Internet DRAFT - draft-jiang-l2vpn-vpls-pe-etree
draft-jiang-l2vpn-vpls-pe-etree
Internet Working Group Y. Jiang
L. Yong
Internet Draft Huawei
Intended status: Standards Track M. Paul
Deutsche Telekom
F. Jounay
Orange CH
F. Balus
W. Henderickx
Alcatel-Lucent
A. Sajassi
Cisco
Expires: December 2012 June 14, 2012
VPLS PE Model for E-Tree Support
draft-jiang-l2vpn-vpls-pe-etree-06.txt
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Abstract
A generic VPLS solution for E-Tree services is proposed which uses
VLANs to indicate root/leaf traffic. A VPLS Provider Edge (PE) model
is illustrated as an example for the solution. In the solution, E-
Tree VPLS PEs are interconnected by 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 before. A
signaling mechanism for E-Tree capability and VLAN mapping
negotiation is further described.
Table of Contents
1. Introduction .............................................. 3
2. Conventions used in this document ......................... 4
3. Terminology ............................................... 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 ........................................... 9
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. LDP Extensions for E-Tree Support ........................ 14
7. BGP Extensions for E-Tree Support ........................ 16
8. OAM Considerations ....................................... 17
9. Applicability ............................................ 18
10. Security Considerations .................................. 18
11. IANA Considerations ...................................... 18
12. References ............................................... 19
12.1. Normative References ............................... 19
12.2. Informative References ............................. 19
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13. Acknowledgments ........................................... 20
Appendix A. Other PE Models for E-Tree ......................... 21
A.1. A PE Model With a VSI and No bridge .................... 21
A.2. A PE Model With external E-Tree interface .............. 22
1. Introduction
The E-Tree service is defined in Metro Ethernet Forum (MEF) as a
Rooted-Multipoint EVC service. It is a multipoint Ethernet service
with special restrictions: the 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 VPMS
or P2MP multicast is a somewhat simplified version of this service,
in fact, there is no exact corresponding terminology in IETF.
[Etree-req] gives the requirements for providing E-Tree solutions in
the VPLS and the need to filter leaf-to-leaf traffic.
[Vpls-etree] describes a PW control word based E-Tree solution, where
a bit in the PW control word is used to indicate the root/leaf
attribute for a packet. The Ethernet forwarder in the VPLS is also
extended to filter the leaf-to-leaf traffic based on the <ingress
port, egress port, CW L-bit> tuple.
[Etree-2PW] proposes another E-Tree solution where root and leaf
traffic are classified and forwarded in the same VSI but with two
separate PWs.
Both solutions are only applicable to "VPLS only" networks.
In fact, VPLS PE usually consists of a bridge module itself (see
[RFC4664] and [RFC6246]); 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 in the latest
version of 802.1Q [802.1aq], which is just an improvement on the
traditional asymmetric VLAN mechanism the use of different VLANs to
indicate E-Tree root/leaf attributes and prohibiting leaf-to-leaf
traffic with the help of VLANs was first standardized in IEEE 802.1Q-
2003 . In the solution, VLANs are used to indicate root/leaf
attribute of a packet: one VLAN ID is used to indicate the frames
originated from the roots and another VLAN ID is used to indicate the
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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. The latter will introduce more complexity to
interwork with IEEE 802.1Q solution.
This document introduces how the Ethernet VLAN solution can be used
to support generic E-Tree services in the VPLS. The solution proposed
here is fully compatible with the IEEE bridge architecture and the
IETF 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
is also well kept. With this mechanism, it is also convenient to
deploy a converged E-Tree service across both Ethernet and MPLS
networks.
Firstly, 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.
This document then discusses the PW encapsulation and PW processing
such as VLAN mapping options for transporting E-Tree services in a
VPLS.
Finally, it describes the signaling extensions for E-Tree support and
PE processing procedures.
2. 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].
3. Terminology
E-Tree: a Rooted-Multipoint EVC service as defined in MEF 6.1
EVC: Ethernet Virtual Connection, as defined in MEF 4.0
FIB: Forwarding Information Base, or forwarding table
T-VSI: Tree VSI, a VSI with E-Tree support
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Root AC, an AC attached with a root
Leaf AC, an AC attached with a leaf
C-VLAN, Customer VLAN
S-VLAN, Service VLAN
B-VLAN, Backbone VLAN
Root VLAN, a VLAN ID used to indicate all the frames that are
originated at a root AC
Leaf VLAN, a VLAN ID used to indicate all the frames that are
originated at a leaf AC
I-SID, Backbone Service Instance Identifier, as defined in IEEE
802.1ah
4. PE Model with E-Tree Support
"VPLS only" PE architecture as shown in Fig. 1 of [Etree-req] is a
simplification of the VPLS and PWE3 architecture, several common VPLS
PE architectures are discussed in more details in [RFC4664] and
[RFC6246].
