Network Working Group X. Xu
Internet-Draft M. Chen
Intended status: Standards Track Huawei
Expires: March 26, 2016 K. Patel
I. Wijnands
Cisco
A. Przygienda
Ericsson
September 23, 2015
BGP Extensions for BIER
draft-ietf-bier-idr-extensions-00
Abstract
Bit Index Explicit Replication (BIER) is a new multicast forwarding
architecture which doesn't require an explicit tree-building protocol
and doesn't require intermediate routers to maintain any multicast
state. BIER is applicable in a multi-tenant data center network
environment for efficient delivery of Broadcast, Unknown-unicast and
Multicast (BUM) traffic while eliminating the need for maintaining a
huge amount of multicast state in the underlay. This document
describes BGP extensions for advertising the BIER-specific
information. These extensions are applicable in those multi-tenant
data centers where BGP instead of IGP is deployed as an underlay for
network reachability advertisement. These extensions may also be
applicable in other scenarios.
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
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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
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 March 26, 2016.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. BIER Path Attribute . . . . . . . . . . . . . . . . . . . . . 3
4. Originating BIER Attribute . . . . . . . . . . . . . . . . . 4
5. Restrictions on Sending/Receiving . . . . . . . . . . . . . . 5
6. Deployment Considerations . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
9. Security Considerations . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . 6
10.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Bit Index Explicit Replication (BIER) [I-D.ietf-bier-architecture] is
a new multicast forwarding architecture which doesn't require an
explicit tree-building protocol and doesn't require intermediate
routers to maintain any multicast state. BIER is applicable in a
multi-tenant data center network environment for efficient delivery
of Broadcast, Unknown-unicast and Multicast (BUM) traffic while
eliminating the need for maintaining a huge amount of multicast state
in the underlay [I-D.ietf-bier-use-cases]. This document describes
BGP extensions for advertising the BIER-specific information. More
specifically, in this document, we define a new optional, non-
transitive BGP attribute, referred to as the BIER attribute, to
convey the BIER-specific information such as BFR-ID, BitString Length
(BSL) and so on. In addition, this document specifies procedures to
prevent the BIER attribute from "leaking out" of a BIER domain .
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These extensions are applicable in those multi-tenant data centers
where BGP instead of IGP is used as an underlay
[I-D.ietf-rtgwg-bgp-routing-large-dc]. These extensions may also be
applicable to other BGP based network scenarios.
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].
2. Terminology
This memo makes use of the terms defined in [RFC4271] and
[I-D.ietf-bier-architecture].
3. BIER Path Attribute
This draft defines a new optional, transitive BGP path attribute,
referred to as the BIER attribute. This attribute can be attached to
a BGP UPDATE message by the originator so as to indicate the BIER-
specific information of a particular BFR which is identified by the
/32 or /128 address prefix contained in the NLRI. In other words, if
the BIER path attribute is present, the NLRI is treated by BIER as a
"BFR-prefix". When creating a BIER attribute, a BFR needs to include
one BIER TLV for every <Sub-domain, BFR-ID> pair that it supports.
The attribute type code for the BIER Attribute is TBD. The value
field of the BIER Attribute contains one or more BIER TLV as shown in
Figure 1.
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=TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-domain | BFR-ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
| Sub-TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+..........................
Figure 1:BIER TLV
Type: Two octets encoding the BIER TLV Type: TBD.
Length: Two octets encoding the length in octets of the TLV,
including the type and length fields. The length is encoded as an
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unsigned binary integer. (Note that the minimum length is 8,
indicating that no sub-TLV is present.)
Sub-domain: a one-octet field encoding the sub-domain ID
corresponding to the BFR-ID.
BFR-ID: a two-octet field encoding the BFR-ID.
Sub-TLVs: contains one or more sub-TLV. The BIER MPLS
Encapsulation sub-TLV is one of such sub-TLVs.
The BIER MPLS Encapsulation sub-TLV is encoded as follows:
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=TBD | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Range Base |Lbl Range Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BSL | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2:BIER MPLS Encapsulation sub-TLV
Type:TBD
Length:12
Label Range Size: a one-octet field indicating the size of the
label range.
Label Range Base: a 3-octet field where the 20 rightmost bits
represent the first label in the label range while the other bits
MUST be set to 0 when transmitting, and MUST be ignored upon
receipt.
