Internet DRAFT - draft-zzhang-bier-php
draft-zzhang-bier-php
BIER Z. Zhang
Internet-Draft Juniper Networks
Intended status: Standards Track August 3, 2018
Expires: February 4, 2019
BIER Penultimate Hop Popping
draft-zzhang-bier-php-01
Abstract
Bit Index Explicit Replication (BIER) can be used as provider tunnel
for MVPN/GTM [RFC6514] [RFC7716] or EVPN BUM [RFC7432]. It is
possible that not all routers in the provider network support BIER
and there are various methods to handle BIER incapable transit
routers. However the MVPN/EVPN PEs are assumed to be BIER capable -
they are BFIRs/BFERs. This document specifies a method to allow BIER
incapable routers to act as MVPN/EVPN PEs with BIER as the transport,
by having the upstream BFR (connected directly or indirectly via a
tunnel) of a PE remove the BIER header and send the payload to the
PE.
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 RFC2119.
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 https://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 February 4, 2019.
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Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
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described in the Simplified BSD License.
Table of Contents
1. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Specifications . . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Terminologies
Familiarity with BIER/MVPN/EVPN protocols and procedures is assumed.
Some terminologies are listed below for convenience.
[To be added].
2. Introduction
The BIER architecture includes three layers: the "routing underlay",
the "BIER layer", and the "multicast flow overlay". The multicast
flow overlay is responsible for the BFERs to signal to BFIRs that
they are interested in receiving certain multicast flows so that
BFIRs can encode the correct bitstring for BIER forwarding by the
BIER layer.
MVPN and EVPN are two similar overlays where BGP Auto-Discovery
routes for MVPN/EVPN are exchanged among all PEs to signal which PEs
need to receive multicast traffic for all or certain flows.
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Typically the same provider tunnel type is used for traffic to reach
all receiving PEs.
Consider an MVPN/EVPN deployment where enough P/PE routers are BIER
capable for BIER to become the preferred the choice of provider
tunnel. However, some PEs cannot be upgraded to support BIER
forwarding. While there are ways to allow an ingress PE to send
traffic to some PEs with one type of tunnel and send traffic to some
other PEs with a different type of tunnel, the procedure becomes
complicated and forwarding is not optimized.
One way to solve this problem is to use Penultimate Hop Popping (PHP)
so that the upstream BFR can pop the BIER header and send the payload
"natively" (note that the upstream BFR can be connected directly or
indiretly via a tunnel to the PE). This is similar to MPLS PHP
though it is the BIER header that is popped. In case of MPLS
encapsulation, even the signaling is similar - a BIER incapable
router signals as if it supported BIER, but to request PHP at the
penultimate hop, it signals an Implicit Null label instead of a
regular BIER label as the Label Range Base in its BIER MPLS
Encapsulation sub-TLV.
In order for the PE to be able to correctly forward the packets
resulting from the PHP, certain conditions must be met, as specified
in Section 3.
While the above text uses MVPN/EVPN as example, BIER PHP is
applicable to any scenario where the multicast flow overlay edge
router does not support BIER.
This works well if a BIER incapable PE only needs to receive
multicast traffic. If it needs to send multicast traffic as well,
then it must Ingress Replicate to a BIER capable helper PE, who will
in turn relay the packet to other PEs. The helper PE is either a
Virtual Hub as specified in [RFC7024] for MVPN and [I-D.keyupate-
bess-evpn-virtual-hub] for EVPN, or an AR-Replicator as specified in
[I-D.ietf-bess-evpn-optimized-ir] for EVPN.
3. Specifications
The procedures in this section can be applied only if, by means
outside the scope of this document, it is known that one of the
following conditions is met.
o The payload after BIER header is IPv4 or IPv6 (i.e., the Proto
field in the BIER header is 4 or 6).
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Notice that in this case the Destination Address in the IPv4/IPv6
header must be in the address space for the BIER layer.
o The payload after BIER header is MPLS packet with downstream-
assigned label at top of stack (i.e., the Proto field in the BIER
header is 1). For example, a label from a Domain-wide Common
Block (DCB) is used as specified in [I-D.zzhang-bess-mvpn-evpn-
aggregation-label].
A BIER incapable router, if acting as a multicast flow overlay
router, MUST signal its BIER information as specified in [RFC8401] or
[I-D.ietf-bier-ospf-bier-extensions] or [I-D.ietf-bier-idr-
extensions], with a PHP sub-sub-TLV included in the BIER sub-TLV
attached to the BIER incapable router's BIER prefix to request BIER
PHP from other BFRs. The sub-sub-TLV's type is TBD, and the length
is 0.
