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Network Working Group R. Aggarwal (Editor)
Internet Draft Juniper Networks
Expiration Date: May 20, 2008
Y. Kamite
NTT Communications
L. Fang
Cisco Systems, Inc
November 17, 2007
Multicast in VPLS
draft-ietf-l2vpn-vpls-mcast-03.txt
Status of this Memo
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Abstract
This document describes a solution for overcoming a subset of the
limitations of existing VPLS multicast solutions. It describes
procedures for VPLS multicast that utilize multicast trees in the
sevice provider (SP) network. One such multicast tree can be shared
between multiple VPLS instances. Procedures by which a single
multicast tree in the backbone can be used to carry traffic belonging
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only to a specified set of one or more IP multicast streams from one
or more VPLSs are also described.
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Table of Contents
1 Specification of requirements ......................... 4
2 Contributors .......................................... 4
3 Terminology ........................................... 5
4 Introduction .......................................... 5
5 Existing Limitations of VPLS Multicast ................ 5
6 Overview .............................................. 6
6.1 Inclusive and Selective Multicast Trees ............... 6
6.2 BGP-Based VPLS Membership Auto-Discovery .............. 7
6.3 IP Multicast Group Membership Discovery ............... 7
6.4 Advertising P-Tree to VPLS / C-Multicast Binding ...... 8
6.5 Aggregation ........................................... 8
6.6 Inter-AS VPLS Multicast ............................... 9
7 VPLS Multicast/Broadcast/Unknown Unicast Data Packet Treatment 10
8 Intra-AS Inclusive Multicast Tree Auto-Discovery/Binding ..11
8.1 Originating (intra-AS) auto-discovery routes .......... 12
8.2 Receiving (intra-AS) auto-discovery routes ............ 13
9 Demultiplexing Multicast Tree Traffic ................. 14
9.1 One Multicast Tree - One VPLS Mapping ................. 14
9.1.1 One Multicast Tree - Many VPLS Mapping ................ 14
10 Establishing Multicast Trees .......................... 15
10.1 RSVP-TE P2MP LSPs ..................................... 15
10.1.1 P2MP TE LSP - VPLS Mapping ............................ 15
10.1.2 Demultiplexing C-Multicast Data Packets ............... 16
10.2 Receiver Initiated MPLS Trees ......................... 16
10.2.1 P2MP LSP - VPLS Mapping ............................... 17
10.2.2 Demultiplexing C-Multicast Data Packets ............... 17
10.3 Encapsulation of the Aggregate Inclusive and Selective Tree 17
11 Inter-AS Inclusive Multicast Tree Auto-Discovery/Binding ..17
11.1 VSIs on the ASBRs ..................................... 18
11.1.0.1 VPLS Inter-AS Auto-Discovery Binding .................. 18
11.2 Option (b) - Segmented Inter-AS Trees ................. 19
11.2.1 Segmented Inter-AS Trees VPLS Inter-AS Auto-Discovery/Binding 19
11.2.2 Propagating VPLS BGP Auto-Discovery routes to other ASes - Overview 20
11.2.2.1 Propagating Intra-AS VPLS Auto-Discovery routes in E-BGP ..21
11.2.2.2 Auto-Discovery route received via E-BGP ............... 22
11.2.2.3 Leaf Auto-Discovery Route received via E-BGP .......... 24
11.2.2.4 Inter-AS Auto-Discovery Route received via I-BGP ...... 24
11.3 Option (c) ............................................ 25
12 Optimizing Multicast Distribution via Selective Trees . 26
12.1 Protocol for Switching to Selective Trees ............. 27
12.2 Advertising C-(S, G) Binding to a Selective Tree using BGP 28
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12.2.1 Explicit Tracking ..................................... 29
12.3 Inter-AS Selective Tree ............................... 29
12.3.1 VSIs on the ASBRs ..................................... 30
12.3.1.1 VPLS Inter-AS Selective Tree Auto-Discovery Binding ... 30
12.3.2 Inter-AS Segmented Selective Trees .................... 30
12.3.3 Inter-AS Non-Segmented Selective Trees ................ 32
13 BGP Extensions ........................................ 32
13.1 Inclusive Tree/Selective Tree Identifier .............. 32
13.2 MCAST-VPLS NLRI ....................................... 33
13.2.1 Selective Tree auto-discovery route ................... 34
13.2.2 Leaf auto-discovery route ............................. 35
14 Aggregation Methodology ............................... 35
15 Data Forwarding ....................................... 36
15.1 MPLS Tree Encapsulation ............................... 36
16 Security Considerations ............................... 37
17 IANA Considerations ................................... 38
18 Acknowledgments ....................................... 38
19 Normative References .................................. 38
20 Informative References ................................ 39
21 Author's Address ...................................... 40
22 Intellectual Property Statement ....................... 40
23 Full Copyright Statement .............................. 41
1. Specification of requirements
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].
2. Contributors
Rahul Aggarwal
Yakov Rekhter
Juniper Networks
Yuji Kamite
NTT Communications
Luyuan Fang
AT&T
Chaitanya Kodeboniya
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3. Terminology
This document uses terminology described in [RFC4761] and [RFC4762].
4. Introduction
[RFC4761] and [RFC4762] describe a solution for VPLS multicast that
relies on ingress replication. This solution has certain limitations
for certain VPLS multicast traffic profiles.
This document describes procedures for overcoming the limitations of
existing VPLS multicast solutions. It describes procedures for VPLS
multicast that utilize multicast trees in the Sevice Provider (SP)
network. The procedures described in this document are applicable to
both [RFC4761] and [RFC4762].
It provides mechanisms that allow a single multicast distribution
tree in the backbone to carry all the multicast traffic from a
specified set of one or more VPLSs. Such a tree is referred to as an
"Inclusive Tree" and more specifically as an "Aggregate Inclusive
Tree" when the tree is used to carry multicast traffic from more than
one VPLS.
This document also provides procedures by which a single multicast
distribution tree in the backbone can be used to carry traffic
belonging only to a specified set of one or more IP multicast
streams, from one or more VPLSs. Such a tree is referred to as a
"Selective Tree" and more specifically as an "Aggregate Selective
Tree" when the IP multicast streams belong to different VPLSs. So
traffic from most multicast streams could be carried by an Inclusive
Tree, while traffic from, e.g., high bandwidth streams could be
carried in one of the "Selective Trees".
5. Existing Limitations of VPLS Multicast
One of the limitations of existing VPLS multicast solutions described
in [RFC4761] and [RFC4762] is that they rely on ingress replication.
Thus the ingress PE replicates the multicast packet for each egress
PE and sends it to the egress PE using a unicast tunnel.
This is a reasonable model when the bandwidth of the multicast
traffic is low or/and the number of replications performed on an
average on each outgoing interface for a particular customer VPLS
multicast packet is small. If this is not the case it is desirable to
utilize multicast trees in the SP network to transmit VPLS multicast
packets [MCAST-VPLS-REQ]. Note that unicast packets that are flooded
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to each of the egress PEs, before the ingress PE performs learning
for those unicast packets, MAY still use ingress replication.
6. Overview
This document describes procedures for using multicast trees in the
SP network to transport VPLS multicast data packets. RSVP-TE P2MP
LSPs described in [RFC4875] are an example of such multicast trees.
The use of multicast trees in the SP network can be beneficial when
the bandwidth of the multicast traffic is high or when it is
desirable to optimize the number of copies of a multicast packet
transmitted by the ingress. This comes at a cost of state in the SP
network to build multicast trees and overhead to maintain this state.
This document describes procedures for using multicast trees for VPLS
multicast when the provider tunneling technology is either P2MP RSVP-
PE or mLDP [MLDP]. The protocol architecture described herein is
considered to be flexible to support other P-tunneling technologies
as well.
This document uses the prefix 'C' to refer to the customer control or
data packets and 'P' to refer to the provider control or data
packets. An IP multicast source, group tuple is abbreviated to (S,
G).
6.1. Inclusive and Selective Multicast Trees
Multicast trees used for VPLS can be of two types:
1. Inclusive Trees. A single multicast distribution tree in the
SP network is used to carry all the multicast traffic from a
specified set of one or more VPLSs. A particular multicast
distribution tree can be set up to carry the traffic of a single
VPLS, or to carry the traffic of multiple VPLSs. The ability to carry
the traffic of more than one VPLS on the same tree is termed
'Aggregation'. The tree will include every PE that is a member of any
of the VPLSs that are using the tree. This implies that a PE may
receive multicast traffic for a multicast stream even if it doesn't
have any receivers on the path of that stream.
An Inclusive tree as defined in this document is a source tree. A
source tree is used to carry traffic only for VPLS sites that are
connected to the PE that is the root.
2. Selective Trees. A Selective Tree is used by a PE to send IP
multicast traffic for one or more multicast streams, that belong to
the same or different VPLSs, to a subset of the PEs that belong to
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those VPLSs. Each of the PEs in the subset should be on the path to a
receiver of one or more multicast streams that are mapped onto the
tree. The ability to use the same tree for multicast streams that
belong to different VPLSs is termed have the ability to create
separate SP multicast trees for high bandwidth multicast groups. This
allows traffic for these multicast groups to reach only those PE
routers that have receivers in these groups. This avoids flooding
other PE routers in the VPLS.
A SP can use both Inclusive Trees and Selective Trees or either of
them for a given VPLS on a PE, based on local configuration.
Inclusive Trees can be used for both IP and non-IP data multicast
traffic, while Selective Trees can be used only for IP multicast data
traffic.
