Network Working Group J. Dong
Internet-Draft M. Chen
Intended status: Standards Track D. Dhody
Expires: December 26, 2016 Huawei Technologies
J. Tantsura
Individual
K. Kumaki
KDDI Corporation
T. Murai
Furukawa Network Solution Corp.
June 24, 2016
BGP Extensions for Path Computation Element (PCE) Discovery
draft-dong-pce-discovery-proto-bgp-05
Abstract
In networks where Path Computation Element (PCE) is used for
centralized path computation, it is desirable for the Path
Computation Clients (PCCs) to automatically discover a set of PCEs
and select the suitable ones to establish the PCEP session. RFC 5088
and RFC 5089 define the PCE discovery mechanisms based on Interior
Gateway Protocols (IGP). This document describes several scenarios
in which the IGP based PCE discovery mechanisms cannot be used
directly. In such scenarios, BGP might be suitable, thus this
document specifies the BGP extensions for PCE discovery. The BGP
based PCE discovery mechanism is complementary to the existing IGP
based mechanisms.
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 http://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
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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 December 26, 2016.
Copyright Notice
Copyright (c) 2016 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
(http://trustee.ietf.org/license-info) in effect on the date of
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Carrying PCE Discovery Information in BGP . . . . . . . . . . 4
2.1. PCE Address Information . . . . . . . . . . . . . . . . . 4
2.2. PCE Discovery TLVs . . . . . . . . . . . . . . . . . . . 5
3. Operational Considerations . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
In network scenarios where Path Computation Element (PCE) is used for
centralized path computation, it is desirable for the Path
Computation Clients (PCCs) to automatically discover a set of PCEs
and select the suitable ones to establish the PCEP session.
[RFC5088] and [RFC5089] define the PCE discovery mechanisms based on
Interior Gateway Protocols (IGP).
The IGP based discovery mechanism requires the PCE participate in the
IGP network, which usually requires that the PCE is directly adjacent
to at least one of the IGP routers in the network. In some scenarios
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such requirement cannot be satisfied. For example, a PCE may need to
provide path computation service to some subsidiary networks of an
operator, which typically locate in different geographical region
(and not IGP adjacent). Also when PCE function is implemented in a
central server running IGP on individual interfaces to each IGP area
can be cumbersome.
The requirement on PCE discovery, as described in [RFC4674], also
include the automatic discovery of the PCEs in other domains, as it
is a desirable function in the case of inter-domain path computation.
The IGP based discovery mechanisms cannot meet such requirement.
For example, Backward Recursive Path Computation (BRPC) [RFC5441] can
be used by cooperating PCEs to compute an inter-AS path, in which
case these cooperating PCEs should be known to each other in advance.
In this case the PCEs belongs to different AS and do not participate
in a common IGP, the IGP based discovery mechanisms are not
applicable.
Another example is the hierarchical PCE scenario [RFC6805], in which
the child PCEs need to know the information of the parent PCEs. This
cannot be achieved via IGP based discovery, as the child PCEs and the
parent PCE are usually in different domains.
In some BGP IP-VPN networks, an end-to-end TE LSP between the CEs
(Customer Edges) of a particular VPN is required [RFC5824]. In this
case, CEs need the information of the PCE which can perform the CE to
CE path computation for that VPN. Since the PCE may locate in a VPN
site different from the site of the requesting CE, the IGP based
discovery mechanism is not directly applicable, and some BGP based
discovery mechanism is required to distribute the per-VPN PCE
information to the VPN sites.
Since BGP has been extended for north-bound distribution of routing
and Label Switched Path (LSP) information to PCE [RFC7752]
[I-D.ietf-idr-te-lsp-distribution] and [I-D.ietf-idr-te-pm-bgp], PCEs
can obtain the routing information without participating in IGP. In
this scenario, a new BGP based PCE discovery mechanism is needed.
This document proposes to extend BGP for PCE discovery in the above
scenarios. In networks where BGP-LS is used for the north-bound
routing information distribution to PCE, the BGP based PCE discovery
can make use of the existing BGP sessions and mechanisms to achieve
automatic PCE discovery. Further IGP may be used to redistribute
remote PCE information, the detailed mechanism is out of the scope of
this document. Thus the BGP based PCE discovery is complementary to
the existing IGP based mechanisms.
