Network Work group P. Psenak, Ed.
Internet-Draft N. Nainar, Ed.
Intended status: Standards Track I. Wijnands
Expires: May 3, 2018 Cisco Systems, Inc.
October 30, 2017
OSPFv3 Extensions for BIER
draft-psenak-bier-ospfv3-extensions-00
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 OSPFv3 protocol extensions required for
BIER.
Status of This Memo
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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 May 3, 2018.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Requirements notation . . . . . . . . . . . . . . . . . . 3
3. Flooding of BIER information in OSPFv3 . . . . . . . . . . . 3
3.1. BIER Sub-TLV . . . . . . . . . . . . . . . . . . . . . . 4
3.2. BIER MPLS Encapsulation Sub-TLV . . . . . . . . . . . . . 5
3.3. Flooding scope of BIER Information . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
[I-D.ietf-bier-architecture] introduces and explains BIER
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.
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BIER architecture requires the distribution of BIER specific
information among the routers participating within a BIER domain.
BIER architecture permits link-state routing protocol to perform the
distribution of such information.
[I-D.ietf-bier-ospf-bier-extensions] proposes the OSPFv2 protocol
extensions to distribute BIER specific information. This document
describes the OSPFv3 protocol extensions required to advertise BIER
specific information.
2. Conventions used in this document
2.1. Terminology
BFER - Bit Forwarding Egress Router
BFIR - Bit Forwarding Ingress Router
BFR - Bit-Forwarding Router
BIER - Bit Index Explicit Replication
ECMP - Equal Cost Multi-Path
SI - Set Identifier
2.2. Requirements notation
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].
3. Flooding of BIER information in OSPFv3
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 IPv4 or
IPv6 address that is assigned to each BFR as described in more detail
in [I-D.ietf-bier-architecture].
[I-D.ietf-ospf-ospfv3-lsa-extend] defines the encoding of OSPFv3 LSA
in TLV format that allows to carry additional informations. This
section defines the required Sub-TLVs to carry BIER information that
is associated with the BFR-Prefix. The Sub-TLV defined in this
section MAY be carried in the below OSPFv3 Extended LSA TLVs
[I-D.ietf-ospf-ospfv3-lsa-extend]:
Intra-Area-Prefix TLV
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Inter-Area-Prefix TLV
3.1. BIER Sub-TLV
A Sub-TLV of the above mentioned Prefix TLVs is defined for
distributing BIER information. The Sub-TLV is called the BIER Sub-
TLV. Multiple BIER Sub-TLVs MAY be included in any of the above
mentioned 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 | BAR | BFR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) |
+- -+
| |
Type
Set to TBD1
Length
Variable, dependent on sub-TLVs.
Sub-domain-ID
Unique value identifying the BIER sub-domain within the BIER
domain, as described in [I-D.ietf-bier-architecture]
BAR
Single octet BIER Algorithm. 0 is the only supported value defined
in this document and represents Shortest Path First (SPF)
algorithm based on IGP link metric. This is the standard shortest
path algorithm as computed by the OSPF protocol. Other values may
be defined in the future.
BFR-id
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A 2 octet field encoding the BFR-id, as documented in
[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].
Flags
The C flag (BSL Conversion flag) is set to 1 if the node is
capable of imposing a different BSL than the one it received in a
BIER encapsulated packet. More details about the usage of this
conversion is discussed in Section 2.3 of
[I-D.ietf-bier-ospf-bier-extensions]. Other flags MUST be set to
0 and receiver MUST ignore the other flags. New flags may be
defined in future.
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 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.
The supported algorithm MUST be consistent for all routers supporting
a given BFR sub-domain. A router receiving BIER Sub-TLV
advertisement with a BAR which does not match the locally configured
value MUST report a misconfiguration for the given BIER sub-domain
and MUST ignore such BIER sub-TLV.
3.2. BIER MPLS Encapsulation Sub-TLV
The BIER MPLS Encapsulation Sub-TLV is a Sub-TLV of the BIER Sub-TLV
defined in Section 3.1. This Sub-TLV is used to carry MPLS
encapsulation specific information for BIER in MPLS networks.
The BIER MPLS Encapsulation Sub-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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Lbl Range Size | Label Range Base |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|BS Len | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: Set to TBD2.
Length: 8 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. The 4 leftmost bits
MUST be ignored.
Bit String Length: A 4 bits 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.
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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.
3.3. Flooding scope of BIER Information
The BIER Sub-TLV is included as part of OSPFv3 Extended LSAs as
defined in Section 3. The flooding scope of the BIER Sub-TLV is
decided by the flooding scope of the Extended LSA carrying the Sub-
TLV. Any OSPFv3 router SHOULD include the local BIER information in
BIER Sub-TLV and advertise it using Intra-Area-Prefix LSA.
When an OSPFv3 Area Border Router (ABR) originates E-Inter-Area-
Prefix-LSA for a Prefix P, it follows the below procedure to
propagate the BIER information between areas:
o Examine if the Prefix P is a BFR-Prefix. This could be done by
checking the presence of BIER Sub-TLV in Intra-Area-Prefix-TLV of
E-Intra-Area-Prefix-LSA for Prefix P.
o If the above is TRUE, copy the BIER Sub-TLV to Inter-Area-Prefix
TLV.
4. IANA Considerations
The document requests two new allocations from the OSPFv3 Extended-
LSA sub-TLV registry as defined in [I-D.ietf-ospf-ospfv3-lsa-extend].
BIER Sub-TLV: TBD1
BIER MPLS Encapsulation Sub-TLV: TBD2
5. Security Considerations
This document defines additional Sub-TLVs for OSPFv3 Extended-LSAs
and does not impose any changes in flooding scope or Path
computation.
Implementations must assure that any malformed TLVs or Sub-TLVs must
not result in errors that causes hard OSPFv3 failures.
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6. Acknowledgement
TBD
7. References
7.1. 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-08 (work in
progress), September 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-12 (work in progress),
October 2017.
[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-16 (work in progress), October 2017.
[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>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
7.2. Informative References
[I-D.ietf-bier-ospf-bier-extensions]
Psenak, P., Kumar, N., Wijnands, I., Dolganow, A.,
Przygienda, T., Zhang, Z., and S. Aldrin, "OSPF Extensions
for BIER", draft-ietf-bier-ospf-bier-extensions-09 (work
in progress), October 2017.
Authors' Addresses
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Peter Psenak (editor)
Cisco Systems, Inc.
Apollo Business Center
Mlynske nivy 43, Bratislava 821 09
Slovakia
Email: ppsenak@cisco.com
Nagendra Kumar Nainar (editor)
Cisco Systems, Inc.
7200 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: naikumar@cisco.com
IJsbrand Wijnands
Cisco Systems, Inc.
De Kleetlaan 6a
Diegem 1831
Belgium
Email: ice@cisco.com
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