Network Working Group C. Cardona
Internet-Draft P. Lucente
Intended status: Standards Track NTT
Expires: July 6, 2020 P. Francois
INSA-Lyon
Y. Gu
Huawei
T. Graf
Swisscom
January 03, 2020
BMP Extension for Path Marking TLV
draft-cppy-grow-bmp-path-marking-tlv-02
Abstract
The BGP Monitoring Protocol (BMP) provides an interface for obtaining
BGP Path information. BGP Path Information is conveyed within BMP
Route Monitoring (RM) messages. This document proposes an extension
to BMP to convey the status of a BGP path after being processed by
the BGP best-path selection algorithm. This extension makes use of
the TLV mechanims described in draft-lucente-bmp-tlv
[I-D.lucente-bmp-tlv].
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 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when, they
appear in all capitals, as shown here.
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
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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."
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This Internet-Draft will expire on July 6, 2020.
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Path Marking TLV for the RM Message . . . . . . . . . . . . . 3
2.1. Path Status . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.1. IANA-registered Path Status Encoding . . . . . . . . 4
2.1.2. Enterprise-specific Path Status Encoding . . . . . . 5
2.2. Reason Code . . . . . . . . . . . . . . . . . . . . . . . 6
2.2.1. IANA-registered Reason Code Encoding . . . . . . . . 6
2.2.2. Enterprise-specific Reason Code Encoding . . . . . . 6
3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
4.1. Path Marking TLV . . . . . . . . . . . . . . . . . . . . 7
4.2. Path Marking TLV Reason Code . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. Normative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
For a given prefix, multiple paths with different path status, e.g.,
the "best-path", "back-up path" and so on, may co-exist in the BGP
RIB after being processed by the local policy and the BGP decision
process. The path status information is currently not carried in the
BGP Update Message RFC4271 [RFC4271] or in the BMP Update Message
RFC7854 [RFC7854].
External systems can use the path status for various applications.
The path status is commonly checked by operators when performing
troubleshooting. Having such status stored in a centralized system
can enable the development of tools facilitating this process.
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Optimisation systems can include the path status in their process,
and also use the status as a validation source (since it can compare
the calculated state to the actual outcome of the network, such as
primary and backup path). As a final example, path status
information can complement other centralized sources of data, for
example, flow collectors.
This document defines a so-called Path Marking TLV to convey the BGP
path status information to the BMP server. The BMP Path Marking is
defined to be prepended in the BMP Route Monitoring (RM) Message.
2. Path Marking TLV for the RM Message
As per RFC4271 [RFC4271], the BMP RM Message consists of the Common
Header, Per-Peer Header, and the BGP Update PDU. According to draft-
lucente-bmp-tlv [I-D.lucente-bmp-tlv] , optional trailing data in TLV
format is allowed in the BMP RM Message to convey characteristics of
transported NLRIs (i.e. to help stateless parsing) or vendor-specific
data. Such TLV types are to be defined for each application.
To include the path status along with each BGP path, we define the
Path Marking TLV, shown as follows.
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 (2 octets) | Length (2 octets) |
+-------------------------------+-------------------------------+
|E| Path Status(variable) |
+---------------------------------------------------------------+
|E| Reason Code(variable) |
+---------------------------------------------------------------+
Figure 1: Path Marking TLV
o Type = TBD1 (2 Octets): indicates that it's the Path Marking TLV.
o Length (2 Octets): indicates the length of the value field of the
Path Marking TLV. The value field further consists of the Path-
Status field and Reason Code field.
o E bit (1 Bit) for Path Status: indicates if any enterprise-
specific path status is used after the IANA-registered path status
code.
o Path Status (4 Octets): indicates the path status of the BGP
Update PDU encapsulated in the RM Message. Currently 7 types of
path status are defined, as shown in Table 1.
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o E bit (1 Bit) for Reason Code: indicates if any enterprise-
specific reason code is used after the IANA-registered reason
code.
o Reason Code (Variable): indicates the reasons/explanations of the
path status indicated in the Path Type field. The detailed Reason
Code field is defined in Section 2.2.
2.1. Path Status
The Path Status field contains a bit field where each bit encodes a
specific role of the path. Multiple bits may be set when multiple
path status apply to a path.
Two encoding options for Path Status are described in the following
two sections.
2.1.1. IANA-registered Path Status Encoding
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-------------------------------+
|E| IANA registered path status |
+-------------------------------+
Figure 2: IANA-registered encoding of Path Status
o E bit (1 Bit): set to 0, indicating that only IANA-registered path
status is used in this TLV.
o IANA-registered Path Status (2 octets): indicates the IANA-
registered path status, as specified in Table 1.
+--------+----------------------+
| Value | Path type |
+-------------------------------+
| 0x0000 | Unknown |
| 0x0001 | Invalid |
| 0x0002 | Best |
| 0x0004 | Non-selected |
| 0x0008 | Primary |
| 0x0010 | Backup |
| 0x0020 | Non-installed |
| 0x0040 | Best external |
| 0x0080 | Add-Path |
+--------+----------------------+
Table 1: Path Type
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The best-path is defined in RFC4271 [RFC4271] and the best-external
path is defined in draft-ietf-idr-best-external
[I-D.ietf-idr-best-external].
