BGP-LS Extend for Inter-AS Topology Retrieval
draft-wang-idr-bgpls-inter-as-topology-ext-01
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| Document | Type |
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|---|---|---|---|
| Author | Aijun Wang | ||
| Last updated | 2018-06-28 | ||
| Replaced by | draft-ietf-idr-bgpls-inter-as-topology-ext | ||
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draft-wang-idr-bgpls-inter-as-topology-ext-01
IDR Working Group A. Wang
Internet-Draft China Telecom
Intended status: Standards Track June 28, 2018
Expires: December 30, 2018
BGP-LS Extend for Inter-AS Topology Retrieval
draft-wang-idr-bgpls-inter-as-topology-ext-01
Abstract
This document describes the process to build BGP-LS key parameters in
Native IP multi-domain scenario and defines some new inter-AS TE
related TLVs for BGP-LS to let SDN controller retrieve the network
topology automatically under various environments.
Such process and extension can expand the usage of BGP-LS protocol to
multi- domain, enable the network operator to collect the connection
relationship between different AS domains and then calculate the
overall network topology automatically based on the information
provided by BGP-LS protocol.
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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material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 30, 2018.
Copyright Notice
Copyright (c) 2018 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
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Inter-AS Domain Scenarios. . . . . . . . . . . . . . . . . . 3
3.1. IS-IS/OSPF Inter-AS Native IP Scenario . . . . . . . . . 3
3.2. IS-IS/OSPF Inter-AS TE Scenario . . . . . . . . . . . . . 4
4. Inter-AS TE related TLVs . . . . . . . . . . . . . . . . . . 5
5. Topology Reconstruction. . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 5
9. Normative References . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
BGP-LS [RFC7752] describes the methodology that using BGP protocol to
transfer the Link-State information. Such method can enable SDN
controller to collect the underlay network topology automatically,
but normally it can only get the information within one IGP domain.
If the operator has more than one IGP domain, and these domains
interconnect with each other, there is no general TLV within current
BGP- LS to transfer the interconnect information.
Draft [I-D.ietf-idr-bgpls-segment-routing-epe] defines some
extensions for exporting BGP peering node topology information
(including its peers, interfaces and peering ASs) in a way that is
exploitable in order to compute efficient BGP Peering Engineering
policies and strategies. Such information can also be used to
calculate the interconnection topology among different IGP domains,
but it requires the border routers to run BGP-LS protocol to collect
this information and report them to the PCE/SDN controller, which
restricts the deployment flexibility of BGP-LS protocol.
This draft analysizes the situations that the PCE/SDN controller
needs to get about the inter-connected information between different
AS domains, defines new TLVs to extend the BGP-LS protocol to
transfer the key information related to the interconnect TE topology.
After that, the SDN controller can then deduce the multi-domain
topology automatically based on the information from BGP-LS protocol.
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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] .
3. Inter-AS Domain Scenarios.
Fig.1 illustrates the multi-domain scenarios that this draft
discussed. Normally, SDN Controller can get the topology of IGP A
and IGP B individually via the BGP-LS protocol, but it can't get the
topology connection information between these two IGP domains because
there is generally no IGP protocol run on the connected links.
+-----------------+
+----+IP SDN Controller+----+
| +-----------------+ |
| |
|BGP-LS |BGP-LS
| |
+---------------+-----+ +-----+--------------+
| +--+ +-++ ++-+ +-++ +|-+ +--+|
| |S1+--------+S2+---+B1+-----------+B2+---+T1+--------+T2||
| +-++ N1 +-++ ++-+ +-++ ++++ N2 +-++|
| | | | | || | |
| | | | | || | |
| +-++ +-++ ++-+ +-++ ++++ +-++|
| |S4+--------+S3+---+B3+-----------+B4+---+T3+--------+T4||
| +--+ +--+ ++-+ +-++ ++-+ +--+|
| | | |
| | | |
| IGP A | | IGP B |
+---------------------+ +--------------------+
Fig.1 Inter-AS Domain Scenarios
3.1. IS-IS/OSPF Inter-AS Native IP Scenario
When the IGP A or IGP B runs native IS-IS/OSPF protocol, the operator
often redistributes the IPv4/IPv6 prefixes of interconnect links into
IS-IS/OSPF protocol to ensure the inter-domain connectivity.
If the IGP runs IS-IS protocol, the redistributed link information
will be carried in IP External Reachability Information TLV within
the Level 2 PDU type that defined in [RFC1195], every router within
the IGP domain can deduce the redistributed router from the IS-IS
LSDB.
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If the IGP runs OSPF protocol,[RFC2328]defines the type 5 external
LSA to transfer the external IPv4 routes;
[I-D.ietf-ospf-ospfv3-lsa-extend] defines the "External-Prefix TLV"
to transfer the external IPv6 routes; these LSAs have also the
advertising router information that initiates the redistribute
activity. Every router within IGP domain can also deduce the
redistributed router from the OSPF LSDB.
