OSPF P. Psenak, Ed.
Internet-Draft N. Kumar
Intended status: Standards Track IJ. Wijnands
Expires: December 22, 2017 Cisco
A. Dolganow
Nokia
T. Przygienda
J. Zhang
Juniper Networks, Inc.
S. Aldrin
Google, Inc.
June 20, 2017
OSPF Extensions for BIER
draft-ietf-bier-ospf-bier-extensions-06.txt
Abstract
Bit Index Explicit Replication (BIER) is an architecture that
provides multicast forwarding through a "BIER domain" without
requiring intermediate routers to maintain multicast related per-flow
state. Neither does BIER require an explicit tree-building protocol
for its operation. A multicast data packet enters a BIER domain at a
"Bit-Forwarding Ingress Router" (BFIR), and leaves the BIER domain at
one or more "Bit-Forwarding Egress Routers" (BFERs). The BFIR router
adds a BIER header to the packet. Such header contains a bit-string
in which each bit represents exactly one BFER to forward the packet
to. The set of BFERs to which the multicast packet needs to be
forwarded is expressed by the according set of bits set in BIER
packet header.
This document describes the OSPF protocol extension required for BIER
with MPLS encapsulation.
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 22, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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. Flooding of the BIER Information in OSPF . . . . . . . . . . 3
2.1. BIER Sub-TLV . . . . . . . . . . . . . . . . . . . . . . 3
2.2. BIER MPLS Encapsulation Sub-TLV . . . . . . . . . . . . . 4
2.3. Optional BIER Tree Type Sub-TLV . . . . . . . . . . . . . 5
2.4. Flooding scope of BIER Information . . . . . . . . . . . 6
3. Security Considerations . . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
6. Normative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Bit Index Explicit Replication (BIER) is an architecture that
provides optimal multicast forwarding through a "BIER domain" without
requiring intermediate routers to maintain any multicast related per-
flow state. Neither does BIER explicitly require a tree-building
protocol for its operation. A multicast data packet enters a BIER
domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the
BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs).
The BFIR router adds a BIER header to the packet. The BIER header
contains a bit-string in which each bit represents exactly one BFER
to forward the packet to. The set of BFERs to which the multicast
packet needs to be forwarded is expressed by setting the bits that
correspond to those routers in the BIER header.
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BIER architecture requires routers participating in BIER to exchange
BIER related information within a given domain. BIER architecture
permits link-state routing protocols to perform distribution of such
information. This document describes extensions to OSPF necessary to
advertise BIER specific information in the case where BIER uses MPLS
encapsulation as described in [I-D.ietf-bier-mpls-encapsulation].
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].
2. Flooding of the BIER Information in OSPF
All BIER specific information that a Bit-Forwarding Router (BFR)
needs to advertise to other BFRs is associated with a BFR-Prefix. A
BFR prefix is a unique (within a given BIER domain) routable IP
address that is assigned to each BFR as described in more detail in
section 2 of [I-D.ietf-bier-architecture].
Given that BIER information must be associated with a BFR prefix, the
OSPF Extended Prefix Opaque LSA [RFC7684] has been chosen for
advertisement.
2.1. BIER Sub-TLV
A Sub-TLV of the Extended Prefix TLV (defined in [RFC7684]) is
defined for distributing BIER information. The Sub-TLV is called the
BIER Sub-TLV. Multiple BIER Sub-TLVs may be included in the Extended
Prefix TLV.
The BIER Sub-TLV has the following format:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-domain-ID | MT-ID | BFR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) |
+- -+
| |
Type: TBD1
Length: variable
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Sub-domain-ID: Unique value identifying the BIER sub-domain within
the BIER domain, as described in section 1 of
[I-D.ietf-bier-architecture].
MT-ID: Multi-Topology ID (as defined in [RFC4915]) that identifies
the topology that is associated with the BIER sub-domain.
BFR-id: A 2 octet field encoding the BFR-id, as documented in
section 2 of [I-D.ietf-bier-architecture]. If the BFR is not
locally configured with a valid BFR-id, the value of this field is
set to invalid BFR-id per [I-D.ietf-bier-architecture].
Each BFR sub-domain MUST be associated with one and only one OSPF
topology that is identified by the MT-ID. If the association between
BIER sub-domain and OSPF topology advertised in the BIER sub-TLV by
other BFRs is in conflict with the association locally configured on
the receiving router, the BIER Sub-TLV MUST be ignored.
If a BFR advertises the same Sub-domain-ID in multiple BIER sub-TLVs,
the BRF MUST be treated as if it did not advertise a BIER sub-TLV for
such sub-domain.
All BFRs MUST detect advertisement of duplicate valid BFR-IDs for a
given MT-ID and Sub-domain-ID. When such duplication is detected all
BFRs advertising duplicates MUST be treated as if they did not
advertise a valid BFR-id.
2.2. BIER MPLS Encapsulation Sub-TLV
The BIER MPLS Encapsulation Sub-TLV is a Sub-TLV of the BIER Sub-TLV.
The BIER MPLS Encapsulation Sub-TLV is used in order to advertise
MPLS specific information used for BIER. It MAY appear multiple
times in the BIER Sub-TLV.
The BIER MPLS Encapsulation Sub-TLV has the following format:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Lbl Range Size | Label Range Base |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BS Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD2
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Length: 4 octets
Label Range Size: A 1 octet field encoding the label range size of
the label range. It MUST be greater then 0, otherwise the
advertising router MUST be treated as if it did not advertise a
BIER sub-TLV.
Label Range Base: A 3 octet field, where the 20 rightmost bits
represent the first label in the label range.
