Network Working Group Zhang
Internet-Draft Rekhter
Updates: 6514 (if approved) Juniper Networks
Intended status: Standards Track Dolganow
Expires: December 5, 2013 Alcatel-Lucent
June 3, 2013
Simulating "Partial Mesh of MP2MP P-Tunnels" with Ingress Replication
draft-zzhang-l3vpn-mvpn-bidir-ingress-replication-00.txt
Abstract
RFC 6513 described a method to support bidirectional C-flow using
"Partial Mesh of MP2MP P-Tunnels". This document describes how
partial mesh of MP2MP P-Tunnels can be simulated with Ingress
Replication, instead of a real MP2MP tunnel.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on December 5, 2013.
Copyright Notice
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5
3. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Control State . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Forwarding State . . . . . . . . . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
7. Normative References . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
Section 11.2 of RFC 6513, "Partitioned Sets of PEs", describes two
methods of carrying bidirectional C-flow traffic over a provider core
without using the core as RPL or requiring Designated Forwarder
election.
With these two methods, all PEs of a particular VPN are separated
into partitions, with each partition being all the PEs that elect the
same PE as the UMH wrt the C-RPA. A PE must discard bidirectional
C-flow traffic from PEs that are not in the same partition as the PE
itself.
In particular, Section 11.2.3 of RFC 6513, "Partial Mesh of MP2MP
P-Tunnels", guarantees the above discard havavior without using an
extra PE Distinguisher label by having all PEs in the same partition
join a single MP2MP tunnel dedicated to that partition and use it to
transmit traffic. All traffic arriving on the tunnel will be from
PEs in the same partition, so it will be always accepted.
RFC 6514 specifies BGP encodings and procedures used to implement
MVPN as specified in RFC 6513, while the details related to MP2MP
tunnels are specified in [draft-ietf-l3vpn-mvpn-bidir-05].
[draft-ietf-l3vpn-mvpn-bidir-05] assumes that an MP2MP P-tunnel is
realized either via PIM-Bidir, or via MP2MP mLDP. Each of them would
require signaling and state not just on PEs, but on the P routers as
well. This document describes how the MP2MP tunnel can be simulated
with a mesh of P2P or MP2P LSPs, i.e. Ingress Replication. The
advantage is that existing P2P/MP2P LSPs created for unicast can be
used for multicast as well w/o introducing additional signaling or
state in the core. While there may be concerns with traffic
replication in the core, in many situations the traffic could be low-
rate and/or sporadic and the advantage of signaling and state savings
will outweight the concerns with traffic replication, making Ingress
Replication an applicable and attractive alternative.
This documentation specifies the BGP signaling and procedures used to
simulate "Partial Mesh of MP2MP P-Tunnels" with Ingress Replication.
1.1. Terminology
This document uses terminology from [RFC6513], [RFC6514], and
[draft-ietf-l3vpn-mvpn-bidir-05]. In particular, the following new
term is defined:
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o C-G-BIDIR: A C-G where G is a Bidir-PIM group.
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2. 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].
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3. Operation
3.1. Control State
If a PE, say PEx, is connected to a site of a given VPN, and that
site hosts the C-RPA for some Bidir-PIM groups, i.e., the route to
the C-RPA is through a local PE-CE interface, then PEx MUST
advertises a (C-*,C-BIDIR) S-PMSI A-D route, regardless of whether it
has any local Bidir-PIM join states corresponding to the C-RPA
learned from its CEs. It MAY also advertise a (C-*,C-G-BIDIR) S-PMSI
A-D route, just like how any other S-PMSI A-D routes are triggered
(e.g, when the (C-*,C-G-BIDIR) traffic rate goes above a threshold).
Here the C-G-BIDIR refers to a C-G where G is a Bidir-PIM group, and
the corresponding C-RPA is in the site that the PEx connects to.
The S-PMSI A-D routes include a Provider Tunnel Attribute (PTA) with
tunnel type set to Ingress Replication, with Leaf Information
Required flag set, and with a downstream allocated MPLS label that
other PEs in the same partition MUST use when sending relevant
C-bidir flows to this PE.
