Internet DRAFT - draft-ietf-l2vpn-vpls-pe-etree
draft-ietf-l2vpn-vpls-pe-etree
Network Working Group Y. Jiang, Ed.
Internet Draft L. Yong
Intended status: Standards Track Huawei
M. Paul
Deutsche Telekom
Expires: June 2016 December 18, 2015
Ethernet-Tree (E-Tree) Support in Virtual Private LAN Service (VPLS)
draft-ietf-l2vpn-vpls-pe-etree-11.txt
Abstract
This document specifies a generic Virtual Private LAN Service (VPLS)
solution which uses VLANs to indicate root or leaf traffic to
support Ethernet-Tree (E-Tree) services. A VPLS Provider Edge (PE)
model is illustrated as an example for the solution. In the solution,
E-Tree VPLS PEs are interconnected by Pseudo Wires (PWs) which carry
the VLAN indicating the E-Tree attribute. The MAC address-based
Ethernet forwarding engine and the PW work in the same way as
specified in RFC 4762 and RFC 4448 respectively. A signaling
mechanism is described to support E-Tree capability and VLAN mapping
negotiation.
Status of this Memo
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This Internet-Draft will expire on June 18, 2015.
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Copyright Notice
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Conventions used in this document ......................... 3
2. Terminology ............................................... 3
3. Introduction .............................................. 4
4. PE Model with E-Tree Support .............................. 5
4.1. Existing PE Models ..................................... 5
4.2. A New PE Model with E-Tree Support ..................... 8
5. PW for E-Tree Support ..................................... 9
5.1. PW Encapsulation ....................................... 9
5.2. VLAN Mapping .......................................... 10
5.3. PW Processing ......................................... 11
5.3.1. PW Processing in the VLAN Mapping Mode .......... 11
5.3.2. PW Processing in the Compatible Mode ............ 12
5.3.3. PW Processing in the Optimized Mode ............. 13
6. Signaling for E-Tree Support ............................. 14
6.1. LDP Extensions for E-Tree Support ..................... 14
6.2. BGP Extensions for E-Tree Support ..................... 16
7. OAM Considerations ....................................... 19
8. Applicability ............................................ 19
9. Security Considerations .................................. 19
10. IANA Considerations ...................................... 19
11. References ............................................... 20
11.1. Normative References ............................... 20
11.2. Informative References ............................. 21
12. Acknowledgments .......................................... 22
Appendix A. Other PE Models for E-Tree ........................ 23
A.1. A PE Model With a VSI and No bridge ................... 23
A.2. A PE Model With external E-Tree interface ............. 24
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1. Conventions used in this document
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. Terminology
AC: Attachment Circuit
B-VLAN: Backbone VLAN
C-VLAN: Customer VLAN
E-Tree: Ethernet Tree, a Rooted-Multipoint EVC service as defined in
[MEF6.2]
EVC: Ethernet Virtual Connection, as defined in [MEF4]
FIB: Forwarding Information Base, also known as forwarding table
I-SID: Backbone Service Instance Identifier, as defined in IEEE
802.1ah
Leaf AC: an AC attached with a leaf
Leaf VLAN: a VLAN Identifier (ID) used to indicate all the frames
that are originated at a leaf AC, it may be a C-VLAN, an S-VLAN or a
B-VLAN
OAM: Operations, Administration and Maintenance
PBB: Provider Backbone Bridge
PE: Provider Edge
PW: Pseudo Wire
Root AC: an AC attached with a root
Root VLAN: a VLAN ID used to indicate all the frames that are
originated at a root AC, it may be a C-VLAN, an S-VLAN or a B-VLAN
S-VLAN: Service VLAN
T-VSI: Tree VSI, a VSI with E-Tree support
VLAN: Virtual Local Area Network
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VPLS: Virtual Private LAN Service
VSI: Virtual Switching Instance as defined in [RFC4664], also known
as VPLS Forwarder in [RFC7041]
3. Introduction
The Ethernet-Tree (E-Tree) service is defined in Metro Ethernet
Forum (MEF) Technical Specification MEF 6.2 [MEF6.2] as a Rooted-
Multipoint Ethernet Virtual Connection (EVC) service. An MEF 6.2 E-
Tree solution must meet the following design requirements: the
Ethernet frames from a root may be received by any other root or
leaf, and the frames from a leaf may be received by any root, but
must not be received by a leaf. Further, an E-Tree service may
include multiple roots and multiple leaves. Although Virtual Private
Multicast Service (VPMS) [VPMS] or Point-to-Multipoint (P2MP)
multicast is a somewhat simplified version of this service, in fact,
they are both multicast services and are different from an E-Tree
service which may include both unicast and multicast traffic.