A variety of transport technologies may be used in the backbone. For
inclusive trees, these transport technologies include point-to-
multipoint LSPs created by RSVP-TE or mLDP. For selective trees, only
unicast PE-PE tunnels (using MPLS or IP/GRE encapsulation) and
unidirectional single-source trees are supported, and the supported
tree signaling protocols are RSVP-TE, and mLDP.
This document also describes the data plane encapsulations for
supporting the various SP multicast transport options.
6.2. BGP-Based VPLS Membership Auto-Discovery
In order to establish Inclusive P-trees for one or more VPLSs, when
Aggregation is performed or when the tunneling technology is P2MP
RSVP-TE, the root of the tree must be able to discover the other PEs
that have membership in one or more of these VPLSs. This document
uses the BGP-based procedures described in [RFC4761] and [L2VPN-SIG]
for discovering the VPLS membership of all PEs.
6.3. IP Multicast Group Membership Discovery
The setup of a Selective P-tree for one or more IP multicast (S, G)s,
when aggregation is used or when the tunneling technology is P2MP
RSVP-TE, requires the ingress PE to learn the PEs that have receivers
in one or more of these (S, G)s. For discovering the IP multicast
group membership, procedures described in [VPLS-CTRL] should be used.
Procedures in [VPLS-CTRL] can also be used with ingress replication
to send traffic for an IP multicast stream to only those PEs that are
on the path to receivers for that stream.
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6.4. Advertising P-Tree to VPLS / C-Multicast Binding
This document also describes procedures based on BGP VPLS Auto-
Discovery that are used by the root of an Aggregate Tree to advertise
the Inclusive or Selective tree binding and the de-multiplexing
information to the leaves of the tree. A new BGP attribute called the
PMSI Tunnel Attribute is introduced for this purpose.
Once a PE decides to bind a set of VPLSes or customer multicast
groups to an Inclusive Tree or a Selective Tree, it needs to announce
this binding to other PEs in the network. This procedure is referred
to as Inclusive Tree or Selective Tree binding distribution and is
performed using BGP.
For an Inclusive Tree this discovery implies announcing the binding
of all VPLSs bound to the Inclusive Tree. The inner label assigned by
the ingress PE for each VPLS MUST be included, if more than one VPLS
is bound to the same tree. The Inclusive Tree Identifier MUST be
included.
For a Selective Tree this discovery implies announcing all the
specific <C-Source, C-Group> entries bound to this tree along with
the Selective Tree Identifier. The inner label assigned for each <C-
Source, C-Group> MUST be included if <C-Source, C-Group>s from
different VPLSes are bound to the same tree. The labels MUST be
distinct on a per VPLS basis and MAY be distinct on a per <C-Source,
C-Group> basis. The Selective Tree Identifier MUST be included.
6.5. Aggregation
As described above the ability to carry the traffic of more than one
VPLS on the same tree is termed 'Aggregation'. Both Inclusive and
Selective trees support aggregation.
Aggregation enables the SP to place a bound on the amount of
multicast tree forwarding and control plane state which the P routers
must have. Let us call the number of VPLSes aggregated onto a single
P-tree as the "Aggregation Factor". When Inclusive source trees are
used the number of trees that a PE is the root of is proportional to:
+ (Number of VPLSes on the PE / Aggregation Factor).
In this case the state maintained by P routers is proportional to:
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+ (Average number of VPLSes on a PE / Aggregation Factor) * number
of PEs
Thus the state does not grow linearly with the number of VPLSes.
Aggregation requires a mechanism for the egresses of the tree to
demultiplex the multicast traffic received over the tree. This
document describes how upstream-assigned labels can be assigned and
distributed by the root of aggregate tree and then used by the
egresses to perform this demultiplexing.
6.6. Inter-AS VPLS Multicast
This document supports three models of inter-AS VPLS service, option
(a), (b) and (c) which are very similar conceptually to option (a),
(b) and (c) specified in [RFC4364] for IP VPNs. The three options
described here are also similar to the three options described in in
[RFC4761], which in turn extends the concepts of [RFC4364] to inter-
AS VPLS.
For option (a) and option (b) support this document specifies a model
where Inter-AS VPLS service can be offered without requiring a single
P-multicast tree to span multiple ASes. There are two variants of
this model.
In the first variant, the Autonomous System Border Routers (ASBRs)
perform a MAC lookup, in addition to any MPLS lookups, to determine
the forwarding decision on a VPLS packet. In this variant the
multicast trees are confined to an AS. Hence each AS may use a
different P-tunneling technology. An ASBR on receiving a VPLS packet
from another ASBR is required to perform a MAC lookup to determine
how to forward the packet. Thus an ASBR is required to keep a VPLS
Switching Instance (VSI) for the VPLS. This variant is applicable to
option (a). In the case of option (a) an ASBR in one AS treats an
adjoining ASBR in another AS as a CE and determines the VSI for
packets received from another ASBR based on the incoming ethernet
interface. It is possible to extend this model by using a PW, per
VPLS instance, to interconnect the adjoining ASBRs.
In the second variant, an inter-AS multicast tree, rooted at a
particular PE for a particular VPLS instance, consists of a number of
"segments", one per AS, which are stitched together at Autonomous
System Border Routers (ASBRs). These are known as "segmented inter-AS
trees". Each segment of a segmented inter-AS tree may use a
different multicast transport technology. In this variant, an ASBR is
not required to keep a a VSI for the VPLS and is not required to
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perform a MAC lookup in order to forward the VPLS packet. This
variant is applicable to option (b) as in the case of option (b) the
BGP-VPLS NLRIs or Auto-Discovery routes are redistributed by the
ASBRs.
For option (c) support this document specifies a model where Inter-AS
VPLS service is offered by requiring a single P-multicast tree to
span multiple ASs. This is because in the case of option (c) the
ASBRs do not exchange BGP-VPLS NLRIs or Auto-Discovery routes.
7. VPLS Multicast/Broadcast/Unknown Unicast Data Packet Treatment
If the destination MAC address of a VPLS packet received by a PE from
a VPLS site is a multicast adddress, a multicast tree SHOULD be used
to transport the packet, if possible. If the packet is an IP
multicast packet and a Selective tree exists for that multicast
stream, the Selective tree SHOULD be used. Else if an Inclusive tree
exists for the VPLS, it SHOULD be used.
If the destination MAC address of a VPLS packet is a broadcast
address, it is flooded. If Inclusive tree is already established, PE
SHOULD flood over it. If Inclusive Tree cannot be used for some
reason, PE MUST flood over multiple PWs, based on [RFC4761] or
[RFC4762].
If the destination MAC address of a packet is a unicast address and
it has not been learned, the packet MUST be sent to all PEs in the
VPLS. Inclusive multicast trees SHOULD be used for sending unknown
unicast MAC packets to all PEs. When this is the case the receiving
PEs MUST support the ability to perform MAC address learning for
packets received on a multicast tree. In order to perform such
learning, the receiver PE MUST be able to determine the sender PE
when a VPLS packet is received on a multicast tree. This further
implies that the MPLS multicast tree technology MUST allow the egress
PE to determine the sender PE from the received MPLS packet.
When a receiver PE receives a VPLS packet with a source MAC address,
that has not yet been learned, on a multicast tree, the receiver PE
determines the PW to the sender PE. The receiver PE then creates
forwarding state in the VPLS instance with a destination MAC address
being the same as the source MAC address being learned, and the PW
being the PW to the sender PE.
It should be noted that when a sender PE that is sending packets
destined to an unknown unicast MAC address over a multicast tree
learns the PW to use for forwarding packets destined to this unicast
MAC address, it might immediately switch to transport such packets
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over this particular PW. Since the packets were initially being
forwarded using a multicast tree, this could lead to packet
reordering. This constraint should be taken into consideration if
unknown unicast frames are forwarded using a Inclusive Tree, instead
of multiple PWs based on [RFC4761] or [RFC4762].
An implementation MUST support the ability to transport unknown
unicast traffic over Inclusive multicast trees. Further an
implementation MUST support the ability to perform MAC address
learning for packets received on a multicast tree.
8. Intra-AS Inclusive Multicast Tree Auto-Discovery/Binding
This section specifies procedures for the intra-AS auto-discovery (A-
D) of VPLS membership and the distribution of information used to
instantiate P-Multicast Tunnels.
VPLS auto-discovery/binding consists of two components: intra-AS and
inter-AS. The former provides VPLS auto-discovery/binding within a
single AS. The latter provides VPLS auto-discovery/binding across
multiple ASes. Inter-AS auto-discovery/binding is described in
section 11.
VPLS auto-discovery using BGP as described in [RFC4761, L2VPN-SIG]
enables a PE to learn the VPLS membership of other PEs. A PE that
belongs to a particular VPLS announces a BGP Network Layer
Reachability Information (NLRI) that identifies the Virtual Switch
Instance (VSI). This NLRI is constructed from the <Route-
Distinguisher (RD), VPLS Edge Device Identifier (VE-ID)> tuple. The
NLRI defined in [RFC4761] comprises the <RD, VE-ID> tuple and label
blocks for PW signaling. The VE-ID in this case is a two octet
number. While the NLRI defined in [L2VPN-SIG] comprises only the <RD,
VE-ID> where the VE-ID is a four octet number.
The procedures for constructing Inclusive intra-AS and inter-AS trees
as specified in this document require the BGP Auto-Discovery NLRI to
carry only the <RD, VE-ID>. Hence these procedures can be used for
both BGP-VPLS and LDP-VPLS with BGP Auto-Discovery.