For prefix information that associated with each router, BGP-LS
[RFC7752] defines the Prefix NLRI which is illustrated 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
+-+-+-+-+-+-+-+-+
| Protocol-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
| (64 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Local Node Descriptors (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Prefix Descriptors (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: The IPv4/IPv6 Topology Prefix NLRI Format
For these redistributed inter-domain links, their prefix information
should be included in the "Prefix Descriptor", and the associated
redistributed router information should be included in the "Local
Node Descriptors".
When such information is reported via the BGP-LS protocol, the PCE/
SDN controller can construct the underlay inter-domain topology
according to procedure described in section 5
3.2. IS-IS/OSPF Inter-AS TE Scenario
[RFC5316] and [RFC5392] define the IS-IS and OSPF extensions
respectively to deal with the requirements for inter-AS traffic
engineering. They define some new sub-TLVs(Remote AS
Number、IPv4 Remote ASBR ID、IPv6 Remote ASBR ID) which
are associated with the inter-AS TE link TLVs to report the TE
topology between different domains.
These TLVs are flooded within the IGP domain automatically. If the
PCE/SDN controller can know these information via one of the interior
router that runs BGP-LS protocol, the PCE/SDN controller can rebuild
the inter-AS TE topology correctly.
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4. Inter-AS TE related TLVs
This draft proposes to add three new TLVs that is included within the
inter-AS TE link NLRI to transfer the information via BGP-LS, which
are required to build the inter-AS related topology by the PCE/SDN
controller.
The following Link Descriptor TLVs are added into the Link NLRI in
BGP-LS protocol :
+-----------+---------------------+--------------+----------------+
| TLV Code | Description |IS-IS/OSPF TLV| Reference |
| Point | | /Sub-TLV | (RFC/Section) |
+-----------+---------------------+--------------+----------------+
| TBD |Remote AS Number | 24/21 | [RFC5316]/3.3.1|
| | | | [RFC5392]/3.3.1|
| TBD |IPv4 Remote ASBR ID | 25/22 | [RFC5316]/3.3.2|
| | | | [RFC5392]/3.3.2|
| TBD |IPv6 Remote ASBR ID | 26/24 | [RFC5316]/3.3.3|
| | | | [RFC5392]/3.3.3|
+-----------+---------------------+--------------+----------------+
5. Topology Reconstruction.
When SDN Controller gets such information from BGP-LS protocol, it
should compares the proximity of the redistributed prefixes. If they
are under the same network scope, then it should find the
corresponding associated router information, build the link between
these two border routers.
After iterating the above procedures for all of the redistributed
prefixes, the SDN controller can then retrieve the connection
topology between different domains automatically.
6. Security Considerations
TBD.
7. IANA Considerations
TBD.
8. Acknowledgement
The author would like to thank Acee Lindem and Ketan Talaulikar for
their valuable comments and suggestions, thank also the comments from
Jeff Tantsura and Dhruv Dhody.
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9. Normative References
[I-D.ietf-idr-bgp-ls-segment-routing-ext]
Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H.,
and M. Chen, "BGP Link-State extensions for Segment
Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-08
(work in progress), May 2018.
[I-D.ietf-idr-bgpls-segment-routing-epe]
Previdi, S., Filsfils, C., Patel, K., Ray, S., and J.
Dong, "BGP-LS extensions for Segment Routing BGP Egress
Peer Engineering", draft-ietf-idr-bgpls-segment-routing-
epe-15 (work in progress), March 2018.
[I-D.ietf-ospf-ospfv3-lsa-extend]
Lindem, A., Roy, A., Goethals, D., Vallem, V., and F.
Baker, "OSPFv3 LSA Extendibility", draft-ietf-ospf-ospfv3-
lsa-extend-23 (work in progress), January 2018.
[I-D.ietf-teas-native-ip-scenarios]
Wang, A., Huang, X., Qou, C., Huang, L., and K. Mi, "CCDR
Scenario, Simulation and Suggestion", draft-ietf-teas-
native-ip-scenarios-00 (work in progress), February 2018.
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, DOI 10.17487/RFC1195,
December 1990, <https://www.rfc-editor.org/info/rfc1195>.
[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>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in
Support of Inter-Autonomous System (AS) MPLS and GMPLS
Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316,
December 2008, <https://www.rfc-editor.org/info/rfc5316>.
[RFC5392] Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in
Support of Inter-Autonomous System (AS) MPLS and GMPLS
Traffic Engineering", RFC 5392, DOI 10.17487/RFC5392,
January 2009, <https://www.rfc-editor.org/info/rfc5392>.
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[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>.
[RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
March 2016, <https://www.rfc-editor.org/info/rfc7794>.
[RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and
F. Baker, "OSPFv3 Link State Advertisement (LSA)
Extensibility", RFC 8362, DOI 10.17487/RFC8362, April
2018, <https://www.rfc-editor.org/info/rfc8362>.
Author's Address
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing, Beijing 102209
China
Email: wangaj.bri@chinatelecom.cn
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