[RFC7152] gives the requirements for providing E-Tree solutions in
the VPLS and the need to filter leaf-to-leaf traffic. [RFC7387]
further describes a Multiprotocol Label Switching (MPLS) framework
for providing E-Tree. Though there were proposals on using the
Pseudowire (PW) control word or PWs to indicate the root/leaf
attribute of an E-Tree frame, both methods are limited in that they
are only applicable to "VPLS only" networks.
A VPLS PE usually consists of a bridge module itself (see [RFC4664]
and [RFC6246]); and moreover, E-Tree services may cross both
Ethernet and VPLS domains. Therefore, it is necessary to develop an
E-Tree solution both for "VPLS only" scenarios and for interworking
between Ethernet and VPLS.
IEEE 802.1 has incorporated the generic E-Tree solution into 802.1Q
[802.1Q-2014], which is an improvement on the traditional asymmetric
VLAN mechanism. In the asymmetric VLAN mechanism as described in
Section B.1.3 of IEEE 802.1Q-2003 [802.1Q-2003], a VLAN ID is used
to indicate the traffic from a server, and multiple VLAN IDs are
used to indicate the traffic from the clients (one VLAN ID per
client). In the new IEEE 802.1Q solution, only two VLANs are used to
indicate root/leaf attributes of a frame: one VLAN ID is used to
indicate the frames originated from the roots and another VLAN ID is
used to indicate the frames originated from the leaves. At a leaf
port, the bridge can then filter out all the frames from other leaf
ports based on the VLAN ID. It is better to reuse the same mechanism
in VPLS than to develop a new mechanism. A new mechanism would
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introduce more complexity to interwork with the new IEEE 802.1Q
solution.
This document specifies how the Ethernet VLAN solution can be used
to support generic E-Tree services in VPLS. The solution specified
here is fully compatible with the IEEE bridge architecture and with
IETF Pseudo Wire Emulation Edge-to-Edge (PWE3) technology, thus it
will not change the FIB (such as installing E-Tree attributes in the
FIB), or need any specially tailored implementation. Furthermore,
VPLS scalability and simplicity are also maintained. With this
mechanism, it is also convenient to deploy a converged E-Tree
service across both Ethernet and MPLS networks.
A typical VPLS PE model is introduced as an example; the model is
then extended in which a Tree VSI is connected to a VLAN bridge with
a dual-VLAN interface.
The document then discusses the PW encapsulation and PW processing
such as VLAN mapping options for transporting E-Tree services in
VPLS.
Finally, the document describes the signaling extensions and
processing procedures for E-Tree support in VPLS.
4. PE Model with E-Tree Support
The problem scenario of E-Tree as shown in Fig. 1 of [RFC7152] is a
simplification of the L2VPN architecture, several common VPLS PE
architectures are discussed in more details in [RFC4664] and
[RFC6246].
Below, an E-Tree solution in VPLS is demonstrated with the help of a
typical VPLS PE model. Its use in other PE models is discussed in
Appendix A.
4.1. Existing PE Models
According to [RFC4664], there are at least three models possible for
a VPLS PE, including:
o A single bridge module, a single VSI;
o A single bridge module, multiple VSIs;
o Multiple bridge modules, each attaches to a VSI.
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The second PE model is commonly used. A typical example is further
depicted in Fig. 1 and Fig. 2 (both figures are extracted from
[RFC6246]), where an S-VLAN bridge module is connected to multiple
VSIs each with a single VLAN virtual interface.
+-------------------------------+
| 802.1ad Bridge Module Model |
| |
+---+ AC | +------+ +-----------+ |
|CE |---------|C-VLAN|------| | |
+---+ | |bridge|------| | |
| +------+ | | |
| o | S-VLAN | |
| o | | | ---> to VSI
| o | Bridge | |
+---+ AC | +------+ | | |
|CE |---------|C-VLAN|------| | |
+---+ | |bridge|------| | |
| +------+ +-----------+ |
+-------------------------------+
Figure 1 A model of 802.1ad Bridge Module
+----------------------------------------+
| VPLS-capable PE model |
| +---------------+ +------+ |
| | | |VSI-1 |------------
| | |==========| |------------ PWs
| | Bridge ------------ |------------
| | | S-VLAN-1 +------+ |
| | Module | o |
| | | o |
| | (802.1ad | o |
| | bridge) | o |
| | | o |
| | | S-VLAN-n +------+ |
| | ------------VSI-n |-------------
| | |==========| |------------- PWs
| | | ^ | |-------------
| +---------------+ | +------+ |
| | |
+-------------------------|--------------+
LAN emulation Interface
Figure 2 A VPLS-capable PE Model
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In this PE model, Ethernet frames from Customer Edges (CEs) will
cross multiple stages of bridge modules (i.e., C-VLAN and S-VLAN
bridge) and a VSI in a PE before being sent on the PW to a remote PE.
