Internet DRAFT - draft-chunduri-idr-bgp-ls-ppr-ext
draft-chunduri-idr-bgp-ls-ppr-ext
IDR Working Group U. Chunduri
Internet-Draft P. Pillay-Esnault
Intended status: Standards Track Huawei USA
Expires: November 18, 2019 M. Nanduri
Oracle
May 17, 2019
BGP-LS extensions for Preferred Path Routing
draft-chunduri-idr-bgp-ls-ppr-ext-00
Abstract
This document describe extensions to BGP-LS protocol to include
Preferred Path Routing (PPR) information. This document also extends
BGP-LS protocol and define new SAFIs and NLRIs for propagating path
information from a central entity to a node in the network in the
south bound direction.
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],
RFC8174 [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
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This Internet-Draft will expire on November 18, 2019.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3
2. PPR-ID TLVs Supported by a Prefix . . . . . . . . . . . . . . 3
2.1. PPR-ID Encoding . . . . . . . . . . . . . . . . . . . . . 4
3. Southbound BGP-LS SAFI and NLRIs . . . . . . . . . . . . . . 5
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5.1. New BGP-LS Attribute . . . . . . . . . . . . . . . . . . 6
5.2. New BGP-LS SAFIs . . . . . . . . . . . . . . . . . . . . 6
5.3. New BGP-LS NLRIs . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Preferred Path Routing (PPR) is a path routing mechanism where
routing happens on path identifier in the packet as opposed to
individual segments in the packet as defined in [RFC8402]. PPRs
allow path routing for any underlying data plane with abstracted path
identifier to represent the path of the data packet. Definition and
usage of PPRs by the link state routing protocols ( IS-IS, OSPFv2 and
OSPFv3) within IGP topologies are detailed in
[I-D.chunduri-lsr-isis-preferred-path-routing] and
[I-D.chunduri-lsr-ospf-preferred-path-routing].
PPR-Identifier (PPR-ID) TLV 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 PPRs is an IGP area/
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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 IGP alone it is not enough to
construct PPRs across multiple IGP Areas or AS boundaries.
Even though a central entity provisions the PPRs at one of the
network node, not all PPRs are active and advertised in IGPs as these
could be subjected to the local policies of the network node. PPRs
can also be potentially created locally by operators, it is critical
to have a complete view of currently active PPRs in the network for
creating end-to-end paths crossing multiple IGP areas and AS
boundaries.
To take care of the above cases, this document describe extensions to
BGP-LS to advertise PPR information in Prefix NLRI as described in
Section 2. An external component, which is a BGP-LS [RFC7752]
speaker (e.g., a controller) then can collect active PPR information
in the network in "north bound" direction across IGP areas or ASes.
In some environments, where single protocol is desired for controller
communication with the network nodes, new SAFIs and new NLRI types
are defined to signal the PPR paths from external BGP-LS speaker to
the network nodes in Section 3. This information is subjected to the
local policies of the network node and eventually can be signaled in
an IGP as defined in IGP PPR extensions.
1.1. Acronyms
IGP - Interior Gateway Protocols
MTU - Maximum Transferrable Unit
PPR - Preferred Path Route/Routing
SID - Segment Identifier
SR - Segment Routing
TE - Traffic Engineering
2. PPR-ID TLVs Supported by a Prefix
This section defines a new TLV, PPR-ID TLV in BGP-LS Prefix
Attributes of Prefix NLRI and describes the encoding of the same.
The BGP-LS Prefix attribute, PPR-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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Prefix (continued, variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// PPR-ID Encoding //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Prefix attribute - PPR-ID TLV Format
Type - TBD (Suggested Value 1174, IANA TBD).
Length - Total length of the value field in bytes (variable).
AF - See Section 2.1.
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.
Prefix - represents the the tail-end node address of the
advertised PPR. Value of this field MUST be encoded as a 32-bit
value for IPv4 "Prefix". Value of this field MUST be 16 octets
for IPv6 "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 PPR-ID TLV has flags as defined in
respective IGP and encoded based on the Protocol-ID field in BGP-
LS node NLRI.
2.1. PPR-ID Encoding
This TLV can be seen as having 3 logical section viz., encoding of
Prefix, encoding of PPR-ID with description of ordered path with sub-
TLVs and a set of optional PPR-Attribute Sub-TLVs, which can be used
to describe one or more parameters of the PPR. Out of the above only
the first logical section i.e., encoding Prefix is described here in
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IGP agnostic way. The remaining 2 sections MUST be encoded as
defined in [I-D.chunduri-lsr-isis-preferred-path-routing] and
[I-D.chunduri-lsr-ospf-preferred-path-routing] drafts. This MUST be
based on the Protocol-ID field as defined in section 3.2 of [RFC7752]
'The Prefix NLRI Format'.