With MPLS encapsulation, the BIER incapable multicast flow overlay
router MAY omit the BIER MPLS Encapsulation sub-sub-TLV, or MUST set
the Label Range Base in BIER MPLS Encapsulation sub-sub-TLV to
Implicit Null Label [RFC3032].
With MPLS encapsulation, if a BFER does not support certain BSL, it
MAY still advertise a corresponding BIER MPLS Encapsulation sub-TLV
but set the Label Range Base to Implicit Null Label.
If a BFR follows section 6.9 of [RFC8279] to handle BIER incapable
routers, it must treat a router as BIER incapable if the Label Range
Base dvertised by the router is Implicit Null, or if the router
advertises a PHP sub-sub-TLV, so that the router is not used as a
transit BFR.
If the downstream neighbor for a BIER prefix is the one advertising
the prefix with a PHP sub-sub-TLV or with an Implicit Null Label as
the Label Range Base in its BIER MPLS Encapsulation sub-sub-TLV, then
when the corresponding BIRT or BIFT entry is created/updated, the
forwarding behavior MUST be that the BIER header is removed and the
payload be sent to the downstream router without the BIER header,
either directly or over a tunnel.
4. Security Considerations
This specification does not introduce additional security concerns
beyond those already discussed in BIER architecture and OSPF/ISIS/BGP
exentions for BIER signaling.
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5. IANA Considerations
This document requests a new sub-sub-TLV type value from the "Sub-
sub-TLVs for BIER Info Sub-TLV" registry in the "IS-IS TLV
Codepoints" registry:
Type Name
---- ----
TBD BIER PHP Request
This document also requests a new sub-TLV type value from the OSPFv2
Extended Prefix TLV Sub-TLV registry:
Type Name
---- ----
TBD BIER PHP Request
6. Acknowledgements
The author wants to thank Eric Rosen and Antonie Przygienda for their
review, comments and suggestions. The author also wants to thank
Senthil Dhanaraj for his suggestion of requesting PHP if a BFER does
not support certain BSL.
7. References
7.1. Normative References
[I-D.ietf-bess-evpn-optimized-ir]
Rabadan, J., Sathappan, S., Henderickx, W., Sajassi, A.,
Isaac, A., and M. Katiyar, "Optimized Ingress Replication
solution for EVPN", draft-ietf-bess-evpn-optimized-ir-03
(work in progress), February 2018.
[I-D.ietf-bier-idr-extensions]
Xu, X., Chen, M., Patel, K., Wijnands, I., and T.
Przygienda, "BGP Extensions for BIER", draft-ietf-bier-
idr-extensions-05 (work in progress), March 2018.
[I-D.ietf-bier-ospf-bier-extensions]
Psenak, P., Kumar, N., Wijnands, I., Dolganow, A.,
Przygienda, T., Zhang, Z., and S. Aldrin, "OSPFv2
Extensions for BIER", draft-ietf-bier-ospf-bier-
extensions-18 (work in progress), June 2018.
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[I-D.keyupate-bess-evpn-virtual-hub]
Patel, K., Sajassi, A., Drake, J., Zhang, Z., and W.
Henderickx, "Virtual Hub-and-Spoke in BGP EVPNs", draft-
keyupate-bess-evpn-virtual-hub-00 (work in progress),
March 2017.
[I-D.zzhang-bess-mvpn-evpn-aggregation-label]
Zhang, Z., Rosen, E., Lin, W., Li, Z., and I. Wijnands,
"MVPN/EVPN Tunnel Aggregation with Common Labels", draft-
zzhang-bess-mvpn-evpn-aggregation-label-01 (work in
progress), April 2018.
[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>.
[RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
Explicit Replication (BIER)", RFC 8279,
DOI 10.17487/RFC8279, November 2017,
<https://www.rfc-editor.org/info/rfc8279>.
[RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
for Bit Index Explicit Replication (BIER) in MPLS and Non-
MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
2018, <https://www.rfc-editor.org/info/rfc8296>.
[RFC8401] Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z.
Zhang, "Bit Index Explicit Replication (BIER) Support via
IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018,
<https://www.rfc-editor.org/info/rfc8401>.
7.2. Informative References
[RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
2012, <https://www.rfc-editor.org/info/rfc6513>.
[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
<https://www.rfc-editor.org/info/rfc6514>.
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[RFC7024] Jeng, H., Uttaro, J., Jalil, L., Decraene, B., Rekhter,
Y., and R. Aggarwal, "Virtual Hub-and-Spoke in BGP/MPLS
VPNs", RFC 7024, DOI 10.17487/RFC7024, October 2013,
<https://www.rfc-editor.org/info/rfc7024>.
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
2015, <https://www.rfc-editor.org/info/rfc7432>.
Author's Address
Zhaohui Zhang
Juniper Networks
EMail: zzhang@juniper.net
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