Therefore, the association between an AC port and a PW on a VSI is
difficult.
This model could be further enhanced: When Ethernet frames arrive at
an ingress PE, a root VLAN or a leaf VLAN tag is added. At an egress
PE, the frames with the root VLAN tag are transmitted both to the
roots and the leaves, while the frames with the leaf VLAN tag are
transmitted to the roots but dropped for the leaves (these VLAN tags
are removed before the frames are transmitted over the ACs). It was
demonstrated in [802.1Q-2014] that the E-Tree service in Ethernet
networks can be well supported with this mechanism.
Assuming this mechanism is implemented in the bridge module, it is
quite straightforward to infer a VPLS PE model with two VSIs to
support the E-Tree (as shown in Fig. 3). But this model will require
two VSIs per PE and two sets of PWs per E-Tree service, which is
poorly scalable in a large MPLS/VPLS network; in addition, both
these VSIs have to share their learned MAC addresses.
+----------------------------------------+
| VPLS-capable PE model |
| +---------------+ +------+ |
| | | |VSI-1 |------------
| | |==========| |------------ PWs
| | Bridge ------------ |------------
| | | Root +------+ |
| | Module | S-VLAN |
| | | |
| | (802.1ad | |
| | bridge) | |
| | | Leaf |
| | | S-VLAN +------+ |
| | ------------VSI-2 |-------------
| | |==========| |------------- PWs
| | | ^ | |-------------
| +---------------+ | +------+ |
| | |
+-------------------------|--------------+
LAN emulation Interface
Figure 3 A VPLS PE Model for E-Tree with 2 VSIs
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4.2. A New PE Model with E-Tree Support
In order to support the E-Tree in a more scalable way, a new VPLS PE
model with a single Tree VSI (T-VSI, a VSI with E-Tree support) is
specified. As depicted in Fig. 4, the bridge module is connected to
the T-VSI with a dual-VLAN virtual interface, i.e., both the root
VLAN and the leaf VLAN are connected to the same T-VSI, and they
share the same FIB and work in shared VLAN learning. In this way,
only one VPLS instance and one set of PWs is needed per E-Tree
service, and the scalability of VPLS is improved.
+----------------------------------------+
| VPLS-capable PE model |
| +---------------+ +------+ |
| | |==========|TVSI-1|------------
+---+ AC | | ------------ |------------ PWs
|CE |--------| Bridge ------------ |------------
+---+ | | | Root & +------+ |
| | Module | Leaf VLAN o |
| | | o |
| | | o |
| | | o |
| | | o |
+---+ AC | | | VLAN-n +------+ |
|CE |--------| ------------VSI-n |-------------
+---+ | | |==========| |------------- PWs
| | | ^ | |-------------
| +---------------+ | +------+ |
| | |
+-------------------------|--------------+
LAN emulation Interface
Figure 4 A VPLS PE Model for E-Tree with a Single T-VSI
For an untagged AC port (frames over this port are untagged) or
VLAN-unaware port (VLAN tags in the frames are ignored), and the
bridge module is a C-VLAN bridge, the Ethernet frames received from
the root ACs MUST be tagged with a root C-VLAN. When the bridge
module is an 802.1ad bridge, the Ethernet frames received from the
root ACs MUST be tagged with a root S-VLAN. Note, this can be done
by adding a root C-VLAN first in a C-VLAN bridge but this is out of
the scope of this document.
For a C-VLAN tagged port, the Ethernet frames received from the root
ACs MUST be tagged with a root S-VLAN.
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For an S-VLAN tagged port, the S-VLAN tag in the Ethernet frames
received from the root ACs SHOULD be translated to the root S-VLAN
in the VPLS network domain.
Alternatively, for an S-VLAN tagged port, the PBB VPLS PE model
(where an IEEE 802.1ah bridge module is embedded in the PE) as
described in [RFC7041] MAY be used. A root B-VLAN or leaf B-VLAN MAY
be added. The E-Tree attribute may also be indicated with two I-SID
tags in the bridge module, and the frames are then encapsulated and
transported transparently over a single B-VLAN. Thus the PBB VPLS
works in the same way as described in [RFC7041] and will not be
discussed further in this document. When many S-VLANs are
multiplexed in a single AC, PBB VPLS has the advantages of both VLAN
scalability and MAC address scalability.
In a similar way, the traffic from the leaf ACs is tagged and
transported on the leaf C-VLAN, S-VLAN or B-VLAN.
In all cases, the outermost VLAN in the resulting Ethernet header is
used to indicate the E-Tree attribute of an Ethernet frame; this
document uses VLAN to refer to this outermost VLAN for simplicity in
the latter sections.