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8.1. Originating (intra-AS) auto-discovery routes
To participate in the VPLS auto-discovery/binding a PE router that
has a given VSI of a given VPLS originates an auto-discovery route
and advertises this route in I-BGP. The route is constructed as
described in [RFC4761] and [L2VPN-SIG].
The route carries a single L2VPN NLRI with the RD set to the RD of
the VSI, and the VE-ID set to the VE-ID of the VSI.
If a P-Multicast tree is used to instantiate the provider tunnel for
VPLS multicast on the PE, and either (a) this tree exists at the time
of discovery, or (b) the PE doesn't need to know the leaves of the
tree before hand in order to advertise the P-Multicast tree
identifier, then the advertising PE MUST advertise the type and the
identity of the P-Multicast tree in a new BGP attribute called the
the PMSI Tunnel attribute. This attribute is described in section
13.1.
If a P-Multicast tree is used to instantiate the provider tunnel for
VPLS multicast on the PE, and in order to advertise the P-Multicast
tree identifier the advertising PE needs to know the leaves of the
tree beforehand, then the PE obtains this information from the intra-
AS auto-discovery routes received from other PEs. Once the PE obtains
the information about the leaves (this information is obtained from
the auto-discovery routes received by the PE), the PE then advertises
the binding of the tree to the VPLS using the same route as the one
used for the auto-discovery, with the addition of carrying in the
route the PMSI Tunnel attribute that contains the type and the
identity of the P-Multicast tree. If at some later point a new PE
advertises participation in the same VPLS, the initial binding P-
Tunnel binding information SHOULD NOT change (though the leaves of
the corresponding P-Multicast tree may change).
A PE that uses a P-Multicast tree to instantiate the provider tunnel
MAY aggregate two or more VPLSs present on the PE onto the same tree.
If the PE already advertises intra-AS auto-discovery routes for these
VPLSs, then aggregation requires the PE to re-advertise these routes.
The re-advertised routes MUST be the same as the original ones,
except for the PMSI Tunnel attribute. If the PE has not previously
advertised intra-AS auto-discovery routes for these VPLSs, then the
aggregation requires the PE to advertise (new) intra-AS auto-
discovery routes for these VPLSs. The P-Tunnel attribute in the
newly advertised/re-advertised routes MUST carry the identity of the
P-Multicast tree that aggregates the VPLSs, as well as an MPLS
upstream-assigned label [MPLS-UPSTREAM]. Each re-advertised route
MUST have a distinct label.
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Discovery of PE capabilities in terms of what tunnels types they
support is outside the scope of this document. Within a given AS PEs
participating in a VPLS are expected to advertise tunnel bindings
whose tunnel types are supported by all other PEs that are
participating in this VPLS and are part of the same AS.
8.2. Receiving (intra-AS) auto-discovery routes
When a PE receives a BGP Update message that carries an auto-
discovery route such that (a) the route was originated by some other
PE within the same AS as the local PE, (b) at least one of the Route
Targets of the route matches one of the import Route Targets
configured for a particular VSI on the local PE, (c) the BGP route
selection determines that this is the best route with respect to the
NLRI carried by the route, and (d) the route carries the PMSI Tunnel
attribute, the PE performs the following.
If the route carries the PMSI Tunnel attribute then:
+ If the Tunnel Type in the PMSI Tunnel attribute is set to LDP
P2MP LSP, the PE SHOULD join the P-Multicast tree whose identity
is carried in the PMSI Tunnel Attribute.
+ If the Tunnel Type in the PMSI Tunnel attribute is set to RSVP-TE
P2MP LSP, the receiving PE has to establish the appropriate state
to properly handle the traffic received over that LSP. The PE
that originated the route MUST establish an RSVP-TE P2MP LSP with
the local PE as a leaf. This LSP MAY have been established before
the local PE receives the route.
+ If the PMSI Tunnel attribute does not carry a label, then all
packets that are received on the P-Multicast tree, as identified
by the PMSI Tunnel attribute, are forwarded using the VSI that
has at least one of its import Route Targets that matches one of
the Route Targets of the received auto-discovery route.
+ If the PMSI Tunnel attribute has the Tunnel Type set to LDP P2MP
LSP or RSVP-TE P2MP LSP, and the attribute also carries an MPLS
label, then the egress PE MUST treat this as an upstream-assigned
label, and all packets that are received on the P-Multicast tree,
as identified by the PMSI Tunnel attribute, with that upstream
label are forwarded using the VSI that has at least one of its
import Route Target that matches one of the Route Targets of the
received auto-discovery route.
Irrespective of whether the route carries the PMSI Tunnel
attribute, if the local PE uses RSVP-TE P2MP LSP for sending
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(multicast) traffic from the VRF to the sites attached to other
PEs, then the local PE uses the Originating Router's IP address
information carried in the route to add the PE that originated
the route as a leaf node to the LSP.
9. Demultiplexing Multicast Tree Traffic
Demultiplexing received VPLS traffic requires the receiving PE to
determine the VPLS instance the packet belongs to. The egress PE can
then perform a VPLS lookup to further forward the packet. It also
requires the egress PE to determine the identity of the ingress PE
for MAC learning, as described in section 7.
9.1. One Multicast Tree - One VPLS Mapping
When a multicast tree is mapped to only one VPLS, determining the
tree on which the packet is received is sufficient to determine the
VPLS instance on which the packet is received. The tree is determined
based on the tree encapsulation. If MPLS encapsulation is used, eg:
RSVP-TE P2MP LSPs, the outer MPLS label is used to determine the
tree. Penultimate-hop-popping MUST be disabled on the MPLS LSP (RSVP-
TE P2MP LSP or LDP P2MP LSP).
9.1.1. One Multicast Tree - Many VPLS Mapping
As traffic belonging to multiple VPLSs can be carried over the same
tree, there is a need to identify the VPLS the packet belongs to.
This is done by using an inner label that determines to the VPLS for
which the packet is intended. The ingress PE uses this label as the
inner label while encapsulating a customer multicast data packet.
Each of the egress PEs must be able to associate this inner label
with the same VPLS and use it to demultimplex the traffic received
over the Aggregate Inclusive Tree or the Aggregate Selective Tree. If
downstream label assignment were used this would require all the
egress PEs in the VPLS to agree on a common label for the VPLS.
This document requires the use of upstream label assignment by the
ingress PE [MPLS-UPSTREAM]. Hence the inner label is assigned by the
ingress PE. Each egress PE maintains a separate label space for every
other PE that is the root of an Aggregate Tree. The egress PEs create
a forwarding entry for the inner VPLS label, assigned by the ingress
PE, in this label space. When the egress PE receives a packet over
an Aggregate Tree, the outer encapsulation [in the case of MPLS P2MP
LSPs, the outer MPLS label] specifies the label space to perform the
inner label lookup. The same label space MUST be used by the egress
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PE for all P-multicast trees that have the same root [MPLS-UPSTREAM].
If the tree uses MPLS encapsulation the outer MPLS label and the
incoming interface provides the label space of the label beneath it.
This assumes that penultimate-hop-popping is disabled. An example of
this is RSVP-TE P2MP LSPs. The outer label and incoming interface
effectively identifies the Tree [MPLS-UPSTREAM, MPLS-MCAST].
The ingress PE informs the egress PEs about the inner label as part
of the tree binding procedures described in section 12.
10. Establishing Multicast Trees
This document does not place any fundamental restrictions on the
multicast technology used to setup P-multicast trees. However
specific procedures are specified currently only for RSVP-TE P2MP
LSPs and LDP P2MP LSPs. An implementation that supports this document
MUST support RSVP-TE P2MP LSPs and MAY support LDP P2MP LSPs.
The P-multicast trees supported in this document are source trees. A
source tree is used to carry traffic only for the VPLSs that exist
locally on the root of the tree i.e. for which the root has local
CEs.
10.1. RSVP-TE P2MP LSPs
This section describes procedures that are specific to the usage of
RSVP-TE P2MP LSPs for instantiating a multicast tree. Procedures in
[RFC4875] are used to signal the P2MP LSP. The LSP is signaled after
the root of the P2MP LSP discovers the leaves. The egress PEs are
discovered using the procedures described in section 9. Aggregation
as described in this document is supported.
10.1.1. P2MP TE LSP - VPLS Mapping
P2MP TE LSP to VPLS mapping is learned at the egress PEs using BGP
based advertisements of the P2MP TE LSP - VPLS mapping. They require
that the root of the tree include the P2MP TE LSP identifier as the
tunnel identifier in the BGP advertisements. This identifier contains
the following information elements:
- The type of the tunnel is set to RSVP-TE P2MP LSP
- RSVP-TE P2MP LSP's SESSION Object
This Tunnel Identifier is described in section 13.1.
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10.1.2. Demultiplexing C-Multicast Data Packets
Demultiplexing the C-multicast data packets at the egress PE requires
that the PE must be able to determine the P2MP TE LSP that the
packets are received on. The egress PE needs to determine the P2MP
LSP to determine the VPLS that the packet belongs to, as described in
section 10. To achieve this the LSP MUST be signaled with
penultimate-hop-popping (PHP) off. This is because the egress PE
needs to rely on the MPLS label, that it advertises to its upstream
neighbor, to determine the P2MP LSP that a C-multicast data packet is
received on.
The egress PE also needs to identify the ingress PE to perform MAC
learning. When P2MP LSPs are used, as source trees, determining the
P2MP LSP that the packets are received on, is sufficient to determine
the ingress PE. This is because the ingress PE is the root of the
P2MP LSP.
