Internet DRAFT - draft-chunduri-idr-bgp-ls-nspfid
draft-chunduri-idr-bgp-ls-nspfid
IDR Working Group U. Chunduri
Internet-Draft Huawei USA
Intended status: Standards Track April 2, 2018
Expires: October 4, 2018
BGP Link-State extensions for NSPF ID
draft-chunduri-idr-bgp-ls-nspfid-00
Abstract
Non Shortest Paths (NSPs) used in routing protocols e.g. by the link
state routing protocols (IS-IS, OSPFv2 and OSPFv3) within IGP
topologies. NSPs help to reduce the data plane path overhead,
mitigate from MTU issues as well as performance related issues in
certain data planes and allows granular traffic accounting in the
network. NSPs are created locally by operator or can be provisioned
through PCE or Yang from outside. This document describes a
mechanism by which NSP information currently active in the network
using the BGP routing protocol by defining extensions to BGP Link-
state address-family.
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 RFC2119 [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
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 4, 2018.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3
2. NSPF ID TLVs Supported by a Node . . . . . . . . . . . . . . 3
3. Elements of Procedure and Encoding . . . . . . . . . . . . . 4
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
In a network implementing source routing, packets may be transported
through the use of segment identifiers (SIDs), where a SID uniquely
identifies a segment as defined in [I-D.ietf-spring-segment-routing].
Usage of Non Shortest Paths (NSPs) with SR SIDs by the link state
routing protocols ( IS-IS, OSPFv2 and OSPFv3) within IGP topologies
can reduce the data plane path overhead, mitigate from MTU and
performance related issues and allow granular traffic accounting in
the network. IGP NSP extensions are detailed in
[I-D.ct-isis-nspfid-for-sr-paths] and
[I-D.ct-ospf-nspfid-for-sr-paths] darfts.
NSP Forwarding Identifier (NSPF ID) TLV can be associated with allows
advertisement of multi-hop Traffic Engineered (TE) paths, Fast Re-
Route (FRR) or certain chained paths. The flooding scope for the IGP
extensions for NSPs is IGP area/domain. Consequently, the contents
of a Link State Database (LSDB) or a Traffic Engineering Database
(TED) has the scope of an IGP area/domain and therefore by using the
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IGP alone it is not enough to construct NSPs across multiple IGP Area
or AS boundaries.
Even though an entity like PCE provisions the NSPs at the ingress
node, not all NSPs are active and advertised in IGPs as these could
be subjected to the local policies of ingress node. Also NSPs can be
potentially created locally by operators too; it is critical to have
a complete view of currently active NSPs in the network for creating
end-to-end paths crossing multiple IGP areas and AS boundaries.
This document describes extensions to BGP-LS to advertise NSP
information. An external component, which is a BGP-LS [RFC7752]
speaker (e.g., a controller) then can collect NSP information in the
"north bound" direction across IGP areas or ASes and construct the
end-to-end path that need to be applied to an incoming packet to
achieve the desired end-to-end forwarding.
1.1. Acronyms
IGP - Interior Gateway Protocols
MTU - Maximum Transferrable Unit
NSP - Non Shortest Path
SID - Segment Identifier
SR - Segment Routing
TE - Traffic Engineering
2. NSPF ID TLVs Supported by a Node
This section defines a new TLV, NSPF ID TLV in BGP-LS Node Attributes
of Node NLRI and describes the encoding of the same. The BGP-LS Node
attribute, NSPF-ID TLV has the following format:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MT-ID | AF | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Len | FEC Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// FEC Prefix (continued, variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// NSPF-ID Encoding //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Node attribute - NSPF ID TLV Format
Type - TBD (IANA) from BGP-LS Node attributes registry.
Length - Total length of the value field in bytes (variable).
AF - See Section 3.
MT-ID - is the multi-topology identifier defined in [RFC5120] with
4 most significant bits reset on transmission and ignored on
receive. The remaining 12-bit field contains the MT-ID. For
OSPFv2 this is as defined in [RFC4915]. For OSPFv3 it MUST be set
to zero.