5. PW for E-Tree Support
5.1. PW Encapsulation
To support an E-Tree service, T-VSIs in a VPLS MUST be
interconnected with a bidirectional Ethernet PW. The Ethernet PW
SHOULD work in the tagged mode (PW type 0x0004) as described in
[RFC4448], in which case a VLAN tag MUST be carried in each frame in
the PW to indicate the frame originated from either root or leaf
(the VLAN tag indicating the frame originated from either root or
leaf can be translated by a bridge module in the PE or added by an
outside Ethernet edge device, even by a customer device). In the
tagged PW mode, two service delimiting VLANs MUST be allocated in
the VPLS domain for an E-Tree. PW processing for the tagged PW will
be described in Section 5.3 of this document.
A raw mode PW (PW type 0x0005 in [RFC4448]) MAY also be used to
carry E-Tree service for a PW in Compatible mode as shown in Section
5.3.2. As defined in [RFC4448], for a raw mode PW, an Ethernet
frame's 802.1Q VLAN tag is not meaningful to the PEs and it passes
transparently through them.
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5.2. VLAN Mapping
There are two ways of manipulating VLANs for an E-Tree in VPLS:
o Global VLAN based, that is, provisioning two global VLANs (Root
VLAN, Leaf VLAN) across the VPLS network, thus no VLAN mapping is
needed at all, or the VLAN mapping is done completely in the
Ethernet domains.
o Local VLAN based, that is, provisioning two local VLANs for each
PE (which participates in the E-Tree) in the VPLS network
independently.
The first method requires no VLAN mapping in the PW, but two unique
service delimiting VLANs must be allocated across the VPLS domain.
The second method is more scalable in the use of VLANs, but needs a
VLAN mapping mechanism in the PW similar to what is already
described in Section 4.3 of [RFC4448].
Global or local VLANs can be manually configured or provisioned by
an Operational Support System. Alternatively, some automatic VLAN
allocation algorithm may be provided in the management plane, but it
is out of scope of this document.
For both methods, VLAN mapping parameters from a remote PE can be
provisioned or determined by a signaling protocol as described in
Section 6 when a PW is being established.
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5.3. PW Processing
5.3.1. PW Processing in the VLAN Mapping Mode
In the VLAN Mapping mode, two VPLS PEs with E-Tree capability are
inter-connected with a PW (For example, the scenario of Fig. 5
depicts the interconnection of two PEs attached with both root and
leaf nodes).
+----------------------------+
| VPLS PE with T-VSI |
| |
+----+ | +------+ Root VLAN +-----+ | PW
|Root|------| VLAN |-----------|T-VSI|----------
+----+ | | BRG | Leaf VLAN | |----------
+----+ | | |-----------| |----------
|Leaf|------| | | |-----+
+----+ | +------+ +-----+ | |
| | |
+----------------------------+ |
|
+----------------------------+ |
| VPLS PE with T-VSI | |
| | |
+----+ | +------+ Root VLAN +-----+ | | PW
|Root|------| VLAN |-----------|T-VSI|-----+
+----+ | | BRG | Leaf VLAN | |----------
+----+ | | |-----------| |----------
|Leaf|------| | | |----------
+----+ | +------+ +-----+ |
| | BRG: Bridge Module
+----------------------------+
Figure 5 T-VSI Interconnected in the Normal Mode
If a PE is in the VLAN mapping mode for a PW, then in the data plane
the PE MUST map the VLAN in each frame as follows:
o Upon transmitting frames on the PW, map from local VLAN to remote
VLAN (i.e., the local leaf VLAN in a frame is translated to the
remote leaf VLAN; the local root VLAN in a frame is translated to
the remote root VLAN).
o Upon receiving frames on the PW, map from remote VLAN to local
VLAN, and the frames are further forwarded or dropped in the egress
bridge module using the filtering mechanism as described in [802.1Q-
2014].
The signaling for VLANs used by E-Tree is specified in Section 6.
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5.3.2. PW Processing in the Compatible Mode
The new VPLS PE model can work in a traditional VPLS network
seamlessly in the compatibility mode. As shown in Fig. 6, the VPLS
PE with T-VSI can be attached with root and/or leaf nodes, while the
VPLS PE with a traditional VSI can only be attached with root nodes.
A raw PW SHOULD be used to connect them.
+------------------------+
| VPLS PE with T-VSI |
| |
+----+ | +------+ +-----+ | PW
|Root|------| VLAN |-------|T-VSI|----------
+----+ | | BRG | | |----------
+----+ | | |-------| |----------
|Leaf|------| | | |---------+
+----+ | +------+ +-----+ | |
| | |
+------------------------+ |
|
+------------------------+ |
| VPLS PE with VSI | |
| | |
+----+ | +------+ +-----+ | PW |
|Root|------| VLAN |-------|VSI |---------+
+----+ | | BRG | | |----------
+----+ | | | | |----------
|Root|------| | | |----------
+----+ | +------+ +-----+ |
| |
+------------------------+
Figure 6 T-VSI interconnected with Traditional VSI
If a PE is in the Compatible mode for a PW, then in the data plane
the PE MUST process the frame as follows:
o Upon transmitting frames on the PW, remove the root or leaf VLAN
in the frames.
o Upon receiving frames on the PW, add a VLAN tag with a value of
the local root VLAN to the frames.