If some other PE, PEy, receives and imports into one of its VRFs such
a (C-*,C-BIDIR) S-PMSI A-D route, and the VRF has any local Bidir-PIM
join state that PEy has received from its CEs, and if PEy chooses PEx
as its UMH wrt the C-RPA for those states, PEy MUST advertise a Leaf
A-D route in response. Or, if PEy has received and imported into one
of its VRFs a (C-*,C-BIDIR) S-PMSI A-D route from PEx before, then
upon receiving in the VRF any local Bidir-PIM join state from its CEs
with PEx being the UMH for those states' C-RPA, PEy MUST advertise a
Leaf A-D route.
The encoding of the Leaf A-D route is as specified in RFC 6514,
except that the Route Targets are set to the same value as in the
corresponding S-PMSI A-D route so that the Leaf A-D route will be
imported by all VRFs that import the corresponding S-PMSI A-D route.
This is irrespective of whether from a receiving PE, PEz's
perspective PEx (oiginator of the S-PMSI A-D route) is the UMH PE or
not. The label in the PTA of the Leaf A-D route originated by PEy
MUST be allocated specifically for PEx, so that when traffic arrives
with that label, the traffic can associated with the partition
(represented by the PEx).
With PEy advertising Leaf A-D route only if it chooses the originator
of the S-PMSI A-D route as its UMH, it won't receive traffic from PEs
in other partitions, so the label is actually useful only when PEy
switches to a different UMH - it will stop accepting traffic before
sending PEs stop sending it traffic (upon the receipt of its Leaf A-D
route withdrawl). To speed up convergency (so that PEy starts
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receiving traffic from its new UMH immediately instead of waiting
until the new Leaf A-D route corresponding to the new UMH is received
by sending PEs), PEy MAY advertise a Leaf A-D route even if does not
choose PEx as its UMH wrt the C-RPA. With that, it will receive
traffic from all PEs, but some will arrive with the label
corresponding to its choice of UMH while some will arrive with a
different label, and the traffic in the latter case will be
discarded.
Similar to the (C-*,C-BIDIR) case, if PEy receives and imports into
one of its VRFs such a (C-*,C-G-BIDIR) S-PMSI A-D route, and PEy
chooses PEx as its UMH wrt the C-RPA, and it has corresponding local
(C-*,C-G-BIDIR) join state that it has received from its CEs in the
VRF, PEy MUST advertise a Leaf A-D route in response. Or, if PEy has
received and imported into one of its VRFs a (C-*,C-G-BIDIR) S-PMSI
A-D route before, then upon receiving its local (C-*,C-G-BIDIR) join
state from its CEs in the VRF, it MUST advertise a Leaf A-D route.
The encoding of the Leaf A-D route is as specified in RFC 6514,
except that the Route Targets are set to the same as in the
corresponding S-PMSI A-D route so that the Leaf A-D route will be
imported by all VRFs that import the corresponding S-PMSI A-D route.
This is irrespective of whether from the receiving PE, PEz's
perspective PEx (oiginator of the S-PMSI A-D route) is the UMH PE or
not. The label in the PTA of the Leaf A-D route originated by PEy
MUST be allocated specifically for PEx, so that when traffic arrives
with that label, the traffic can associated with the partition
(represented by the PEx).
Whenever the (C-*,C-BIDIR) or (C-*,C-G-BIDIR) S-PMSI A-D route is
withdrawn, or if PEy no longer chooses the originator PEx as its UMH
wrt C-RPA and PEy only advertises Leaf A-D routes in response to its
UMH's S-PMSI A-D route, or if relevant local join state is pruned,
PEy MUST withdraw the corresponding Leaf A-D route.
3.2. Forwarding State
The following specification regarding forwarding state matches the
"When an S-PMSI is a 'Match for Transmission'" and "When an S-PMSI is
a 'Match for Reception'" rules for "Flat Partitioning" method in
[draft-ietf-l3vpn-mvpn-bidir-05], except that the rules about
(C-*,C-*) are not applicable, because this document requires that
(C-*,C-BIDIR) S-PMSI A-D routes are always originated for a VPN that
supports C-Bidir flows.