The egress PE relies on receiving the PMSI Tunnel Attribute in BGP to
determine the VPLS instance to P2MP TE LSP mapping.
Once the egress PE receives this mapping:
+ If the egress PE already has RSVP-TE state for the P2MP TE LSP,
it MUST begin to assign a MPLS label from the non-reserved label
range, for the P2MP TE LSP and signal this to the previous hop of
the P2MP TE LSP. Further it MUST create forwarding state to
forward packets received on the P2MP LSP.
+ If the egress PE does not have RSVP-TE state for the P2MP TE LSP,
it MUST retain this mapping. Subsequently when the egress PE
receives the RSVP-TE P2MP signaling message, it creates the RSVP-
TE P2MP LSP state. It MUST then assign a MPLS label from the
non-reserved label range, for the P2MP TE LSP, and signal this to
the previous hop of the P2MP TE LSP.
10.2. Receiver Initiated MPLS Trees
Receiver initiated MPLS trees can also be used. An example of such
trees are LDP setup P2MP MPLS Trees [MLDP].
Procedures in [MLDP] are used to signal the LSP. The LSP is signaled
once the leaves receive the LDP FEC for the tree from the root. The
egress PEs are discovered using the procedures described in section
9. Aggregation as described in this document is supported.
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10.2.1. P2MP LSP - VPLS Mapping
P2MP LSP to VPLS mapping is learned at the egress PEs using BGP based
advertisements of the P2MP LSP - VPLS mapping. They require that the
root of the tree include the P2MP LSP identifier as the tunnel
identifier in the BGP advertisements. This identifier contains the
following information elements:
- The type of the tunnel is set to LDP P2MP LSP
- LDP P2MP FEC which includes an identifier generated by the
root.
Each egress PE "joins" the P2MP MPLS tree by sending LDP label
mapping messages for the LDP P2MP FEC, that was learned in the BGP
advertisement, using procedures described in [MLDP].
10.2.2. Demultiplexing C-Multicast Data Packets
This follows the same procedures described above for RSVP-TE P2MP
LSPs.
10.3. Encapsulation of the Aggregate Inclusive and Selective Tree
An Aggregate Inclusive Tree or an Aggregate Selective Tree MUST use a
MPLS encapsulation. The protocol type in the data link header is as
described in [MPLS-MCAST].
11. Inter-AS Inclusive Multicast Tree Auto-Discovery/Binding
This document supports three models of inter-AS VPLS service, option
(a), (b) and (c) which are very similar conceptually to option (a),
(b) and (c) specified in [RFC4364] for IP VPNs. The three options
described here are also similar to the three options described in
[RFC4761], which in turn extends the concepts of [RFC4364] to inter-
AS VPLS. An implementation MUST support all three of these models.
When there are multiple options for implementing one of these models,
this section specifies which option is mandatory.
For option (a) and option (b) support this section specifies a model
where inter-AS VPLS service can be offered without requiring a single
P-multicast tree to span multiple ASes. This allows individual ASes
to potentially use different P-tunneling technologies.There are two
variants of this model. One that requires MAC lookup on the ASBRs and
another that does not require MAC lookup on the ASBRs and instead
builds segmented inter-AS trees. This applies to both Inclusive and
Selective trees.
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For option (c) support this document specifies a model where Inter-AS
VPLS service is offered by requiring a single Inclusive P-multicast
tree to span multiple ASs. This is referred to as a non-segmented P-
multicast tree. This is because in the case of option (c) the ASBRs
do not exchange BGP-VPLS NLRIs or Auto-Discovery routes. Selective
inter-AS trees for option (c) support may be segmented or non-
segmented.
11.1. VSIs on the ASBRs
In this variant, the ASBRs MUST perform a MAC lookup, in addition to
any MPLS lookups, to determine the forwarding decision on a VPLS
packet. The multicast trees are confined to an AS. An ASBR on
receiving a VPLS packet from another ASBR is required to perform a
MAC lookup to determine how to forward the packet. Thus an ASBR is
required to keep a VSI for the VPLS and MUST be configured with its
own VE ID for the VPLS. When this variant is used with option (a) an
ASBR in one AS treats an adjoining ASBR in another AS as a CE and
determines the VSI for packets received from another ASBR based on
the incoming ethernet interface.
An implementation MUST support this variant for option (a).
11.1.0.1. VPLS Inter-AS Auto-Discovery Binding
In this variant the BGP A-D routes generated by PEs in an AS MUST NOT
be propagated outside the AS. In the case of option (a) the ASBRs do
not exchange A-D routes.
If the interconnect between the ASBRs is a PW, that maps to a VPLS
instance at the ASBR, then the only A-D routes that are propagated
outside the AS are the ones originated by ASBRs. This MPLS PW
connects the VSIs on the ASBRs and MUST be signaled using the
procedures defined in [RFC4761] or [RFC4762].
The multicast trees for a VPLS are confined to each AS and the VPLS
auto-discovery/binding MUST follow the intra-AS procedures described
in section 8.
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11.2. Option (b) - Segmented Inter-AS Trees
In this variant, an inter-AS multicast tree, rooted at a particular
PE for a particular VPLS instance, consists of a number of
"segments", one per AS, which are stitched together at ASBRs. These
are known as "segmented inter-AS trees". Each segment of a segmented
inter-AS tree may use a different multicast transport technology. In
this variant, an ASBR is not required to keep a VSI for the VPLS and
is not required to perform a MAC lookup in order to forward the VPLS
packet. This implies that an ASBR is not required to be configured
with a VE ID for the VPLS. This variant is applicable to option (b).
An implementation MUST support this variant.
The construction of segmented Inter-AS trees requires the BGP-VPLS
Auto-Discovery NLRI described in [RFC4761, RFC4762]. A BGP-VPLS A-D
route for a <RD, VE ID> tuple advertised outside the AS, to which the
originating PE belongs, will be referred to as an inter-AS auto-
discovery route (Though this route is originated by a PE as an intra-
AS route and is referred to as an inter-AS route outside the AS).
In addition to this, segmented inter-AS trees require support for the
PMSI Tunnel Attribute described in section 13.1. They also require
additional procedures in BGP to signal leaf A-D routes between ASBRs
as explained in subsequent sections.
11.2.1. Segmented Inter-AS Trees VPLS Inter-AS Auto-Discovery/Binding
This section specifies the procedures for inter-AS VPLS Auto-
Discovery/binding for segmented inter-AS trees.
An ASBR must be configured to support a particular VPLS as follows:
+ An ASBR MUST be be configured with a set of (import) Route
Targets (RTs) that specifies the set of VPLSes supported by the
ASBR. These Route Targets control acceptance of BGP VPLS auto-
discovery routes by the ASBR. Note that instead of being
configured, the ASBR MAY obtain this set of (import) Route
Targets (RTs) by using Route Target Constrain [RFC4684].
+ The ASBR MUST be configured with the tunnel types for the intra-
AS segments of the VPLSes supported by the ASBR, as well as
(depending on the tunnel type) the information needed to create
the PMSI Tunnel attribute for these tunnel types. Note that
instead of being configured, the ASBR MAY derive the tunnel types
from the intra-AS auto-discovery routes received by the ASBR from
the PEs in its own AS.
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If an ASBR is configured to support a particular VPLS, the ASBR MUST
participate in the intra-AS VPLS auto-discovery/binding procedures
for that VPLS within the ASBR's own AS, as defined in this document.
Moreover, in addition to the above the ASBR performs procedures
specified in the next section.
11.2.2. Propagating VPLS BGP Auto-Discovery routes to other ASes -
Overview
An auto-discovery route for a given VPLS, originated by an ASBR
within a given AS, is propagated via BGP to other ASes. The precise
rules for distributing and processing the inter-AS auto-discovery
routes are given in subsequent sections.
Suppose that an ASBR A receives and installs an auto-discovery route
for VPLS "X" and VE ID "V" that originated at a particular PE, PE1.
The BGP next hop of that received route becomes A's "upstream
neighbor" on a multicast distribution tree for (X, V) that is rooted
at PE1. When the auto-discovery routes have been distributed to all
the necessary ASes, they define a "reverse path" from any AS that
supports VPLS X and VE ID V back to PE1. For instance, if AS2
supports VPLS X, then there will be a reverse path for VPLS X and VE
ID V from AS2 to AS1. This path is a sequence of ASBRs, the first of
which is in AS2, and the last of which is in AS1. Each ASBR in the
sequence is the BGP next hop of the previous ASBR in the sequence on
the given auto-discovery route.
This reverse path information can be used to construct a
unidirectional multicast distribution tree for VPLS X and VE ID V,
containing all the ASes that support X, and having PE1 at the root.
We call such a tree an "inter-AS tree". Multicast data originating in
VPLS sites for VPLS X connected to PE1 will travel downstream along
the tree which is rooted at PE1.
The path along an inter-AS tree is a sequence of ASBRs. It is still
necessary to specify how the multicast data gets from a given ASBR to
the set of ASBRs which are immediately downstream of the given ASBR
along the tree. This is done by creating "segments": ASBRs in
adjacent ASes will be connected by inter-AS segments, ASBRs in the
same AS will be connected by "intra-AS segments".
For a given inter-AS tree, there MUST be only one ASBR that accepts
traffic into a given AS. Further there MUST be only one ASBR that
sends traffic from a particular AS on the tree to another adjacent
AS. The precise rules for accomplishing this are given in subsequent
sections.
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An ASBR initiates creation of an intra-AS segment when the ASBR
receives an auto-discovery route from an E-BGP neighbor. Creation of
the segment is completed as a result of distributing, via I-BGP, this
route within the ASBR's own AS.
