Internet DRAFT - draft-psenak-ospf-bier-extensions
draft-psenak-ospf-bier-extensions
OSPF P. Psenak, Ed.
Internet-Draft N. Kumar
Intended status: Standards Track IJ. Wijnands
Expires: August 29, 2015 Cisco
A. Dolganow
Alcatel-Lucent
T. Przygienda
Ericsson
J. Zhang
Juniper Networks, Inc.
S. Aldrin
Huawei Technologies
February 25, 2015
OSPF Extensions For BIER
draft-psenak-ospf-bier-extensions-02.txt
Abstract
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. BIER also does not require any 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. 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.
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
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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 August 29, 2015.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Flooding of the BIER Information in OSPF . . . . . . . . . . 3
2.1. The BIER Sub-TLV . . . . . . . . . . . . . . . . . . . . 3
2.2. The BIER MPLS Encapsulation Sub-TLV . . . . . . . . . . . 4
2.3. Flooding scope of BIER Information . . . . . . . . . . . 5
3. Security Considerations . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
6. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
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 within a
given BIER domain to exchange some BIER specific information among
themselves. BIER architecture allows link-state routing protocols to
perform the distribution of these information. In this document we
describe extensions to OSPF to distribute BIER specific information
for the case where BIER uses MPLS encapsulation as described in
[I-D.wijnands-mpls-bier-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 the BIER specific information that a BIER router needs to
advertise to other BIER routers are associated with the BFR-Prefix, a
unique (within a given BIER domain), routable IP address that is
assign to each BIER router as described in section 2 of
[I-D.wijnands-bier-architecture].
Given that the BIER information is associated with the prefix, the
OSPF Extended Prefix Opaque LSA [I-D.ietf-ospf-prefix-link-attr] is
used to flood BIER related information.
2.1. The BIER Sub-TLV
A new Sub-TLV of the Extended Prefix TLV (defined in
[I-D.ietf-ospf-prefix-link-attr]) is defined for distributing BIER
information. The new Sub-TLV is called BIER Sub-TLV. Multiple BIER
Sub-TLVs may be included in the Extended Prefix TLV.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subdomain-ID | MT-ID | BFR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) |
+- -+
| |
Type: TBD
Length: 4 bytes
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Subdomain-ID: Unique value identifying the BIER subdomain within
the BIER domain, as described in section 1 of
[I-D.wijnands-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 [I-D.wijnands-bier-architecture]. If the BFR-id is
zero, it means, the advertising router is not advertising any
BIER-id.
Each BFR sub-domain MUST be associate with a single OSPF topology
that is identified by the MT-ID. If the association between BEIR
sub-domain and OSPF topology advertised in the BIER sub-TLV is in
conflict with the association locally configured on the receiving
router, BIER sub-TLV SHOULD be ignored.
2.2. The BIER MPLS Encapsulation Sub-TLV
BIER MPLS Encapsulation Sub-TLV is a sub-TLV of the BIER Sub-TLV.
BIER MPLS Encapsulation Sub-TLVt is used in order to advertise MPLS
specific information used for BIER. It MAY appear multiple times in
the BIER Sub-TLV.
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: TBD
Length: 4 bytes
Label Range Size: A 1 octet field encoding the label range size of
the label range. It MUST be greater then 0, otherwise the TLV
MUST be ignored.
Label Range Base: A 3 octet field, where the 20 rightmost bits
represent the first label in the label range.
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BS 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 3 of
[I-D.wijnands-mpls-bier-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 Multi-Topology ID. These labels are used for BIER forwarding
as described in [I-D.wijnands-bier-architecture] and
[I-D.wijnands-mpls-bier-encapsulation].
The size of the label range is determined by the number of Set
Identifiers (SI) (section 2 of [I-D.wijnands-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 first BIER MPLS
Encapsulation Sub-TLV with such BS length MUST be used and any
subsequent BIER MPLS Encapsulation Sub-TLVs with the same BS length
MUST be ignored.
Label ranges within all BIER MPLS Encapsulation Sub-TLV inside the
same BIER Sub-TLV SHOULD NOT overlap. If the overlap is detected,
overlapping BIER MPLS Encapsulation Sub-TLV SHOULD be ignored.
2.3. Flooding scope of BIER Information
Flooding scope of the OSPF Extended Prefix Opaque LSA
[I-D.ietf-ospf-prefix-link-attr] that is used for advertising BIER
Sub TLV is set to area. If (and only if) a single BIER domain
contains multiple OSPF areas, OSPF must propagate BIER information
between areas. The following procedure is used in order to propagate
BIER related information between areas:
When an OSPF ABR advertises a Type-3 Summary LSA from an intra-
area or inter-area prefix to all its connected areas, it will also
originate an Extended Prefix Opaque LSA, as described in
[I-D.ietf-ospf-prefix-link-attr]. The flooding scope of the
Extended Prefix Opaque LSA type will be set to area-scope. 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 ABR will:
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- look at 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, ABR will copy the information from
such BIER MPLS Sub-TLV when advertising BIER MPLS Sub-TLV to
each connected area.
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 two new allocations from the OSPF Extended
Prefix sub-TLV registry as defined in
[I-D.ietf-ospf-prefix-link-attr].
BIER Sub-TLV: TBD
BIER MPLS Encapsulation Sub-TLV: TBD
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-ospf-prefix-link-attr]
Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", draft-ietf-ospf-prefix-link-attr-03 (work
in progress), February 2015.
[I-D.wijnands-bier-architecture]
Wijnands, I., Rosen, E., Dolganow, A., and T. Przygienda,
"Multicast using Bit Index Explicit Replication", draft-
wijnands-bier-architecture-00 (work in progress),
September 2014.
[I-D.wijnands-mpls-bier-encapsulation]
Wijnands, I., Rosen, E., Dolganow, A., and J. Tantsura,
"Encapsulation for Bit Index Explicit Replication in MPLS
Networks", draft-wijnands-mpls-bier-encapsulation-00 (work
in progress), September 2014.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", RFC
4915, June 2007.
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
Alcatel-Lucent
600 March Rd.
Ottawa, Ontario K2K 2E6
Canada
Email: andrew.dolganow@alcatel-lucent.com
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Tony Przygienda
Ericsson
300 Holger Way
San Jose, CA 95134
USA
Email: antoni.przygienda@ericsson.com
Jeffrey Zhang
Juniper Networks, Inc.
10 Technology Park Drive
Westford, MA 01886
USA
Email: zzhang@juniper.net
Sam Aldrin
Huawei Technologies
2330 Central Expressway
Santa Clara, CA 95051
USA
Email: zzhang@juniper.net
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