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5.3.3. PW Processing in the Optimized Mode
When two PEs (both have E-Tree capability) are inter-connected with
a PW and one of them (e.g., PE2) is attached with only leaf nodes,
as shown in the scenario of Fig. 7, its peer PE (e.g., PE1) should
then work in the optimized mode for this PW. In this case, PE1
should not send the frames originated from the local leaf VLAN to
PE2, i.e., these frames are dropped rather than transported over the
PW. The bandwidth efficiency of the VPLS can thus be improved. The
signaling for the PE attached with only leaf nodes is specified in
Section 6.
+------------------------+
|VPLS PE with T-VSI (PE1)|
| |
+----+ | +------+ +-----+ | PW
|Root|------| VLAN |-------|T-VSI|----------
+----+ | | BRG | | |----------
+----+ | | |-------| |----------
|Leaf|------| | | |---------+
+----+ | +------+ +-----+ | |
| | |
+------------------------+ |
|
+------------------------+ |
|VPLS PE with T-VSI (PE2)| |
| | |
+----+ | +------+ +-----+ | PW |
|Leaf|------| VLAN |-------|T-VSI|---------+
+----+ | | BRG | | |----------
+----+ | | |-------| |----------
|Leaf|------| | | |----------
+----+ | +------+ +-----+ |
| |
+------------------------+
Figure 7 T-VSI interconnected with PE attached with only leaf nodes
If a PE is in the Optimized Mode for a PW, upon transmit, the PE
SHOULD first operate as follows:
o Drop a frame if its VLAN ID matches the local leaf VLAN ID.
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6. Signaling for E-Tree Support
6.1. LDP Extensions for E-Tree Support
In addition to the signaling procedures as specified in Section
5.3.3 of [RFC4447], this document specifies a new interface
parameter sub-TLV to provision an E-Tree service and negotiate the
VLAN mapping function, as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| E-Tree(0x1A) | Length=8 | Reserved |P|V|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ | Root VLAN ID | MBZ | Leaf VLAN ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8 E-Tree Sub-TLV
Where:
o E-Tree is the sub-TLV identifier (0x1A) as assigned by IANA.
o Length is the length of the sub TLV in octets.
o Reserved, bits MUST be set to zero on transmit and be ignored on
receive.
o P is a Leaf-only bit, it is set to 1 to indicate that the PE is
attached with only leaf nodes, and set to 0 otherwise.
o V is a bit indicating the sender's VLAN mapping capability. A PE
capable of VLAN mapping MUST set this bit, and clear it otherwise.
o MBZ, Must Be Zero, 4 bits MUST be set to zero on transmit and be
ignored on receive.
o Root VLAN ID is the value of the local root VLAN.
o Leaf VLAN ID is the value of the local leaf VLAN.
When setting up a PW for the E-Tree based VPLS, two peer PEs
negotiate the E-Tree support using the above E-Tree sub-TLV. Note PW
type of 0x0004 SHOULD be used during the PW negotiation.
A PE that wishes to support E-Tree service MUST include an E-Tree
Sub-TLV in its PW label mapping message and include its local root
VLAN ID and leaf VLAN ID in the TLV. A PE that has the VLAN mapping
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capability MUST set the V bit to 1, and a PE attached with only leaf
nodes SHOULD set the P bit to 1.
A PE that receives a PW label mapping message with an E-Tree Sub-TLV
from its peer PE, after saving the VLAN information for the PW, MUST
process it as follows:
1) For this PW, set VLAN-Mapping-Mode, Compatible-Mode, and
Optimized-Mode to FALSE.
2) If either the root VLAN ID in the message is not equal to the
local root VLAN ID or the leaf VLAN ID in the message is not equal
to the local leaf VLAN ID {
If the bit V is cleared {
If the PE is capable of VLAN mapping, it MUST set VLAN-
Mapping-Mode to TRUE;
Else {
A label release message with the error code "E-
Tree VLAN mapping not supported" is sent to the
peer PE and exit the process;
}
}
If the bit V is set, and the PE is capable of VLAN mapping,
the PE with the minimum IP address MUST set VLAN-Mapping-Mode
to TRUE;
}
3) If the P bit is set
{
If the PE is a leaf-only node itself, a label release message
with a status code "Leaf to Leaf PW released" is sent to the peer
PE and exit the process;
Else the PE SHOULD set the Optimized-Mode to TRUE.
