BMP Extension for Path Marking TLV
draft-cppy-grow-bmp-path-marking-tlv-03
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
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|---|---|---|---|
| Authors | Camilo Cardona , Paolo Lucente , Pierre Francois , Yunan Gu , Thomas Graf | ||
| Last updated | 2020-03-09 | ||
| Replaced by | draft-ietf-grow-bmp-path-marking-tlv | ||
| RFC stream | (None) | ||
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draft-cppy-grow-bmp-path-marking-tlv-03
Network Working Group C. Cardona
Internet-Draft P. Lucente
Intended status: Standards Track NTT
Expires: September 9, 2020 P. Francois
INSA-Lyon
Y. Gu
Huawei
T. Graf
Swisscom
March 08, 2020
BMP Extension for Path Marking TLV
draft-cppy-grow-bmp-path-marking-tlv-03
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-ietf-grow-bmp-tlv
[I-D.ietf-grow-bmp-tlv] and draft-lucente-grow-bmp-tlv-ebit
[I-D.lucente-grow-bmp-tlv-ebit].
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
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."
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This Internet-Draft will expire on September 9, 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Prefix Information TLV for the RM Message . . . . . . . . . . 3
3. Path Marking sub-TLV . . . . . . . . . . . . . . . . . . . . 3
3.1. IANA-registered Path Markinig sub-TLV . . . . . . . . . . 4
3.2. Enterprise-specific Path Marking sub-TLV . . . . . . . . 6
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. 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.
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
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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. Prefix Information TLV for the RM Message
As per RFC7854 [RFC7854], the BMP RM Message consists of the Common
Header, Per-Peer Header, and the BGP Update PDU. According to draft-
grow-bmp-tlv [I-D.ietf-grow-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.
This document defines the Prefix Information TLV to convey
descriptional information for route prefixes. The format is shown
below.
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) |
+---------------------------------------------------------------+
| Count (2 octets) |
+-------------------------------+-------------------------------+
| Prefix information value(variable) |
+---------------------------------------------------------------+
Figure 1: Prefix Information TLV
o Type = TBD1 (2 Octets): Prefix Information TLV.
o Length (2 Octets): indicates the length of the value field of the
Prefix Information TLV.
o Count (2 Octets): indicates the number of sub TLVs followed in the
Prefix Information Value field.
o Prefix information value (Variable): indicates the value of the
Prefix Informtion TLV, which consists of one or multiple sub TLVs.
3. Path Marking sub-TLV
As stated in Appendix F.1 of RFC4271 [RFC4271], multiple address
prefixes with the same path attributes are allowed to be specified in
one message. However, such multiple prefixes may have different
prefix information, e.g., path status. Thus, to indicate the path
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status for each BGP prefix, we define the Path Marking sub-TLV. The
order of the Path Marking sub-TLVs MUST be in accordance with the
prefix order of the Update PDU.
The E-bit [I-D.lucente-grow-bmp-tlv-ebit] mechanism allows the usage
of vendor-specific TLVs in addition to IANA-registered one. In this
document, both encoding options for the Path Marking sub-TLV are
described.
3.1. IANA-registered Path Markinig sub-TLV
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| Type (15 bits) | Length (2 octets) |
+-------------------------------+-------------------------------+
| Path Status(4 octets) |
+---------------------------------------------------------------+
| Reason Code(4 octets) |
+---------------------------------------------------------------+
Figure 2:IANA-Registered Encoding of Path Marking sub-TLV
o E bit: For an IANA-registered sub-TLV, the E bit MUST be set to 0.
o Type = TBD2 (15 Bits): Path Marking sub-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 Path Status (4 Octets): indicates the path status of the BGP
Update PDU encapsulated in the RM Message. Currently 9 types of
path status are defined, as shown in Table 1.
o Reason Code (4 Octets): indicates the reasons/explanations of the
path status indicated in the Path Type field. The detailed Reason
Code bitmap remains to be defined.
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+------------+------------------+
| Value | Path type |
+-------------------------------+
| 0x00000000 | Unknown |
| 0x00000001 | Invalid |
| 0x00000002 | Best |
| 0x00000004 | Non-selected |
| 0x00000008 | Primary |
| 0x00000010 | Backup |
| 0x00000020 | Non+installed |
| 0x00000040 | Best external |
| 0x00000080 | Add-Path |
+------------+------------------+
Table 1: IANA-Registered Path Type
The Path Status field contains a bitmap where each bit encodes a
specific role of the path. Multiple bits may be set when multiple
path status apply to a path.
o 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].
o An invalid path is a route that does not enter the BGP decision
process.
o A non-selected path is a route that is not selected in the BGP
decision process. Back-up routes are considered non-selected,
while the best and ECMP routes are not considered as non-selected.
o 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.
o 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.
o A non-installed path refers to the route that is not installed
into the IP routing table.
o 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].
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3.2. Enterprise-specific Path Marking sub-TLV
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| Type (15 bits) | Length (2 octets) |
+-------------------------------+-------------------------------+
| PEN number (4 octets) |
+---------------------------------------------------------------+
| Path Status(4 octets) |
+---------------------------------------------------------------+
| Reason Code(variable) |
+---------------------------------------------------------------+
Figure 3: Enterprise-specific encoding of Path Markiing sub-TLV
o E bit: For an Enterprise-specific sub-TLV, the E bit MUST be set
to 1.
o Type = 1 (15 Bits): indicates that it's the Enterprise-specific
Path Marking sub-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 PEN Number (4 octets): indicates the IANA enterprise number IANA-
PEN.
o Path Status (4 Octets): indicates enterprise-specific path status,
which remains to be defined.
o Reason Code (Variable): indicates the reasons/explanations of the
path status indicated in the Path Type field. The detailed Reason
Code string is to be defined.
4. Acknowledgements
We would like to thank Jeff Haas for his valuable comments.
5. IANA Considerations
This document requests that IANA assign the following new parameters
to the BMP parameters name space.
Type = TBD1 (2 Octets): Prefix Information TLV.
Type = TBD2 (15 Bits): Path Marking sub-TLV.
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6. Security Considerations
It is not believed that this document adds any additional security
considerations.
7. Normative References
[I-D.ietf-grow-bmp-tlv]
Lucente, P., Gu, Y., and H. Smit, "TLV support for BMP
Route Monitoring and Peer Down Messages", draft-ietf-grow-
bmp-tlv-01 (work in progress), October 2019.
[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-11
(work in progress), February 2020.
[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-grow-bmp-tlv-ebit]
Lucente, P. and Y. Gu, "Support for Enterprise-specific
TLVs in the BGP Monitoring Protocol", draft-lucente-grow-
bmp-tlv-ebit-00 (work in progress), November 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>.
[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>.
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[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
Yunan Gu
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: guyunan@huawei.com
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Thomas Graf
Swisscom
Binzring 17
Zurich 8045
Switzerland
Email: thomas.graf@swisscom.com
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