For a given inter-AS tunnel each of its intra-AS segments could be
constructed by its own independent mechanism. Moreover, by using
upstream-assigned labels within a given AS multiple intra-AS segments
of different inter-AS tunnels of either the same or different VPLSs
may share the same P-Multicast tree.
If the P-Multicast tree instantiating a particular segment of an
inter-AS tunnel is created by a multicast control protocol that uses
receiver-initiated joins (e.g, mLDP), and this P-Multicast tree does
not aggregate multiple segments, then all the information needed to
create that segment will be present in the inter-AS auto-discovery
routes received by the ASBR from the neighboring ASBR. But if the P-
Multicast tree instantiating the segment is created by a protocol
that does not use receiver-initiated joins (e.g., RSVP-TE, ingress
unicast replication), or if this P-Multicast tree aggregates multiple
segments (irrespective of the multicast control protocol used to
create the tree), then the ASBR needs to learn the leaves of the
segment. These leaves are learned from A-D routes received from other
PEs in the AS, for the same VPLS (i.e. same VE-ID) as the one that
the segment belongs to.
The following sections specify procedures for propagation of auto-
discovery routes across ASes in order to construct inter-AS segmented
trees.
11.2.2.1. Propagating Intra-AS VPLS Auto-Discovery routes in E-BGP
For a given VPLS configured on an ASBR when the ASBR determines
(using the intra-AS auto-discovery procedures) that one or more PEs
of its own AS has (directly) connected site(s) of the VPLS, the ASBR
MUST originate an BGP VPLS auto-discovery route and advertise it in
E-BGP. This procedure MUST be performed for each of the VPLSs
configurd on the ASBR. Each of these routes is constructed as
follows:
+ The route carries a single BGP VPLS A-D NLRI with the RD and VE
ID being the same as the received NLRI.
+ The Next Hop field of the MP_REACH_NLRI attribute is set to a
routable IP address of the ASBR.
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+ The route carries the PMSI Tunnel attribute with the Tunnel Type
set to Ingress Replication; the attribute carries no MPLS labels.
+ The route MUST carry the export Route Target used by the VPLS.
11.2.2.2. Auto-Discovery route received via E-BGP
When an ASBR receives from one of its E-BGP neighbors a BGP Update
message that carries an auto-discovery route, if (a) at least one of
the Route Targets carried in the message matches one of the import
Route Targets configured on the ASBR, and (b) the ASBR determines
that the received route is the best route to the destination carried
in the NLRI of the route, the ASBR re-advertises this auto-discovery
route to other PEs and ASBRs within its own AS. The best route
selection procedures MUST ensure that for the same destination, all
ASBRs in an AS pick the same route as the best route. This ensures
that if multiple ASBRs, in an AS, receive the same inter-AS A-D route
from their E-BGP neighbors, only one of these ASBRs propagates this
route in I-BGP. This ASBR becomes the root of the intra-AS segment of
the inter-AS tree and ensures that this is the only ASBR that accepts
traffic into this AS from the inter-AS tree.
When re-advertising an inter-AS auto-discovery route the ASBR MUST
set the Next Hop field of the MP_REACH_NLRI attribute to a routable
IP address of the ASBR.
Depending on the type of a P-Multicast tree used to instantiate the
intra-AS segment of the inter-AS tunnel, the PMSI Tunnel attribute of
the re-advertised inter-AS auto-discovery route is constructed as
follows:
+ If the ASBR uses ingress replication to instantiate the intra-AS
segment of the inter-AS tunnel, the re-advertised route MUST NOT
carry the PMSI Tunnel attribute.
+ If the ASBR uses a P-Multicast tree to instantiate the intra-AS
segment of the inter-AS tunnel, the PMSI Tunnel attribute MUST
contain the identity of the tree that is used to instantiate the
segment (note that the ASBR could create the identity of the tree
prior to the actual instantiation of the segment). If in order to
instantiate the segment the ASBR needs to know the leaves of the
tree, then the ASBR obtains this information from the auto-
discovery routes received from other PEs/ASBRs in ASBR's own AS.
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+ An ASBR that uses a P-Multicast tree to instantiate the intra-AS
segment of the inter-AS tunnel MAY aggregate two or more VPLSs
present on the ASBR onto the same tree. If the ASBR already
advertises inter-AS auto-discovery routes for these VPLSs, then
aggregation requires the ASBR to re-advertise these routes. The
re-advertised routes MUST be the same as the original ones,
except for the PMSI Tunnel attribute. If the ASBR has not
previously advertised inter-AS auto-discovery routes for these
VPLSs, then the aggregation requires the ASBR to advertise (new)
inter-AS auto-discovery routes for these VPLSs. The PMSI Tunnel
attribute in the newly advertised/re-advertised routes MUST carry
the identity of the P-Multicast tree that aggregates the VPLSs,
as well as an MPLS upstream-assigned label [MPLS-UPSTREAM]. Each
re-advertised route MUST have a distinct label.
In addition the ASBR MUST send to the E-BGP neighbor, from whom it
receives the inter-AS auto-discovery route, a BGP Update message that
carries a "leaf auto-discovery route". The exact encoding of this
route is described in section 13. This route contains the following
information elements:
+ The route carries a single NLRI with the Route Key field set to
the <RD, VE ID> tuple of the BGP VPLS Auto-Discovery NLRI of the
inter-AS auto-discovery route received from that neighbor. The
NLRI also carries the IP address of the ASBR (this MUST be a
routable IP address).
+ The leaf auto-discovery route MUST include the PMSI Tunnel
attribute with the Tunnel Type set to Ingress Replication, and
the Tunnel Identifier set to a routable address of the
advertising router. The PMSI Tunnel attribute MUST carry a
downstream assigned MPLS label that is used to demultiplex the
VPLS traffic received over a unicast tunnel by the advertising
router.
+ The Next Hop field of the MP_REACH_NLRI attribute of the route
SHOULD be set to the same IP address as the one carried in the
Originating Router's IP Address field of the route.
+ To constrain the distribution scope of this route the route MUST
carry the NO_ADVERTISE BGP community ([RFC1997]).
+ The Route Targets associated with the VPLS MUST be included in
the route.
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11.2.2.3. Leaf Auto-Discovery Route received via E-BGP
When an ASBR receives via E-BGP a leaf auto-discovery route, the ASBR
accepts the route only if if (a) at least one of the Route Targets
carried in the message matches one of the import Route Targets
configured on the ASBR, and (b) the ASBR determines that the received
route is the best route to the destination carried in the NLRI of the
route.
If the ASBR accepts the leaf auto-discovery route, the ASBR finds an
auto-discovery route whose BGP-VPLS A-D NLRI has the same value as
the <RD, VE-ID> field of the the leaf auto-discovery route.
The MPLS label carried in the PMSI Tunnel attribute of the leaf auto-
discovery route is used to stitch a one hop ASBR-ASBR LSP to the tail
of the intra-AS tunnel segment associated with the found auto-
discovery route.
11.2.2.4. Inter-AS Auto-Discovery Route received via I-BGP
In the context of this section we use the term "PE/ASBR router" to
denote either a PE or an ASBR router.
Note that a given inter-AS auto-discovery route is advertised within
a given AS by only one ASBR as described above.
When a PE/ASBR router receives from one of its I-BGP neighbors a BGP
Update message that carries an inter-AS auto-discovery route, if (a)
at least one of the Route Targets carried in the message matches one
of the import Route Targets configured on the PE/ASBR, and (b) the
PE/ASBR determines that the received route is the best route to the
destination carried in the NLRI of the route, the PE/ASBR performs
the following operations.
If the router is an ASBR then the ASBR propagates the route to its E-
BGP neighbors. When propagating the route to the E-BGP neighbors the
ASBR MUST set the Next Hop field of the MP_REACH_NLRI attribute to a
routable IP address of the ASBR.
If the received inter-AS auto-discovery route carries the PMSI Tunnel
attribute with the Tunnel Type set to LDP P2MP LSP, the PE/ASBR
SHOULD join the P-Multicast tree whose identity is carried in the
PMSI Tunnel Attribute.
If the received inter-AS auto-discovery route carries the PMSI Tunnel
attribute with the Tunnel Identifier set to RSVP-TE P2MP LSP, then
the ASBR that originated the route MUST establish an RSVP-TE P2MP LSP
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with the local PE/ASBRas a leaf. This LSP MAY have been established
before the local PE/ASBR receives the route, or MAY be established
after the local PE receives the route.
If the received inter-AS auto-discovery route carries the PMSI Tunnel
attribute with the Tunnel Type set to LDP P2MP LSP, or RSVP-TE P2MP
LSP, but the attribute does not carry a label, then the P-Multicast
tree, as identified by the PMSI Tunnel Attribute, is an intra-AS LSP
segment that is part of the inter-AS Tunnel for the <VPLS, VE ID>
advertised by the inter-AS auto-discovery route and rooted at the PE
that originated the auto-discovery route. If the PMSI Tunnel
attribute carries a (upstream-assigned) label, then a combination of
this tree and the label identifies the intra-AS segment. If the
received router is an ASBR, this intra-AS segment may further be
stitched to ASBR-ASBR inter-AS segment of the inter-AS tunnel. If the
PE/ASBR has local receivers in the VPLS, packets received over the
intra-AS segment must be forwarded to the local receivers using the
local VSI.