Prefix Len - contains the length of the prefix in bits.
FEC Prefix - represents the Forwarding Equivalence Class at the
tail-end of the advertised NSP. Value of this field MUST be
encoded as a 32-bit value for IPv4 "FEC Prefix". Value of this
field MUST be 16 octets for IPv6 "FEC Prefix", encoded as an even
multiple of 32-bit words, padded with zeroed bits as necessary.
This encoding consumes ((PrefixLength + 31) / 32) 32-bit words.
Flags: 1 octet field of NSPD ID TLV has flags as defined in
respective IGP and encoded based on the Protocol-ID field in BGP-
LS node NLRI.
3. Elements of Procedure and Encoding
This TLV can be seen as having 3 logical section viz., encoding of
FEC Prefix, encoding of NSPF-ID with description of ordered path with
sub-TLVs and a set of optional non-NSP sub-TLVs which can be used to
describe one or more parameters of the NSP. Out of the above only
the first logical section i.e., encoding FEC Prefix is described here
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in IGP agnostic way. The remaining 2 sections MUST be encoded as
defined in [I-D.ct-isis-nspfid-for-sr-paths] and
[I-D.ct-ospf-nspfid-for-sr-paths] darfts. This MUST be based on the
Protocol-ID field as defined in section 3.2 of [RFC7752] 'The Node
NLRI Format'.
The advertisement of NSPF ID TLV in OSPF has following semantics:
The OSPFv2/OSPFv3 "NSPF-ID Encoding" as defined in Section 2 is
encoded in the BGP-LS Node Attribute and the format is as defined in
[I-D.ct-ospf-nspfid-for-sr-paths] including all possible Non-NSP sub-
TLVs. The flags and AF of the NSPF ID TLV are semantically mapped to
the definition in [I-D.ct-ospf-nspfid-for-sr-paths] section 2 for
OSPFv2 or section 3 for OSPFv3.
The advertisement of NSPF ID TLV in IS-IS has following semantics:
The IS-IS 'NSPF-ID Encoding' as defined in Section 2 is encoded in
the BGP-LS Node Attribute and the format is as defined in
[I-D.ct-isis-nspfid-for-sr-paths] including all possible Non-NSP sub-
TLVs. The AF field for IS-IS MUST be set to zero. The flags of the
NSPF ID TLV are semantically mapped to the definition in
[I-D.ct-isis-nspfid-for-sr-paths] section 2.
4. Acknowledgements
TBD.
5. IANA Considerations
This document requests IANA to assign a code point from the "BGP-LS
Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute
TLVs" registry as follows: BGP-LS Node Attribute - NSPF ID TLV as
described in Section 2.
TLV # Name
----- ------------------------------
TBD NSPF ID TLV in Node attribute
6. Security Considerations
This document does not introduce security issues beyond those
discussed in [RFC7752]
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7. References
7.1. Normative References
[I-D.ct-isis-nspfid-for-sr-paths]
Chunduri, U., Tantsura, J., and Y. Qu, "Usage of Non
Shortest Path Forwarding (NSPF) IDs in IS-IS", draft-ct-
isis-nspfid-for-sr-paths-01 (work in progress), March
2018.
[I-D.ct-ospf-nspfid-for-sr-paths]
Chunduri, U., Qu, Y., and J. Tantsura, "Usage of Non
Shortest Path Forwarding (NSPF) IDs in OSPF", draft-ct-
ospf-nspfid-for-sr-paths-00 (work in progress), March
2018.
[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>.
[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>.
7.2. Informative References
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing
Architecture", draft-ietf-spring-segment-routing-15 (work
in progress), January 2018.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007,
<https://www.rfc-editor.org/info/rfc4915>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<https://www.rfc-editor.org/info/rfc5120>.
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Author's Address
Uma Chunduri
Huawei USA
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: uma.chunduri@huawei.com
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