Bit String Length: A 1 octet field encoding the supported
BitString length associated with this BFR-prefix. The values
allowed in this field are specified in section 2 of
[I-D.ietf-bier-mpls-encapsulation].
The "label range" is the set of labels beginning with the label
range base and ending with ((label range base)+(label range size)-
1). A unique label range is allocated for each BitStream length
and Sub-domain-ID. These labels are used for BIER forwarding as
described in [I-D.ietf-bier-architecture] and
[I-D.ietf-bier-mpls-encapsulation].
The size of the label range is determined by the number of Set
Identifiers (SI) (section 1 of [I-D.ietf-bier-architecture]) that
are used in the network. Each SI maps to a single label in the
label range. The first label is for SI=0, the second label is for
SI=1, etc.
If same BS length is repeated in multiple BIER MPLS Encapsulation
Sub-TLV inside the same BIER Sub-TLV, the BIER sub-TLV MUST be
ignored.
Label ranges within all BIER MPLS Encapsulation Sub-TLV inside the
same BIER Sub-TLV MUST NOT overlap. If the overlap is detected, the
advertising router MUST be treated as if it did not advertise a BIER
sub-TLV.
All advertised labels MUST be valid, otherwise the BIER sub-TLV MUST
be ignored.
2.3. Optional BIER Tree Type Sub-TLV
This Sub-TLV carries the information associated with the supported
BIER tree type for a sub-domain. This Sub-TLV is optional and its
absence has the same semantics as its presence with Tree Type value 0
(SPF). When Tree Type 0 is used, it is RECOMMENDED that this Sub-TLV
is omitted in order to reduce the space consumed in the parent TLV.
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This Sub-TLV MAY occur no more than once in a BIER sub-TLV. If
multiple occurences of this Sub-TLV are present in a single BIER Sub-
TLV, the BIER sub-TLV MUST be ignored.
If the tree type (implied or explicitly advertised) does not match
the locally configured tree type associated with the matching sub-
domain, the BIER sub-TLV MUST be ignored.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tree Type |
+-+-+-+-+-+-+-+-+
Type: TBD3.
Length: 1 octet.
Tree Type: 1 octet
2.4. Flooding scope of BIER Information
The flooding scope of the OSPF Extended Prefix Opaque LSA [RFC7684]
that is used for advertising the BIER Sub-TLV is set to area-local.
To allow BIER deployment in a multi-area environment, OSPF must
propagate BIER information between areas. The following procedure is
used in order to propagate BIER related information between areas:
When an OSPF Area Border Router (ABR) advertises a Type-3 Summary
LSA from an intra-area or inter-area prefix to all its attached
areas, it will also originate an Extended Prefix Opaque LSA, as
described in [RFC7684]. The flooding scope of the Extended Prefix
Opaque LSA type will be set to area-local. The route-type in the
OSPF Extended Prefix TLV is set to inter-area. When determining
whether a BIER Sub-TLV should be included in this LSA, an OSPF ABR
will:
- Examine its best path to the prefix in the source area and
find the advertising router associated with the best path to
that prefix.
- Determine if such advertising router advertised a BIER Sub-
TLV for the prefix. If yes, the ABR will copy the information
from such BIER MPLS Sub-TLV when advertising BIER MPLS Sub-TLV
to each attached area.
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3. Security Considerations
Implementations must assure that malformed TLV and Sub-TLV
permutations do not result in errors which cause hard OSPF failures.
4. IANA Considerations
The document requests three new allocations from the OSPF Extended
Prefix sub-TLV registry as defined in [RFC7684].
BIER Sub-TLV: TBD1
BIER MPLS Encapsulation Sub-TLV: TBD2
BIER Tree Type Sub-TLV: TBD3
5. Acknowledgments
The authors would like to thank Rajiv Asati, Christian Martin, Greg
Shepherd and Eric Rosen for their contribution.
6. Normative References
[I-D.ietf-bier-architecture]
Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
S. Aldrin, "Multicast using Bit Index Explicit
Replication", draft-ietf-bier-architecture-06 (work in
progress), April 2017.
[I-D.ietf-bier-mpls-encapsulation]
Wijnands, I., Rosen, E., Dolganow, A., Tantsura, J.,
Aldrin, S., and I. Meilik, "Encapsulation for Bit Index
Explicit Replication in MPLS and non-MPLS Networks",
draft-ietf-bier-mpls-encapsulation-07 (work in progress),
June 2017.
[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>.
[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,
<http://www.rfc-editor.org/info/rfc4915>.
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[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <http://www.rfc-editor.org/info/rfc7684>.
Authors' Addresses
Peter Psenak (editor)
Cisco
Apollo Business Center
Mlynske nivy 43
Bratislava 821 09
Slovakia
Email: ppsenak@cisco.com
Nagendra Kumar
Cisco
7200 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: naikumar@cisco.com
IJsbrand Wijnands
Cisco
De Kleetlaan 6a
Diegem 1831
Belgium
Email: ice@cisco.com
Andrew Dolganow
Nokia
750 Chai Chee Rd
06-06 Viva Business Park
Singapore 469004
Email: andrew.dolganow@alcatel-lucent.com
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Tony Przygienda
Juniper Networks, Inc.
10 Technology Park Drive
Westford, MA 01886
USA
Email: prz@juniper.net
Jeffrey Zhang
Juniper Networks, Inc.
10 Technology Park Drive
Westford, MA 01886
USA
Email: zzhang@juniper.net
Sam Aldrin
Google, Inc.
1600 Amphitheatre Parkway
Mountain View, CA
USA
Email: aldrin.ietf@gmail.com
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