11.3. Option (c)
In this method, there is a multi-hop E-BGP peering between the PEs
(or a Route Reflector) in one AS and the PEs (or Route Reflector) in
another AS. The PEs exchange BGP-VPLS NLRI or BGP-VPLS A-D NLRI,
along with PMSI Tunnel Attribute, as in the intra-AS case described
in section 8. An implementation MUST support this method.
The PEs in different ASs use a non-segmented inter-AS P2MP tunnel for
VPLS multicast. A non-segmented inter-AS tunnel is a single tunnel
which spans AS boundaries. The tunnel technology cannot change from
one point in the tunnel to the next, so all ASes through which the
tunnel passes must support that technology. In essence, AS boundaries
are of no significance to a non-segmented inter-AS
This method requires no VPLS information (in either the control or
the data plane) on the ASBRs. The ASBRs only need to participate in
the non-segmented P2MP tunnel setup in the control plane, and do MPLS
label forwarding in the data plane.
The setup of non-segmented inter-AS P2MP tunnels MAY require the P-
routers in one AS to have IP reachability to the loopback addresses
of the PE routers in another AS, depending on the tunneling
technology chosen. If this is the case, reachability to the loopback
addresses of PE routers in one AS MUST be present in the IGP in
another AS.
The data forwarding in this model is the same as in the intra-AS case
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described in section 8.
12. Optimizing Multicast Distribution via Selective Trees
Whenever a particular multicast stream is being sent on an Inclusive
Tree, it is likely that the data of that stream is being sent to PEs
that do not require it. If a particular stream has a significant
amount of traffic, it may be beneficial to move it to a Selective
Tree which has at its leaves only those PEs that have receivers for
the multicast stream (or at least includes fewer PEs that have no
receivers compared to an Inclusive tree).
If the PE connected to the multicast source is performing explicit
tracking Selective Trees can also be triggered on other criteria. For
instance there could be a "pseudo wasted bandwidth" criteria:
switching to a Selective Tree would be done if the bandwidth
multiplied by the number of uninterested PEs (PE that are receiving
the stream but have no receivers) is above a specified threshold. The
motivation is that (a) the total bandwidth wasted by many sparsely
subscribed low-bandwidth groups may be large, and (b) there's no
point to moving a high-bandwidth group to a Selective Tree if all the
PEs have receivers for it.
Switching a (C-S, C-G) stream to a Selective Tree may require the
root of the tree to determine the egress PEs that need to receive the
(C-S, C-G) traffic. This is true in the following cases:
+ If the tunnel is a source initiated tree, such as a RSVP-TE P2MP
Tunnel, the PE needs to know the leaves of the tree before it can
instantiate the Selective Tree.
+ If a PE decides to send traffic for multicast streams, belonging
to different VPLSs, using one P-multicast Selective Tree, such a
tree is termed an Aggregate Tree with a selective mapping. The
setting up of such an Aggregate Tree requires the ingress PE to
know all the other PEs that have receivers for multicast groups
that are mapped onto the tree.
For discovering the IP multicast group membership, for the above
two cases, procedures described in [VPLS-CTRL] SHOULD be used.
These cases require that explicit tracking be done for the (C-S,
C-G) stream. The root of the Selective P-tree MAY decide to do
explicit tracking of this stream only after it has determined to
move the stream to a Selective tree, or it MAY have been doing
explicit tracking all along.
The PE at the root of the tree MUST signal the leaves of the tree
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that the (C-S, C-G) stream is now bound to the to the Selective
Tree. Note that the PE could create the identity of the P-
multicast tree prior to the actual instantiation of the tunnel.
If the Selective Tree is instantiated by a source-initiated P-
multicast tree (e.g., an RSVP-TE P2MP tunnel), the PE at the root
of the tree MUST establish the source-initiated P-multicast tree
to the leaves. This tree MAY have been established before the
leaves receive the Selective Tree binding, or MAY be established
after the leaves receives the binding. The leaves MUST not
switch to the Selective Tree until they receive both the binding
and the tree signaling message.
12.1. Protocol for Switching to Selective Trees
Selective Trees provide a PE the ability to create separate P-
multicast trees for certain <C-S, C-G> streams. The source PE, that
originates the Selective Tree, and the egress PEs, MUST switch to the
Selective Tree for the <C-S, C-G> streams that are mapped to it.
Once a source PE decides to setup an Selective Tree, it MUST announce
the mapping of the <C-S, C-G> streams (which may be in different
VPLSs) that are mapped to the tree to the other PEs using BGP.
Depending on the P-multicast technology used, this announcement may
be done before or after setting up the Selective Tree. After the
egress PEs receive the announcement they setup their forwarding path
to receive traffic on the Selective Tree if they have one or more
receivers interested in the <C-S, C-G> streams mapped to the tree.
Setting up the forwarding path requires setting up the demultiplexing
forwarding entries based on the top MPLS label (if there is no inner
label) or the inner label (if present) as described in section 9. The
egress PEs may perform this switch to the Selective Tree once the
advertisement from the ingress PE is received or wait for a
preconfigured timer to do so.
A source PE MUST use the following approach to decide when to start
transmitting data on the Selective tree. A certain pre-configured
delay after advertising the <C-S, C-G> streams mapped to an Selective
Tree, the source PE begins to send traffic on the Selective Tree. At
this point it stops to send traffic for the <C-S, C-G> streams, that
are mapped on the Selective Tree, on the Inclusive Tree. This traffic
is instead transmitted on the Selective Tree.
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12.2. Advertising C-(S, G) Binding to a Selective Tree using BGP
The ingress PE informs all the PEs that are on the path to receivers
of the C-(S, G) of the binding of the Selective Tree to the C-(S, G).
The BGP announcement is done by sending update for the MCAST-VPLS
address family. A Selective Tree A-D route is used, containing the
following information:
+ a) IP address of the originating PE
b) The RD configured locally for the MVPN. This is required to
uniquely identify the <C-Source, C-Group> as the addresses could
overlap between different VPLSs. This is the same RD value used
in the VPLS auto-discovery process.
c) The C-Source address.
d) The C-Group address.
e) A PE MAY aggregate two or more (C-S, C-G)s originated by the
PE onto the same P-Multicast tree. If the PE already advertises
Selective Tree auto-discovery routes for these Selective Trees,
then aggregation requires the PE to re-advertise these routes.
The re-advertised routes MUST be the same as the original ones,
except for the PMSI tunnel attribute. If the PE has not
previously advertised Selective Tree auto-discovery routes for
these (C-S, C-G)s, then the aggregation requires the PE to
advertise (new) Selective Tree auto-discovery routes for these
(C-S, C-G)s. The PMSI Tunnel attribute in the newly
advertised/re-advertised routes MUST carry the identity of the P-
Multicast tree that aggregates the (C-S, C-G)s. If at least some
of the (C-S, C-G)s aggregated onto the same P-Multicast tree
belong to different VPLSs, then all these routes MUST carry an
MPLS upstream assigned label [MPLS-UPSTREAM]. If all these
aggregated (C-S, C-G)s belong to the same VPLS, then the routes
MAY carry an MPLS upstream assigned label [MPLS-UPSTREAM]. The
labels MUST be distinct on a per VPLS basis, and MAY be distinct
on a per route basis.
When a PE distributes this information via BGP, it must include the
following:
+ 1. A PMSI Tunnel Attribute to identify the Selective Tree to
which the stream is bound.
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+ Route Target Extended Communities attribute. This is used as
described in section 8.
12.2.1. Explicit Tracking
If the PE wants to enable explicit tracking for the specified flow,
it also indicates this in the A-D route it uses to bind the flow to a
particular Selective Tree. Then any PE which receives the A-D route
will respond with a "Leaf A-D Route" in which it identifies itself as
a receiver of the specified flow. The Leaf A-D route will be
withdrawn when the PE is no longer a receiver for the flow.
If the PE needs to enable explicit tracking for a flow before binding
the flow to an Selective Tree, it can do so by sending an A-D route
identifying the flow but not specifying an Selective Tree. This will
elicit the Leaf A-D Routes. This is useful when the PE needs to know
the receivers before selecting an Selective Tree.
12.3. Inter-AS Selective Tree
Inter-AS Selective Trees support all three models of inter-AS VPLS
service, option (a), (b) and (c), that are supported by Inter-AS
Inclusive Trees. They are constructed in a manner that is very
similar to Inter-AS Inclusive Trees.
For option (a) and option (b) support inter-AS Selective Trees are
constructed without requiring a single P-multicast tree to span
multiple ASes. This allows individual ASes to potentially use
different P-tunneling technologies.There are two variants of this
model. One that requires MAC and IP multicast lookup on the ASBRs and
another that does not require MAC/IP multicast lookup on the ASBRs
and instead builds segmented inter-AS Selective trees.
Segmented Inter-AS Selective trees can also be used with option (c)
unlike Segmented Inter-AS Inclusive trees. This is because the
Selective tree A-D routes can be exchanged via ASBRs (even though
BGP-VPLS NLRI or A-D routes are not exchanged via ASBRs).
In the case of Option (c) an Inter-AS Selective tree may also be a
non-segmented P-multicast tree that spans multiple ASs.
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12.3.1. VSIs on the ASBRs
The requirements on ASBRs in this model include the requirements
presented in section 11. The source ASBR (that receives traffic from
another AS) may independently decide whether it wishes to use
Selective Trees or not. If it uses Selective Trees the source ASBR
MUST perform an IP multicast lookup to determine the Selective Tree
to forward the VPLS packet on.
