Internet DRAFT - draft-xu-ospf-bier-cap
draft-xu-ospf-bier-cap
Network Working Group X. Xu
Internet-Draft Huawei
Intended status: Standards Track October 16, 2014
Expires: April 19, 2015
Advertising Bit Index Explicit Replication (BIER) Capability Using OSPF
draft-xu-ospf-bier-cap-00
Abstract
Bit Index Explicit Replication (BIER) is a new multicast forwarding
paradigm which doesn't require an explicit tree-building protocol and
doesn't require intermediate routers to maintain any multicast state.
A BFR cannot send a BIER packet to a given nexthop router unless that
nexthop router has indicated that it can support the BIER forwarding
procedure. This document defines a mechanism to signal that
capability using OSPF. This mechanism is useful when the unicast
route distribution is also done via OSPF.
Status of This Memo
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This Internet-Draft will expire on April 19, 2015.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Advertising BIER Capability . . . . . . . . . . . . . . . . . 3
3.1. BIER Capability TLV . . . . . . . . . . . . . . . . . . . 3
3.2. BFR-ID Sub-TLV . . . . . . . . . . . . . . . . . . . . . 4
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
Bit Index Explicit Replication (BIER)
[I-D.wijnands-bier-architecture] is a new multicast forwarding
paradigm which doesn't require an explicit tree-building protocol and
doesn't require intermediate routers to maintain any multicast state.
As described in [I-D.wijnands-bier-architecture], BIER requires that
a multicast data packet (e.g., an IP packet or an MPLS packet) to be
encapsulated with a BIER header that carries the information needed
for supporting the BIER forwarding procedures.
[I-D.xu-bier-encapsulation] proposes a transport-indepedent BIER
encapsulation header which is applicable in any kind of transport
networks. A BFR cannot send a BIER packet to a given nexthop router
unless that nexthop router has indicated that it can support the BIER
forwarding procedure. This document defines a mechanism to signal
that capability using OSPF. This mechanism is useful when the
unicast route distribution is also done via OSPF.
1.1. 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 RFC 2119 [RFC2119].
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2. Terminology
This memo makes use of the terms defined in [RFC4970] and
[I-D.wijnands-bier-architecture].
3. Advertising BIER Capability
BIER-capable routers need to advertise their capabilities of
performing BIER forwarding procedures by using a TLV within the body
of the OSPF Router Information (RI) Opaque LSA [RFC4970], referred to
as BIER Capability TLV. The format of the BIER Capability TLV is
shown in Section 3.1.
3.1. BIER Capability TLV
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=TBD1 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BS Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Sub-TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD1.
Length: variable.
BS Length: This 8-bit field indicates the length of the BitString
in 4-byte unit. In other words, if the BitString length is 4*n
byte, this field should be filled with n (e.g., if the length of
the BitString is 32 bits, the length field is set to 1, if the
length of the BitString is 64 bits, the length field is set to
2...). For more details about the BS Length, see section 3 of
[I-D.xu-bier-encapsulation].
Sub-TLVs: contains zero or more sub-TLVs corresponding to the
particular BIER-capability related attributes. The BFR-ID sub-TLV
as defined in Section 3.2 is one such sub-TLV which is used to
indicate the corrresponding BFR-ID of the originating router.
Other sub-TLVs are to be defined in the future.
The BIER Capability TLV could not appear more than once wihin a given
OSPF RI LSA. The scope of the advertisement depends on the
application but it is recommended that it SHOULD be domain-wide.
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3.2. BFR-ID Sub-TLV
The type of BFR-ID sub-TLV is TBD2 and the length is 2, the value
field is filled with the BFR-ID of the originating router.
By carrying the BIER Capability TLV (with the BFR-ID sub-TLV
contained) and the Routable IP address TLV
[I-D.ietf-ospf-routable-ip-address] concurrently within the body of
the OSPF RI LSA, the mapping between BFR-ID (contained in the BFR-ID
sub-TLV) and BFR-prefix (contained in the Routable IP Address TLV)
can be extracted accordingly.
4. Acknowledgements
TBD
5. IANA Considerations
TBD.
6. Security Considerations
This document does not introduce any new security risk.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4970] Lindem, A., Shen, N., Vasseur, JP., Aggarwal, R., and S.
Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 4970, July 2007.
7.2. Informative References
[I-D.ietf-ospf-routable-ip-address]
Xu, X., Chunduri, U., and M. Bhatia, "Carrying Routable IP
Addresses in OSPF RI LSA", draft-ietf-ospf-routable-ip-
address-00 (work in progress), September 2014.
[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.
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[I-D.xu-bier-encapsulation]
Xu, X. and S. Somasundaram, "BIER Encapsulation", draft-
xu-bier-encapsulation-00 (work in progress), September
2014.
Author's Address
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.com
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