}
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A PE SHOULD send a Label Mapping message with an E-Tree Sub-TLV as
per Section 5.3.3 of [RFC4447]. A PE MUST send a Label Mapping
message with an updated E-Tree Sub-TLV to all other PEs over
corresponding LDP sessions when its role changes from leaf-only to
not leaf-only (i.e., when a root node is added to a PE attached with
only leaf nodes).
If a PE has sent a Label Mapping message with an E-Tree Sub-TLV but
does not receive any E-Tree Sub-TLV in its peer's PW label mapping
message, The PE SHOULD then establish a raw PW with this peer as in
traditional VPLS and set Compatible-Mode to TRUE for this PW.
Data plane processing for this PW is as following:
If Optimized-Mode is TRUE, then data plane processing as described
in Section 5.3.3 applies.
If VLAN-Mapping-Mode is TRUE, then data plane processing as
described in Section 5.3.1 applies.
If Compatible-Mode is TRUE, then data plane processing is as
described in Section 5.3.2.
PW processing as described in [RFC4448] proceeds as usual for all
cases.
When VPLS is set up using Pseudowire ID (PWid) Forwarding
Equivalence Class (FEC) Element (see Appendix A of [RFC4762]), its
E-Tree signaling is similar to the above process. Dynamic re-
configuration of E-Tree should be avoided for this case, however,
when re-configuration of E-Tree is forced on a PE for some reason
(e.g., a configuration error), the PE may close the LDP sessions
with its peer PEs for this VPLS instance, and re-install its PW
labels, so that its peer PEs can send out the LDP label mapping
messages again.
6.2. BGP Extensions for E-Tree Support
A new E-Tree extended community (0x800b) is allocated by IANA for E-
Tree signaling in BGP VPLS:
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+------------------------------------+
| Extended community type (2 octets) |
+------------------------------------+
| MBZ | Root VLAN (12 bits) |
+------------------------------------+
| MBZ | Leaf VLAN (12 bits) |
+------------------------------------+
| Reserved |P|V|
+------------------------------------+
Figure 9 E-Tree Extended Community
Where:
o MBZ, Must Be Zero, 4 bits MUST be set to zero on transmit and be
ignored on receive.
o Root VLAN ID is the value of the local root VLAN.
o Leaf VLAN ID is the value of the local leaf VLAN.
o Reserved, 14 bits MUST be set to zero on transmit and be ignored
on receive.
o P is a Leaf-only bit, it is set to 1 to indicate that the PE is
attached with only leaf nodes, and set to 0 otherwise.
o V is a bit indicating the sender's VLAN mapping capability. A PE
capable of VLAN mapping MUST set this bit, and clear it otherwise.
The PEs attached with both leaf and root nodes MUST support BGP E-
Tree signaling as described in this document, and SHOULD support
VLAN mapping in their data planes. The traditional PE attached with
only root nodes may also participate in an E-Tree service. If some
PEs don't support VLAN mapping, global VLANs as per Section 5.2 MUST
be provisioned for an E-Tree service.
In BGP VPLS signaling, besides attaching a Layer2 Info Extended
Community as detailed in [RFC4761], an E-Tree Extended Community
MUST be further attached if a PE wishes to participate in an E-Tree
service. The PE MUST include its local root VLAN ID and leaf VLAN ID
in the E-Tree Extended Community. A PE attached with only leaf nodes
of an E-Tree SHOULD set the P bit in the E-Tree Extended Community
to 1.
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A PE that receives a BGP UPDATE message with an E-Tree Extended
Community from its peer PE, after saving the VLAN information for
the PW, MUST process it as follows (after processing procedures as
specified in Section 3.2 of [RFC4761]):
1) For this PW, set VLAN-Mapping-Mode, Compatible-Mode, and
Optimized-Mode to FALSE.
2) If either the root VLAN ID in the E-Tree Extended Community is
not equal to the local root VLAN ID or the leaf VLAN ID in the E-
Tree Extended Community is not equal to the local leaf VLAN ID {
If the bit V is cleared {
If the PE is capable of VLAN mapping, it MUST set VLAN-
Mapping-Mode to TRUE;
Else {
Log with a message "E-Tree VLAN mapping not
supported" and exit the process;
}
}
If the bit V is set, and the PE is capable of VLAN mapping,
the PE with the minimum IP address MUST set VLAN-Mapping-Mode
to TRUE;
}
3) If the P bit is set {
If the PE is a leaf-only PE itself, forbids any traffic on the
PW;
Else the PE SHOULD set the Optimized-Mode to TRUE.
}
A PE which does not recognize this attribute SHALL ignore it
silently. If a PE has sent an E-Tree Extended Community but does not
receive any E-Tree Extended Community from its peer, the PE SHOULD
then establish a raw PW with this peer as in traditional VPLS, and
set Compatible-Mode to TRUE for this PW.