An invalid path is a route that does not enter the BGP decision
process.
A non-selected path is a route that is not selected in the BGP
decision process. In other words, Best route and ECMP routes are not
considered as non-selected.
A primary path is a recursive or non-recursive path whose nexthop
resolution ends with an adjacency draft-ietf-rtgwg-bgp-pic
[I-D.ietf-rtgwg-bgp-pic]. A prefix can have more than one primary
path if multipath is configured draft-lapukhov-bgp-ecmp-
considerations [I-D.lapukhov-bgp-ecmp-considerations]. A best-path
is also considered as a primary path.
A backup path is also installed in the RIB, but it is not used until
some or all primary paths become unreachable. Backup paths are used
for fast convergence in the event of failures.
A non-installed path refers to the route that is not installed into
the IP routing table.
For the advertisement of multiple paths for the same address prefix
without the new paths implicitly replacing any previous ones, the
add-path status is applied RFC7911 [RFC7911].
2.1.2. Enterprise-specific Path Status Encoding
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
+---------------------------------------------------------------+
|E| Enterprise-Specific Path Type (4 octets) |
+---------------------------------------------------------------+
| Enterprise Number(4 octets) |
+---------------------------------------------------------------+
Figure 3: Enterprise-specific encoding of Path Status
o E bit (1 Bit): set to 1, indicating enterprise-specific path
status is used in this TLV.
o Enterprise-specific Path Type (4 octets): indicates enterprise-
specific path status, which remains to be defined.
o Enterprise Number (4 octets): indicates the IANA enterprise number
IANA-PEN.
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2.2. Reason Code
The Reason Code field contains a bit field where each bit encodes a
specific reason. Multiple bits may be set when multiple reasons
apply to a path.
2.2.1. IANA-registered Reason Code Encoding
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
+---------------------------------------------------------------+
|E| IANA-registered Reason Code(4 octets) |
+---------------------------------------------------------------+
Figure 4: IANA-registered encoding of Reason Code
o E bit (1 Bit): set to 0, indicating that only IANA-registered
reason code is used in this TLV. With the E bit set to 0, the
Length field of the Path Marking TLV SHOULD be set to 8.
o IANA-registered Reason Code (4 octets): indicates the IANA-
registered reason code of the path status.
2.2.2. Enterprise-specific Reason Code Encoding
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
+---------------------------------------------------------------+
|E| Enterprise Number(4 octets) |
+---------------------------------------------------------------+
+ E-specific Reason Code(variable) +
~ ~
+---------------------------------------------------------------+
Figure 5: Enterprise-specific encoding of Reason Code
o E bit (1 Bit): set to 1, indicating enterprise-specific reason
code is also used in this TLV.
o IANA-registered Reason Code (4 octets): indicates the IANA-
registered reason code of the path status.
o Enterprise Number (4 octets): indicates the IANA enterprise number
IANA-PEN.
o E-specific Reason Code (Variable): indicates enterprise-specific
reason code of the path status.
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3. Acknowledgements
We would like to thank Jeff Haas for his valuable comments.
4. IANA Considerations
This document requests that IANA assign the following new parameters
to the BMP parameters name space.
4.1. Path Marking TLV
This document defines the Path Marking TLV with Type = TBD1: Path
Marking (Section 2).
4.2. Path Marking TLV Reason Code
5. Security Considerations
It is not believed that this document adds any additional security
considerations.
6. Normative References
[I-D.ietf-idr-best-external]
Marques, P., Fernando, R., Chen, E., Mohapatra, P., and H.
Gredler, "Advertisement of the best external route in
BGP", draft-ietf-idr-best-external-05 (work in progress),
January 2012.
[I-D.ietf-rtgwg-bgp-pic]
Bashandy, A., Filsfils, C., and P. Mohapatra, "BGP Prefix
Independent Convergence", draft-ietf-rtgwg-bgp-pic-10
(work in progress), October 2019.
[I-D.lapukhov-bgp-ecmp-considerations]
Lapukhov, P. and J. Tantsura, "Equal-Cost Multipath
Considerations for BGP", draft-lapukhov-bgp-ecmp-
considerations-03 (work in progress), November 2019.
[I-D.lucente-bmp-tlv]
Lucente, P., Gu, Y., and H. Smit, "TLV support for BMP
Route Monitoring and Peer Down Messages", draft-lucente-
bmp-tlv-00 (work in progress), July 2019.
[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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[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>.
[RFC7854] Scudder, J., Ed., Fernando, R., and S. Stuart, "BGP
Monitoring Protocol (BMP)", RFC 7854,
DOI 10.17487/RFC7854, June 2016,
<https://www.rfc-editor.org/info/rfc7854>.
[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>.
[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>.
Authors' Addresses
Camilo Cardona
NTT
164-168, Carrer de Numancia
Barcelona 08029
Spain
Email: camilo@ntt.net
Paolo Lucente
NTT
Siriusdreef 70-72
Hoofddorp, WT 2132
Netherlands
Email: paolo@ntt.net
Pierre Francois
INSA-Lyon
Lyon
France
Email: Pierre.Francois@insa-lyon.fr
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Yunan Gu
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: guyunan@huawei.com
Thomas Graf
Swisscom
Binzring 17
Zurich 8045
Switzerland
Email: thomas.graf@swisscom.com
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