The advertisement of PPR-ID TLV in IS-IS has following semantics:
The IS-IS 'PPR-ID Encoding' as defined in Section 2 is encoded in the
BGP-LS Prefix Attribute TLV and the format is as defined in
[I-D.chunduri-lsr-isis-preferred-path-routing] including PPR-ID, PPR-
PDE Sub-TLVs and all possible PPR-Attribute Sub-TLVs. The AF field
for IS-IS MUST be set to zero. The flags of the PPR-ID TLV are
semantically mapped to the definition in
[I-D.chunduri-lsr-isis-preferred-path-routing] section 2.
The advertisement of PPR-ID TLV in OSPF has following semantics:
The OSPFv2/OSPFv3 "PPR-ID Encoding" as defined in Section 2 is
encoded in the BGP-LS Prefix Attribute TLV and the format is as
defined in [I-D.chunduri-lsr-ospf-preferred-path-routing] including
PPR-ID, PPR-PDE Sub-TLVs and all possible PPR-Attribute Sub-TLVs.
The flags and AF of the PPR-ID TLV are semantically mapped to the
definition in [I-D.chunduri-lsr-ospf-preferred-path-routing] section
2 for OSPFv2 or section 3 for OSPFv3.
3. Southbound BGP-LS SAFI and NLRIs
This document extends the [RFC7752] by defining two new South Bound
(SB) SAFIs to be used with BGP-LS AFI 16388. All non-VPN SB prefix
information SHALL be encoded using AFI 16388 / SAFI 75 (suggested
value for SB-BGP-LS SAFI, IANA TBD). VPN SB prefix information SHALL
be encoded using AFI 16388 / SAFI 76 (suggested value for SB-BGP-LS-
VPN SAFI, IANA TBD).
This document also extends then BGP-LS by defining 2 new south bound
NLRI types, one for SB IPv4 Topology Prefix (type 5, suggested value,
IANA TBD) and one for SB IPv6 Topology Prefix NLRI (type 6, suggested
value, IANA TBD). As with other BGP-LS SAFIs, in order for two BGP
speakers to exchange SB Link-State NLRI, they MUST use BGP
Capabilities Advertisement to advertise SB SAFIs to ensure that they
are both capable of properly processing such NLRI.
Encoding for the new SB SAFIs and new SB NLRIs are applicable to
[RFC7752], including the parameters as defined in "BGP-LS Protocol-
IDs", "BGP-LS Well-Known Instance-IDs" and "BGP-LS Node Descriptor,
Link Descriptor, Prefix Descriptor, and Attribute TLVs".
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PPR-ID Prefix Attribute TLV as defined in Section 2 can be advertised
with SB IPv4/IPv6 Topology Prefix NLRIs. When this is done this
information is advertised in the corresponding underlying IGP
subjected to the local node policy.
4. Acknowledgements
TBD.
5. IANA Considerations
5.1. New BGP-LS Attribute
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 - PPR-ID TLV as
described in Section 2.
TLV # Name
----- ------------------------------
TBD PPR-ID TLV in Prefix attribute
5.2. New BGP-LS SAFIs
This document defines a new SAFIs in the registry "Subsequent Address
Family Identifiers (SAFI) Parameters" that has been assigned by IANA:
SAFI # Description Reference
----- -------------------- ------------
75 SB-BGP-LS SAFI This Document
76 SB-BGP-LS-VPN SAFI This Document
5.3. New BGP-LS NLRIs
This document requests IANA to assign a code point from the"BGP-LS
NLRI-Types" registry as follows:
NLRI # Description Reference
----- ------------------------ ---------------
5 SB IPv4 Topology Prefix This Document
6 SB IPv6 Topology Prefix This Document
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6. Security Considerations
This document does not introduce security issues beyond those
discussed in [RFC7752]
7. References
7.1. Normative References
[I-D.chunduri-lsr-isis-preferred-path-routing]
Chunduri, U., Li, R., White, R., Tantsura, J., Contreras,
L., and Y. Qu, "Preferred Path Routing (PPR) in IS-IS",
draft-chunduri-lsr-isis-preferred-path-routing-03 (work in
progress), May 2019.
[I-D.chunduri-lsr-ospf-preferred-path-routing]
Chunduri, U., Qu, Y., White, R., Tantsura, J., and L.
Contreras, "Preferred Path Routing (PPR) in OSPF", draft-
chunduri-lsr-ospf-preferred-path-routing-03 (work in
progress), May 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>.
[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>.
[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>.
7.2. Informative References
[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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[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
Authors' Addresses
Uma Chunduri
Huawei USA
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: uma.chunduri@huawei.com
Padma Pillay-Esnault
Huawei USA
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: padma@huawei.com
Mohan Nanduri
Oracle
USA
Email: mohan.nanduri@oracle.com
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