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+-----------+
| PCE |
+-----------+
|
v
+-----------+
| BGP | +-----------+
| Speaker | | PCE |
+-----------+ +-----------+
| | | |
| | | |
+---------------+ | +-------------------+ |
v v v v
+-----------+ +-----------+ +-----------+
| BGP | | BGP | | BGP |
| Speaker | | Speaker | . . . | Speaker |
| & PCC | | & PCC | | & PCC |
+-----------+ +-----------+ +-----------+
Figure 1: BGP for PCE discovery
As shown in the network architecture in Figure 1, BGP is used both
for routing information distribution and for PCE information
discovery. The routing information is collected from the network
elements and distributed to PCE, while the PCE discovery information
is advertised from PCE to PCCs, or among different PCEs. The PCCs
maybe co-located with the BGP speakers as shown in Figure 1.
2. Carrying PCE Discovery Information in BGP
2.1. PCE Address Information
The PCE discovery information is advertised in BGP UPDATE messages
using the MP_REACH_NLRI and MP_UNREACH_NLRI attributes [RFC4760].
The AFI and SAFI defined in [RFC7752] are re-used. For the PCEs in
public network, the AFI / SAFI pair is 16388 / 71, while for the PCEs
of a particular VPN, the AFI / SAFI pair is set to 16388 / 72.
A new NLRI Type is defined for PCE discovery information as below:
o Type = TBD: PCE Discovery NLRI
The format of PCE Discovery NLRI is shown in the following figure:
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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
+-+-+-+-+-+-+-+-+
| Protocol-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
| (64 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ PCE-Address (4 or 16 octets) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2. PCE Discovery NLRI
The 'Protocol-ID' field SHOULD be set to the appropriate value which
indicates the source of the PCE discovery information. If BGP
speaker and PCE are co-located, the Protocol-ID SHOULD be set to
"Direct". In other cases, it is RECOMMENDED that the Protocol-ID
value be set to "Static configuration".
As defined in [RFC7752], the 64-Bit 'Identifier' field is used to
identify the "routing universe" where the PCE belongs.
2.2. PCE Discovery TLVs
The detailed PCE discovery information is carried in the BGP-LS
attribute [RFC7752] with a new "PCE Discovery TLV", which contains a
set of sub-TLVs for specific PCE discovery information. The PCE
Discovery TLV and sub-TLVs SHOULD only be used with the PCE Discovery
NLRI.
The format of the PCE Discovery TLV is shown as below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ PCE Discovery Sub-TLVs (variable) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3. PCE Discovery TLV
The PCE Discovery sub-TLVs are listed as below. The format of the
PCE Discovery sub-TLVs are consistent with the IGP PCED sub-TLVs as
defined in [RFC5088] and [RFC5089]. The PATH-SCOPE sub-TLV MUST
always be carried in the PCE Discovery TLV. Other PCE Discovery sub-
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TLVs are optional and may facilitate the PCE selection process on the
PCCs.
Type | Length | Name
------+------------+--------------------------------
1 | 3 | PATH-SCOPE sub-TLV
2 | variable | PCE-CAP-FLAGS sub-TLV
3 | variable | OSPF-PCE-DOMAIN sub-TLV
4 | variable | IS-IS-PCE-DOMAIN sub-TLV
5 | variable | OSPF-NEIG-PCE-DOMAIN sub-TLV
6 | variable | IS-IS-NEIG-PCE-DOMAIN sub-TLV
More PCE Discovery sub-TLVs may be defined in future. The format and
semantic of new PCE Discovery sub-TLVs SHOULD be consistent in BGP
and IGP based PCE discovery.
3. Operational Considerations
Existing BGP operational procedures apply to the advertisement of PCE
discovery information. This information is treated as pure
application level data which has no immediate impact on forwarding
states. Normal BGP path selection can be applied to PCE Discovery
NLRI only for the information propagation in the network, while on
PCCs the PCE selection is based on the information carried in the PCE
Discovery TLV. The PCE discovery information SHOULD be advertised
only to the domains where such information is allowed to be used.
This can be achieved by policy control on the ASBRs.
The PCE discovery information is considered relatively stable and
does not change frequently, thus this information will not bring
significant impact on the amount of BGP updates in the network.
4. IANA Considerations
IANA needs to assign a new NLRI Type for 'PCE Discovery NLRI' from
the "BGP-LS NLRI-Types" registry.
IANA needs to assign a new TLV code point for 'PCE Discovery TLV'
from the "node anchor, link descriptor and link attribute TLVs"
registry.
IANA needs to create a new registry for "PCE Discovery Sub-TLVs".