BSL: a one-octet field indicating the length of the Bitstring in
4-octets. The field MUST be filled with one of the valid BSL
values as specified in [I-D.ietf-bier-architecture]. Upon
receiving a BSL-TLV containing an invalid BSL value, it MUST be
ignored.
4. Originating BIER Attribute
An implementation that supports the BIER attribute MUST support a
policy to enable or disable the creation of the BIER attribute and
its attachment to specific BGP routes. An implementation MAY disable
the creation of the BIER attribute unless explicitly configured to do
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so otherwise. A BGP speaker MUST only attach the locally created
BIER attribute to a BGP UPDATE message in which at least one of its
BFR-prefixes is contained in the NLRI.
5. Restrictions on Sending/Receiving
An implementation that supports the BIER attribute MUST support a
per-EBGP-session policy, that indicates whether the attribute is
enabled or disabled for use on that session. The BIER attribute MUST
NOT be sent on any EBGP peers for which the session policy is not
configured. If an BIER attribute is received on a BGP session for
which session policy is not configured, then the received attribute
MUST be treated exactly as if it were an unrecognised non-transitive
attribute. That is, "it MUST be quietly ignored and not passed along
to other BGP peers".
To prevent the BIER attribute from "leaking out" of an BIER domain,
each BGP router on the BIER domain MUST support an outbound route
announcement policy. Such a policy MUST be disabled on each EBGP
session by default unless explicitly configured.
6. Deployment Considerations
It's assumed by this document that the BIER domain is aligned with
the Administrative Domain (AD) which are composed of multiple ASes
(either private or public ASes). Use of the BIER attribute in other
scenarios is outside the scope of this document.
Since the BIER attribute is an optional, transitive BGP path
attribute, a non-BFR BGP speakers could still advertise the received
route with a BIER attribute. This is desirable in the incremental
deployment scenario where a BGP speaker could tunnel a BIER packet or
the payload of a BIER packet to a BFER directly if the BGP next-hop
of the route for that BFER is a non-BFR. Furthermore, a BGP speaker
is allowed to tunnel a BIER packet to the BGP next-hop if these two
BFR-capable BGP neighbors are not directly connected (e.g., multi-hop
EBGP) .
7. Acknowledgements
Thanks a lot for Eric Rosen and Peter Psenak for their valuable
comments on this document.
8. IANA Considerations
IANA is requested to assign a codepoint in the "BGP Path Attributes"
registry to the BIER attribute. IANA shall create a registry for
"BGP BIER Attribute Types". The type field consists of two octets,
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with possible values from 1 to 655355 (The value 0 is "reserved".)
The allocation policy for this field is to be "First Come First
Serve". Type codes should be allocated for BIER TLV and BIER MPLS
Encapsulation sub-TLV respectively.
9. Security Considerations
This document introduces no new security considerations beyond those
already specified in [RFC4271].
10. References
10.1. 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-02 (work in
progress), July 2015.
[I-D.ietf-bier-mpls-encapsulation]
Wijnands, I., Rosen, E., Dolganow, A., Tantsura, J., and
S. Aldrin, "Encapsulation for Bit Index Explicit
Replication in MPLS Networks", draft-ietf-bier-mpls-
encapsulation-02 (work in progress), August 2015.
[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>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<http://www.rfc-editor.org/info/rfc4271>.
10.2. Informative References
[I-D.ietf-bier-use-cases]
Kumar, N., Asati, R., Chen, M., Xu, X., Dolganow, A.,
Przygienda, T., arkadiy.gulko@thomsonreuters.com, a.,
Robinson, D., and V. Arya, "BIER Use Cases", draft-ietf-
bier-use-cases-01 (work in progress), August 2015.
[I-D.ietf-rtgwg-bgp-routing-large-dc]
Lapukhov, P., Premji, A., and J. Mitchell, "Use of BGP for
routing in large-scale data centers", draft-ietf-rtgwg-
bgp-routing-large-dc-07 (work in progress), August 2015.
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Authors' Addresses
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.com
Mach Chen
Huawei
Email: mach.chen@huawei.com
Keyur Patel
Cisco
Email: keyupate@cisco.com
IJsbrand Wijnands
Cisco
Email: ice@cisco.com
Antoni Przygienda
Ericsson
Email: antoni.przygienda@ericsson.com
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