Key Data: the byte string representing the opaque key
contents.
o Opaque Value Data: The length of this field is determined by
subtracting the length of all previous fields from the total
length of MP_REACH_NLRI attribute. This field MAY be empty.
The maximum size of the Opaque "Key" and "Value" fields together is
limited by the BGP UPDATE message size. With the default BGP
protocol implementation the mssage may not exceed 4096 octets (see
[RFC4271] Section 4). However, if
[I-D.ietf-idr-bgp-extended-messages] is implemented, the UPDATE
message size could be as large as 65536 octets.
6.2. Removing a Key-Value binding
The removal procedure follows the regular MP-BGP route withdrawal,
using the MP_UNREACH_NLRI attribute. This section defines the
attribute structure for the new AFI/SAFI.
The specific MP_UNREACH_NLRI format is shown on Figure 2. This
message instructs the receiving BGP speaker to delete the N
associations corresponding to Key 1, Key 2 ... Key N if the keys have
been previously learned from the withdrawing speaker. If any of the
keys could not be found in the LocRIB or the keys have not been
previously received from the withdrawing BGP peer, such key removal
request MUST be ignored and the event MAY be logged. For the Key-
Value SAFI, each "Key Length" field must have the value of at least
"1". For the VPN Key-Value SAFI, each "Key Length" must be at least
9 octets long. Violation of of these constraints MUST cause the
receiver of the UPDATE message to ignore the corresponding key
withdrawal.
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+---------------------------------------------------------+
| Address Family Identifier (2 octets) |
+---------------------------------------------------------+
| Subsequent Address Family Identifier (1 octet) |
+---------------------------------------------------------+
| Opaque Key 1 Length (1 octet) |
+---------------------------------------------------------+
| Opaque Key 1 Data (variable) |
+---------------------------------------------------------+
~ ~
| Opaque Key N Length (1 octet) |
+---------------------------------------------------------+
| Opaque Key N Data (variable) |
+---------------------------------------------------------+
Figure 2: MP_UNREACH_NLRI attribute layout
7. Manageability Considerations
7.1. Propagating multiple values for the same key
It is possible to propagate multiple values associated with the same
key using the Add-Path extension defined in [RFC7911]. However, this
document recommends that instead unique key values SHOULD be used for
this purpose. It is up to the consumers and publishers of the opaque
data to settle on single unique value using some kind of consensus
protocol.
As a recommendation, the originators of key-value pairs may use the
origin ASN and the IPv4 or IPv6 address assigned to the originating
BGP speaker to create a unique key prefix. Alternatively, UUIDs
could be used to generate the unique key names, see [RFC4122]
7.2. Automatic filtering
It is possible to leverage mechanics described in [RFC4684] and use
the route-target extended community attribute to identify "channels"
where Key-Value associations are published. The consumers would
signal their interest in particular "channel" by advertising the
corresponding router-target membership. The publications then need
to carry the router-target extended community attribute to restrict
information propagation scope.
7.3. Filtering via policy
Ad-doc message filtering could be implemented using BGP standard (see
[RFC4271]) or extended community attributes (see [RFC4360]). The
semantic of these attributes is to determined by the policy and
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publishers/consumers. Filtering could be done locally on receiving
BGP speaker, or on remote BGP speaker, by using outbound route
filtering feature defined in [RFC5291].
8. IANA Considerations
For the purpose of this work, IANA would be asked to allocate values
for the new AFI and SAFIs.
9. Security Considerations
This document does not introduce any changes in terms of BGP
security. The usual set of issues that arise from running multiple
AFI/SAFI's over single BGP session would apply in this case.
Additional concerns may be raised due to increase of the volume and
rate of change of the information distributed by means of opaque
signaling.
10. Acknowledgements
Keyur Patel provided useful feedback and suggested a practical
implementation of unique key semantic and support for VPN Key-Value
SAFI.
11. References
11.1. Normative References
[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>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
11.2. Informative References
[I-D.ietf-idr-bgp-extended-messages]
Bush, R., Patel, K., and D. Ward, "Extended Message
support for BGP", draft-ietf-idr-bgp-extended-messages-22
(work in progress), August 2017.
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[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/info/rfc4122>.
[RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
Communities Attribute", RFC 4360, DOI 10.17487/RFC4360,
February 2006, <https://www.rfc-editor.org/info/rfc4360>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <https://www.rfc-editor.org/info/rfc4364>.
[RFC4684] Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk,
R., Patel, K., and J. Guichard, "Constrained Route
Distribution for Border Gateway Protocol/MultiProtocol
Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual
Private Networks (VPNs)", RFC 4684, DOI 10.17487/RFC4684,
November 2006, <https://www.rfc-editor.org/info/rfc4684>.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760,
DOI 10.17487/RFC4760, January 2007,
<https://www.rfc-editor.org/info/rfc4760>.
[RFC5291] Chen, E. and Y. Rekhter, "Outbound Route Filtering
Capability for BGP-4", RFC 5291, DOI 10.17487/RFC5291,
August 2008, <https://www.rfc-editor.org/info/rfc5291>.
[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,
<https://www.rfc-editor.org/info/rfc5575>.
[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>.
[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>.
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Authors' Addresses
Petr Lapukhov
Facebook
1 Hacker Way
Menlo Park, CA 94025
US
Email: petr@fb.com
Ebben Aries (editor)
Juniper Networks
1133 Innovation Way
Sunnyvale, CA 94089
US
Email: exa@juniper.net
Pedro Marques
Juniper Networks
1194 N. Mathilda Ave
Sunnyvale, CA 94089
US
Email: roque@juniper.net
Edet Nkposong
Salesforce.com Inc
The Landmark @ One Market, ST 300
San Francisco, CA 94105
US
Email: enkposong@salesforce.com
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