12.3.1.1. VPLS Inter-AS Selective Tree Auto-Discovery Binding
The mechanisms for propagating Selective Tree A-D routes are the same
as the intra-AS case described in section 12.2. The BGP Selective
Tree A-D routes generated by PEs in an AS MUST NOT be propagated
outside the AS.
12.3.2. Inter-AS Segmented Selective Trees
Inter-AS Segmented Selective trees MUST be used when option (b) is
used to provide the inter-AS VPLS service. They MAY be used when
option (c) is used to provide the inter-AS VPLS service.
A Segmented inter-AS Selective Tunnel is constructed similar to an
inter-AS Segmented Inclusive Tunnel. Namely, such a tunnel is
constructed as a concatenation of tunnel segments. There are two
types of tunnel segments: an intra-AS tunnel segment (a segment that
spans ASBRs within the same AS), and inter-AS tunnel segment (a
segment that spans adjacent ASBRs in adjacent ASes). ASes that are
spanned by a tunnel are not required to use the same tunneling
mechanism to construct the tunnel - each AS may pick up a tunneling
mechanism to construct the intra-AS tunnel segment of the tunnel, in
its AS.
The PE that decides to set up a Selective Tree, advertises the
Selective Tree to (C-S, C-G) binding using a Selective Tree A-D route
as per procedures in section 12.2, to the routers in its own AS.
A Selective Tree A-D route advertised outside the AS, to which the
originating PE belongs, will be referred to as an inter-AS Selective
Tree A-D route (Although this route is originated by a PE as an
intra-AS route it is referred to as an inter-AS route outside the
AS).
An ASBR that receives the information from its upstream ASBR using E-
BGP sends back a tunnel binding for AS <C-S, C-G> information if:
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a) At least one of the Route Targets carried in the message
matches one of the import Route Targets configured on the ASBR,
and
b) The ASBR determines that the received route is the best route
to the destination carried in the NLRI of the route.
If the ASBR instantiates a Selective Tree for the AS <C-S, C-G> it
sends back a downstream label that is used to forward the packet
along its intra-AS Selective Tree segment for <C-S, C-G>. However, in
the case of option (b) the ASBR may decide to use an AS Inclusive
Tree segment instead, in which case it sends back the same label that
it advertised for the AS-AS segment of the inter-AS segmented
Inclusive tree. (This is not possible in option (c) as in option (c)
the ASBRs do not participate in inter-AS Inclusive tree setup). If
the downstream ASBR instantiates a Selective Tree, it further
propagates the <C-S, C-G> membership to its downstream ASes, else it
does not.
An AS can instantiate an intra-AS Selective Tree segment for the
inter-AS Selective tunnel only if the upstream AS instantiates a
Selective Tree. The procedures allow each AS to determine whether it
wishes to setup a Selective Tree or not and the AS is not forced to
setup a Selective Tree just because the upstream AS decides to do so.
The leaves of an intra-AS Selective Tree will be the PEs that have
local receivers that are interested in <C-S, C-G> and the ASBRs that
have received VPLS control information for <C-S, C-G>.
The C-multicast data traffic is sent on the Selective Tree by the
originating PE. When it reaches an ASBR that is on the spanning tree,
it is delivered to local receivers, if any, and is also forwarded to
the neighbor ASBR after being encapsulated in the label advertised by
the neighbor. The neighbor ASBR either transports this packet on the
Selective Tree segment for the multicast stream or an Inclusive Tree
segment, delivering it to the ASBRs in its own AS. These ASBRs in
turn repeat the procedures of the origin AS ASBRs and the multicast
packet traverses the spanning tree.
The (C-S, C-G) membership for which the Selective Tree is
instantiated, is propagated inter-AS using procedures in [VPLS-CTRL].
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12.3.3. Inter-AS Non-Segmented Selective Trees
Inter-AS Non-segmented Selective trees may be used in the case of
option (c).
In this method, there is a multi-hop E-BGP peering between the PEs
(or a Route Reflector) in one AS and the PEs (or Route Reflector) in
another AS. The PEs exchange BGP Selective tree A-D routes, along
with PMSI Tunnel Attribute, as in the intra-AS case described in
section 12.2.
The PEs in different ASs use a non-segmented Selective inter-AS P2MP
tunnel for VPLS multicast.
This method requires no VPLS information (in either the control or
the data plane) on the ASBRs. The ASBRs only need to participate in
the non-segmented P2MP tunnel setup in the control plane, and do MPLS
label forwarding in the data plane.
The data forwarding in this model is the same as in the intra-AS case
described in section 9.
13. BGP Extensions
This section describes the encoding of the BGP extensions required by
this document.
13.1. Inclusive Tree/Selective Tree Identifier
Inclusive Tree and Selective Tree advertisements carry the Tree
identifier.
This document defines and uses a new BGP attribute, called PMSI
Tunnel Attribute. This is an optional transitive BGP attribute. The
format of this attribute is defined as follows:
+---------------------------------+
| Flags (1 octet) |
+---------------------------------+
| Tunnel Type (1 octets) |
+---------------------------------+
| MPLS Label (3 octets) |
+---------------------------------+
| Tunnel Identifier (variable) |
+---------------------------------+
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The Flags field has the following format:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| reserved |L|
+-+-+-+-+-+-+-+-+
This document defines the following flags:
+ Leaf Information Required (L)
The Tunnel Type identifies the type of the tunneling technology used
to establish the P-tunnel. The type determines the syntax and
semantics of the Tunnel Identifier field. This document defines the
following Tunnel Types:
+ 1 - RSVP-TE P2MP LSP
+ 2 - LDP P2MP LSP
+ 6 - Ingress Replication
If the MPLS Label field is non-zero, then it contains an MPLS
label encoded as 3 octets, where the high-order 20 bits contain
the label value. Absence of MPLS Label is indicated by setting
the MPLS Label field to zero.
When the type is set to RSVP-TE P2MP LSP, the Tunnel Identifier
contains the RSVP-TE P2MP LSP's SESSION Object.
When the type is set to LDP P2MP LSP, the Tunnel Identifier is
<P-Root Node Address, Variable length opaque identifier>.
When the type is set to Ingress Replication the Tunnel Identifier
carries the unicast tunnel endpoint.
13.2. MCAST-VPLS NLRI
This document defines a new BGP NLRI, called the MCAST-VPLS NLRI.
Following is the format of the MCAST-VPLS NLRI:
+-----------------------------------+
| Route Type (1 octet) |
+-----------------------------------+
| Length (1 octet) |
+-----------------------------------+
| Route Type specific (variable) |
+-----------------------------------+
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The Route Type field defines encoding of the rest of MCAST-VPLS NLRI
(Route Type specific MCAST-VPLS NLRI).
The Length field indicates the length in octets of the Route Type
specific field of MCAST-VPLS NLRI.
This document defines the following Route Types for auto-discovery
routes:
+ 1 - Selective Tree auto-discovery route;
+ 2 - Leaf auto-discovery route.
The MCAST-VPLS NLRI is carried in BGP using BGP Multiprotocol
Extensions [RFC4760] with an AFI of 25 (L2VPN AFI), and an SAFI of
MCAST-VPLS. The NLRI field in the MP_REACH_NLRI/MP_UNREACH_NLRI
attribute contains the MCAST-VPLS NLRI (encoded as specified above).
In order for two BGP speakers to exchange labeled MCAST-VPLS NLRI,
they must use BGP Capabilities Advertisement to ensure that they both
are capable of properly processing such NLRI. This is done as
specified in [RFC4760], by using capability code 1 (multiprotocol
BGP) with an AFI of 25 and an SAFI of MCAST-VPLS.
The following describes the format of the Route Type specific MCAST-
VPLS NLRI for various Route Types defined in this document.
13.2.1. Selective Tree auto-discovery route
An Selective Tree A-D route type specific MCAST-VPLS NLRI consists of
the following:
+-----------------------------------+
| RD (8 octets) |
+-----------------------------------+
| Multicast Source Length (1 octet) |
+-----------------------------------+
| Multicast Source (Variable) |
+-----------------------------------+
| Multicast Group Length (1 octet) |
+-----------------------------------+
| Multicast Group (Variable) |
+-----------------------------------+
| Originating Router's IP Addr |
+-----------------------------------+
The RD is encoded as described in [RFC4364].
The Multicast Source field contains the C-S address. If the Multicast
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Source field contains an IPv4 address, then the value of the
Multicast Source Length field is 32. If the Multicast Source field
contains an IPv6 address, then the value of the Multicast Source
Length field is 128.
The Multicast Group field contains the C-G address. If the Multicast
Group field contains an IPv4 address, then the value of the Multicast
Group Length field is 32. If the Multicast Group field contains an
IPv6 address, then the value of the Multicast Group Length field is
128.
Usage of Selective Tree auto-discovery routes is described in Section
12.
13.2.2. Leaf auto-discovery route
A leaf auto-discovery route type specific MCAST-VPLS NLRI consists of
the following:
+-----------------------------------+
| Route Key (variable) |
+-----------------------------------+
| Originating Router's IP Addr |
+-----------------------------------+
Usage of Leaf auto-discovery routes is described in sections "Inter-
AS Inclusive Multicast Tree Auto-Discovery/Binding" and "Optimizing
Multicast Distribution via Selective Trees".
14. Aggregation Methodology
In general the herustics used to decide which VPLS instances or <C-S,
C-G> entries to aggregate is implementation dependent. It is also
conceivable that offline tools can be used for this purpose. This
section discusses some tradeoffs with respect to aggregation.
The "congruency" of aggregation is defined by the amount of overlap
in the leaves of the client trees that are aggregated on a SP tree.