Therefore, VLAN based E-Tree solution are demonstrated with the help
of a typical VPLS PE model. It can also be used by other PE models
which are 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.
The second PE model is commonly used. A typical example is further
depicted in Fig. 1 and Fig. 2 [RFC6246], where an S-VLAN bridge
module is connected to multiple VSIs each with a single VLAN virtual
interface.
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+-------------------------------+
| 802.1ad Bridge Module Model |
| |
+---+ | +------+ +-----------+ |
|CE |---------|C-VLAN|------| | |
+---+ | |bridge|------| | |
| +------+ | | |
| o | S-VLAN | |
| o | | |
| o | Bridge | |
+---+ | +------+ | | |
|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
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 as
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required in [Vpls-etree] or [Etree-2PW] is difficult, sometimes even
impossible.
This model could be further enhanced: When Ethernet frames arrive at
a PE, a root VLAN or a leaf VLAN tag is added. Then 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 wire). It was demonstrated in
[802.1aq] 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
proposed. 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 port (customer sites attached to the PEs with
untagged ports), the Ethernet frames received from the root ACs can
be tagged with a root C-VLAN, and optionally be added with another
root S-VLAN. Alternatively, the frames from the root ACs can be
tagged with the root S-VLAN tag directly in the VPLS network domain.
For a C-VLAN tagged port, the Ethernet frames received from the root
ACs can be added with a root S-VLAN. Alternatively, the C-VLAN can be
translated to the root S-VLAN in the VPLS network domain.
For an S-VLAN tagged port, the S-VLAN tag in the Ethernet frames
received from the root ACs can be translated to the root S-VLAN in
the VPLS network domain. Alternatively, the PBB VPLS PE model (where
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an IEEE 802.1ah bridge module is embedded in the PE) as described in
[PBB-VPLS] can be used, and a root B-VLAN or leaf B-VLAN can be added
in this case (the E-Tree attribute may also be indicated with two I-
SID tags in the bridge module, and the frames are further
encapsulated and transported transparently over a single B-VLAN, thus
the PBB VPLS works just in the same way as described in [PBB-VPLS]
and will be discussed no more in this document). When many S-VLANs
are multiplexed in a single AC, the 2nd option has an advantage 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 resulted Ethernet header is
used to indicate the E-Tree attribute of an Ethernet frame; this
document will use 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 may work in the
tagged mode (PW type 0x0004) as described in [RFC4448], and 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.
Raw PW (PW type 0x0005 in [RFC4448]) may be used to carry E-Tree
service for a PW in Compatible mode as shown in Section 5.3.2.
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.
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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
OSS system. Alternatively, some automatic VLAN allocation algorithm
may be provided in the management plane, but it is out 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 miscellaneously attached with
both root and leaf nodes).
+------------------------+
| VPLS PE with T-VSI |
| |
+----+ | +------+ +-----+ | PW
|Root|------| VLAN |-------|T-VSI|----------
+----+ | | BRG | | |----------
+----+ | | |-------| |----------
|Leaf|------| | | |---------+
+----+ | +------+ +-----+ | |
| | |
+------------------------+ |
|
+------------------------+ |
| VPLS PE with T-VSI | |
| | |
+----+ | +------+ +-----+ | PW |
|Root|------| VLAN |-------|T-VSI|---------+
+----+ | | BRG | | |----------
+----+ | | |-------| |----------
|Leaf|------| | | |----------
+----+ | +------+ +-----+ |
| |
+------------------------+
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 [802.1aq].
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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.
Raw PW should be used to connect with a traditional PE.
+------------------------+
| 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 are connected with their T-VSIs and one PE (e.g., PE2)
is attached with only leaf nodes, as shown in the scenario of Fig. 6,
the peer PE (e.g., PE1) should then work in the optimization mode. 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. LDP Extensions for E-Tree Support
In addition to the signaling procedures as specified in [RFC4447],
this document proposes 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 | Length=8 | Reserved |P|V|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Root VLAN ID | Leaf VLAN ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8 E-Tree Sub-TLV
Where:
o E-Tree is the sub-TLV identifier to be 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 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 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
capability MUST set the V bit to 1, and a PE is attached with only
leaf nodes SHOULD set the P bit to 1.
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In default, for each PW, VLAN-Mapping-Mode, Compatible-Mode, and
Optimized-Mode are all set to FALSE.