The registry will be initialized as shown in section 2.2 of this
document.
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5. Security Considerations
Procedures and protocol extensions defined in this document do not
affect the BGP security model. See the 'Security Considerations'
section of [RFC4271] for a discussion of BGP security. Also refer to
[RFC4272] and [RFC6952] for analysis of security issues for BGP.
6. Contributors
The following individuals gave significant contributions to this
document:
Takuya Miyasaka
KDDI Corporation
ta-miyasaka@kddi.com
7. Acknowledgements
The authors would like to thank Zhenbin Li, Hannes Gredler, Jan
Medved, Adrian Farrel, Julien Meuric and Jonathan Hardwick for the
valuable discussion and comments.
8. References
8.1. 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,
<http://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,
<http://www.rfc-editor.org/info/rfc4271>.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760,
DOI 10.17487/RFC4760, January 2007,
<http://www.rfc-editor.org/info/rfc4760>.
[RFC5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
Zhang, "OSPF Protocol Extensions for Path Computation
Element (PCE) Discovery", RFC 5088, DOI 10.17487/RFC5088,
January 2008, <http://www.rfc-editor.org/info/rfc5088>.
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[RFC5089] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
Zhang, "IS-IS Protocol Extensions for Path Computation
Element (PCE) Discovery", RFC 5089, DOI 10.17487/RFC5089,
January 2008, <http://www.rfc-editor.org/info/rfc5089>.
[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,
<http://www.rfc-editor.org/info/rfc7752>.
8.2. Informative References
[I-D.ietf-idr-te-lsp-distribution]
Dong, J., Chen, M., Gredler, H., Previdi, S., and J.
Tantsura, "Distribution of MPLS Traffic Engineering (TE)
LSP State using BGP", draft-ietf-idr-te-lsp-
distribution-04 (work in progress), December 2015.
[I-D.ietf-idr-te-pm-bgp]
Previdi, S., Wu, Q., Gredler, H., Ray, S.,
Tantsura, j., Filsfils, C., and L. Ginsberg,
"BGP-LS Advertisement of IGP Traffic Engineering
Performance Metric Extensions", draft-ietf-idr-te-pm-
bgp-03 (work in progress), May 2016.
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis",
RFC 4272, DOI 10.17487/RFC4272, January 2006,
<http://www.rfc-editor.org/info/rfc4272>.
[RFC4674] Le Roux, J., Ed., "Requirements for Path Computation
Element (PCE) Discovery", RFC 4674, DOI 10.17487/RFC4674,
October 2006, <http://www.rfc-editor.org/info/rfc4674>.
[RFC5441] Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux,
"A Backward-Recursive PCE-Based Computation (BRPC)
Procedure to Compute Shortest Constrained Inter-Domain
Traffic Engineering Label Switched Paths", RFC 5441,
DOI 10.17487/RFC5441, April 2009,
<http://www.rfc-editor.org/info/rfc5441>.
[RFC5824] Kumaki, K., Ed., Zhang, R., and Y. Kamite, "Requirements
for Supporting Customer Resource ReSerVation Protocol
(RSVP) and RSVP Traffic Engineering (RSVP-TE) over a BGP/
MPLS IP-VPN", RFC 5824, DOI 10.17487/RFC5824, April 2010,
<http://www.rfc-editor.org/info/rfc5824>.
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[RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the
Path Computation Element Architecture to the Determination
of a Sequence of Domains in MPLS and GMPLS", RFC 6805,
DOI 10.17487/RFC6805, November 2012,
<http://www.rfc-editor.org/info/rfc6805>.
[RFC6952] Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
BGP, LDP, PCEP, and MSDP Issues According to the Keying
and Authentication for Routing Protocols (KARP) Design
Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013,
<http://www.rfc-editor.org/info/rfc6952>.
Authors' Addresses
Jie Dong
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095
China
Email: jie.dong@huawei.com
Mach(Guoyi) Chen
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095
China
Email: mach.chen@huawei.com
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: dhruv.ietf@gmail.com
Jeff Tantsura
Individual
US
Email: jefftant.ietf@gmail.com
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Kenji Kumaki
KDDI Corporation
Garden Air Tower, Iidabashi, Chiyoda-ku
Tokyo 102-8460
Japan
Email: ke-kumaki@kddi.com
Tomoki Murai
Furukawa Network Solution Corp.
5-1-9, Higashi-Yawata, Hiratsuka
Kanagawa 254-0016
Japan
Email: murai@fnsc.co.jp
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