For the (C-*,C-G-BIDIR) S-PMSI A-D route that a PEy receives and
imports into one of its VRFs from its UMH wrt the C-RPA, or if PEy
itself advertises the S-PMSI A-D route in the VRF, PEy maintains a
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(C-*,C-G-BIDR) forwarding state in the VRF, with the Ingress
Replication provider tunnel leaves being the originators of the
S-PMSI A-D route and all relevant Leaf-A-D routes. The relevant Leaf
A-D routes are the routes whose Route Key field contains the same
information as the MCAST-VPN NLRI of the (C-*, C-G-BIDIR) S-PMSI A-D
route advertised by the UMH.
For the (C-*,C-BIDIR) S-PMSI A-D route that a PEy receives and
imports into one of its VRFs from its UMH wrt a C-RPA, or if PEy
itself advertises the S-PMSI A-D route in the VRF, it maintains
appropriate forwarding states in the VRF for the ranges of
bidirectional groups for which the C-RPA is responsible. The
provider tunnel leaves are the originators of the S-PMSI A-D route
and all relevant Leaf-A-D routes. The relevant Leaf A-D routes are
the routes whose Route Key field contains the same information as the
MCAST-VPN NLRI of the (C-*, C-BIDIR) S-PMSI A-D route advertised by
the UMH. This is for the so-called "Sender Only Branches" where a
router only has data to send upstream towards C-RPA but no explicit
join state for a particular bidirectional group. Note that the
traffic must be sent to all PEs (not just the UMH) in the partition,
because they may have specific (C-*,C-G-BIDIR) join states that this
PEy is not aware of, while there is no corresponding (C-*,C-G-BIDIR)
S-PMSI A-D and Leaf A-D routes.
For a (C-*,C-G-BIDIR) join state that a PEy has received from its CEs
in a VRF, if there is no corresponding (C-*,C-G-BIDIR) S-PMSI A-D
route from its UMH in the VRF, PEy maintains a corresponding
forwarding state in the VRF, with the provider tunnel leaves being
the originators of the (C-*,C-BIDIR) S-PMSI A-D route and all
relevant Leaf-A-D routes (same as the above Sender Only Branch case).
The relevant Leaf A-D routes are the routes whose Route Key field
contains the same information as the MCAST-VPN NLRI of the (C-*,
C-BIDIR) S-PMSI A-D route originated by the UMH. If there is no
(C-*,C-BIDIR) S-PMSI A-D route from its UMH either, then the provider
tunnel has an empty set of leaves and PEy does not forward relevant
traffic across the provider network.
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4. Security Considerations
This document raises no new security issues. Security considerations
for the base protocol are covered in [RFC6514].
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5. IANA Considerations
This document has no IANA considerations.
This section should be removed by the RFC Editor prior to final
publication.
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6. Acknowledgements
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7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6513] Rosen, E. and R. Aggarwal, "Multicast in MPLS/BGP IP
VPNs", RFC 6513, February 2012.
[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, February 2012.
[RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
"Bidirectional Protocol Independent Multicast (BIDIR-
PIM)", RFC 5015, October 2007.
[I-D.ietf-l3vpn-mvpn-bidir]
Rosen, E., Wijnands, I., Cai, Y., and A. Boers, "MVPN:
Using Bidirectional P-Tunnels",
draft-ietf-l3vpn-mvpn-bidir-05 (work in progress),
April 2013.
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Authors' Addresses
Jeffrey Zhang
Juniper Networks
10 Technology Park Dr.
Westford, MA 01886
US
Email: zzhang@juniper.net
Yakov Rekhter
Juniper Networks
1194 North Mathilda Ave.
Sunnyvale, CA 94089
US
Email: yakov@juniper.net
Andrew Dolganow
Alcatel-Lucent
600 March Rd.
Ottawa, ON K2K 2E6
CANADA
Email: andrew.dolganow@alcatel-lucent.com
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