For Aggregate Inclusive Trees the congruency depends on the overlap
in the membership of the VPLSs that are aggregated on the Aggregate
Inclusive Tree. If there is complete overlap aggregation is perfectly
congruent. As the overlap between the VPLSs that are aggregated
reduces, the congruency reduces.
If aggregation is done such that it is not perfectly congruent a PE
may receive traffic for VPLSs to which it doesn't belong. As the
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amount of multicast traffic in these unwanted VPLSs increases
aggregation becomes less optimal with respect to delivered traffic.
Hence there is a tradeoff between reducing state and delivering
unwanted traffic.
An implementation should provide knobs to control the congruency of
aggregation. This will allow a SP to deploy aggregation depending on
the VPLS membership and traffic profiles in its network. If
different PEs or shared roots' are setting up Aggregate Inclusive
Trees this will also allow a SP to engineer the maximum amount of
unwanted VPLSs that a particular PE may receive traffic for.
The state/bandwidth optimality trade-off can be further improved by
having a versatile many-to-many association between client trees and
provider trees. Thus a VPLS can be mapped to multiple Aggregate
Trees. The mechanisms for achieving this are for further study. Also
it may be possible to use both ingress replication and an Aggregate
Tree for a particular VPLS. Mechanisms for achieving this are also
for further study.
15. Data Forwarding
15.1. MPLS Tree Encapsulation
The following diagram shows the progression of the VPLS IP multicast
packet as it enters and leaves the SP network when MPLS trees are
being used for multiple VPLS instances. RSVP-TE P2MP LSPs are
examples of such trees.
Packets received Packets in transit Packets forwarded
at ingress PE in the service by egress PEs
provider network
+---------------+
|MPLS Tree Label|
+---------------+
| VPLS Label |
++=============++ ++=============++ ++=============++
||C-Ether Hdr || || C-Ether Hdr || || C-Ether Hdr ||
++=============++ >>>>> ++=============++ >>>>> ++=============++
|| C-IP Header || || C-IP Header || || C-IP Header ||
++=============++ >>>>> ++=============++ >>>>> ++=============++
|| C-Payload || || C-Payload || || C-Payload ||
++=============++ ++=============++ ++=============++
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The receiver PE does a lookup on the outer MPLS tree label and
determines the MPLS forwarding table in which to lookup the inner
MPLS label. This table is specific to the tree label space. The inner
label is unique within the context of the root of the tree (as it is
assigned by the root of the tree, without any coordination with any
other nodes). Thus it is not unique across multiple roots. So, to
unambiguously identify a particular VPLS one has to know the label,
and the context within which that label is unique. The context is
provided by the outer MPLS label [MPLS-UPSTREAM].
The outer MPLS label is stripped. The lookup of the resulting MPLS
label determines the VSI in which the receiver PE needs to do the C-
multicast data packet lookup. It then strips the inner MPLS label and
sends the packet to the VSI for multicast data forwarding.
16. Security Considerations
Security considerations discussed in [RFC4761] and [RFC4762] apply to
this document. This section describes additional considerations.
As mentioned in [RFC4761], there are two aspects to achieving data
privacy in a VPLS: securing the control plane and protecting the
forwarding path. Compromise of the control plane could result in a PE
sending multicast data belonging to some VPLS to another VPLS, or
blackholing VPLS multicast data, or even sending it to an
eavesdropper; none of which are acceptable from a data privacy point
of view. The mechanisms in this document use BGP for the control
plane. Hence techniques such as in [RFC2385] help authenticate BGP
messages, making it harder to spoof updates (which can be used to
divert VPLS traffic to the wrong VPLS) or withdraws (denial-of-
service attacks). In the multi-AS methods (b) and (c) described in
Section 11, this also means protecting the inter-AS BGP sessions,
between the ASBRs, the PEs, or the Route Reflectors.
Note that [RFC2385] will not help in keeping MPLS labels, associated
with P2MP LSPs or the upstream MPLS labels used for aggregation,
private -- knowing the labels, one can eavesdrop on VPLS traffic.
However, this requires access to the data path within a Service
Provider network.
One of the requirements for protecting the data plane is that the
MPLS labels are accepted only from valid interfaces. This applies
both to MPLS labels associated with P2MP LSPs and also applies to the
upstream assigned MPLS labels. For a PE, valid interfaces comprise
links from P routers. For an ASBR, a valid interface is a link from
another ASBR in an AS that is part of a given VPLS. It is especially
important in the case of multi-AS VPLSs that one accept VPLS packets
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only from valid interfaces.
17. IANA Considerations
This document defines a new NLRI, called MCAST-VPLS, to be carried in
BGP using multiprotocol extensions. It requires assignment of a new
SAFI. This is to be assigned by IANA.
This document defines a BGP optional transitive attribute, called
PMSI Attribute. This is the same attribute as the one defined in
[BGP-MVPN] and the code point for this attribute has already been
assigned by IANA as 22 [BGP-IANA]. Hence no further action is
required from IANA regarding this attribute.
18. Acknowledgments
Many thanks to Thomas Morin for his support of this work. We would
also like to thank authors of [BGP-MVPN] and [MVPN] as the details of
the inter-AS segmented tree procedures in this document have
benefited from those in [BGP-MVPN] and [MVPN].
19. Normative References
[RFC2119] "Key words for use in RFCs to Indicate Requirement
Levels.", Bradner, March 1997
[RFC4761] K. Kompella, Y. Rekther, "Virtual Private LAN Service",
draft-ietf-l2vpn-vpls-bgp-02.txt
[RFC4762] M. Lasserre, V. Kompella, "Virtual Private LAN Services
over MPLS", draft-ietf-l2vpn-vpls-ldp-03.txt
[RFC4760] T. Bates, et. al., "Multiprotocol Extensions for BGP-4",
January 2007
[MPLS-UPSTREAM] R. Aggarwal, Y. Rekhter, E. Rosen, "MPLS Upstream
Label Assignment and Context Specific Label Space", draft-ietf-mpls-
upstream-label-00.txt
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20. Informative References
[VPLS-CTRL] R. Aggarwal, Y. Kamite, L. Fang, "Propagation of VPLS IP
Multicast Group Membership Information", draft-raggarwa-l2vpn-vpls-
mcast-ctrl-00.txt
[L2VPN-SIG] E. Rosen et. al., "Provisioning, Autodiscovery, and
Signaling in L2VPNs", draft-ietf-l2vpn-signaling-08.txt
[MPLS-MCAST] T. Eckert, E. Rosen, R. Aggarwal, Y. Rekhter, "MPLS
Multicast Encapsulations", draft-ietf-mpls-multicast-encaps-00.txt
[MVPN] E. Rosen, R. Aggarwal, "Multicast in 2547 VPNs", draft-ietf-
l3vpn-2547bis-mcast-05.txt"
[BGP-MVPN] R. Aggarwal, E. Rosen, Y. Rekhter, T. Morin, C.
Kodeboniya. "BGP Encodings for Multicast in 2547 VPNs", draft-ietf-
l3vpn-2547bis-mcast-bgp-03.txt
[RFC4875] R. Aggarwal et. al, "Extensions to RSVP-TE for Point to
Multipoint TE LSPs", draft-ietf-mpls-rsvp-te-p2mp-07.txt
[MLDP] I. Minei et. al, "Label Distribution Protocol Extensions for
Point-to-Multipoint and Multipoint-to-Multipoint Label Switched
Paths", draft-ietf-mpls-ldp-p2mp-02.txt
[RFC4364] "BGP MPLS VPNs", E. Rosen, Y.Rekhter, February 2006
[MCAST-VPLS-REQ] Y. kamite, et. al., "Requirements for Multicast
Support in Virtual Private LAN Services", draft-ietf-l2vpn-vpls-
mcast-reqts-05.txt
[RFC1997] R. Chandra, et. al., "BGP Communities Attribute", August
1996
[BGP-IANA] http://www.iana.org/assignments/bgp-parameters
[RFC4684] P. Marques et. al., "Constrained Route Distribution for
Border Gateway Protocol/MultiProtocol Label Switching (BGP/MPLS)
Internet Protocol (IP) Virtual Private Networks (VPNs)", RFC 4684,
November 2006
[RFC2385] Heffernan, A., "Protection of BGP Sessions via the TCP MD5
Signature Option", RFC 2385, August 1998.
Raggarwa, Kamite & Fang [Page 39]
Internet Draft draft-ietf-l2vpn-vpls-mcast-03.txt November 2007
21. Author's Address
Rahul Aggarwal
Juniper Networks
1194 North Mathilda Ave.
Sunnyvale, CA 94089
USA
Phone: +1-408-936-2720
Email: rahul@juniper.net
Yuji Kamite
NTT Communications Corporation
Tokyo Opera City Tower
3-20-2 Nishi Shinjuku, Shinjuku-ku,
Tokyo 163-1421,
Japan
Email: y.kamite@ntt.com
Luyuan Fang
Cisco Systems
300 Beaver Brook Road
BOXBOROUGH, MA 01719
USA
Email: lufang@cisco.com
Yakov Rekhter
Juniper Networks
1194 North Mathilda Ave.
Sunnyvale, CA 94089
USA
Email: yakov@juniper.net
Chaitanya Kodeboniya
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on the procedures with respect to rights in RFC documents can be
Raggarwa, Kamite & Fang [Page 40]
Internet Draft draft-ietf-l2vpn-vpls-mcast-03.txt November 2007
found in BCP 78 and BCP 79.
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Raggarwa, Kamite & Fang [Page 41]
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