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Data plane in the VPLS is the same as described in Section 4.2 of
[RFC4761], and data plane processing for a PW is the same as
described at the end of Section 6.1 in this document.
7. OAM Considerations
VPLS OAM requirements and framework as specified in [RFC6136] are
applicable to E-Tree, as both Ethernet OAM frames and data traffic
are transported over the same PW.
Ethernet OAM for E-Tree including both service OAM and segment OAM
frames SHALL undergo the same VLAN mapping as the data traffic; and
root VLAN SHOULD be applied to segment OAM frames so that they are
not filtered.
8. Applicability
The solution specified in this document is applicable to both LDP
VPLS [RFC4762] and BGP VPLS [RFC4761].
This solution is applicable to both "VPLS Only" networks and VPLS
with Ethernet aggregation networks.
This solution is also applicable to PBB VPLS networks.
9. Security Considerations
This solution requires implementations to prevent leaf to leaf
communication in the data plane of VPLS when its PEs are
interconnected with PWs. If all PEs enforce that then network
attacks from one leaf to another leaf are avoided, and security can
be enhanced for customers with this solution. However, if a PE is
compromised or inappropriately configured, a leaf node may be taken
as a root node and may receive traffic from other leaf nodes
inappropriately. Authenticity and integrity measures for LDP need to
be considered as in RFC 5036 [RFC5036]. Security considerations as
described in [RFC4448], [RFC4761] and [RFC4762] also apply.
10. IANA Considerations
IANA allocated a value for E-Tree in the registry of Pseudowire
Interface Parameters Sub-TLV type.
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Parameter ID Length Description
=======================================
0x1A 8 E-Tree
IANA allocated two new LDP status codes from the registry of name
"STATUS CODE NAME SPACE".
Range/Value E Description
------------- ----- ----------------------
0x20000003 1 E-Tree VLAN mapping not supported
0x20000004 0 Leaf to Leaf PW released
IANA allocated a value for E-Tree in the registry of BGP Extended
Community.
Type Value Sub-Type Value Name
========== ============== ============
0x80 0x0b E-Tree Info
11. References
11.1. Normative References
[802.1Q-2014] IEEE Std 802.1Q-2014, Bridges and Bridged Networks,
November 2014.
[MEF6.2] Metro Ethernet Forum, "EVC Ethernet Services Definitions
Phase 3", Technical Specification MEF 6.2, August 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and Heron,
G., "Pseudowire Setup and Maintenance Using Label
Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC4448] Martini, L., Rosen, E., El-Aawar, N., and Heron,G.,
"Encapsulation Methods for Transport of Ethernet over MPLS
Networks", RFC 4448, April 2006.
[RFC4761] Kompella, K., and Rekhter, Y., "Virtual Private LAN
Service (VPLS) Using BGP for Auto-Discovery and Signaling",
RFC 4761, January 2007.
[RFC4762] Lasserre, M. and Kompella, V., "Virtual Private LAN
Services using LDP", RFC 4762, January 2007.
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[RFC5036] Andersson, L. Minei, I. and Thomas, B., "LDP
Specification", RFC 5036, October 2007.
11.2. Informative References
[802.1Q-2003] IEEE Std 802.1Q-2003, Virtual Bridged Local Area
Networks, May 2003.
[MEF4] Metro Ethernet Forum, Metro Ethernet Network Architecture
Framework - Part 1: Generic Framework, Technical
Specification MEF 4, May 2004.
[RFC3985] Bryant, S., and Pate, P., "Pseudo Wire Emulation Edge-to-
Edge (PWE3) Architecture", RFC 3985, March 2005.
[RFC4664] Andersson, L., and Rosen, E., "Framework for Layer 2
Virtual Private Networks (L2VPNs)", RFC 4664, September
2006.
[RFC6136] Sajassi, A. and Mohan, D., "L2VPN OAM Requirements and
Framework", RFC 6136, March 2011.
[RFC6246] Sajassi, A., Brockners, F., Mohan, D., and Serbest, Y.,
"Virtual Private LAN Service (VPLS) Interoperability with
Customer Edge (CE) Bridges", RFC 6246, June 2011.
[RFC7041] Balus, F., Sajassi, A., and Bitar, N., Extensions to VPLS
PE model for Provider Backbone Bridging, RFC 7041,
November 2013.
[RFC7152] Key, R., DeLord, S., Jounay, F., Huang, L., Liu, Z., and M.
Paul, "Requirements for Metro Ethernet Forum (MEF)
Ethernet-Tree (E-Tree) Support in Layer 2 Virtual Private
Network (L2VPN)", RFC 7152, March 2014.