A PE that receives a PW label mapping message with an E-Tree Sub-TLV
from its peer PE must process it as follows:
1) if the root and leaf VLAN ID in the message match the local root
and leaf VLAN ID, then continue to 3);
2) else {
if the bit V is cleared, then {
if the PE is capable of VLAN mapping, then 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,
then the PE with the minimum IP address MUST set VLAN-Mapping-
Mode to TRUE;
}
3) If the P bit is set, then:
{
If the PE is a leaf-only node itself, then 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.
}
If a PE has sent 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
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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.
7. BGP Extensions for E-Tree Support
A new E-Tree extended community is proposed for E-Tree signaling in
BGP VPLS:
+------------------------------------+
| Extended community type (2 octets) |
+------------------------------------+
| Root VLAN (2 octets) |
+------------------------------------+
| Leaf VLAN (2 octets) |
+------------------------------------+
| Reserved |P|
+------------------------------------+
Figure 9 E-Tree Extended Community
Where:
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, 15 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.
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The PEs attached with both leaf and root nodes must support BGP E-
Tree signaling as described in this document, and must support VLAN
mapping in their data planes. The traditional PE attached with only
root nodes may also participate in 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.
A PE that receives a BGP UPDATE message with an E-Tree Extended
Community from its peer PE must process it as follows (after
processing procedures as specified in Section 3.2 of [RFC4761]):
1) if the root and leaf VLAN ID in the E-Tree Extended Community
match the local root and leaf VLAN ID, then continue to 3);
2) else {
the PE with the minimum IP address MUST set VLAN-Mapping-Mode
to TRUE;
}
3) If the P bit is set, then 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.
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.
8. 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.
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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.
9. Applicability
The solution is applicable to both LDP VPLS [RFC4762] and BGP VPLS
[RFC4761].
The solution is applicable to both "VPLS Only" networks and VPLS with
Ethernet aggregation networks.
The solution is also applicable to PBB VPLS networks.
10. Security Considerations
Besides security considerations as described in [RFC4448], [RFC4761]
and [RFC4762], this solution prevents leaf to leaf communication in
the data plane of VPLS when its PEs are interconnected with PWs. In
this regard, security can be enhanced for customers with this
solution.
11. IANA Considerations
IANA is requested to allocate a value for E-Tree in the registry of
Pseudowire Interface Parameters Sub-TLV type.
Parameter ID Length Description
=======================================
TBD 8 E-Tree
IANA is requested to allocate two new LDP status codes from the
registry of name "STATUS CODE NAME SPACE". The following values are
suggested:
Range/Value E Description
------------- ----- ----------------------
TBD 1 E-Tree VLAN mapping not supported
TBD 0 Leaf to Leaf PW released
IANA is requested to allocate a value for E-Tree in the registry of
BGP Extended Community.
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Type Value Name
=======================================
TBD E-Tree Info
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4447] Martini, L., and et al, "Pseudowire Setup and Maintenance
Using Label Distribution Protocol (LDP)", RFC 4447, April
2006.
[RFC4448] Martini, L., and et al, "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.
[RFC6136] Sajassi, A. and Mohan, D., "L2VPN OAM Requirements and
Framework", RFC 6136, March 2011
12.2. Informative References
[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.
[RFC6246] Sajassi, A., and et al, "Virtual Private LAN Service (VPLS)
Interoperability with Customer Edge (CE) Bridges", RFC 6246,
June 2011
[ETree-req] Key, R., et al, "Requirements for MEF E-Tree Support in
VPLS", draft-ietf-l2vpn-etree-reqt-01, Work in Progress
[Vpls-etree] Key, R., and et al, "Extension to VPLS for E-Tree",
draft-key-l2vpn-vpls-etree-06, October 2011
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[802.1aq] IEEE 802.1aq D4.3, Virtual Bridged Local Area Networks -
Amendment 9: Shortest Path Bridging, September 2011
[Etree-2PW] Ram, R., and et al., Extension to LDP-VPLS for E-Tree
Using Two PW, draft-ram-l2vpn-ldp-vpls-etree-2pw-02, May
2011
[PBB-VPLS] Balus, F., and et al., Extensions to VPLS PE model for
Provider Backbone Bridging, draft-ietf-l2vpn-pbb-vpls-pe-
model-04, October 2011
13. Acknowledgments
The authors would like to thank Adrian Farrel, Susan Hares and Shane
Amante 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 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 an MTU-s in an H-VPLS network, or an 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 (NNI) 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
1700 Alma Dr. Suite 500
Plano, TX 75075, USA
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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