[RFC7387] Key, R., Yong, L., DeLord, S., Jounay, F., and Jin, L., "A
Framework for Ethernet Tree (E-Tree) Service over a
Multiprotocol Label Switching (MPLS) Network", RFC 7387,
October 2014.
[VPMS] Kamite, Y., Jounay, F., Niven-Jenkins, B., Brungard, D.,
and L. Jin, "Framework and Requirements for Virtual
Private Multicast Service (VPMS)", Work in Progress,
draft-ietf-l2vpn-vpms-frmwk-requirements-05, October 2012.
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12. Acknowledgments
The authors would like to thank Stewart Bryant, Lizhong Jin, Deborah
Brungard, Russ Housley, Stephen Farrell, Sheng Jiang, Alvaro Retana
and Ben Campbell for their detailed reviews and suggestions, thank
Adrian Farrel, Susan Hares, Shane Amante and Andrew Malis for their
valuable advices, thank Ben Mack-crane, Edwin Mallette, Donald Fedyk,
Dave Allan, Giles Heron, Raymond Key, Josh Rogers, Sam Cao and
Daniel Cohn for their valuable comments and discussions.
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Appendix A. Other PE Models for E-Tree
A.1. A PE Model With a VSI and No bridge
If there is no bridge module in a PE, the PE may consist of Native
Service Processors (NSPs) as shown in Figure A.1 (adapted from Fig.
5 of [RFC3985]) where any transformation operation for VLANs (e.g.,
VLAN insertion/removal or VLAN mapping) may be applied. Thus a root
VLAN or leaf VLAN can be added by the NSP depending on the User
Network Interface (UNI) type (root/leaf) associated with the AC over
which the packet arrives.
Further, when a packet with a leaf VLAN exits a forwarder and
arrives at the NSP, the NSP must drop the packet if the egress AC is
associated with a leaf UNI.
Tagged PW and VLAN mapping work in the same way as in the typical PE
model.
+----------------------------------------+
| PE Device |
Multiple+----------------------------------------+
AC | | | Single | PW Instance
<------>o NSP # + PW Instance X<---------->
| | | |
|------| VSI |----------------------|
| | | Single | PW Instance
<------>o NSP #Forwarder + PW Instance X<---------->
| | | |
|------| |----------------------|
| | | Single | PW Instance
<------>o NSP # + PW Instance X<---------->
| | | |
+----------------------------------------+
Figure A.1 A PE model with a VSI and no bridge module
This PE model may be used by a Multi-Tenant Unit switch (MTU-s) in a
Hierarchical VPLS (H-VPLS) network, or a Network-facing PE (N-PE) in
an H-VPLS network with non-bridging edge devices, wherein a spoke PW
can be treated as an AC in this model.
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A.2. A PE Model With external E-Tree interface
+----------------------------------------+
| PE Device |
Root +----------------------------------------+
VLAN | | Single | PW Instance
<------>o + PW Instance X<---------->
| | |
| VSI |----------------------|
| | Single | PW Instance
| Forwarder + PW Instance X<---------->
| | |
Leaf | |----------------------|
VLAN | | Single | PW Instance
<------>o + PW Instance X<---------->
| | |
+----------------------------------------+
Figure A.2 A PE model with external E-Tree interface
A more simplified PE model is depicted in A.2, where Root/Leaf VLANs
are directly or indirectly over a single PW connected to a same VSI
forwarder in a PE, any transformation of E-Tree VLANs, e.g., VLAN
insertion/removal or VLAN mapping, can be performed by some outer
equipments, and the PE may further translate these VLANs into its
own local VLANs. This PE model may be used by an N-PE in an H-VPLS
network with bridging-capable devices, or scenarios such as
providing E-Tree Network-to-Network interfaces.
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Authors' Addresses
Yuanlong Jiang
Huawei Technologies Co., Ltd.
Bantian, Longgang district
Shenzhen 518129, China
Email: jiangyuanlong@huawei.com
Lucy Yong
Huawei USA
207 Estrella Xing
Georgetown TX, USA 78628
Email: lucyyong@huawei.com
Manuel Paul
Deutsche Telekom
Winterfeldtstr. 21
10781 Berlin, Germany
Email: manuel.paul@telekom.de
Frederic Jounay
Orange CH
4 rue caudray 1020 Renens, Switzerland
Email: frederic.jounay@orange.ch
Florin Balus
Alcatel-Lucent
701 E. Middlefield Road
Mountain View, CA, USA 94043
Email: florin.balus@alcatel-lucent.com
Wim Henderickx
Alcatel-Lucent
Copernicuslaan 50
2018 Antwerp, Belgium
Email: wim.henderickx@alcatel-lucent.com
Ali Sajassi
Cisco
170 West Tasman Drive
San Jose, CA 95134, USA
Email: sajassi@cisco.com
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